An Absurdly Deep Dive into Apollo 13

Okay, Houston, we've had a problem. >> Houston, we've had a problem. We've had a main bus. >> Apollo 13 is a familiar story. The third lunar landing aborted after an in-flight emergency turned a nominal flight into a rescue mission. The story has been told in documentaries with astronauts and flight controllers and an amazing movie starring Tom Hanks. So, what do I have in my office that those Hollywood level productions don't have? Freedom from the need to satisfy shareholders and recruit money spent. We're going into the mission through the voice recordings. Hi, I'm Amy, an author, historian, and someone who's been researching Apollo Air Space Flight for most of my life. Apollo 13 is one of my favorite movies and for me, a gold standard of science depicted on film, but it's still Hollywoodized. Years ago, I talked to Jerry Griffin about this. Jerry was the flight director and leader of the gold team on this mission and also a technical consultant on the movie. He told me that when he first met with Ron Howard, I think he said that Dave Scott, Jim Levelvel, and Glenn Lenny were there as well. They met in the old mission control room and walked Ron Howard through the flight. Jerry said he left that meeting feeling like there wasn't enough there for a movie. From his perspective, they were trained for emergencies and they just leaned on their training. Everyone did their jobs very well. In rereading the transcript and reports to write this, I kind of see where he was coming from. It's interesting because, as we'll see when we get into the details, the emergency was so much worse when you really unpack it and understand it, but it was also less chaotic. Jerry told me that Ron Howard added background actors walking in the halls to create a sense of tension and urgency that wasn't really present in Mission Control. The truth is, Houston wasn't blindsided or caught off guard by anything once they were in emergency mode. It's really interesting to see through the source material just how they worked the problem. This might not be the version Hollywood told to satisfy audiences, but I think you'll still be satisfied at the end of this. All right, let's go to the moon. [music] Fair warning, I'm about to hit you with a lot of names, but we've got to meet our cast of characters, both human and machine. The original crew for Apollo 13 was Commander Jim Levelvel, lunar module pilot Fred Hayes, and command module pilot Ken Mattingley. To ground you in more familiar faces, that's Tom Hanks, Bill Paxton, and Gary Cise. They started training for their mission on August 1st of 1969, just one week after Apollo 11 splashed down. They had been the backup crew for Apollo 11, which as per the flight assignment rotation, put them in line to fly on Apollo 14. But Apollo 13 commander Al Shepard, recently back to flight status after successful experimental surgery to correct Menè's disease, needed more time to train, so the crew swapped missions. Jim Level's crew was announced publicly on August 6th. At the time, he was the most experienced astronaut in NASA's roster, having flown on Geminy 7, commanded Gemini 12, and had already gone to the moon on Apollo 8. Full video about that mission is right up here for you to check out after this one. Both Fred Hayes and Ken Mattingly were rookies, but not without relevant experience. Every astronaut was assigned to work closely with some part of Apollo's hardware, and in Fred's case, he had been heavily involved in development and testing of the lunar module with its manufacturer, Grumman. The backup crew was Commander John Young, another Geminy veteran who'd flown to the moon on Apollo 10, and two more rookies, lunar module pilot Charlie Duke, and command module pilot Jack Swagert, who's probably in your head right now looking like Kevin Bacon. Jack came to NASA from North American Aviation, North American Rockwell, after a merger in 1967, which was the company that built the command service module. The same way Fred was assigned to the lunar module, Jack had been integral in developing troubleshooting and emergency procedures for the command module. He was considered one of the foremost experts on the spacecraft. The command service module for Apollo 13 christened Odyssey was internally known as spacecraft CSM 109. And its story starts long before it was assigned a crew or a mission all the way back on February 26th, 1966. And I promise this isn't just superolous detail. We do have to go back this far. This is the date that North American awarded the Beach Aircraft Corporation a contract to build the service module's cryogenic gas storage tanks to hold super cold liquid oxygen and hydrogen. The service module was what made Apollo missions possible. This largest piece of the stack held most of the consumables used on a mission and its engine, the service propulsion system or SPS was the one the crews needed for critical events like slowing down into lunar orbit and adjusting their trajectory. The service module was where those cryogenic oxygen and hydrogen tanks lived as part of the fuel cell system. And the fuel cells were how Apollo missions had power. Each fuel cell, and there were three, had 31 separate but connected cells. The electrochemical reaction of combining the reactants of cryogenic hydrogen and oxygen produced electricity as well as heat and portable water as byproducts. These two gases are what kept the crew alive and in contact with the ground. Each fuel cell produced between 400 and 1,420 watts at 31 to 27 volts direct current. For perspective, with three fuel cells at max output, the system could produce 4,260 watts or 4.26 kW per hour times 24, that's 102.4 kwatt hours in a day, which is nearly four times what my house uses. And they typically weren't running at full power. In short, they had plenty of power on an Apollo mission. And I know this is deeply technical, but this is the key part of Apollo 13's story. The fuel cells were tied to two buses that distributed the power. Fuel cell one was connected to main DC bus A. Fuel cell 2 was connected to DC main buses A and B. And fuel cell 3 was connected to main DC bus B. Solid state inverters converted that direct current power into alternating current power that was then distributed through the spacecraft's electrical system in the command module via an external umbilical. The service module also supplied some power to the lunar module during the coast to the moon. The oxygen and hydrogen tanks in the fuel cells weren't connected to each other. Neither were the fuel cells connected to one another. The astronauts were also able to manually isolate individual fuel cells and control the direction of power flow if something malfunctioned. These were all built-in safety measures to prevent one failure in the system from crippling an entire mission. The oxygen tanks themselves were insulated spheres with an inner and outer shell and a dome over top to enclose the lines that carried fluids and wires for electrical power and signals. Inside each tank, there were two cylindrical units. One was a heating coil with small fans to stir the cryogenic oxygen and prevent stratification and the other was a quantity probe. The tank whose story we want to tell is oxygen tank 100024x-ta00009 and it also starts in 1966. Initial testing at Beach found minor flaws. The tank was disassembled, the heater and fans replaced, and then the whole thing reassembled, and testing resumed. There were still a few problems, but they weren't critical. And the tank was shipped to North American on May 3rd of 1967. It was paired with oxygen tank-a00008 to create oxygen shelf 0632A G3277. I know some of you out there love the detail of serial numbers. On June 4th, 1968, that shelf was installed in service module 106 and assigned to Apollo 10. Then an overall design flaw was found and every oxygen tank needed to be updated, which meant removing the shelf installed in Apollo 10 service module. The removal on October 21st, 1968 was a finicky process of disconnecting all the wires, unscrewing bolts, and lifting the shelf out of the spacecraft with a huge crane. But one bolt was still in place. When technicians lifted the shelf, it caught on the bolt, the fixture broke, and the shelf fell about 2 in. The stray bolt was removed, and the shelf lifted away on the second attempt. No one thought much of the incident. Engineers calculated the forces associated with a 2-in drop were so low, it was unlikely anything was seriously damaged, so the tanks were updated, and in January of 1969, the shelf was reinstalled in service module 109. A month later, that spacecraft was assigned to Apollo 13. Apollo 13 Saturn 5 rolled out to the launch pad on December 15th. The next day, the launch was pushed back from its early mid-March target date to April 11th to give the crew a little more time to prepare for their landing at Frammoro. Pre-launch tests with the Saturn 5 on the pad revealed an ongoing problem with that one oxygen tank. Technicians could fill and pressurize it just fine, but it didn't empty like it was supposed to. And it happened more than once, so it wasn't an isolated incident. The only way technicians could empty the tank was to use the heater and fans to boil off the oxygen. A fill test on March 30th, 12 days before launch, saw the same problem. Both oxygen tanks could be filled just fine, but tank 2 needed its heater and fan turned on to empty. But it wasn't a dealbreaker, and nothing looked a miss with the boiloff procedure. Every time they boiled off the oxygen, the temperature gauge didn't register above 80° F or 26.6° centigrade, which was acceptable. Never mind that the gauge didn't have numbers beyond 80 degrees. More to the point, the tanks didn't need to be emptied in flight. They needed to hold liquid oxygen, which tank 2 could do just fine. A few days after this troubling test, there was another anomaly. This one in backup lunar module pilot Charlie Duke's body. He'd picked up German measles from one of his kids' friends. He wasn't seriously ill, but he'd been in close contact with a prime crew, whose blood test revealed that only Jim and Fred had the disease and were immune. Ken's results were inconclusive. It was possible he'd start to exhibit symptoms in flight, and NASA couldn't risk him being out of action at a critical moment. The decision was finally made, though not without pleading from Jim Levelville to ground Ken Mattingley and swap him out with Jack Swagger just 8 days before launch. The new crew had days to get into sync of working together. It was never about getting Jack up to speed. It was making sure they could react as a team. And so, the stage is set for the third lunar landing mission. A minor technical issue and a last minute crew change, but this is exactly why NASA has such rigorous training and testing and backup crews. [music] On the morning of launch, Apollo 13 isn't the biggest story. The third lunar landing doesn't feel exciting, especially in light of the news that Paul McCartney is going for a solo career and the Beatles future is looking grim. Still, some 100,000 people show up to watch Apollo 13 leave the Earth. >> 8 7 6 ignition 4 3 2 1 >> zero liftoff. >> The clock is running. All engines, >> clear the tower. >> Clear the >> clearing the tower is a huge moment. The Saturn 5's first stage, the S1C, is powered by five massive F1 engines for a total of 7.5 million pounds of thrust. But the whole stack is insanely heavy. 6.2 million pounds or 2.8 million kg. For the first 10 seconds of launch, four engines can't lift the stack. So, if one engine fails, it'll crash back down. Once the Saturn 5 clears the tower, the rocket can lose one engine and keep flying to orbit. >> Complete pitching. Okay, we're going here. Good. >> 13 Houston trajectory is good. Thrust is good. >> The second stage, the S2, also has five engines and is annoyingly susceptible to a phenomenon known as the pogo effect, which for once in NASA's life isn't an acronym. It's a reference to a pogo stick. The force of the thrusting engines, the pumps managing the fluids, and the resonance of the propellant ducts combined to create longitudinal vibrations, and the rocket bounces like a giant pogo stick. The center engine number five is shaking so much that it shuts down early. >> Roger. We confirm in 13 standby for S4B to COI capability. >> S4B to CO. Roger. >> COI is contingency to orbit. This is an abort mode for if the second stage fails, but the spacecraft is otherwise fine. They can use their third stage, the S4B, to go into Earth orbit, but that's as far as it'll be able to take them. They'd have to go through a backup Earth orbital Apollo flight, which no one wants to do. >> Uh, negative. Not right now, flight. All the other engines are go. >> Flight confirmed. >> Houston, we don't have a story on why the inboard out was early, but the uh other engines are go and you're go. >> Should be no problem. All right. >> Apollo 13 gets lucky here. By the time engine 5 fails, they're above enough atmosphere that there's less drag on the rocket. They can burn the remaining engines longer to compensate without threatening their lunar mission. >> Roger station. >> S4B looks good. Flight. >> Okay, >> we should have the predicted cut off. >> Once in orbit, there's a bit of a rest period to make sure everything's running as it should. The crew also gets the first of many computer updates known as pre-advisory data or pads. These are instructions the crew inputs into the computer through the display known as the disc key that tells the computer how to manage the upcoming event. This pad is data for their trans lunar injection or TLIB burn done with the S4B stage on the opposite side of the planet from their target. This puts them into a massively elliptical orbit the apogee of which will intersect the moon in 3 days time. and you are you are go for TLI. >> Now on their trans lunar coast, the next big event is transposition and docking, which is the formal term for getting their lunar module out of storage. The lunar module or just LEM is stored underneath the main spacecraft during launch. So they have to get it. They separate from the S4B, then turn around and carefully dock with the LEM, pulling it out of its protective casing. And that's the Apollo stack complete, ready for a lunar landing. I'm a little bit >> hard to use. >> Roger. Understand. Hard dock. Good deal. >> The S4B, meanwhile, has an interesting mission of its own on Apollo 13. It's remotely put on a course to the moon where it will impact and trigger the seismometer left by Apollo 12 on November of 1969. Crashing something with a known mass and a known velocity is an excellent way to get data about the moon's inner structure. For the first 3 days, the flight is routine, or as routine as you can be, going to the moon. There's a lot of housekeeping and checking on systems. The astronaut's primary companion is Capcom, short for capsule communicator. Capcom shifts with the whole team in mission control. He's the only one who has a comms link with the crew to keep tower to a minimum. And he's always an astronaut. The astronauts know the systems. In some cases, they've flown, so know the sensations, and they are the experts at interpreting the data from engineers and controllers into astronaut speak. They also do a lot of daily news updates, usually over breakfast. >> Guys, we forgot. We'd like to hear what the news is. >> Okay. There's not a whole lot to it. Uh let's see. We'll start with the uh let's start with sports. What the heck? The uh Astros survived 8 to7. Okay. Let's see. The Beatles have announced they will no longer perform as a group. The quartet is reported to have made in excess of a half billion dollars during their short musical career. However, rumors that they will use this money to start their own space program uh are false. >> Okay, we can borrow some. >> Okay. Many uh air traffic controllers are still out, but reports indicate that they are slowly returning to work and uh you'll be happy to know that the controllers here in the Mocher are still on the job. >> Thank goodness for that. >> Okay, today's favorite pastime across the U. Uh oh. Have you guys completed your income tax? How do I apply for the detention? >> Yeah. No. Uh, I got a Hey, that's that ain't a funny kind of things got to happen real fast down there. And I I do need an extension. >> Huh? >> I didn't get mine filed. I was serious. Would you >> You're breaking up the room time in >> I may be spending time in I may be spending time in another quarantine besides the one that they they're planning for me. We'll see what we can do, Jack. We'll get with recovery and see if we can get the uh the agent out there in the Pacific when you come back. >> One of the bigger items on a coast of the moon are midcourse correction burns. These are done to fine-tune the spacecraft's trajectory. When it started its trip, Apollo 13 was in a free return trajectory, a path that would see them swing around the moon and head home if they didn't slow themselves into orbit. This is a safety measure, a way to make sure they have a ride home if their SPS engine doesn't work. But a midcourse burn at 30 hours and 40 minutes changes that. They go from a free return trajectory to a path that better aligns them for their landing at Frammorro. After entering lunar orbit spacecraft's in real good shape as far as we're concerned, Jim, we're boards down here. >> Their trajectory is so good after this midcourse burn that they're able to cancel another one planned for day three, opening their schedule for the main event, a televised tour of the lunar module Aquarius. It might be interesting. Just after we went to sleep last night, we had a master alarm and uh it really scared us and we rolled over the cockpit like a wet noodle. >> Sorry it wasn't something more significant. Uh uh I've also got a a procedure for you on that H2 tank. Uh simple thing after you get done stirring up the cryos. >> There's just one anomaly that pops up on that third day. Oxygen tank 2 is reading offscale high. >> Ready to copy. And on the O2 we have 81%. However, we show the O2 tank 2 reading offscale high. Now, we're quite sure it's a uh it's a sensor failure. We'd like you to verify it with your onboard reading. >> Okay, stand by. Uh Joe, we confirm uh our gauge reading is uh the number 202 high now, but just tell me that uh it was okay when you first went this morning. Uh we we verify that at uh 4645 we had 82% and uh apparently uh uh when he stirred the uh the cryos uh the sensor broke. >> Okay. >> The sensor in question is the quantity gauge. One of the two elements built inside the tank. It's made of two nested aluminum tubes that act as a capacitor. When a static charge is set up between the tubes, the density of the oxygen in that space affects their ability to store an electric charge, properly called capacitance. It's a good way of measuring the amount of oxygen in the tank. But it's somehow stopped providing useful data. The solution is to stir the tanks. The hope is that the fans will jiggle the inner pieces and resolve the contact issue. This isn't an irregular procedure. The tanks are regularly stirred. But cycling the fans doesn't fix the telemetry from tank 2's quantity gauge. It's a nuisance, but they're fine on consumables and it's not a critical failure. They can work around the problem by keeping the contents in the tanks well mixed. And since tank one sensor is working just fine and they know the rate of oxygen usage, they can reasonably infer tank 2's oxygen levels. >> Go ahead. >> Uh, roger 13. uh because of the uh O2 tank 2 quantity sensor uh dropout u uh ECOM wants to keep a little closer track of the uh of the cryo quantities and he's going to be asking you to stir all the cryotanks at slightly more frequent intervals than um than have been planned. And the first time is now and we'll be calling you probably every 5 or 6 hours except during sleep periods and uh and high activity periods. We'd like you to do it now. Over. >> Okay, we'll start a cry soon now. >> Thank you. >> It's such a non-issue that Gene Crance, current flight director on shift and mission control, whom you're imagining is Ed Harris, notes it as no sweat in the flight director's mission log. They just need to keep an eye on it. That job falls to ECOM, the electrical, environmental, and consumables manager. On Jean's white team, that's Sai Liberot, dramatized by Clint Howard. >> Okay, sounds good. We'll get the TV started right away. Roger. The Capcom on Jean's white team is Jack Lusma. And I'm sorry, we do have two Jacks in play. I know it's confusing. Jack Lusma doesn't tell the crew that none of the major US networks broadcast their TV transmission. It's 8:30 p.m. in Houston prime time, and a tour of the LM isn't as exciting as baseball, the Dick Cavit Show, or a rerun of I Love Lucy. >> Okay, 13. We got on TV. >> Your TV operator is now resting on the center couch looking at Fred Hayes, whose head is now just about at the beginning of the tunnel. and Fred will now transport himself into the tunnel and into the uh spaceship aquarius. Uh there's a little bit of an orientation change that uh been through it once in a water tank. It's still pretty unusual. Right under uh Jim now he's actually standing on a what looks to be a can here. Housed inside this can is the the mass engine where hopefully you can see my hand resting on top of right now. Fred's now looking through our optical device. Uh it's an instrument in which to uh align our platform. Look outside picture. You might be able to get we might be able to use a TV camera to uh look through our optical instrument to the outside of the command module. Okay. It's uh looking through the AOT and uh we're looking back uh toward the uh over the side hatch at the M side of the service module. Okay, Jack. I'm looking out the uh right window now and you can see the the objective. And now Fred's engaged in his favorite pastime I found out on this flight so far. >> He's not in the food locker, is he? >> That's his second favorite pastime. He's he's rigging his hammock for sleep on the lunar surface now to try it out to see what it's going to be like. >> Roger. Uh sleeping and then eating. >> Okay. Well, we show you now a little added benefit. And uh we've got the drove on Fred's uh couch in the command module right now. And underneath his uh couch, we've got the uh probe stowed. Quite a big coloring device. Uh we might uh give you a quick uh a quick shot of our entertainment on board the spacecraft, which is keeping us company for some time. And it's rather odd to see a floating like this in uh in Odyssey while it's playing uh the scenes of 2001. >> Okay, Jim. Uh it's been a real good TV show. Uh we think we ought to conclude it from here now. Uh what do you think? >> Roger. Sounds good. And this is the crew of Apollo 13. Wishing everybody there a nice evening and uh we're just about ready to close out our inspection of Aquarius and get back for a pleasant evening at Odyssey. Good night. >> After the broadcast, it's back to housekeeping. Houston has the crew adjust their attitude to photograph the comet Bennett. They check the high gain antenna configuration. They finish charging battery B, one of the three batteries in the command module they need for their return to Earth. The service module that powers the mission doesn't come home. Only the command module is equipped with a heat shield to protect the crew during their fall through the atmosphere. So, the command module has three batteries on board to provide the re-entering spacecraft with power for the last couple hours of a mission. These batteries can be used in flight if the crew needs more power than the fuel cells alone can generate, but it's a short-term power boost, and it's crucial they be recharged immediately after to make sure they're full for that final mission phase. They also check the reading on the docking index at this point. The docking index number tells them the relative position of the command and lunar modules while docked, which is important for when they configure the lunar modules attitude reference before Jim and Fred take it down to the lunar surface. This one's a little tricky to get your head around. In transposition and docking, when they collected the limb from its stowed position, both spacecraft were moving freely in space, but their docking mechanism is symmetrical. So, it doesn't matter if they're twisted relative to one another. They can dock but be offset around their X-axis, which runs from engine bell to engine bell. Because they'll use the command module's inertial platform orientation to set up the limbs. They need to know this angle to translate the data accurately. In this bout of housekeeping, Sai also has them stir their cryotanks. >> 13, we've got one more item for you when you get a chance. We'd like you to uh stir up your cryotanks. >> Okay, stand by. Hitting the switch to stir oxygen tank 2 sends power through tefloncoated wires inside the tank to the fans. Remember how during the pre-launch test, technicians had to heat the tank to boil out the oxygen. The test wherein it didn't look like the temperature gauge is going above 80° F or 26.6 C, but also the numbers on the gauge didn't go any higher. Technicians had no reason not to trust the gauge because thermostatic switches were in place to cut the power to prevent the temperature in the tank from going above that critical 80°. But they didn't, and that was because they were rated for the wrong voltage. The spacecraft worked on 28 volts DC, but at some point during Apollo's development and construction, the ground systems at the pad were changed to work on 65 volts DC. The change had gone out to all the contractors to make sure their systems could tolerate this higher voltage. But the change somehow didn't get to the company that made the thermostatic switches for Beach, who made the tanks for North American, who made the CSM for NASA. So, we're looking at a subcontractor supplier here. The thermostatic switches designed to interrupt power to the heaters to protect the tanks couldn't function at this higher voltage. So, instead of cutting power, they welded themselves shut. This left the heaters running, raising the internal temperature to more than 900 degrees Fahrenheit or a little over 500 centrade, hot enough to leave the electrical insulation cracked and brittle, damaging the Teflon coating. But why did they need to use the heaters in the first place? Well, that goes back to when the tank was dropped during its removal for refurbishment, October 21st, 1968. The jolt from that 2-in fall might have damaged the fitting used to fill and drain the tank, leaving it able to fill but not drain. That set up the scenario where the tanks reached unsafe high temperatures during not one but two separate tests. Now Apollo 13 is about 204,839 mi or 329,656 km from Earth with badly damaged Teflon insulation around wires feeding power into a tank of compressed pure oxygen. It's a bomb. When Jack flips a switch and the power flows, the insulation finally fails. The exposed wires come close enough to spark. The teflon ignites and the resulting fire very quickly ruptures the tank with the force of about seven pounds of TNT, enough to shear an entire side panel of the spacecraft clear off. The force is enough to knock out two of the three fuel cells, causing a dip in voltage. The remaining fuel cell, number two, is still working and getting oxygen from tank one, but the pipe leading to that tank has also been damaged and it's leaking. Of course, neither the crew on board nor the team in Houston know any of this. This was all determined after the postfight investigation, but I want you to know what happened right now. When Jack flips the switch, he's in the lefth hand seat in the command module Odyssey. Jim is in the lower equipment bay and Fred is in the limb. The crew hears a dull but definite bang, just the noise moving through the spacecraft structure. Fred feels a slight shudder and Jim, who's floating freely, doesn't feel anything at all. The dip in voltage triggers the caution and warning system and that gives the crew a master alarm. In that same instant in Houston, Inko, the instrument and communications officer, sees on his console that the spacecraft suddenly switches to widebeam communications, then hears a strange crackle over the radio, almost like it veered off course, which is exactly what happens. The force of the oxygen tank rupturing knocks the stack off kilter and it starts wildly rotating, triggering the clusters of reaction control or RCS thrusters to fire in a losing battle to restore the spacecraft's attitude. Okay, Houston, we got a problem here. >> Hatch is closed. >> Five guidance. >> Go guidance. >> This is Houston. Say again, please. >> We've had a hardware restart. I don't know what it was. >> Houston, we've had a problem. We've had a main bus undervolt. >> You see an AC bus undervolt? Third guidance or uh ECOM? >> Okay. Flight. We've got some instrumentation flags. Let me let me add them up. Roger. >> Fred floats up into the command module and Houston immediately jumps into troubleshooting. The loss of power. The main bus B undervolt suggests it could be an instrumentation issue. Everyone's leaning towards this being a false alarm generated from the faulty sensor readings because in the immediate aftermath of the warning, the power supply seems to be stabilizing. And caution and warnings alarm aren't uncommon. It's already been tripped on this flight from pressure transducers in the suit loop and an issue measuring the quality of the drinking water. Caution and warning alarms aren't always critical, but the readings from the cryogenic system are worrying and so is the bang the crew heard. In the inter room here, we're starting to go ahead and button up the tunnel again. >> Fred starts buttoning up the tunnel connecting the command module and the LEM. Thinking that if the issue is with the lunar spacecraft, they need to isolate themselves in the vehicle that can get them home. A minute and a half after the explosion, Jim adds an abnormality of the high pressure helium gas system that delivers propellant to the RCS thrusters. The indicators, which are called talkbacks, are barber pulled. Gray means normal, striped black and white means trouble. There are magnetic solenoid valves in the propellant lines that are fairly sensitive. They can close from a jolt like when the CM separates from the S4B, but they haven't done any maneuvers that would jolt them for a while, which is the first indication that the bang they heard wasn't just a noise. >> Okay, AC2 is showing zip. I'm going to try to reconfigure on that. Jon, you were seeing any AC problems. Looked like a lot of instrumentation problems there. Go ahead. >> That's firm. >> Well, let's get some you got any better ideas? Main bus a undervolt now too. Sean >> main A undervolt. >> He's got uh fuel cells one and three are offline. We've got main A volts. We have no main B volts. Have him attempt to re uh reconnect the fuel cells. Fuel cell one to main A. Fuel cell uh three to main B. >> Okay. Fuel cell. >> Just try that. >> Okay. Now, is there do we have instrumentation problems? >> Okay. Uh is that all we come up with for him? Uh we got any other recommendations? Yeah, we wanted to get fuel cell one configured to main A, fuel cell three to main B. Did you pass that up? >> Let's attempt that flight. >> And call this seems to BAC type problems and maybe tied into that tie gain thing you got. >> We went went to wide beam with flight at 55504. The best we can tell. >> I copy flight. Let me let me miserate on that. >> Is there any kind of leads we can give them or we looking at instrumentation or we got a real problem or what? Fred can see that their AC current supply is cut and tries to bring it back by changing the distribution grid configuration, but AC2 is powered by main bus B, which is reading nothing. Main A is low, which triggers an alarm. Houston sees the same thing, and at this point, 6 minutes since the explosion, the situation is entirely unclear to both the crew and in mission control. The immediate troubleshooting suggestion is to reset the connections between the fuel cells and the power system and put the fuel cells back to their usual configuration. Then Houston wants them to check the helium valve on a bank of RCS thrusters that doesn't seem to be firing properly. But there's a bigger indication of trouble. Their reactants, the cryogenic hydrogen and oxygen that react in the fuel cells are no longer flowing to fuel cells one and three. >> You got Can we review our status here, Sai, and see what we've got from a standpoint of status? What do you think we got in a spacecraft that's good? >> 8 minutes since the explosion and it's starting to become clear that this isn't an instrumentation problem or something to do with the high gain antenna. Fred connects battery A, one of the re-entry batteries into the power grid to boost their failing voltage and keep their systems running. >> Okay, Houston, are you still stand? >> That's affirmative. We're reading you. We're trying to come up with some good ideas here for you. >> 13 Houston, we'd like you to verify a couple readings for us. We'd like the hardware. >> Nitrogen pressure on fuel cell one. >> We need the oxygen pressure on fuel celling. >> Nitrogen gas maintains pressure in the fuel cells and it's calibrated closely with the oxygen. So checking the nitrogen pressure can be a roundabout way of gauging the oxygen level. But none of the data they're seeing in Houston makes any sense. And Sai Libergot is especially baffled that his displays are telling him that two fuel cells have completely stopped working. Compounding the problem is incomplete data. The spacecraft stack's erratic movements is making it so the antenna that's sending the data back via the radio down link is drifting away from a clear line of sight with receiving stations on Earth and that's interrupting the signal on board. The crew doesn't have every single piece of information on hand because of the physical limitations in the spacecraft. Even though the command module is wallto-wall displays and switches, they don't have a light or a gauge for every system. What they don't have on board Houston can usually see, but right now there's gaps in their combined knowledge. The onboard backup is the systems test meter, which is just a voltmeter showing a value from 0 to 5. They can take a measurement, scale it, digitize it, and send it to Earth for interpretation. And the erratic movement is raising a new worry for Gene Crants. RCS fuel is a consumable like anything else. They have a finite amount, and it's pretty strictly rationed to make sure they can manage their attitude throughout the flight. They need RCS fuel and they're using way more than they should be right now. Meanwhile, Telmu, who's the LEM electrical, environmental, and EVA mobility officer, basically the ECOM equivalent for the lunar module, notices that the LEM's heater's current is also behaving erratically. But it's one more piece of information than Gene can deal with for the moment. >> I tell you, >> go tell me the LEM heater currents become essentially static. >> Raj, let's solve one problem at a time. come back to me later on in >> the LEM's heater seems minor, but it's actually indicating the breadth of the problem because everything right now is tied to the SM's power, including the LEM. It's drawing power from the fuel cells to run heaters that keep vital systems from freezing on the transenter coast. Usually, when that power transfer is cut, when the spacecraft separate, the LEM switches to its own internal power. But telemetry says that hasn't happened. So, the stirrus module's fuel cells are also affecting the lunar module's heater. At this point, 12 minutes after the explosion, Fred finally manages to get a reading on the nitrogen tanks. There are two of them, and they should be at 53 PSI and 62.5 PSI, but they're reading 0 and 0.6, respectively. So, as far as they can tell, either the oxygen pressure is nothing, or there's another sensor problem, which would just add another layer of confusion to the unbelievable data marred by patchy communications. Sigh directs Jack Luzman on Capcom to tell the crew to leave fuel cell 2 alone and disconnect fuel cells one and three. He's hoping that taking the load off these cells will let them recover, but they can't keep them offline for long. The system relies on the heat of the fuel cells working to keep them working. Then Jim calls down that the sensor that was reading off scale high a few hours ago is now reading zero. So it still looks like this could be a faulty signal owing to the loss of AC bus 2 that powers the tank 2's systems. O2 quantity number two is zero. >> That's AC. Okay. >> Yeah, that's that's AC. And I was looking out the hatch that we are venting something. >> Crew thinks they're venting. So >> we are we are venting something out into the uh into space. >> Roger. We copy your venting. >> Copy this. >> Okay, let's everybody think of the kind of things we'd be venting. GNC, you got anything that looks abnormal in your system? Negative. >> How about you, Ecom? You see anything that uh with the instrumentation you've got, it could be vending. >> Nearly 15 minutes after the explosion and Jim sees the gas out the window and realizes what's happened or at least why their oxygen levels have plummeted. It's not instrumentation and it doesn't resolve everything, but the picture starts to get clearer. Now they have to figure out, are they leaking or venting? In either case, Jean Cray is eyeing the lunar module. >> Okay, now let's everybody keep cool. We got the limb still attached. The limb spacecraft's good. So, if we need uh to get back home, we got a limb to do a good portion of it with. Okay. Let's make sure that we don't do anything that's going to blow our CSM electrical power with the batteries or that will cause us to lose the main or the fuel cell number two. Okay? We want to keep the O2 and that kind of stuff working. We'd like to have RCS, but we got the command module system. So, we're in good shape. If we need to get home, let's solve the problem, but let's not make it any worse by guessing. The venting also explains why they're having such a hard time with their attitude. The oxygen is acting like a thruster, shoving them off course, and the RCS is trying to cancel out that motion. It's a tugof-war that's putting Apollo 13 at risk of getting lost in space. >> 13 Houston, we see you getting close to gimbal lock there. >> Gimbal lock is a constant threat on Apollo, though it's rarely this immediate. And to understand it, we need to look at the guidance computer. At the heart of the Apollo guidance computer is the inertial measurement unit or IMU. This is a unit about the size of a soccer ball containing three nested gimbals. A gimbal is just a pivoting support that allows for rotation around an axis. Three gimbals in the IMU correspond to three axes of motion, pitch, yaw, and roll, and they're set at right angles to one another with a central platform mounted in the innermost gimbal. The outer gimbal is mounted to the navigation base that is itself mounted rigidly to the spacecraft. The system doesn't have any gears, so there are no concerns about wear or accuracy, and the gimbals are able to move freely. In flight, from the IMU's perspective, the spacecraft moves freely around it while it stays rigid in space. As the IMU moves, it gives the guidance computer mathematical information about the spacecraft's position relative to its last calibration. Data from the IMU was displayed to the crew on the flight director attitude indicators, what's commonly referred to as the eightball. and Houston has a digital version in mission control. But there's an inherent limitation to the IMU having only three gimbals. And we have to remember that the IMU works in mathematical terms. The way the system works, the middle gimbal moving also moves the inner gimbal. It's possible for the middle gimbal to move away from the zero orientation while the spacecraft moves in such a way as to carry the outer gimbal to where it lands parallel with the inner gimbal. This leaves them in a single plane and now there's no freedom for the gimbals to unwind. The system loses its ability to isolate the platform from the spacecraft, leaving it with only two degrees of freedom, and that's not enough to regain usable guidance data. This problem of gimbal lock could be saved by adding a fourth gimbal. Both the Saturn 5's IMU and the Gemini spacecraft had a four gimbal setup, but using three was good enough for navigation on Apollo, and it had the benefit of being lighter. Gimbal lock itself won't end a mission. The crew can realign the platform and they're trained in celestial navigation. But right now, with everything going on, they don't want to have to pause their troubleshooting to realign their guidance platform, which is why everyone is keeping a close eye on that middle gimbal. By now, mission control is jammed. Not only are we coming up on a shift change, so controllers are passing over their stations, astronauts are converging on the Capcom console, eager to help. Jerry Griffin told me he and a few other guys were playing baseball that afternoon, and when he got home, his wife passed on an urgent message to get to mission control. He went in sweatpants. The classic image of white shirts and skinny black ties broke down pretty quickly. 20 minutes after the explosion, it's becoming clear that the Odyssey's electrical power system is dying, and ECOM controllers are trying to figure out whether they've lost both oxygen tanks. Either way, they can see this mission is about to become a task of power management. They start by having the crew reduce their power consumption by 10 amps to keep the power systems on a single fuel cell and take their re-entry battery offline. Remember, they don't want to be draining this vital source. None of this is standard procedure, but the crew has the thankfully weightless 20 lb flight data file on board that has all the checklists, flight plans, star charts, and references, and in this case, emergency plans. Half an hour after the explosion, and Houston wants a proper look at oxygen tank 2 status. The sensors measuring the quantity and temperature drop power from AC bus 2, which isn't working. So, Houston has the crews switch to using inverter 1 to supply alternating current to both AC buses. The worry is the burden on bus A will cause another undervolt. Houston also has them turn off fuel cell pumps that circulate liquid hydrogen and provide pressurization and cooling, another temporary power saving measure that could see a drop in performance from the remaining fuel cell. The venting has now pushed the spacecraft off its flight path. It doesn't take a lot of energy to shift an object in space since there's no air resistance. So, a steady vent over time can build up to a large change over distance and there's plenty of distance going to the moon. >> Okay, Jack. And the way configuration we're sitting in now is we have the hatch installed. We still have the probe and drogue inside the command module. We're going to stay in this situation till you uh kind of give us an okay to reinstall the probe and drone >> right >> or if necessary to use the lamp consables. >> Fred said what Jean CR noted a few minutes earlier. They still have Aquarius attached and it seems to be okay and they know there's power and oxygen in that spacecraft. The LEM as a lifeboat is fast becoming an option. Sai Liberot is laser focused on keeping the Odyssey able to return to Earth. He requests the crew reduce their power output even more. Re-entry battery A has been online now for 32 minutes and they can't recharge it without the fuel cells. So that becomes a priority which means they need to troubleshoot the cryotanks. They've tried to recover fuel cell one by removing it from the power grid. Now they're trying the same thing on fuel cell 3, the other one that's malfunctioning. They also want to reconfigure the RCS thruster power to try to manage their attitude issues. Then Sai has the crew isolate the surge tank, a small oxygen tank in the command module they'll need for re-entry. Oxygen tank one should be pressurized at a little over 900 PSI, but it's plummeting. There's a chance they can restore the pressure a little using the tank's heaters, but that could also help it vent faster, and it's going to trigger another main bus a undervolt since they're already in a low power state. They try it and it doesn't help. And Sai comes to the same conclusion as both Gene and Fred. >> Well, you better think about getting in the limb or using the limb system. I'm going to have to power way down. I don't know if I'm going to be able to save the O2 for the third fuel cell for fuel cell 2 rather. 50 minutes after the explosion, Gan directs the LEM team to start figuring out a minimum power setup they can use to keep the crew alive. Meanwhile, Jack calls down that he's seeing fewer particles out the window, so maybe whatever is venting has stopped, which sounds promising until they look at the numbers and realize it's because the oxygen in the tank is completely gone. The cloud of oxygen surrounding Apollo 13 right now is so big it's visible through telescopes on Earth. The crew keeps powering down systems to conserve what power they have, but it's fast becoming a race against time. >> Flight, we're going to hit 100 PSI in an hour and 54 minutes. That's the end right there. >> Whatever planning you do, I want to do assuming that we're going around the moon and we're using the limb for performing the maneuver because in the present configuration, unless we get a heck of a lot smarter, I think we're wasting our time planning and using the SPS. >> Okay. Fly. So I think all of our return to earth type planning should be assuming the uh use of the lamb dips and or RCS and I think third priority down the line should be CSM RCS. >> Okay. And I'm assuming you you'd want fastest possible return. >> Uh yeah, I think that's the case. >> Okay, we'll we'll work on it from that sideline. Fine. Should be no problem. >> I copy that. Just about 55 minutes since the explosion and Gene Crance has pretty much written off the main spacecraft, the command service module. The LEM dips is properly the LEM DPS, the descent propulsion system pronounced dips. We'll go through the LEM systems in more detail in just a minute. The pho who Jean's talking to is the flight dynamics officer and he's responsible for the flight path. Now that the mission has changed, Phto needs to figure out how to amend their trajectory. Remember, Apollo 13 left its free return trajectory yesterday. They can't just swing around the moon and come home anymore. They have to make a course correction burn. The other controller who's about to get very busy with planning is retro, the retro fire officer. He's the one who draws up abort plans throughout a mission should the crew need the fastest way home possible. His role is even more vital now. Jean's directive to start planning to use the LEM's engine to get the crew home fast wasn't the first time they thought of it. And this is where I kind of see what Jerry Griffin meant when he said they were just doing their jobs. The contingency plan of using the LEM's descent engine to bring the crew home faster was proposed in 1963. The crew even has a procedure for it on board the spacecraft. In a nominal mission, the SPS engine burns to slow the spacecraft enough that it's captured by the moon's gravity and enters into lunar orbit. This engine fires again on the trans Earth injection burn that starts their trip home. It's a pretty foolproof engine that uses hypergalls, fuel and oxidizer that burn on contact without an ignition source. Open a valve, the propellants flow, you burn. But there's always a chance for something to fail. So there was a contingency in place to use the LEM's descent engine in lie of a faulty SPS if it failed to fire at the moon. There's no scenario on the books for a LEM dips burn and a command service module that can't provide life support. So Houston knows they can use the LEM to do the burn to get them home, but that's only part of the battle. 56 minutes from the explosion, Sia Liberot realizes he only has one move left. >> Go ahead. >> Okay, listen. There is a possibility that we blew a O2 line in one of the fuel cells and it's effectively manifolded there. Of course, now I'm I want to shut off one of the re the reactant valves to one of the fuel cells and that would be fuel cell 3 since its O2 pressure is gone. Now, fuel cell one's O2 pressure is trying to stay up there at 45 PSI. Maybe the problem is in fuel cell 3. That sounds like a good assumption right there. >> Yeah, fuel cell 3 is lost anyway as far as flight GNC go. >> Size thinking is that if fuel cell 3 is damaged and that's where they're losing oxygen, physically isolating the fuel cell by closing the reactant valves that control the flow of oxygen and hydrogen to that cell might stop the leak and leave them with one oxygen tank and at least one working fuel cell, fuel cell 2, which would leave them enough power and oxygen to get home. Sigh has effectively written off onethird of the SM's power capacity. >> Okay. 13, this is Houston. It appears to us that we're losing O2 flow through uh fuel cell 3. So, we want you to close the react valve on fuel cell 3. Looks like fuel cell one and two are trying to hold up. Okay. just holding out a few better from a standpoint of thermal control anyway. >> You're saying fuel cell one and two and one and two are trying to hold up, but we're leaking O2 out of fuel cell 3, >> and you want me to uh shut the react valve on fuel cell 3. Did I hear you right? >> That's affirmative. Close the react valve on fuel cell 3. >> Fred's disbelief is warranted. Once closed, the react valves can't be reopened, and it's a move that forces their abandoning a lunar landing. Mission rules say you can't land on the moon with only two fuel cells. At this point, they're a day away from the moon. If they're somehow able to figure out the source of the issue and get the remaining fuel cells up and running, there's no question of going for a landing anymore. Jack Swigert starts going through the fuel cell shutdown procedure on board, which conveniently he wrote. An hour and 10 minutes after the explosion, there's a shift change in mission control with Glenn Lunny's black team taking over. Gan's white team, though, isn't going home. >> Uh, let me go back over this again. We're heading over to Glenn. I suggest the white team goes back and starts going through the dlog of the data. In other words, let's see if we can go back to the initial conditions and work in that problem to see if we can find out what happened and we may find some better clues as to what to do and let the fresh guys come on and try to figure out where do we go from here. They all moved to room 210 to review telemetry dlogs and figure out the LEM low power profile because the situation hasn't improved. Closing the reactant flow to fuel cell 3 didn't fix the oxygen tank pressure. >> Okay, Jack, we want you to uh go >> leave the bus configuration as it is. Fuel cell 2 on main A. >> Omni Bravo 2 Jack >> and we need Omni Bravo. >> Okay, Jack, we're proceeding with a shutdown procedure for fuel cell one. An hour and 20 minutes after the explosion, Jack shuts down fuel cell one, leaving fuel cell 2 on main A. It's another kind of unbelievable direction, but at this point, normal is out the window, and he doesn't hesitate. Jack Luzma also tells Jack Swagger to isolate the repress package, the oxygen they'll need for re-entry. Sai asked for this to happen a while ago, but it got lost in the shuffle. In another powersaving measure, Houston has the crew turn off high gain power, saving them another 2.9 amps at the cost of clear communications. Working the problem without being able to hear clearly promises to add another layer to an already complex emergency. [music] Now in command of mission control, Glenn Lenny dives into the task of turning the LEM into a lifeboat, which means now is a great time to get acquainted with the lunar module Aquarius. The LEM was a pretty phenomenal spacecraft built specifically to land on the moon. It can't fly another mission, and it certainly can't return to Earth. Not only does it not have a heat shield, it doesn't have fuel cells like the service module, it has batteries. There are four 400 amp hour batteries in the descent stage that provides a nominal output of 30 volts. The ascent stage has two 296 amp batteries. Each stage has two electrical control assembly units that manage power output through two8volt direct current power buses while alternating current at 115 volts comes from two inverters. Electronic control boxes connect the systems in both stages. In English, they have a decent amount of power and a complicated system for accessing the two separate systems. But it's specifically designed to support the LEM's own mission, which is a two or three-day, depending on the flight, trip down to the lunar surface. On a normal mission, the LEM separates from the main spacecraft once in orbit around the moon. It uses its big descent engine, the LEM dips, to land on the surface. It provides life support for the crew between their EVAs. Then, the descent stage serves as the launch pad for the ascent engine to fire and get the crew off the moon. The LEM rendevous and docks at the CSM waiting in orbit. Then the crew jettison the LEM ascent stage, crashing it into the moon as a seismic data point. More on that soon. And we're back to the SPS engine for the TEI burn. The LEM being purpose-built like this is how Apollo made it to the moon within a decade. It's how the mission fits on a single Saturn 5 rocket. Keeping the LEM's mass to necessities and leaving the heaviest spacecraft in orbit kept the overall mission mass down. And amazing as the spacecraft is, it's also very utilitarian, issuing things like hot water or a heater to prepare warm meals. These higher power systems are only available in the command module. So, the LEM's mission can run on batteries, but Aquarius isn't landing on the moon anymore, and its batteries can't provide enough power for the four or 5 days it's going to take Apollo 13 to get home. The main LEM lifeboat contingency NASA had planned for was a scenario where the ascent engine failed and the two moonwalking astronauts had to wait in orbit for the CSM to be the active party to meet and recover them. The idea of using the LEM as a lifeboat for the trans earth coast has been investigated over the course of Apollo's development with a fairly detailed plan emerging in August of 1968. So that's what Telmu Merlin Merritt starts building a plan on. The plan, as it exists, calls for jettisoning the service module and using the dips for the TEI burn, then the LEM as a lifeboat all the way home. They could then transfer power to the command module to maintain its onboard computer. But that plan imagines a scenario where the service module becomes inactive after flying past the moon. They're still 24 hours from the moon. So, working from the few contingencies they've thought about, the thinking is to fly with the tunnel open so the crew has access to both spacecraft and to use the LEM's batteries to supply low power to the SM's main BB bus for anything they might need in the Odyssey. Things like navigation, but they might not have the option of relying on anything in the service module. Readings in the Odyssey show the pressure in the remaining oxygen tank is still dropping. In 10 minutes, it falls from 300 PSI to 200. If it gets below 150, they can't be sure the fuel cell will work at all. Anything below 100, which ECOM says is now about 40 minutes away, will leave the Odyssey entirely without power. >> Looks like we got about 40 minutes left in that town. >> Okay. Does it look like it's still going down? >> Yes. >> It's slowly going to zero and uh we're starting to think about Lamb Life. >> Yeah, that's what we're thinking about, too. Do you want me to do a quick T-52? Well, it kind of looks like uh we've been talking it over and it kind of looks like we probably align our plat lab platform with our platform and then power down the CM uh and keep the lamp powered up doing a dips uh whatever dip spurn you give us. >> Capcom, just for his information, we're not going to do a dip burn until we hook around the moon. Let them know that it's and that's at about 79 plus 30. >> P-52 is a program to realign the guidance platform, the IMU. This is especially important because the lunar module gets its initial guidance data from the command module. And right now, as they're moving into the LEM, Odyssey has guidance and Aquarius is unpowered. Getting the platform as accurate as possible before the transfer would make it easier on the crew, but it takes 5 minutes they don't have. Besides, they can fine-tune their platform once the LEM is up and running, and there's more pressing needs for their remaining power. They need to try to get as much power into battery A as possible so it's ready for re-entry. 13 Houston, we'd like to charge battery A now. >> I don't know if we want to keep that platform up. >> Keep that thing running for all that time. >> Go ahead. Okay, got an update on the time. Look like we got about 18 minutes until we get down to 100 PSI and that's a cut off point. >> All right, but we charging battery. Well, that doesn't mean much in 18 minutes, though. But we're doing all we can do. >> All right. >> While Jack is managing the Odyssey, Fred's in Aquarius. But powering up the spacecraft isn't as simple as flipping on a switch. The powerup procedure is a 59page several hour checklist and they don't even have a normal starting point. Remember that the SM usually provides power to the LEM from main bus B just enough to keep the onboard equipment warm. The sudden loss of external power has interrupted that process and left the LEM totally lifeless. It needs to be reset and they can't rely on main bus B. So they opt for a process to hack the LEM's power system without any external sources. >> It's not a very long procedure, Fred. Uh, >> we figure we've got about 15 minutes worth of power left in the command module. So, we want you to start uh getting over in the limb and getting some power on that. And uh, you ready to copy your procedure? >> Okay. >> It's been an hour and 41 minutes since the explosion, and this is the first time Houston has given the crew a firm deadline. As Jack on Capcom talks Fred through setting up the LEM, they skip things they don't need, like the VHF radio that's used to talk between spacecraft when they're flying separately, which they won't be. They focus on vital systems like the sublimator. Heat is always a delicate balance on Apollins. Space is cold but unfiltered sunlight is hot. Not to mention the instruments generate heat as well. The LEM sublimator dissipates the excess heat. Water is fed through a set of porous plates, one side of which is exposed to the vacuum of space. So the water turns into ice than sublimates away. The challenge is that sublimating water can nudge Apollo 13's trajectory. But not using the sublimator is worse. On Apollo 11, the crew left the Eagle's instruments running without the cooling system after it was jettisoned just as a test and system started failing after 8 hours. Apollo 13 needs instruments for a lot more than 8 hours. Jim soon joins Fred in the LM, which has no comms yet, and Jack is up in the CM managing their last bits of power, shouting instructions from Houston down through the tunnel. The next task in the LM is getting the life support up. Then they open the oxygen tanks and power up the cabin repress system to send oxygen into the cabin. They turn on suit fans to circulate that oxygen through both spacecraft and through the scrubbers to remove carbon dioxide and replenish the oxygen. Without the fans, they might have oxygen, but they could also have pockets of CO2 forming in dead air. And that could be extremely dangerous. Then they get the telemetry sorted so they can talk to Houston and send back data. >> Okay, Jack. >> Pressure in tank one is approaching 100 PSI. What's going to be the symptoms of this fuel cell to drop off? the uh the voltage is going going to begin to drop and we'll need to power down with it. >> Okay. What do you want them to do? Turn everything off. >> Leave the lights on and uh leave the lights on. >> The only concern we have, >> Jack, this is Houston. >> We want you to keep the IMU up and keep the lights on so you can see in there. >> And leave battery A off. And at the appropriate time, we'll put it on main A. And we're going to keep the IMU up so as we can get a course of line in the limb. >> A corsal line C O A R S E not C O U R S E is vital for bringing the LEM computer up and giving it guidance data. Remember how it usually gets that initial information from the command module? That's what we're doing. The lunar guidance computer or LGC is the counterpart to the system in the command module. And like that system, it controls the spacecraft's attitude by firing the RCS thrusters, controls the big engines on their burns, keeps track of the spacecraft's position, and had programs for the lunar module specific tasks like lunar landing and rendevous. It also has its own inertial reference system, its own IMU that needs some information to start getting it oriented. To do the course align, they have to take the CM gimbal angles, adjust them to compensate for the orientation of the limb. This is the docking index they checked right before the explosion and use that to reorient the limb's own IMU. This is all normal procedure and it has room for small errors like the docking angle. They can fine-tune this rough or coarse alignment, but right now they just need any alignment. >> Okay, tank two fans going off. >> Okay, that leaves me with tank one fans on and uh tank one heater on. Jack is trying to keep the pressure in tank one as long as possible to squeeze the last bits of power out of the SM. >> I was just making a comp check here. I'm on high rolling steps. >> Roger. We're saying Fred and I'm reading you loud and clear. >> Didn't think I'd be back this soon. >> With both spacecraft up, the crew has to swap controls from the Odyssey to Aquarius. They turn off automatic control so the LE's RCS jets don't start firing. Jack is keeping things carefully in check so he doesn't disrupt the guidance data he's shouting down to Jim and Fred in the LM. Any movement of the stack between the time the gimbals are read in the Odyssey and input into the Aquarius will make the alignment less accurate. >> Okay, I want you to double check my arithmetic to make sure we got a good course of line. >> Translating this data is simple addition, but it makes sense in all the chaos and how important it is that Jim wants a double check. And right in the middle of all this, Jack and Ecom simultaneously see that the fuel cell is on its last breath. Jack turns battery A on right as the call to do so comes up from Houston. Apparently, Glenn Lenny's reaction to this was, "He got it. Good boy." Which is mostly funny because he's 5 years younger than Jack Swagger. Once they get the LM's IMU up, they can see that they've drifted more off course just in the time since they powered up the spacecraft, which is information Phido and Retro will have to take into consideration. Odyssey Houston, we need a command reset on your uh on your comm. And uh then we'd like you to power down the CMC, power down the IMU. Heater's off on the IMU, but leave your battery AM. >> Yeah. Got just about 80 hours out of the two primary cartridges. That's two guys. 24 is what LCA got to be 88 hours. We got a secondary. You're right. >> Fred has already identified a problem for later. Carbon dioxide. The lunar module is designed to keep two guys alive for two days. Now it's three people for maybe 4 days. They don't know exactly how they're getting home, but Fred notes out loud that they have a limited number of lithium hydroxide canisters on board that they need to absorb the toxic exhaled carbon dioxide. He also knows that the ones in the Odyssey aren't compatible. It's literally a square peg in a round hole. There are more lithium hydroxide canisters for the LEM, but they're in the modular equipment stowage assembly or MISA, which is a very handy compartment in the descent stage that they can only reach from the lunar surface. The only way to get them in flight is to do an EVA. And not only do they not have the spare oxygen to decompress and recompress the cabin, the crew isn't trained in deep space EVA. They do have PLSS canisters though that are designed to be used with the EVA suits that fit into the secondary slot in the LEM's life support system. Uh, yes, Jack. I read it back twice to you. Command reset, which I've done. I'm about to power down the IMU. Power down the CMC. Turn the IMU heaters off. Leave that A on. >> Turning off the IMU heaters is a bit of a big decision. The initial plan of keeping some power from the LEM into the SM bus to flow into the CM was partially to keep vital systems like the IMU heaters on. They need guidance and navigation for re-entry, and they obviously can't use the CM's batteries. The IMU is delicate, and there's never been a test on it restarting after sitting in the cold for days. The one data point NASA has is that someone once left an IMU in their car overnight in the winter, and it still worked once it warmed up. >> Advantage to doing it early is we can power that back the limb back down. The only advantage to doing early is you could do a big burn now and a midcourse and then power the limb down. If we otherwise we got to keep the limb powered up clear till we get around the moon. Plus they'd be in sight of the burn. >> I just hope the GN hangs up on this one. I sure can do that with manual. >> Oh boy. >> Fred has just had another very precient moment. He has already realized that their power management could get so tight they might not be able to power up the computer to do a midcourse correction burn, forcing them to do it manually. >> Okay, Jack. Now I have power down uh the IMU. I have uh no control at all. I'm going to turn my 16 jets off. Uh take any other things you wanted. >> That's O2 tank one heaters and fans. >> Okay. Uh Jack, we'd like you to turn off your O2 tank 2 heaters and fans. One >> correction tank one. >> Okay. Jack, can we turn on the FDI trigger breaker so we can have a call to see if we want to lock or not? >> Standby. >> RCS heater on and >> yeah, RCS pressurized. We didn't tell him to pull the FDI in the lamb. >> No, CSM. >> Yeah. >> Uh Jim, we didn't want you to power down the ball in the limb. We wanted you to power down the ball in the uh CSM. >> Uh Jack, they haven't powered down. Uh Jack, we don't have the balls powered up in the lamp. >> I have the CMC and I command module is powered down. The heaters are out. >> Okay, Jack, we need to know when we're getting close to gimble lock in the lamp. We have no balls right now. >> Okay, we want you to power up your eight ball. >> Hey, flight GNC. The CMC and the IMU are completely powered down. >> Okay. Okay, Jack, I got the two uh Commander FCI breakers in, AC and DC, and the two gas breakers in AC and DC. And Nick, you want the RCS heaters all on with the pressure at the RCS and in the main size open. And I think they're already open. >> Roger. >> Brian, put the TCA breakers in last. The TCA breakers in last. Okay. TCA breakers in last. >> And Fredo, get the TCA breakers in last, please. Jack, are you ready? >> In the final stages before CM shutdown as the LEM is still getting all its guidance data up, things are messy. The two spacecraft are talking to Houston with sometimes patchy comms overlapping. Instructions are getting jumbled, and it's a bad time to mishar or misinterpret something. Aquarius's displays aren't fully up yet, and while the guidance information is in the computer, the RCS thrusters they need to control attitude aren't online. But Jack has already powered down the RCS in the Odyssey so that they aren't fighting Aquarius for control. So right now, Apollo 13 is without any means of control. Remember, they need to manage their attitude to point the antenna to talk to Earth. Losing comms now could be disastrous. There's also the threat of gimbal lock. Houston catches the issue, which Jane Crance later admits was a significant operational error, and has Jack repower the Odyssey's RCS to keep things steady before the LM is able to take over attitude control. Glenn Lenny later said this error was a low point in morale, but they get the RCS back and Jack is flying by looking at the lunar terminator and keeping it aligned to hatch marks on the window. Fred and Jim get the LM thrusters up by detonating small explosives called squibs that open valves in the propellant lines. They're shut to protect them from jostling during launch, but it's not as simple as Fred just taking control. No one's ever flown in this configuration. The LEM isn't meant to fly the CSM stacked on its head. They do have a digital autopilot or DAP on board, a forerunner of a digital flyby wire system that can manage RCS thrusters automatically. >> Okay, we need to change that CSM weight. >> Okay, Aquarius, your CSM weight is 63 4 0. >> Again, Fred brings up a big issue almost the instant mission control sees it. The DAP needs to know the CSM's mass so it can properly calculate the thrust it needs for engine burns. They're hauling 40,529 pounds or 18,384 kg of propellant with them. And they aren't using it for the LOI burn. They're bringing it home. 2 hours and 45 minutes after the explosion, Jack closes the reactant valves on fuel cell 2, then powers down his inverters, the battery relay bus, the battery ties, and pulls the entry circuit breakers on batteries A, B, and C. It was a simple six-step procedure. >> Go ahead, Aquarius. Okay, Odyssey is completely powered down now according to the procedure that you read to Jack. >> Roger. We copy. That's where we want to be. Jim >> Jack said that once the Odyssey was completely powered down, it felt like a tomb. That was a lot, but things are stable enough on board that we can take a quick breather with an adbreak. >> [music] >> 58 hours and 40 minutes into Apollo 13's mission, 2 hours and 45 minutes after the explosion, the crew is in the limb. There are some issues on the horizon, namely the CO2 level, the Odyssey's cold IMU and semi- depleted re-entry battery, as well as their trajectory. But the crew isn't in immediate danger. There's also a lot of debris out the window affecting their visibility. But what both the crew and the teams in mission control have right now is time to work the problem. In Houston, it's about 1 in the morning and Glenn Lenny has all the offline people working on the long range problems and the men in mission control making sure the stuff that's working stays working. In a conference room, a team is already working on how to use what the crew has on board to figure out an adapter to get the CM's lithium hydroxide canister into the LM's ports. Simulators are up and running so the backup crew can try to get some navigational reference points and burn characteristics up to the crew before they have to do any major events. Okay, that's uh concludes the power uh down of displays and I have a uh P30 pad for you. >> Okay, go ahead. >> Okay, the purpose is a uh paracion plus 2 hours depths abort. >> So, let's talk about abort maneuvers. Almost immediately, there were a few options on the table. The first being a direct abort. In this scenario, the crew would use their big SPS engine to negate their velocity towards the moon, slowing them enough that the Earth's gravity would pull them back, effectively starting their fall back home. The window for that option came and went pretty quickly. Jack called down about the explosion at 55 hours and 55 minutes. At that point, their trajectory had them crossing into the moon's sphere of influence, meaning the moon's gravity is stronger than the Earth's at 60 hours. A direct abort only works if the spacecraft is in the Earth's sphere of influence. That's how the gravity can pull them back. And this direct abort would have also demanded the crew jettison the lunar module to lighten the mass and get the thrust they needed. Since it was clear pretty quickly that they needed the LEM's consumables, that option didn't remain in play for long. The next option was a PC plus X burn. Parasynthion is the point in an elliptical lunar orbit that passes closest to the moon. So, this burn would happen X hours after that closest approach, giving them a burst of speed to get them home faster. There were three possible options. One was a PC plus1 burn 1 hour after Parisynthion using the entire delta V capacity of the descent engine with a large burn of 4,728 ft pers. This would give the crew the fastest return ending with a splashdown in the mid Pacific at just 118 hours elapse time or just under 40 hours after the burn. To get that much thrust, they would have to jettison the service module first because it's really nothing more than dead weight. The second option was a PC plus2 burn of 845 ft per second, less than half the engine's capacity. They wouldn't need to separate the service module for this burn, and it would see them splash down in the mid-pacific around 142 hours get. The final option was a PC plus2 burn using all the engines capacity and keeping the inert SM attached, putting them in the Atlantic Ocean at about 133 hours get. So, if getting the crew home as fast as possible was ideal, why not ditch the dead weight of the service module and go with the first option, the PC+1? On the surface, it sounds great, but there are two potentially huge long-term complications. The first is trajectory. Yes, that burn profile would get them home faster, but it also opens the door for more errors building up over time. We've already seen how a little nudge over a big distance turns into a shove. If they use all of their fuel on this big burn, they wouldn't have anything left to do a midcourse correction. They do still have the lunar module ascent stage engine, but using it means jettisoning the descent stage, and that's where most of their consumables like power and oxygen are. The second issue is the Odyssey's heat shield. The heat shield is a fiberglass honeycomb bonded to a steel plate. The honeycomb's 370,000 cells are filled with Avco resin, then cured. Its operating range is between - 150 Fahrenheit or 101 C and plus 200 Fahrenheit or 93 C. It protects the command module as it falls to Earth by burning away. Right now, it's nestled between the CM and the SM. Ditching the service module would expose the heat shield to both the cold of space and direct sunlight and possibly to something like a micromedorite strike. And you don't want to fracture your heat shield. No one wanted to risk this critical element. Not to mention as little data as NASA had about flying the whole stack from the LEM, there was even less data about flying just the LEM and CM together. So then the third option that gets them home faster and protects the heat shield and saves some fuel for a midcourse correction burn. The downside to this option was landing in the Atlantic, a zone that didn't have as much recovery support. And there's another reason NASA wanted a Pacific splashdown. The LEM was going to burn up in the atmosphere on re-entry, but the graphite cask of plutonium on board wasn't. This was the power source for some of the surface experiments, and NASA wanted to sink it in the Tonga Trench, a resting place that would satisfy the Atomic Energy Commission. The math already said that with proper management, they would have enough power and water to get home. No one wants to add more risk to the situation, so the slowest return is ultimately the safest. But first, they need to get on a free return trajectory, meaning they'll loop around the moon and be shot back towards Earth. And they also need to learn how to fly all over again. >> That's a crap attitude. >> We're okay. >> God damn, I wish you'd get to something I know. and uh Aquarius Houston. Uh we've got you both on Vox. >> Thanks for >> We have you on Vox. We're reading you loud and clear. And the clock took good. >> The CSM's SPS engine, the one they'd normally use for burns, has its axis parallel to the spacecraft's roll axis. So gimbling that engine allows them to adjust in pitch and yaw. The LEM's descent engine runs parallel to the spacecraft's axis of yaw. So gimbling it allows for control in pitch and roll. The Apollo 14 backup crew of Gene Sternin, Ron Evans, and Joe Engel are already in the simulator looking at Doc Burns in this configuration so they can get some kind of information up to the crew. Not only are their axes a little different, they're dealing with an odd center of mass, which is well away from their thrusters, and they don't have any opposing force at the other end, just the fully loaded CSM. Rolling is fine, but pitch and yaw is hard because the offset center of mass keeps imparting rotation. The astronauts in the Sims are also looking for stars. The simulators can mimic exactly what the crew sees, minus debris, so they might be able to help them with some star sightings or with the backup method of using the Earth and Moon for reference. Complicating matters is the sun shining off the spacecraft. And it's bright. >> Okay, we'd like to brief you on uh what our plan is. Uh we're at this time water critical in the limb. So, we'd like to use as little as possible. To do this, we're going to plan to make a pre- returnturn uh maneuver of 16 ft per second at 61 hours, which is 37 minutes from now. So, how do you feel about making a 16 ft per second burn in 37 minutes? >> Well, we'll do it. Can you give us a little more time? >> Well, we can give him another 15 minutes of Yeah, we can give another get a suggestion from him. We can figure it out whenever he wants it. >> Uh we'd like to get a suggested time from you. uh we can figure out a uh free return maneuver for any time you want to give us. So uh if you'll uh give us the time you'd like to shoot for, we'll figure out a pad. >> Okay, that sounds good. Uh I think if we have a little bit more time, we want to do it right. Uh Jim, I want let's shoot for an hour if we can, Jack. How's that? >> Okay, Jim, how about uh 61 hours and 30 minutes? That's an hour and five from now. >> Okay, we'll do it. We want to be sure we bust back and forth now to make sure we get this burn off right. >> That's right. >> A burn. >> With the burn coming up, they're still having a hard time fine-tuning their alignment owing to the sun's angle and the debris. They're storing water using bags from the PLSS, some to drink, and some to avoid dumping overboard, further disrupting their trajectory. And they're having a hard time hearing each other from a wholly unprecedented problem. Their radio frequency is busy. Remember back when Apollo 13 first collected the LEM from the S4B, then left that rocket stage on its mission to crash into the moon? The instrument unit at the top of that stage is still sending data back to Earth, so Houston can track it. And it's on the same frequency as the lunar module, and it's also roughly in the same line of sight. And this S4B has extra batteries to make sure Houston can track it all the way up to the point of impact. The mission plan has the S4B impacting the moon before Fred and Jim transfer into the lunar module. So, the two vehicles with a shared frequency wouldn't be talking at the same time, but now they are. Engineers at the ground stations are using a large narrow beam antenna to d-tune the LEM's unified S-band radio system and pull its frequency away from the S4Bs. It's the best they can do until the stage impacts. With this midcourse maneuver coming up, Fred starts getting the LEM ready with a modified dips activation that saves power by skipping anything that isn't necessary or things Houston can monitor from afar. Okay, the only item on page 10 is to deploy the landing gear. >> Okay, we'll do that now. >> The limb's legs were folded in during launch, so they need to get them out of the way of the engine. >> Stand by in step one, Fred. We're getting a word for you. How do you like this sim? >> It's a beauty. >> This is something you start to see as things get a little more under control. There's more banter and jokes to keep the mood light. And technicians threw all kinds of wild scenarios at crews and simulators. >> Roger, Aquarius, and you're go for the burn. 40%. >> Okay, Aquarius, you're looking good. >> They managed to throttle manually, but the computer started and stopped this burn that lasted just 31 seconds. They're now on a trajectory that will whip them around the moon and back home, landing in the Indian Ocean. >> Kind of hard to do that. 85 now, Jack. >> Okay, you're going in residuals. Proceed. >> Okay. When you say go on residuals, you mean uh don't trim them. Is that right? >> That's affirmative. Uh, no trim required. >> Verb 16, noun 85 entered into the computer shows the residuals. Basically, any discrepancy between the velocity they wanted from the burn and the velocity they got. They can use the RCS thrusters to make up the difference. What's known as nulling the residuals or trimming. But they don't need to in this instance. Instead, they can get right back to powering down the limb. The PC plus2 burn is happening at about 79 hours, 18 hours away. So, they need to keep their power usage low in the meantime. Part of the power saving is water saving. Remember that water is part of the cooling system and the limb supply isn't renewable. The more systems they have on, the more water they use. So powering down everything they can actually saves them water. The crew has a moment of restit at this point and can finally eat and try to settle into a sleep cycle that will always keep one man awake and in contact with Houston. Afraid this could be the last mission for a long time. [music] As we approach the burn, we want to go through the same check that we did for the last burn. That is, we want to make sure we have everything powered up by circuit breaker. Number two, we ought to have a procedure for powering up in that module again. All right, Joe, could you also give us an idea about how far out we could expect to make it mod? >> Uh, okay, Jack. Uh, it sounds as though we probably don't want to power up the command module much before EI minus 2 hours. Okay, this is just communicate something. We have some sort of problem here about how we must go about getting into this module, what we need to power up uh and uh in order to make it back in there. >> Uh right, Jim, it's uh it's quite clear that we're going to have to uh uh very carefully make up a full checklist for you on that and uh we'll do it. 68 hours and 40 minutes into the flight, 12 hours and 45 minutes since the explosion, and Jerry Griffin's gold team is on shift in mission control with Joe Kerwin on Capcom, the crew is thinking well beyond the upcoming burn, specifically about the Odyssey's consumables and the plan for re-entry. The top priority remains power usage. >> My question was, what was the way back whenever the lamp and transferred the lamp power? power. Okay, the uh time of transfer to LM power was 57 hours and 11 minutes. Uh and in fact, we are looking at a procedure that we might recommend to you later on after the burn and so forth of powering up one of the uh command module main buses via the L umbilical. Uh, this would enable us possibly to charge up the command line batteries. >> They're already thinking about how to charge battery A by reversing the flow in the umbilical. >> Jim and J are in the upstairs bedroom taking a nap now. >> I didn't know that was upstairs. >> 73 hours and 46 minutes into the mission. 17 hours and 49 minutes since the explosion, they start some preparations for the PC plus2 burn, which is about 6 hours away. And one increasingly troubling item is the guidance platform. We've talked about the IMU and the guidance computer, but there are other systems in place. So, let's go into a little bit more detail. When it comes to navigating on Apollo, the goal was to align the spacecraft to the basic reference coordinate system or BRCS. The BRCS is defined by the relationship of the Earth Moon system with the Sun as they appeared on a given date since all bodies in question are moving. The Xaxis points toward the Sun on the plane of the ecliptic. The Z ais in the direction of the Earth's north pole and the Yaxis is a right angle from the X-axis. This gives the computer a reference in three-dimensional space, so it knows which way is up and where it's going. But up is relative. On the Earth and the Moon, it's always away from the surface, but those can be different directions. And in space during the coast, it's harder to define. The solution is the refsmat, which stands for reference to stable member matrix. The refsmat adds a sort of mathematical filter to the values generated by the IMU and the desired orientation. With the right refsmat in the computer, the onboard displays put the guidance information into the most useful framework for the crew. So the LEM's IMU was course aligned when they hastily moved in, meaning the computer might not be perfectly aligned to the basic reference coordinate system, meaning the computer might not know which way is up and where it's going. To align the platform, they need to use the AOT or alignment optical telescope, a device that sticks up out of the limb with a little sun shade, can move in 60° increments and extends into the cabin like a periscope. They use it to sight known stars with a target star in the middle of the viewfinder. They can measure two angles in three-dimensional space. Fi on the xyaxis and theta on the z axis. This allows the IMU to adjust itself if needed to make sure the guidance data is accurate. The problem is they can't see stars. When the oxygen tank exploded, everything was moving at the same velocity. So, it's not like they left that cloud of debris and oxygen behind them. Between the particles and the sun glinting off these particles, it's impossible to sight a real star. If they can't verify the accuracy of their alignment, they can't make an accurate burn or align themselves for re-entry. Houston wouldn't be able to give them the right attitude to make the maneuvers they need to get home. And the most important and immediate concern is the PC plus2 burn. If they're out of alignment, they could end up completely missing the Earth. This is actually one of the scariest points since the explosion. Jerry Griffin was so nervous he could barely write legibly in the flight director's log. The solution was genius. Read up to The Crew by Charlie Duke. >> Fred, I'll read you. >> Aquarius, go ahead. >> Okay, Fred, I'll reading you. Bye-bye. Uh, the procedure I'm going to read up to you is a uh the sun check for the uh uh to see if we're going to need an alignment or not. They run P-52, which is the alignment program, but instead of a star, they use the software's ability to aim at a time and coordinates. They have the crew enter data to move the AOT to where the sun should be. If it's there, their alignment is good. It's something NASA has tried before. Neil Armstrong and Buzz Aldrin did it before landing on the moon. >> There's the sun. Give me the uh give me the AOG. Okay. children. We got it, I think. Take a look. Okay, we got it. I think we got it. What diameter? >> We got it. Uh, Houston, Aquarius. >> Go ahead, Aquarius. >> Okay, it looks like the first check passes. >> We understand it checks out. We're kind of glad to hear that. >> There was a cheer in mission control. Jerry said it felt like the last big hurdle. They know their navigation is good and they can get the crew on a path back home. >> Pretty close to the moon. >> Swinging around the moon is the only time the crew is out of radio contact from Houston. Radio waves can't pass through the moon knowing there's 25 minutes where if something happens, they won't know. Gene CR, now back at the flight director's console, goes around the room checking with his team to get a status of every system. The crew also has the information about the coming burn. They've had it for a while. If anything happens and they lose comms, they can still make this critical burn. >> Okay, Jim, we have a little over two minutes till LOS and uh everything's looking good here. >> It's 77 hours and 9 minutes. 21 hours and 14 minutes from the explosion, Apollo 13 slips behind the moon. The moon's far side is really interesting in that it looks nothing like the side we're used to seeing. The near side has a lot of Maria, seas of sorts made of basaltic lava that erupted through the broken crust after large impacts. The far side is pocked marked with craters, making for a more uniform and lighter landscape. It's a view only 12 people have ever seen before, one of whom is Jim. Jack and Fred make 13 and 14, and they turn into tourists. Even with everything going on, they get excited and start taking pictures. And Jim, watching them is a little incredulous. If we don't make this next maneuver correctly, you won't get your pictures developed, he tells them. To which they reply, well, you've been here before and we haven't wor that might be over there. >> If you let me use the 250, there's a beautiful shot of uh of uh which be very seldom. >> By the way, uh Aquarius, we see the results now from 12 seismometer. Looks like your booster just hit the moon and it's uh rocking it a little bit. >> Well, at least something worked on this flight. >> And I just want to uh verify one thing. >> We could go ahead. >> I say I'm too glad we didn't have a limb impact, too. >> Maryland. >> With the burn coming up, the crew powers up the electronics they need and get a data update from Houston. It's pretty quiet on the radio as the crew gets ready. It's a little after 8:30 in the evening in Houston and astronauts are piling into mission control to follow along with this critical moment. >> Jim, you are go for the burn. Go for the burn. >> Roger. Go for the burn. >> We have ignition. >> 40%. They burn at 40% thrust for 21 seconds, then throttle up to 100% thrust, delivering 10,500 lb of thrust for the 3 minutes and 58 seconds left in the burn. >> How you looking, control? Looking good, Mike. How about you, guidance? >> Looking good. >> Roger, Capcom. Looking good here. >> Shut down. >> Roger. Shut down. >> Off. Engine off. >> The burn is good with very little residuals, meaning they don't have much they'll need to adjust later. But there is one odd result. The characteristics Houston sees aren't what was calculated based on simulator data. That's because the Sims were done and the data calculated with Jim and Fred in the LM and Jack in the command module. But Jack isn't in the Odyssey. He's been hanging out on the ascent engine cover most of the time all three astronauts are in Aquarius. And that's where he was during the burn. The descent engine had to gimble to compensate for the unexpected center of mass because of Jack. And Houston can see the effects on their new trajectory. So why was Jack in there? Command module pilots never got to see the LEM burns. They were always alone in the command module when the lunar module was flying. Jean Cray figures he probably just wanted to watch. With the burn done, the crew gets right back into low power mode knowing that Houston can still track them via telemetry. >> Didn't get much work out of the eggs this time. >> Flight. That's a uh first two hours is tracking date as well. >> Really going to pull it in for us. >> Yep. >> Let's pause here for another quick ad break. [music] [music] >> Go ahead. >> Okay. Just some uh info. We're working up a procedure for you to use to to use command module LIO canisters uh to connect to your hoses, the outlet hoses in the lamp. >> Yeah, we wish we could send you a a kit and it'd be kind of like putting a model airplane together or something. Uh >> it turns out this contraption will look like a a mailbox when you get it all put together. >> Uh plastic roofed. The CO2 problem hasn't taken NASA off guard. Remember that Fred called it almost as soon as they got into the LEM. Half an hour after that, about 1:00 a.m. local time in Houston, a team was already in a conference room with training versions of everything the crew had on board and eventually canisters flown in from North American Aviation to figure out how to fit the square lithium hydroxide canisters from the Odyssey into Aquarius's round ports. The LEM measures the amount of CO2 in the atmosphere with a really neat little infrared device and displays the reading to the crew on a gauge that gives them the amount in millimeters mercury. 16 is the upper tolerable limit. Though medically speaking, they want to keep that number below 15 at all costs. Anything higher than 15 puts the crew at risk of sedation or loss of consciousness. The solution came together pretty quickly in that conference room. The initial idea was to tape the liquid cooled garments plastic storage bags around the square canister and use a suit hose in the limb to blow air through the canister. Someone suggested they use the suit inlet hose because that gives warmer and moistister air which helps activate the chemicals in the scrubber. Someone else pointed out that the suction would suck the bag against the filter. So, they came up with the idea of using an EVAQ card from the flight plan to create a protective arch. It did in the end look a bit like a mailbox. But Houston wasn't about to send the crew an untested design. Among all the simulators and test articles NASA had on hand was a LEM cabin. They had this LEM pressurized at the same levels as the Aquarius and injected it with the same levels of CO2 the astronauts were adding to the cabin because they weren't guessing about this either. The crew had done a metabolic calibration on a treadmill before the flight to give the flight surgeons a baseline for biometric data. Houston knew how much CO2 each astronaut exhaled, so knew the total could be as high as 9.6 every hour. The team injected the exact amount of carbon dioxide into the test cabin and confirmed that their makeshift adapter worked. They figured out how long it could last and how to extend its life as the mission wore on. Don't worry about it. >> Then establish your attitude and then you're in a position to start your >> procedure. Right. >> The master alarm trips when the amount of CO2 passes 7.6 on the gauge, but they're still okay. And while the crew is pretty eager to start working on the adapter, Houston doesn't want to throw out the canister they're using just yet. They have a finite supply, so want to push the CO2 level a little more before they start dealing with the problem. >> There she goes. >> Why not? >> Give me the total hours then. Flight retro retro >> midcourse is probably not that big. >> Short amount of track day. >> Okay. And what you're saying is you expect it to grow smaller and control. We've got a new earth. >> Go. >> One other point. Our guys are now investigating a midcourse procedure that would not require powering up the GN. >> Right. >> Okay. >> You don't think that burn was enough? Do you have a midcourse? >> There's going to be another midcourse correction burn. The good news is they're looking really good on consumables. The LEM has 1,498 amp hours remaining and they're expecting to use just 14 amps per hour in their low power state, which should leave them with a reserve of 500 amp hours at the end of the mission. They have 215 pounds of water. With their low power consumption, Houston expects they're only using between 3.2 and 2.7 lb per hour. In dealing with the CO2 buildup, they have 16 lithium hydroxide canisters that last for 12 hours a piece. So that gives them breathable air to 192 hours well after re-entry. They've also got enough oxygen for another 120 hours. So they aren't out of the woods yet, but things are kind of looking okay. The only thing they can't really address is the cold. Without the electronics running in the command module and the LEM mostly inert as well, there's very little heat generated in the cabin. And since they don't have much planned in the next day, it's going to get chilly. The other big item they need to deal with is sleep. No one can function well if they're exhausted. And the crew doesn't exactly have easy tasks to manage. At this point, Jim and Fred take a rest period, leaving Jack to mind the limb and chat with Vance. You wouldn't believe it, but I'm now in command of the limb. Vance, I'm probably the only CMP that's ever witnessed n sitting on the engine kit. >> Tell me, >> hey Jack, we just thought it's about time you got a limb check out. >> But he's giving it an course. I'll give him my command module, too, which is rather inert right now, too. >> Well, you got to walk before you run, you know. >> Yeah, that's pretty straightforward. Okay, I see the Earth, so I've uh very wisely shifted to forward. >> Good boy. And uh we're in a >> This Aquarius has really been a winner winner. >> Well, everybody down here is 100% optimistic. Yeah, looks like we're on the upside of the whole thing now. >> I guess we better be in pretty good shape uh picking ourselves rested uh for that entry day. I think that's going to be a pretty busy one, >> right? And u we're working on procedures for that. Ken's been doing quite a bit of work on getting ready for entry. >> Very good. When this flight's over, we'll really be able to figure out what a lift can do. Maybe they'll make some more of them. They >> had a heat shield. I bring this one home. >> That was a good TV show you put put on the other night, Fred, during le lament. >> Yeah, put him in there even better than about 10 minutes later. >> Yeah, things sure turned to worms there in a hurry after that show. Jim, we got a couple of news types items. A bill giving federal employees a 6% pay raise passed the house and went to the president. You think they'll consider this for flight? >> Okay, Jim. Uh, this is kind of a leadin to this procedure that we're going to use for the midcourse burns. Like to say that we're going to use eggs and it's going to be a manual burn. The attitude will be controlled manually. The start stop on the engine will be controlled manually. We have a pretty good vector on you now. And it turns out you're coming in a little bit too shallow. So what that means is uh we're going to make our burns to come in a little more steeply. And we're going to be coming in around the dark side of the Earth. Therefore, to come in more steep, our thrust should be in the direction of the sun. Does that all make sense to you? >> Re-entering the atmosphere isn't as simple as hitting the atmosphere and falling to the ocean. You can kind of think of the atmosphere like the calm surface of a lake and the spacecraft like a perfect smooth stone. If you throw that stone such that the rounded edge digs into the surface, it'll sink. But if you throw it just the right way, it'll bounce off the surface and skip along. To the Apollo Command module with its rounded blunt bottom, the atmosphere is a dense fluid medium that when you're traveling at close to 25,000 mph, behaves a lot like that calm lake. If the spacecraft digs into the atmosphere, they fall too fast and the re-entry will be unservivable. If they hit at a shallow angle, they'll skip like a stone and might not re-enter at all. The area where they're safe is called the re-entry corridor. Right now, they're just shallow with half a degree between the center and the outer limits of their safe zone. Houston wants to adjust their trajectory to bring them in a little steeper. First, the crew will orient the spacecraft placing the center of the Earth directly on the Z axis. Then rotate the Z axis to get the point of the crescent on the Yaxis on the coass. They'll also control their attitude, thrust, and start and stop the engine manually. The help they'll get will come from the abort guidance system or AGS that will do some of the attitude control and also provide the eightball to show them how to point the ship. Aligning the Earth in the window as navigation data might sound like an insane way to fly in space. But like so many procedures on this mission, it wasn't thought up on the fly. The Terminator aligned burn was a backup method tested on Apollo 8, Jim Levelvel's previous flight to the moon. 90 hours and 8 minutes into Apollo 13, about 34 hours and 13 minutes since the explosion, Joe Kerwin is finally ready to walk the crew through building the lithium hydroxide cancer adapter. But first, Joe's got some good news for Jack. >> Okay, Jack. Uh, did anybody uh ever tell you that you got a 60-day extension on your income check? >> Uh, yeah. I think uh I think somebody said that when you're out of your country, get a 60-day. >> First, they cut the punched holes off a Q card, so they're left with a solid piece of stiff board. Then they cut one of the LCG's outer bags along the heat seal so they're maintaining the largest unbroken piece of plastic. And they do the same with the inner bag. Then they cut two pieces of tape about three feet or an arm's length and fix them sticky side out around the canister as two belts, one toward the top, the other towards the bottom. Then they anchor those belts with two two foot long thin strips at right angles, avoiding the hole so nothing can block the flow. Then they stick the Q card over the canister to make an arc. Next, they stop up the bypass hole in the center of the canister with either a wet wipe, a sock, or even crumpled up tape. Basically, anything to block it. Then they put the whole contraption into a pre-cut plastic bag such that the ears of the bag or the corners stick out on the closed end because they need to snip one of these to stick the suit hose in. Then they press the bag against the sticky belts, pleading any excess. Then wrap more tape on the outside to make the seal as tight as possible. Next, they have to separate the red and blue suit hoses, which is a bit of a challenge. They were wrapped together in beta cloth. The only scissors they have on board are designed for the much easier task of opening food packets. Once separated, they put the red hose into the top of the bag so it goes to the center of the canister, then tape it shut, then stuff a towel in the bypass hole in the bottom. The last step is to use the suit loop configuration to get the adapter working. They end up with one hose by the LMP's window and the other with an extension running up the tunnel toward the command module. The red hose is floating around the docking ring. Then they turn on the cabin gas returned to egress, ensuring the cabin air will flow through the hose plugged into the canister. That's the CO2 problem solved. And another benefit is that it gave the crew something to do to pass the time. >> Uh, roger, Fred. Copy that. Is it uh a little chilly up there? >> Yeah, we made the mistake of putting up the window shades, which we won't do again. And with this power down mode, we're not generating much heat internally. And it really did get chilly. >> Yeah, I guess you'll have to generate your own heat in there for a while. >> Steve says, "Unto the extra money. We need some place to put the ur [music] mark remains the Odyssey. The Apollo command module wasn't designed to be powered down and powered back up during a flight. Once it was powered on ahead of launch, it stayed on until after splashdown. Whatever the power up process is going to be, they can't do it in one go. And they also can't assume everything is in working order without checking. The re-entry batteries are connected to two battery buses, which are connected to two main buses by monitor switches. Houston is worried that these mechanical switches might freeze on the Coast home. So, as a preliminary check, Houston gives Jack a procedure to power both buses with the bus time motor switches. The buses can be powered by connecting the batteries. He checks that there are no loads on the buses. The DC systems all have a proper voltage and shows zero amps, so there's no power flowing. Then he depowers the buses by pulling the circuit breakers. This keeps the bus ties on so he can start everything up when he needs to. The other important update for Jack is a procedure to transfer LEM battery power to the command module by reversing the current in the umbilical. This wasn't in the spacecraft's original design specs, but the system is built in a way that allows for power to flow in both directions and has always been part of the LEM as lifeboat planning. More importantly, the process doesn't abuse any hardware, so there's no reason to think it won't work. >> Okay, good deal. We copied that, Fred. I'm so far and show you how relax is looking at giving you guys a chance prior to uh going into entry prep to snap a few pictures of the service line. >> Yeah, he's got all that film up there and he doesn't want to waste it. >> Oh, I I thought maybe he'd want me to do a fla and go shoot pictures or something. >> Okay. Okay. >> And uh Jack Houston for your information tells me that we are uh in the Earth's sphere of influence and we're starting to accelerate. >> I thought it's about time we cross. Thank you. Those other uh procedures you've been working on there. I thought I was going to have a new one for you. How to get four of tubes apart. I think they were stuck together with a positive. >> This is in the food bank. >> Yeah, >> that's to stand loads of uh launch and boost, >> right? B does the trick. >> Now, you know, I don't have my head on. >> Oh, okay. >> Okay. Now, I won't uh I won't have any boys with you. So, uh is that right? You don't want me to get connected up? Uh, you want me to just take these readings and come back and tell you what I have? Huh? >> That's right, sir. >> Yeah. No voice, flight. >> That's affirm. There'll be uh no voice. And >> Okay. Okay. And we're >> I We presume though that there will be somebody in the Lynn that we can call if we have to get word to you. >> And also the telephone. >> Oh yeah. There'll be somebody be standing by. They'll run up into the bedroom and tell me to stop what I'm doing. Houston has a long procedure for powering up the command module and turning on instrumentation so they can get some telemetry and see how the onboard systems are holding up in their no power state. Before they can start drawing power from the LM, they need to know whether the spacecraft is in good shape. The procedure has Jack close the circuit breakers that power the sensors in the systems they want to check. Then he prepares the inverters to produce the AC power the telemetry sensors need. He starts up the Odyssey's communication system and configures it for a high power signal for the purposes of telemetry. Next, he closes circuit breakers that provide power to the comm's equipment and the central timing equipment. Then he connects the command module batteries to the power distribution system following a very specific pathway that ends with AC power for the telemetry sensors. >> Okay. How does the telemetry look on our uh on the old Odyssey? >> It uh doesn't look too cold. Looks pretty good. Okay. Thank you very much. >> You bet. >> How does it feel, Jack? >> I tell you, Dee, it's cold up in there. I don't know whether we'll be able to sleep up there tonight. It must be about 35 or 40°. >> Right. That's what I was worried about. >> Right now, uh we're uh getting two sets of uh PWGs on. It's not uncomfortable at all in Aquarius, but it uh definitely is cold in Odyssey. The constant wear garment is like a full body long dawn they wear under their flight coveralls, but they're not built for warmth even with two. It's a little more comfortable in the Aquarius where there's a bit more activity and a bit more body heat. So, what about their space suits? Because they each have a full suit on board. Well, there's two issues with putting these on. The first is that they're big and bulky, so it would make it harder for them to move around. The bigger issue is that the suits don't have air flow on their own. Wearing the suit, they'd heat up fast and without cooling, they'd sweat, which isn't ideal when they're rationing water and can't replenish lost fluids. Besides that, they'd have to get out of the bulky suit to cool down again. And being sweaty and damp in a cold spacecraft would make their situation worse. All in all, they opt to just double up on the constant wear garments. [music] Okay, Fred, done my mark. be 35 minutes to the burn. >> Uh, we're counting down, aren't we? Or do you want us to start anytime? >> We can go anytime. >> Your choice. >> You guys are getting easy. >> It's not time critical, Jim. >> I understand. >> Okay, stand by. 2 1 mark. 3 minutes to go. Correction, two minutes to go, Jack. >> Roger. Two minutes. We got it. and mark it. 1 minute. Engine armed to desent. >> Okay. 10 seconds. Lagegnition. Looks good. Slow build up. Shut down. >> Okay, you're looking at 470. >> Beautiful. >> Looks okay. Looks good. Nice work. Okay. >> Let's hope it was. Uh >> just for information, although I thought I'd never have to use it, that that technique looked like it was a pretty good one. The excitement in a manner of speaking of the manual burn is done. It's back to a holding pattern. The crew updates Houston about sleep and medication. Something normally done every morning, but that's obviously gone out the window on this flight. The biggest medical worry is Fred's headaches and a worsening urinary tract infection. >> Well, there's the old terminator at Braaro. We've been landing about two hours ago. >> And the better boat is rather humorous. Fred sleeping station now is in the tunnel upside down with his head resting on the asset engine. >> While Fred sleeps, let's take one more rest break with one more ad break. [music] Jim, we've had a lot of people working on the entry procedures and they'll be continuing to do so. Uh, we got a few ideas we'd like to toss at you so you can start thinking about them if you think you're in a position to discuss them without waking up the other guys. What do you think? >> 110 hours into the mission, Apollo 13 is about 32 hours from re-entry and they don't have a procedure for powering up the Odyssey or getting the batteries charged. For the moment, Jack Lusma only has the broadstrokes on hand. They know they're going to charge the batteries from the limb through the umbilical. There's going to be another midcourse correction burn, but about 5 hours from re-entry, and if they don't need it, they'll just skip it. They'll jettison the service module about 4 and 1/2 hours before entry, which will give them between 3 and 3 and 1/2 hours to take pictures to see if there's any indication of what happened. They can also confirm the command module's guidance platform is aligned, stow whatever needs stowing, and get through any other odds and ends. They'll finally jettison the Aquarius about an hour before entry interface. And when they do, they'll take advantage of an accidental procedure from Apollo 10. On that second lunar flight, a mechanical failure in the docking tunnel venting system forced them to jettison the limb with the tunnel pressurized. This created a burst of thrust from the volume of gas in the tunnel that pushed the LM away at a higher speed than usual. They're going to do this on purpose to put some distance between the Odyssey and Aquarius without spending any of their precious RCS fuel. They're also discussing whether it makes sense to re-enter in suits. Jim isn't keen on wearing suits on re-entry. In part, it's because they're bulky and make it hard to move around, but mostly the three of them suiting up will take upwards of an hour. No crew has re-entered with suits since Apollo 7, but this is the first mission where they haven't had a chance to verify the integrity of the hatch between the two spacecraft. The possible hatch issue doesn't have anything to do with the accident. It has everything to do with Apollo 13 not following a normal mission. On a nominal lunar mission, regular events double as a chance for the crew to verify that the hatch won't leak their oxygen during re-entry. The spacecraft depressurize and repressurize and also dock and undock in lunar orbit. Each of these events has a chance for the hatch to fail. So, if it doesn't, they know it's safe for re-entry. Apollo 13 did none of this, and they won't get to check their hatch until they jettison the limb, and that's an hour before re-entry. That doesn't give them time to troubleshoot if something isn't right. Jim insists their hatch is like any other and he isn't concerned enough to have to go through a suited re-entry. Another question is guidance. Houston is planning to have the crew use the moon and sun for a final platform alignment based on data from mission control. Then they'll let the computer take over >> the GNN entry like going first. At about the 111 hour mark, 55 hours and 5 minutes since the explosion, Jack Luzma reads Jack Swagger the procedure on how to set the breakers and switches to draw current from the limb to the Sam's batteries to get battery A charged up. >> Okay, try it again now, Jack. What does Jim want to know? Okay. He would like to know whether this computer has been dried and whether it has been found to be okay and uh is no danger of shorting out any of our batteries or anything uh that we have on board the left now. >> We looked into that very thoroughly and we don't think that there is. >> But it hasn't been tried. It has not been tried. >> You mean on a simulator somewhere or something >> or hardware somewhere? >> Not as far as I know. But wait a minute. The battery charging procedure. >> Oh yeah. But the uh transfer of Lambda CSN, >> yes, that's >> power has not been tracked. >> Well, the we we've been transferring power all the way to the moon and we haven't had short so far and I don't think they've done anything that uh going to cause anymore. >> In other words, uh the path that we're following >> the same one is a normal CSM limb power. >> Okay. And we won't short out a descent battery. >> No. >> Okay. Uh Jack, this uh procedure has not been tried out as such. However, the hardware path through which the current flows uh are the same ones which we used during trans lunar trajectory. And uh there's not a problem with shorting out a descend battery over. >> That is a stunningly diplomatic no without saying it. They need 20 amp hours. That's what's missing from battery A. If they can get those 20 amp hours, they can get the crew home. The batteries power everything in the spacecraft through re-entry and splashdown. Not just the computer and comms, but things like parachute deployment and oxygen flow. They also might need power for equipment post landing. A full re-entry battery is about 40 amps. So, they have half that in battery A. The procedure Jack Luzma reads up is a long one that has the crew set breakers and switches to direct electric current from the LM batteries through the umbilical to the DC main bus B, which is then connected to one of the inverters to supply AC power. Battery A is connected through the battery bus, allowing it to charge. It's going to take 120 amp hours out of the limb, which will leave the crew with 193 amp hours, which is more than enough to get home, but only 20 of those amp hours will get into the battery. The rest will be lost in the transfer, but that's not important. And it's not a fast process either. It will take hours to get battery A fully charged. >> Go ahead. >> Okay, Jack. Uh, one thing that uh I I guess you probably all have considered it uh but what uh heavy things can we store down there where the SRC's normally go to help you free trial over >> souvenirs I guess. >> What souvenir? All I've got is the Marine Corps hole digging shovel. >> You got all you need then, buddy. >> We talked about how the command module is like a stone on a pond. the flat side able to skip off the atmosphere. Another characteristic of the SAM's shape is that it can generate lift. The rounded bottom behaves almost like a wing. This lift is one of the main forces affecting their re-entry. The other is the drag as they fall through the thickening atmosphere. The command module generates lift because its center of mass is offset from the vehicle's physical center, creating a relationship between these two forces, a usable lifttogra ratio, which is what Jack is thinking about. While the drag slows them down, the lift boosts them up, lengthening their path and carrying them towards their target point. They can manipulate this using RCS thrusters either automatically or manually to rotate the spacecraft around its central X-axis to change the lift vector. It's not much control, but it's some. This slight control becomes important with respect to the entry angle. If they come in too steeply, the high deceleration can lead to high G forces that can damage the spacecraft and harm the crew. In this case, they can aim the lift vector up to glide a bit, keeping the command module in the upper atmosphere a little longer to lengthen their re-entry and pull fewer G's. On the flip side, they can use the lift vector to steepen their re-entry if they're coming in a little shallow and are at a risk of overshooting their landing point. The offc center mass is vital, which is why Jack is already thinking about what they need to bring into the command module with them to get the right balance, the right distribution of mass to maintain the lift to drag ratio. He knows they need enough ballast to take the place of the moon rocks they didn't collect. >> You add up the operating time. I I think the limp beats the CSM by a considerable margin on this flight. >> Roman just hired you and uh that's pretty cold. >> Say again your last. >> And they both came down here rubbing their hands shivering. It's pretty cool upstairs. >> Are you keeping warm in the limb? Yeah, it's uh it's pretty reasonable down here. >> Another interest of the crew system people tell them that they don't have to bother putting the refrigerator on board. I just brought out some hot dogs. Yeah, there was one piece of uh flight data that uh we needed that we didn't bring along this time. >> What was that? It's a big book with a lot of just plain old blank pages in it. >> Yeah. When you when you get off nominal like you just need scratch paper, don't they? >> Yeah. >> Okay. Going back up into the refrigerator. >> Hey, I thought it was the bedroom. >> Well, it's got a new name now because it's about 30° cooler. >> Is it snowing in there yet? >> Oh, snowing. No. Uh, no, not quite. It's not snowing, but there's nearly weather in the command module. The lack of good circulation has left a ton of moisture from their exhalations on pretty much every surface. There are water droplets covering the walls, ceiling, floor, wire harnesses, and panels. The crew figures it's probably the same behind the panels, which open the possibility of a short circuit when they power it on. But the command module has been built with many safeguards against fires following Apollo 1. >> Go ahead, Chris. >> Houston, >> no, not yet. Still must be winner. >> Suspicion confirmed. >> Yeah, I doubt if they'll be blooming even Saturday when you return. >> I confirmed. [music] >> Houston, we really are going to get those checklists up to you. >> Okay. >> With just over 17 hours of splashdown, battery A is charged. They switch over to top off battery B. The bad news is they're out of drinking water. What's left in the command module tank is frozen or the lines are frozen. But either way, all they know on board is that there's nothing left. The good news is Vance is finally ready to read the CM power up procedure to Jack an hour and a half after he promised to have it ready. And right as they're starting, there's another hold. >> Vance, I'm on and ready to come. >> Okay, Jack. Uh, wait one. We want to get one into the hands of Flight ECOM. And, uh, it'll take about a minute or two. Uh, sorry to wake you up for this, but uh, take about a minute and then we'll read it up to you. >> The delay is making copies for everyone in mission control who wants to follow along with the procedure. Finally, Vance starts with an overview of the data he's going to get ready. Lemmpad, SM Jettison, Moon and Sun viewing attitudes, Corsal line angles for re-entry, refsmat, and then they hit another pause in the proceedings. >> Okay, Jack. uh going to hold up one. Uh all the the hordes of people that devised this procedure are going to be coming into the room in a minute and uh they'd like to hold up till everybody can listen in. You get that check. >> They keep going, pausing to check the battery charge readings, and Jim starts to show signs of the strain they've been under. >> We got to realize that we got to establish a work rest cycle up here. So, we just can't wait around here. We just read procedures all the time up to the burn. We've got to get them up here, look at them, and we got to uh get them able to sleep. So, uh take that in consideration when you're getting ready to bed. >> Yeah, I know, Jim. Uh we're very conscious of that. We uh we should be ready to go in about 5 minutes. That's all I can say. Uh >> there's definitely some tension at this point, and understandably so. The crew needs time to get familiar with whatever procedure Houston's cooked up for them. They also need to rest so they don't make any mistakes and then they need to execute this process and do any final checks. It doesn't feel like they have a ton of time. >> Hello Aquarius Houston. How do you rate? >> Okay, very good Ken. >> Okay. Uh let me uh take us from the top here. Just >> Ken is back on Capcom to read the whole procedure up to Jack. And it's a lot. A fivepage sequence of breakers and switches to connect everything together electronically to bring the spacecraft back online. It starts with a very practical item. put a lithium hydroxide canister in the command module since there isn't one right now. If they forget, their atmosphere will become oversaturated with CO2 within 2 hours. The checklist is a delicate balance of turning systems off and on to get everything they need without drawing too much power. Once a CM has power, it will need guidance information. They'll use the LEM to point the command module's optics at the moon and the sun to get the course align angles for the inertial platform. They need that crucial guidance information and to update the ref's map for the Odyssey so it knows which way is up and where it's going on the path to the Pacific Ocean. Once everything is back online, Jack can pull the breakers connecting the CM to the LEM, severing the connection. At that point, the command module will be powered up and the countdown of 120 amp hours will start. This will also restore their comms and data link with Houston. Once running, Jack will activate the breakers that supply main bus A and B power to the flight and post-landing bus, a separate system they'll use post flashdown to keep ventilation going, lights on, and comms active. Then they'll power up the IMU, the optic system, and the guidance and navigation systems. The last item is a moon check right before entry, a simple visual check of their attitude by lining the moon up with a degree line painted on the hatch window. Then gravity will take over. Jack is a little worried that they're doing all of this without a cooling system, but Ken doesn't think it'll be a problem. The systems aren't generating that much heat, and it's so cold in there, they should have enough ambient cooling. >> Okay, let me uh emphasize, Jack, that uh 2 and 1/2 hours is the earliest time we can start in on that power up stuff. Everything else you you can do the way you normally would where you get as far ahead of the game as you can, but the uh 2 and 1/2 hour time is based on saving command module consumables. And if you do that while we're fat, we've got plenty of time. Give you some uh fans on the water even. >> It takes Ken nearly two full hours to read the checklist up to Jack, who's written it all down so he can actually do it tomorrow. With the CM procedure taken care of, focus shifts to the procedure to prepare the LEM for jettison. The LEM procedure is a power down procedure starting with the actions to coordinate with Jack powering up the command module. For half an hour, Vance reads the procedure when Houston hears Jim in the background. I ask him why all these these steps just to get rid of a leather that's going to burn up in a half hour. Seems ridiculous. God damn it. Too many up. >> Hey, Jim. Dee said he thought you were asleep. >> All these steps woke me up. You think it's essential, but uh I just don't want to be throwing witnesses at the last minute. Uh we're really thinking about getting that command module in good shape. >> Hey Jim, this is Tom. The only reason we're bringing up the pings is to have another reference system just to control the limb when you jettison the thing. However, >> okay, okay, Tom, it's uh I thought the uh an exhole would have been sufficient for this when we first thought about this. >> Yeah, I agree. But they decided just in case we have any glitch with the eggs, we want to make sure we get that limb off in good shape. And I agree with you on on keeping out all the garbage on it. >> Fred's ill health has finally caught up with him. About 10 hours before re-entry, he's woken up from a rest period with chills. He said in the mission debriefing that he had to use the washroom, which meant stripping naked in a 42° spacecraft. He ricocheted around touching metal to bare skin and got chilled to the bone and then stayed cold. Jim, meanwhile, is still worried Houston is throwing too many things at them and is asking their workload be managed, not cluttered. >> Hey, Jim. Well, you're up and things are nice and quiet. Let me uh give you a couple other things to think about. one specifically. I know none of you are sleeping worth a damn because it's a cold and uh you might want to dig out the medical kit there around 135 or in that ballpark and uh pull out a couple dexaded a piece and try one about then another around 139 to 140. >> Glad I brought that up. We might uh we might consider it. >> Dexedrrons are a dextro amphetamine stimulant tablet included in their onboard med kits. Given their state and what they have to do today, Dee thinks it's wise to help them get a little bit more energized. Wish we could figure a way to get a hot cup of coffee up to you. It probably tastes pretty good about now, wouldn't it? >> At this point, they're looking so good on consumables, namely power, that Houston gives them the go-ahhead to start up the LEM a little early. This won't impact their re-entry timeline, but having equipment on and generating a little heat will warm up the cabin. And since they have the LEM's computer up, they can take sightings of the moon and sun for a course align before running program P-52 to fine-tune their alignment. This also opens the opportunity for the LEM's IMU to give the CM's IMU its alignment. Same as they did earlier, but with different math. This also saves them the RCS fuel of moving the whole stack around to get the CM's optics lined up for a lunar sighting. Jack is back in the Odyssey starting up the re-entry checklist that Ken read up. Just getting things ready since they're still too far out to turn on the batteries. For now, he's configuring the power system to start the RCS thruster heating so they can have directional control. But it's not starting smoothly. The crew is exhausted and Jack is looking at five handwritten pages of notes for a procedure he's never done. >> Right. I just can't read my writing. Essential instrumentation bar main closed. >> That's affirmative. >> Meanwhile, Jim and Fred preparing for the final course correction burn. A burn so small they do it with the RCS thrusters instead of the main descent propulsion engine. >> [music] >> Hey uh Jim, have you broken into the uh medical kit for my recommendation a few hours ago? >> Yeah, everything taken care of. >> With just 5 hours to go before entry, the pace of critical events is picking up. Jim and Jack have taken the stimulant pill, but Fred has opted for a seasickness pill that has some dextroetamine in it to counter the drowsiness. Jack is moving along, powering up the Odyssey. The next item on their list is SM separation and hopefully getting a look at it. Jack takes his place in the Odyssey while Jim is up at the controls in Aquarius. Fred floats up to give Jack assurance that he hits the CMS set switch and not the CMLM set switch. Jack has gray tape over the CMLM set switch, which Fred thinks is safeguard enough. Jack powers up the switch to separate the spacecraft and hears the relays clicking. The switch starts a sequence that has the electric cabling cut with the pyrochnic guillotine and dead faces the connections and locks them in place so they can't accidentally reconnect. Then a second explosive guillotine severs the umbilical from the command module. Finally, three-shaped charges cut the ties that keep the two spacecraft together, creating a spring action that pushes them gently apart. Normally, the separation triggers electronics in the service module to fire its RCS thrusters until the fuel is gone so it's safely away from the command module. But that's not an option with a totally inert spacecraft on Apollo 13. Instead, Jim thrusts up and Fred controls the pitch using the limb to gain that distance. 82 hours and eight minutes after their explosion, they finally see their spacecraft. >> You got a little more pleasing. >> Copy that. >> How's he looking? Control getting ready to right now. Guidance from flight. I'd like to confirm that you want to go back to the >> Okay, I've got her. >> Beautiful. Beautiful. And uh for your information, Jim, you'll be coming up on an RCS caution light for helium. No sweat over. >> And there's one whole side of that space. >> Is that right? >> Right by the uh look out there. Right by the high gate antenna. The whole panel is blown out almost from the uh base to the engine. >> Copy that. We're going to let it go just a little bit longer. Yeah, it looks like it got to the >> Looks like he's got the data he needs. >> Okay, he's be he's through with the photos. We can stabilize. >> Look, >> he's stabilizing now. Looks like >> it's really a mess. >> Okay, Jim, we'd like you to get some pictures, but we want you to conserve RCS so don't make unnecessary maneuvers. >> All right, she's drifting right down in front of our windows now. Okay, and Joe, I'm now looking down the SCS bell, and it looks uh looks okay on the inside. Maybe it's a straight. >> Okay, copy that, Fred. Was the bell deformed on the outside or just uh nicked or what? >> I think the explosion from what I can see, Joe, had uh had changes. I don't know whether it did any deformation or not. >> Man, that's unbelievable. >> Yeah. And Joe, looks like a lot of uh a lot of debris is just hanging out to the side. Uh near the SP antenna. Uh, I know you're busy, but when Jack gets a chance, uh, we'd like that C current and main A voltage in the command module. >> Joe forcibly breaks the crew's shared moment of shocked reflection and brings them back to the task at hand. They have about 4 hours left before they get home. The Odyssey's thrusters are working. Jack has gone through the reactivation checklist and has the computer on. And with the SM gone, their mass is weighed down. So, the computer needs to readjust its firing commands for the new mass and the new center of mass. Also, this configuration has never flown, so there's no real precedent for how it will fly. In Houston, there's a growing crowd. Top NASA officials, government representatives, program directors, retired NASA alumni, center directors, the president of lunar module manufactured Grman, they all pour into the viewing gallery. The actual room of mission control is increasingly packed with astronauts who have performed various crucial duties throughout the flight. >> Well, I can say that this week hasn't been filled with excitement. Well, uh, James, if you can't take any better care of a spacecraft than that, we might not give you another one. >> Hey, uh, Jim Houston, uh, you might ask Jack while he's down there to take a peek through the telescope and, uh, tell us whether he can see any stars. Over. >> Uh, Jack tells me that there's still a lot of particles floating around and he's he can't pick out any constellations, but he recognized it so far. So, it might quit here in a little while. There are still particles trailing along with the Odyssey, and Jack's having a hard time picking out stars. And ECOM has noted that their battery amperage is a little high, but only by about half an amp. Joe asked that they double check the breakers to make sure there aren't any extra loads on main A, confirming everything is as it should be, according to Ken's checklist. At this point, main A is already powered from the command module's own batteries, and main B is still drawing from the lim, allowing them to save as much of the command module batteries as they can. Ken gets back on Capcom to double check some settings and they find that the command modules RCS jets might be the source of the power drain, but turning them off doesn't seem to help, but they're still in okay shape. >> And when you get that done, I'd like you to copy the entry pad. >> This pad, like everyone the crew has gotten to this point, is telling the computer how to manage the coming event. But there are some differences here than with pads for burns. One notable part of this program is triggering the EMS or entry monitor system. An accelerator detects the moment the spacecraft feels 0.05g. 05gs. That's the signal for the computer's entry software to change from its initialization program to control through the atmosphere. It also starts a monitoring function that updates the crews displays in case they need to take manual control. The important moment for re-entry is the so-called capture point. This is the point where the command module no longer has the energy to leave the Earth's atmosphere. It's falling to the ocean. From here, drag will slow the spacecraft in its initial fall, a phase that comes with a communications blackout that will begin 17 seconds after entry interface and ends three minutes and 22 seconds after entry interface. The parachute sequence will start at EI plus 8 minutes and 14 seconds. >> Okay, in the Mid Pacific landing area, the weather is good. The cloud cover is 2,000 scattered, visibility 10, wind 060 at 10, wave heights are 4 feet, and uh the altimeter 2 niner 86 if you care. Scattered showers less than 10% of the area. The recovery forces are as follows. The Ewima will be at the uh touchdown point. The uh aircraft call sign will be recovery one on station with swimmers on board. The uh we have the constant G backup re-entry area covered with the USS Hall, the good uh Liberty ship and uh the other uh recovery aircraft whose call signs you may hear are Samoa rescue C130s. >> The constant G backup area is pretty interesting. This is a theoretical target point for a landing the crew can do using only accelerometer data and a manual landing. If they're able to maintain a constant G level as the command module decelerates about 4Gs, they'd hit this theoretical point. But it's only something they do if the computer guidance and the entry monitoring system both fail. At 139 hours, 15 minutes, and 48 seconds, after about 76 hours of use, battery 3 in the LEM descent stage fails, fully depleted. But they still have plenty of power, including in the LEM ascent stage, which they've been saving. The LEM power transfer has been terminated and from now on the command module relies on its own batteries. >> Okay, can you give me any stars that I might uh try here? >> That's affirmative Vega and Alter. >> Jack is fine-tuning the Odyssey's alignment with program P-52 targeting the stars Altar and Vega. Their sunmood alignment was good. Jim is really keen for Jack to finish up so they can get out of the limb. The Earth is starting to get really big in the window. Torque flight second to them babe. >> Roger. >> I did a star check and it passes. It put the star right in the telescope. >> Good enough. >> The star angle difference showed up as five zeros, a condition known as all balls. That means there was no discrepancy between his own alignment and the computers. Meaning this final star sighting in this extreme circumstance was perfect. The platform torqus aligning their IMU to the entry refs mat. Okay, we're ready to proceed with hatch closeout. >> Okay. Did Jim get the film out of Aquarius? >> Yeah, we uh You mean the the film we took this morning? >> That's a firm. >> Yes, we transferred that. >> Okay, good deal. >> Okay, Houston, do we have a go for power arm? >> What do you want? Logic's on. >> Uh Odyssey Houston, uh we can give you one. Uh if you'll put the logic on for us momentarily. The logics are on. We're good. >> Capcom, we're go for fire alarm. >> You are go for fire alarm. >> Okay, everybody stand by for limb final set. >> He come. You confirm final set there. Have you seen anything? >> He come. >> Okay. >> Just too short for us to do that thing. >> Roger. >> Okay. Copy that. >> We got the advance flight. Thank you. >> Flight that middle gimbal >> flight guidance just close to gimble. >> Watch the middle gimbal line angle coming back out. >> Yeah, we did. >> Okay, Odyssey Houston, just for your information, uh it looks as though battery C will uh deplete around main shoot time. That's expected. You've got plenty of amp hours on the other batteries. >> A little over an hour from re-entry and the crew on board and in Houston has done everything they can. The math says they're good on battery power and their trajectory is good. Recovery forces are at their stations ready to recover the crew. Houston's calculations show that the extra power Apollo 13 has is almost exactly what they transferred from the LEM batteries. If that charge hadn't worked, they wouldn't have enough power to get home. >> You have a good bedside manner, Joe. >> Say again, Jack. >> You have a good bedside manner. >> That's the nicest thing anybody's ever said. >> I sure wish I could go to the phyto party tonight. >> Yeah, it's going to be a wild one. Somebody said we'll uh we'll we'll cover for you guys. And if Jack's got any phone numbers he wants us to call, I pass them down. Okay, we just had one last uh time around the room and everybody says you're looking great. Okay, los in uh a minute or a minute and a half. Uh at entry attitude, we like Omni Charlie and welcome home. Over. >> Thank you. >> Apollo missions came back to the atmosphere straight from the moon, which meant their re-entry speed was close to 25,000 mph. This is fast enough to create a shock wave as the spacecraft compresses the air molecules beneath it. They start to slow, but it also creates an enormous amount of heat. The heat shield burns away, but the heat is so extreme it actually ionizes the air into plasma, turning a re-entering Apollo capsule into a fireball, completely impenetrable by radio waves. This is the ionization blackout. The blackout kicks in right as they start to feel the effects of gravity. The blackout lasts longer than it should. Odyssey's unexpectedly shallow entry angle might be behind this, but I asked Jerry Griffin about it once, and he said they never really figured out why the blackout was longer on 13 than any other mission. At 10,000 ft, the drug shoots release along with pilot shoots that then pull out the three main parachutes. Once inflated, they bring Apollo 13 down for a nice soft splashdown. By the time Apollo 13 hits the water, Fred has fallen asleep. >> [music] >> Jim Levelvel wrote in a NASA publication about Apollo that came out in 1975 that they had no idea people were so taken in by the fight to bring them home. Even the sailors who welcomed them aboard the Eoima were as cut off from the popular experience as the crew in many ways. They only realized how big a deal everything had been when they reached Honolulu, where they were met by President Nixon, NASA administrator Tom Payne, Jim's wife Marilyn, Fred's wife Mary with a doctor in tow on account of her advanced pregnancy, and Mr. and Mrs. Swagert, as Jim put it, in lie of Jack's usual airline stewardises. One thing that stands out to me is how many times Houston sent up a direction or raised a point that the crew was already thinking about or working on, like Jack turning on battery A as the fuel cell failed in the same moment that ECOM saw it. Also, how many procedures had been done previously? The Earth terminator alignment for the burn, the hatch pressurization during CMLM separation, even knowing how long the LEM systems could run without the cooling system on. This stands out to me especially because of how much the movie Apollo 13 has seeped into our shared memory of the mission. And again, it's one of my favorite movies. I saw it twice when it came back into theaters in IMAX. But it really does present every development like it was a shock, like Houston was taken off guard. Exciting as that makes the movie, it does kind of do a disservice to the guys who worked the problem. Not to mention the extensive training NASA thought through to prepare for every imaginable emergency. And most imaginable emergencies happened on Apollo 13. Fred Hayes said afterwards that they really got to learn what the LM was capable of, which speaks to the incredible engineering that went into the whole of the Apollo program, and Grumman had a good sense of humor about its spacecraft's amended mission. The company somewhat famously sent North American a towing bill for $312,42121, a bill that included a roadside battery jumpstart fee and $8 a night for the extra guest in the room. As for Jim's comment that this might be the last lunar mission for a while, that was picked up by the press and came up in the congressional subcommittee hearing on April 24th that was in part discussing the future of the man spaceflight program in light of the near loss of a crew. He was asked specifically how he felt about it now. In his own words, I made that remark as we swung around the moon and I looked at it and was looking rather wistfully and I said for very good reason at the time we on board the spacecraft did not know exactly what went wrong. And at that time I knew that we were not going to attempt another moon mission unless we had hardware that we were assured was going to operate. After learning the cause, he said, "I do not see any real slowdown in our lunar missions." Tom Payne said that the failure to explore Frammoro was worth another mission and that very much echoing its recovery after the Apollo 1 fire, NASA intended to do everything it could to understand the failure and ensure it was never repeated. And it did. Apollo 14 visited Frammora in 1971 and the missions got better, eventually adding the lunar rover to cover more distance on the moon. But nearly losing the crew deeply affected Nixon, and he toyed with cancelling Apollo 16 and 17. He didn't, but the program was already facing cuts. Apollo 20 had been cancelled and Apollo's 15 and 19 were cut soon after in the hopes of adding funding to the shuttle program. At the end of the day, I just love the story of Apollo 13. It's technically so fascinating and such an amazing look at an era when NASA was creative, daring, and still finding its way. And I hope you love digging into it, too. I need to give a shout out to Johannes Kempan, a contributing author to the Apollo Flight Journal, who answered a not insignificant number of questions. Also, I put the link for the journal in the description. [music] It's a truly phenomenal research. I've met a handful of people who've worked on it, and there's hardly a day I'm not appreciative of their efforts. And a very special thank you to all my Patreon supporters and YouTube members. Your ongoing support not only means a ton, it's making this possible. Content creation is increasingly challenging in the current landscape. So, having you guys behind me means a lot. And it also means I don't have to interrupt my videos with as many ad breaks, which I know a lot of people appreciate. If you like this kind of content and want to help support it, I've got the links you need below. And if you enjoy this video, give the channel a sub. I post shorts five days a week and these long- form videos every few months. They take ages to research and write and edit and it's just me working on it, but still they will exist. Thanks so much for sticking around. Have a wonderful rest of your day and I'll see you in the next one. [music] >> [music] [music]