High-Power Rocketry on the Cheap - EMF 2026

[applause] Hello. So, this is my first time doing something anywhere near this big. So, um, >> thank you very much. [applause] But I couldn't think of a better audience to do it for. So, high power rocketry on the cheap. How do you do one of the most expensive hobbies you could possibly think of, especially in today's climate, and not absolutely destroy your bank account? So, rockets, do you do you do you send stuff to space? Well, not not quite. Rocketry refers to hobby level builds and launches. So, I mean stuff like you can see on the table here like we have, you know, tiny kits and scratch builds like this which fly on a motor like this big to things that can go up to Mac one potentially Mac 2 like this thing. [panting] Now, the the hobby appeals to to all sorts of people, to kids, to families and adults alike. You get a really good mix kind of a similar demographic to EMF, I would say, rocketry launches. Um but recently in the UK there's been a lot more sort of outreach and competitions targeting university students and for example there's so there's UK rock which is for late stage secondary school students and then there's uh NRC the national rocketry competition and MAC which is a yearly competition as well that are for university students or recent grads and that's kind of where I come into this. So, I started doing rocketry via two of those competitions, uh, UK Rock and MAC. And for both of those, I was operating on almost no budget. That's not that unusual for UK Rock, but for MAC, there's teams that come into that with thousands of pounds of funding, tens of thousands of pounds of funding. We had just about a,000 to run our society for the entire year. And yeah, it was it was kind of rough getting there. So, so we we we ended up coming up with some some good ways to save saving on some cash, but yeah, I'm I'm now graduated, so I'm just doing this for fun. And I am still kind of broke, so I'm still trying to save money. So, this talk is laid out as one big high power flight, and I'm going to take you through all of those phases really quickly right now. So, we'll cover our initial takeoff and boost phase where our motor burns, gets us off the pad, and gets us going real fast. Then we'll talk about um during that stage we'll talk about what motors you use in these rockets, how they're classified uh the the classification grading. Then as we continue we'll coast upwards where most of the flight upwards actually happens. Your motor burns generally quite short. Then you spend a long time going up with that that speed that you've gathered. And during that phase we'll cover the aerodynamic forces on the rocket. Um at apogee we want to check our altitude, see how high we got, mostly so we can brag to our friends. And for that we need some electronics. Then we need to safely recover the rocket by deploying our parachute or multiple parachutes and gently drifting down to the ground so we can not damage our pride and joy. Then hopefully we can walk out, collect our rocket, and it'll be ready to fly again in minutes. So boost, how are we getting off the pad? What are we looking at? So we use uh solid rocket motors largely. There are some hybrids in use in the hobby right now, but they're a little bit rarer, a little bit more more edge case. The vast majority of people use these solid rocket motors and they come in a few different sizes. They come in these tiny ones that are literally wrapped in cardboard, like paper that you get from SDS. You can buy those on Amazon. You can, depending on how big of a garden you have, you can potentially fly them in in a back garden or a field. um to stuff that's sort of mid-range that you can see on the right there. That's uh some some mid-range uh what are those? F27s. Yeah, these are these are sort of mid-range rockets that you might fly on like something sort of middle size like this. This would take some of the the SD stuff. This would take the mid-range stuff. And then after that, you get on to the to the much higher higher end stuff where you're getting aluminium casings like precision machined and you're putting you're putting that in bigger stuff like this and you're going up to sort of kilome high Mac one potentially even higher than Mac one and getting up to Mac 2. But yeah, these are single use. They are solid rocket boosters. So you you just slot them in the bottom of your rocket, set them off, and then you can unscrew the tap, take them out and slot the one back in. So these rockets are entirely reusable. Now we tend to categorize these motors by impulse which is the total amount of momentum that the motor imparts to the rocket as it burns. So each each letter of of classification we have uh doubles the impulse we're dealing with. So stage directions lovely. Uh, so we have a motors, those tiny little ones that we saw. Those are about 2.5 Newton seconds, which maybe a little bit deceiving that they actually have the similar amount of impulse to them as a 9 mm handgun bullet in that in that tiny little cardboard package. And then every letter you go up, you double it. So a B is 5 Newton seconds, a C is 10, D is 20, E is 40. And depending on how high you want to go with these uh with these rocket motors, you can get up to some pretty scary numbers pretty fast. So if I remove the log scale off the chart there, you can see how crazy it gets how quickly. I assume a lot of us are familiar with how how mad exponentials get. Um so the high power class quite fittingly starts at Hclass which is covers 160 newtons up to 320 newtons for a H motor and then beyond that for the other classes. Uh high power obviously extends way beyond H motors. But for now, we're just going to look at H and I because those are uh rel you can get your L1 certification to do those high power rocket motors relatively easily and also they're not so insanely expensive that you've priced yourself out of everything else. Um but yeah, that yeah, so they're significantly more affordable than something like a J motor which is going to run you like £100 a flight, maybe more. And yeah, remember that we are doubling in impulse every class, which means we're also doubling our propellant mass and doubling the size of the motor. So either you're getting bigger rockets or those rockets are going much much faster. But before we even think about what kind of speeds we're getting up to, we need to build something that survives this initial kick. So on the on the uh on the slide right now, I've got a thrust curve for a typical high power motor, the H169. Now this thrust curve is a plot of force that is exerted by the motor over time. So if we look at the start of that curve, we can see a punch of of two 200 to 225 newtons which you know in earth gravity rolls out to about 20 22 kg. Now, that's an important thing to realize because if you if you have spent, you know, hours and hours building your beautiful rocket that you're very proud of and the thought of putting 20 kilograms on it terrifies you. Maybe don't put that motor in it. It's very easy to look at all these numbers and go, "Ooh, yeah, the the engineering calculations survive that. That's fine." But if I look at that and go, then then maybe you got something else to think about. But yeah, now we've got some background on how these motor classifications work and what what it means to say high power rocketry. So let's get back to our story. How how do we actually get off the pad? So picture our brand new society. Um we formed in so I'm going back to about 2022 2023 here. Uh we have basically no money and half of it vanishes the moment we actually had to get to a launch site because there are very few launch sites in the UK. None of us had our own cars. So we're having to hire that from the uni. So our our budget is magically disappearing before we've even started. And of course within that society, we want everybody to be able to do something like building one rocket for the whole society. All well and good. That's quite common for competitions. But we were more interested in okay, how can we get all of our members to do a bit of everything? How can we give everybody a grounding in hobby rocketry so they can continue this hobby on their own? So this is Nordri. This is an excerpt from a poster I made a while ago. Um, apologies, it's a little bit small on that screen, but it's mostly there for the images of the rocket itself. Um, so at its core, Nordri is a cardboard tube. It is a postal tube that you can get from the post office for £1. In fact, you can get three of them for £1. So, which I think makes them cheaper than a Fredo. Uh, uh, the fins are plywood, which we laser cut, but you can absolutely cut by hand. Uh the nose cones 3D printed. So that's like, you know, very basic 3D printed PLA. Like literally just bog standard filaments here. And yeah, there's a whole bunch of epoxy slathered on there, which is a little expensive, but you can use, you know, one big bucket of epoxy can do you 20 rockets. So as a society, that was like a really great model for us. Yeah. And we we use some like clever tech clever construction techniques to make sure that these designs are strong enough to survive the forces they're going through. So in Nordri, we had through the wall fins, which means that you cut a slot in the outside of the fin, put the fin through, and then you have an epoxy filler usually both on the inside and on the outside of the rocket, which means you've got multiple bonding points. You've got this whole reinforced structure at the bottom where the motor is putting all of this force. So that's that's getting you a lot of that's buying you a lot of strength despite your simple materials. And yeah, this this this design was um we focused on using entirely open source tooling that anybody could use on like their you know we had a lot of Linux users, we had a Mac user, we had some one or two Windows users. Um so you know Fusion was kind of out of the question unless you wanted to use the terrible web UI. Uh open scared we used a little bit for this rocket. We've we've now CAD software is a whole thing, but the idea of this rocket was for it to be sort of free, open source, very easy for anybody to make and very easy for anybody to pick up the basics of rocketry with. But yeah, we there were there were plenty of problems with it, which have kind of been interesting to watch as more and more people have like built this this archetype of rocket. They've had to go through and solve these problems on their own. And that's been really interesting to see because a lot of them have solved these problems in different ways. They've incorporated uh different types of machining. They've used like uh lathe work to build delrin or aluminium anchor points and they've they've they've redesigned how the shock cods are attached. There's been some really interesting innovation and yeah there's there's like a pricing up on the whole thing. Uh it and yeah that that rocket it was so it was originally made for sort of student outreach but we we we tweaked it so we could enter it into a competition and it it did exactly what it was supposed to do in the test flight [laughter] not at the competition but we know it's capable of doing what it's supposed to and that's what matters in our hearts but yeah so that rocket costs about a tenner to build the entire chassis to build to even put a parachute in it uh if you cut out some of the reusable components then it comes down to a fiver even. So like this this incredibly cheap rocket unfortunately requires motors that cost 30 40 50 quid to fly on. So little bit overoptimized. Would I recommend building this? No. Don't build that. It was a fun exercise but I think if you're going to build a rocket there's no point spending less than it costs to fly it once. you can put a little bit more pride and a little bit more joy and a teensy bit more money into that rocket just to get it, you know, something you can be really proud of and you want to refly multiple times as opposed to throwing something together, flying it once, and then what if I built another one cuz it's so cheap. Good way to learn. But if you want to get into the hobby, I think you want to build something that you can reuse over and over again because that's really how you're going to save money. So, we've made it off the pad. We've hit sort of close to mag one and we're we're going very fast and the air is trying to hold us down as our motor's burning out. We're at the fastest point of the flight. We've stopped accelerating and now we're suddenly decelerating and depending on exactly what we're flying, we might be over the speed of sound. This so the the so-called transonic region between about Mac.8 and Mac 1.2 too. Uh, this absolutely wres havoc on our rocket and on any like aerodynamic sims we want to do cuz they they suddenly all get very very messed up. Uh, transic speeds sort of cause different parts of the air flow around the rocket to become unstable because you have pockets of air that are moving uh faster than they can. You can sort of think of the speed of sound as the speed of information through air, but air can't tell air in front of it to get out the way. So you end up with these shock waves that you're pushing through and that causes real bad disruptions. But yeah, this also causes really really bad forces on on the rocket itself, on the nose cone, and on the fins. Uh so you got to like reinforce the heck out of those to make sure that you can survive these speeds. And yeah, some of you may have seen BPS Spac's video where he um he cooked meat. He cooked a piece of steak on a rocket nose cone that was going at Mac 2. That's that's the sort of energy we're talking about here. So our our little PLA nose cone isn't quite going to survive anymore. So what's our answer to this? Tends to be composites. Composites are a combination of two or more materials chosen for their complimentary properties. Take fiberglass for example. That's something we use all the time in rocketry and it's something we've used from the start on this rocket here, Valkyrie. Uh fiberglass is made of a so there's glass fibers themselves which are very very strong in tension. You cannot like break them by pulling them but they are kind of pathetic when you try and push them or shear them or whatever. So what you do is you bind them together with epoxy and that that gives you the the the compression strength. that gives you the share strength and suddenly you have this material that's really strong in all of these axes and you can you can build something that survives Mac 2. [snorts] So neither is much use alone but yeah in combination very strong. Now most hobby rocketry sort of retailers offer standalone parts or or even full kits made of fiberglass that have been you know a precision machined. They've used all their um all their very fancy techniques. Um and they're usually quite priced relatively reasonably considering like how good they are, how much effort's gone into them. But we're here to do the hobby ourselves, not pay someone else to do it. So, surprisingly to me at least, the basics you need to get started with professional grade composites are really quite affordable. We're talking about the equivalent of two or three high power motor launchers to get you all the kit you need for making a good half a dozen rockets in terms of epoxy like all the brushes and parts you need, all the any other PPE you need even. And you can see on the slide here, uh it's again a little bit small, but uh here are some of the pitfalls of trying to make your own tube. Uh that message on on the right there says is a a friend of mine in Discord that says uh I think the 38 mm coupler is going to come out as a 37 mm coupler which anybody who does know anything about rockets knows that's actually kind of catastrophic. And yeah um we ourselves have have attempted some some fiberglass tubes as well. Um this one was for small mic and again this one on Valkyrie uh actually doesn't have the cardboard tube inside. That one's pure fiberglass. And if anyone wants to come see these rockets at the end, you can feel that one. Victory is incredibly light because of like how little fiberglass you need to reach that level of strength. Now, more recently, uh I've been doing full-on layups for all of my recent rockets. So, like Nova, for example, this one here. Um you may not be able to tell compared to this one, which is very, very textured, but uh there is a fiberglass layup under these fins. So, they're still plywood fins, but a layer of fiberglass on top of them and epoxy impregnated into those uh wooden fins uh really gives you the the strength you need to, you know, not worry about smacking those fins and and you know, I wouldn't want to do it on a plywood one, put it that way. [laughter] Now, there is the downside of epoxy is that you are working with hazardous materials. Um fiberglass and epoxy are both hazardous in their own ways and you do need to use suitable PPE. So, I don't want to just send people out to to buy all these things without mentioning that you do need to look into how to stay safe with them with them. Okay, so we're reaching Apogee. We're at the top of the flight now. And let's do a quick rocket electronics primer so you know what's going on in in in our avionics bay here before we decide what we're going to put it in. So, two quick distinctions is that you can have passive avionics and active avionics. Passive avionics are something simple like a data logger. All it does is tell you what altitude you reached. Maybe like, you know, how fast you got up there, how fast you came down. Uh it doesn't actually control the rocket in any way. Active avionics uh would be something that can detonate a black powder charge to separate the rocket or potentially even to control fins uh which is again a very difficult uh area that's classes experimental rocketry. So tread with caution, but active avionics are safety critical in almost like every scenario. Um, and not only are they safety critical, they can be very, very dangerous if used wrong. They're not just required to make things go right. Then there's also the distinction between commercial offtheshelf and DIY. And um the policies for this are actually kind of been written right now internally by Ukra. But uh so commercial offtheshelf is anything from a fully assembled kit flashed with firmware that you can just plug and play to maybe a kit that comes but disassembled and you have to solder the parts to it. Uh then there's like partially DIY where you've maybe modified one of those kits. And then there's fully DIY where you've designed a board from scratch like the one I'm going to talk about later. Now, what we tend not to want to do is mix the active and DIY components because as soon as you're just trying something out that could set off a black powder charge, steer a rocket into something, you're obviously poking the bear. You do not want your safety critical systems to be controlled by some random student in a field where there's, you know, 40, 50, 60 spectators that cannot easily move out the way of a rocket that's going, again, possibly the speed of sound. Now, commercial deployment computers can be pretty cheap, like those kit ones that you get disassembled. Uh they also can get to be pretty expensive even for the for the relatively simple ones, but they are rigorously tested and trusted and often times they're just worth it. In fact, there's usually not another option. You have to use one of these off-the-shelf dual deploy computers. This is something that we're trying to improve. And by we, I mean myself and a group of friends that are, you know, interested in making these devices ourselves. But for now, what we can do without any approval, without any any sort of safety concerns, is make our DIY data logger because all it does is collect information. So you can just stick it on your rocket and you get information out of it. And what's better is that you can get exactly the information out of it you want. And if you're ordering these in a small amount of bulk, say you're doing a group boy with some with some friends on the hobby, then suddenly it actually comes down to 15 to 20 per unit if you're getting it preassembled even. Um, so that's really quite affordable. Um, it takes a lot of time. It takes a lot of skill, but those, you know, that time and and skill is time you're spending doing the hobby. And, you know, skill that you may already have from your job, you can build as part of the hobby. And again, this is not required for everyone doing the hobby. All each of these like sort of four sections I'm talking about, you don't need to engage in all of them. You can just pick and choose one or two. Now this is my sort of avionics journey. Um we started with uh home homemade DIY PCBs that we edged at our our hackspace uh using uh a laser and feric chloride. So again hazardous chemicals kind of scary but it lets you rapidly prototype at a stage that you cannot reach ordering stuff from from JLC or whatever. And especially if you're using simple modules that just need plugging together in a really like sort of resilient way then that's that's not a bad way to do it. Um, but yeah, so that's that's Titania version one on the left and then on the right we have Titania version 3. Titania 2 never left my laptop. Um, Titania 3 is a uh like a fully featured data logger. It's got um a barometer, an accelerometer. It's uh the size of a UB key. So it it you know it is literally the size of your thumb and it is weighs almost nothing and it will collect as much or more data compared to like any other commercial data logger on the market. Okay so recovery one of the scary things I mentioned earlier was black powder. Black powder is something that you until recently have kind of been forced to deal with a model rocketry. Either it's integrated into the motors you're already flying in which case you don't need a separate license but you're obviously still dealing with some some dangerous material or uh you're making a separate uh black powder charge that you're then wiring into avionics manually and that's got a whole other set of risk associated with it. Now, when we're doing recovery, we want to separate at apogee because this is the point in the flight the rocket is moving the slowest. Apogee being the the top of the flight, the the highest point you get to because obviously you're kind of you're at the top of your imagine throwing an apple in the air. You're at the top of your throw. You're you're you're kind of hanging in the air. This is when you want to be be popping some critical mechanism, not when you're under a huge amount of force. Uh but if we if we're beginning to go like 1 kilometer, 2 km high and we we pop our main chute that lets us come down slowly enough to not get damaged, we're going to be drifting for miles and miles and miles. And that is not practical, especially in the UK where you know the biggest kind of empty area you can get is maybe 2 mi wide. So to combat this, for many high power launches, again apologies for the tiny image, um but uh for many high power launches, we only release a small shooter at Apogee called a Drogue. And what this does is brings the rocket down at a a much faster rate. Not not a rate that you'd want it to hit the ground at, but it lets it get down to a low enough level that you can then pop the main shoot without it drifting too far. Now, what this means is that we need a second deployment event somewhere near the ground. And this is where that manual put together black powder charge comes in. And that's been like the way it's done in the industry, well, in the industry, in the hobby for many, many, many years now. There are and yeah, as I mentioned, black powder is very hazardous and you do not want to be dealing with it if you can avoid it. Like as careful as you may be, accidents are going to happen and like they luckily I've never seen anything too bad happen myself, but I you there's always potential and anywhere you can remove risk from a hobby, that's that's a good thing. So there are devices called shoot releases. Now this pops out. This is a a a parachute wrapped in a bag that is held together by this little computer called a Jolly Logic. And that um so this pops out on the line at Apogee like alongside your tiny chute. Then this little board um releases that shoot at a certain predetermined point uh in your descent. Now this is all well and good, but it's quite difficult to test because you can't, you know, it's getting literally fired out of a cannon by your motor ejection. um which makes it quite difficult to test in realistic conditions. So I've tried to take this concept and make it a little more sturdy by integrating it into the shoulder of the nose cone. So if I come over here and pull out Nova's nose cone, it's a little bit of a tight fit. Uh but you can see that this parachute is totally wrapped up in here and then there's still a bulkhead behind that. So when this ejects, um, all this force is going into this bulkhead here. None of it's touching the parachute, which means you don't need like an extra like bit of fireproof, uh, fabric to protect the chute. And it also means that you can reliably test this system as it would be deployed like in the air just on the ground. And all this does is pull a pin out of an elastic hair band right here. Simple as that. The innovation is not the system. It's very simple. Anybody could build this. The point is that you can test this inside like wherever you want. If you need to do black powder testing, you have to do that on the launch site supervised by you know somebody qualified. And that means that you're rushing your testing on a launch day which is again just adding to the danger. So our shoe release has popped. We've touched down and everything so far gone gone pretty great in our flight. But not every flight works out so well. I I I couldn't come up here and pretend that everything I've ever done has gone perfectly. So I wanted to show you one of my one of my horrible horrible failures. So this is Nasia. Um this uses a a concept called rear rejection where instead of separating above the motor, it actually sort of spits the motor tube out the back. Uh I thought this had totally failed. Turns out it had landed nose down in the field, then ejected late because somebody found the ejected rear 20, 30, 40 meters away from the main rocket. I never recovered the main rocket. I just had the the sort of spat out motor tube. And that meant uh bye-bye beautiful rocket. Such a lovely paint job. Um bye-bye 150 of electronics stuck in the front of it. Um and yeah, maybe um I learned a lot. No, I need to use stronger Kevlar because otherwise that um yeah, the the Kevlar snapped when that thing popped out. So I I don't need to do that. And I also learned that GPS trackers might just be worth it. Okay, so that's that's that's kind of everything I have. Um I have left some time for questions on purpose. If people want to come up and chat to me about anything that's on this table as well, then you're very welcome to. Otherwise, that's me. Thank you. [applause]