Is it practical to launch a model rocket and have it land in a controlled manner, like Falcon 9, using hardware on the level of arduino and open-source software?
The control software is within hobbyist range, if you're prepared to crash a lot of rockets during testing. But the hardware is hard -- you need a throttleable engine.
I’m pretty sure that your problem isn’t going to be the software but rather the engine and the rocket itself.
Hobby rockets use simple solid fuel engines you’ll need to build an actual liquid rocket engine with controlled thrust that can be reignited the rocket it self also need to be large enough to be aerodynamically controlled and hobby rockets tend to be too light so they’ll simply tumble in the wind.
While you don’t need to build something the size of a falcon 9 for propulsive landing you’ll need something way larger than any hobbiest rocket I know of for sure.
If you just want the control part then simulating it is likely going to be a better use of your time, you can even build your own auto-pilot for something like Kerbal Space Program it won’t be the real thing but it would at least be achievable.
It’s undesirable for many reasons but could a small rocket be made to work if you made it really heavy? Of course one would be just pissing away efficiency but would a small heavy software-controlled model rocket work?
Define small, you still need a rocket with some sort of liquid fuel engine with some sort of throttle control and I'm not sure how small can you actually scale those to be.
You might be able to do it with a hybrid rocket engine where the oxidizer is liquid or gaseous but the fuel is solid but I'm not sure.
As for the weight if you make it small but heavy then you are likely to lose aerodynamic control since it essentially will be a free falling brick.
You need something that is massive enough to resist the wind but have a large enough surface area to be aerodynamically stable and controllable, I'm not saying it's not possible I'm just saying that the time and money that you'll have to invest in it is going to be quite likely astronomical and while I don't doubt that there might be individuals that might be able to do it on their own this likely would require a pretty large team of dedicated people to solve.
If you are capable of building a rocket engine I would actually focus on simply building a hovering rocket rather than trying to land it, or at least you better off trying to build a hobbyist grasshopper https://en.wikipedia.org/wiki/Grasshopper_(rocket) than a Falcon 9.
But realistically even for something like this you should be better prepared to spend the better part of a decade building it and likely at least a few $100K's in funding since none of this is going to be cheap to produce.
You don't necessarily need a liquid rocket engine if doing something like the hoverslam, because you'd just time the burn correctly and fire engine at full power.
The problem is that you can't stop a solid fuel engine as it has the oxidizer mixed in it, unless it requires some sort of a catalyst that you can control.
Hybrid engines which use solid fuel and a liquid/gaseous oxidizer can be controlled better but these are often very hard to reignite.
So this means you'll have to have additional engines that are used just for the slam landing, technically possible but again might be harder to construct than a liquid engine since solid fuel engine ignition is also fairly inconsistent.
The Soyuz capsule uses rockets to soften the landing but these technically aren't propulsive landing and the landing forces tend to vary quite a bit between landings.
Overall when I think about this problem as a hobby the software isn't going to be the biggest blocker here especially considering the speeds/altitudes that we are talking about as well as the overall mass of the rocket, in fact since these rockets are going to be considerably smaller and would travel considerably slower you could absorb much more of their relative energy via hydraulics so the amount of precision needed for the slam/hover landing isn't as great.
Couldn't you develop some sort of servo-controlled thrust deflector that allowed you to effectively reduce the net thrust without throttling the engine itself? It would be similar to thrust reversal on jet engines, but you would only do it partially since you're aiming for thrust reduction instead of reversal.
Hybrid motors using solid fuels (plastic, rubber, cardboard, even sausage) and liquid oxidizer (typically nitrous oxide) are pretty common in hobby rocketry. These can be trivially made throttleable within a range by metering the NO2 flow. With the proper fuel core, they can be kept "smoldering" for shutdown / relight by maintaining a trickle of oxidizer to keep the fuel surface at combustion temperature.
A hobby grade throttling and gimbaling rocket engine, with free documentation and open source guidance software sounds like an absolute proliferation nightmare scenario.
Indeed. I have not looked into rocketry for a while, but my recollection is that an active guidance system, active control surfaces, an IMU, all place you squarely under ITAR. Building, much less exporting, without a license is likely a Bad Idea unless you are looking for a Club Fed vacation.
Export doesn’t just mean “shipping a rocket to the Middle East” if you write up a detailed guide on how to build these and supply the code to make it work, you’d likely be at risk.
This is a common rumor but appears not be be based in reality. Lots of hobby rockets have guidance now. It's fairly common to have enough guidance that the thing will go straight up.
Well reading the ITAR guidelines it is clearly covered under Category IV (Launch Vehicles, Guided Missiles, Ballistic Missiles, Rockets, Torpedoes, Bombs, and Mines).
Specifically:
(1) Flight control and guidance systems (including guidance sets) specially designed for articles enumerated in paragraph
(a) of this category (MT for those articles enumerated in paragraphs (a)(1) and (a)(2) of this category);
Note to paragraph (h)(1): A guidance set integrates the process of measuring and computing a vehicle's position and
velocity (i.e., navigation) with that of computing and sending commands to the vehicle's flight control systems
to correct the trajectory.
It isn't quite a model rocket, but there is an interesting video of someone making a single-fan drone using thrust vectoring. Not quite like a Falcon 9 but the same idea, vertical take off and landing, and shaped like a rocket.
This guy [0] does it with regular solid fuel rocket motors. Since the engines cannot be throttled, I think he has to try and light them at just the right moment, which does not seem particularly easy...
This appears to be working with solid rocket motors, thrust vectoring, and a carefully timed ignition. How do they get accurate distance to ground? Is altitude just a constant for these tests?
Ah wow I watched a bunch of his videos last summer but forgot to check up on his progress. Incredible!
I wonder what scale you would need to get the rocket into space/orbit? SpaceX should fund this guy to find out, could prove to be a valuable bootcamp for real SpaceX employees in the future?
The summary is that you may be able to use a stupendously large number of them to get to space, but orbit is physically impossible. You'll need a different propulsion method.
The smallest rocket that has ever carried a payload to orbit is the SS-520. It's ~30 feet tall, ~2 feet in diameter and weighs ~5,700 pounds. It set the record in February 2018, so it's a pretty recent record.
This is incredible, looks like an exact smaller clone of the real thing. More generally, it has to be possible since we went to the moon with much less.
Million thanks for sharing this. And, that guy in the video is incredibly talented. Not sure if he is doing it alone. But, irrespective of that, this video should be an extreme motivation for some of us who are just building a website and think - this is too much, I can't do it.
Joe Barnard is an incredibly smart guy, and his videos always leave me inspired to get off my arse and do something. He has no background in this stuff, and just decided it would be fun to learn and figure it all out, and has come this far in only a few years of tinkering.
It was posible to launch Apollo 11 with less powerful electronics. Mechanicaly it is a bit expensive but many 'amater' clubs achive controled flight, a few to the edge of space.
You may be interested in following Tom Stanton on YouTube. He built a radio controlled SpaceX model a few months ago.[1] It was barely controllable, and wasn't designed with actual propulsion engines, but still very cool.
As others have been commenting, it's a completely different ballgame if you want to use propulsion engines and still be able to land it. At that point, you're just building a smaller version of the real SpaceX rockets, and that sounds much more difficult (not to discourage anyone from trying!).
I can't speak to anything legal, that's its own topic.
But for all the model rockets I've seen, their mass ratios are quite small, and their motors don't allow for throttling. They blow their load as fast as they can and then drift down.
Software is not the biggest problem, you need a hobby quality throttling and gimbaling rocket motor, and I'm not sure if they even exist.
If you dig up archives of Armadillo Aerospace - John Carmack's rocket company - you'll see videos of smallish rockets doing just that. "Smallish" as in "you can lift one from the ground, fueled, with your hands... perhaps".
which is the story of a German rocket club which first got shut down by the Nazis because "somebody could get hurt" and then the Nazis thought it over...
Probably your best bet is a hypergolic monopropellant such as hydrogen peroxide.
I agree, that looking - though very carefully! - into hydrogen peroxide could be a good approach. However, "hypergolic monopropellant" is like clapping with one hand. "Hypergolic" means "self-igniting by the contact with the other component", it's a property of a component of a pair, not of a single substance.
For example (see J. Clark, Ignition!) nitric acid is hypergolic with turpentine, but not hypergolic with kerosene.
30% hydrogen peroxide is commonly used in laboratories and can be used to make Triacetone Triperoxide, which is the reason why you can't take a full-sized bottle of shampoo on a plane.
A bottle that large of TATP could blow up a plane but you'd be lucky to make it to the airport with it before it explodes.
The 90%+ stuff used in rocketry is hard to get because it is dangerous to handle.
High concentration hydrogen peroxide is insanely dangerous, and where I live doing this would be illegal, so I really don't recommend it.
But from previous research it sounds really simple to concentrate (up to 70%) if you can acquire enough low concentration hydrogen peroxide. So much so that it kinda scares me that I have a bottle of 3% hydrogen peroxide in my house.
Edit: Again, this is a bad idea, but here's the title of my source: Methods for Concentration of Hydrogen Peroxide To Obtain It in Anhydrous Form
> Is it practical to create a software-controlled model rocket?
No, but that is what people will tell you about every idea from Facebook to a pet rock.
If you want to do it, good luck. It will not be easy.
If you want a simple project- Add your arduino, get GPS, accelerometer and a noise maker. (Edit: if you are really ambitious, get it to communicate live)
See if you can optimize anything. I would guess your goal is to play in embedded C++ anyway.
It's likely to be difficult. I heard a good analogy once: imagine balancing a broom, handle pointed straight down, on one fingertip. It's not that hard. Now imagine balancing a toothpick. Impossible.
Specifically, you need reaction time faster than sqrt(l/g), where l is the distance between the engine and the center of mass, and g is gravity. But l=30 cm is still with the range of commodity hobby servos to vector the engine.
The same effect makes walking robots harder at small scale, unless they cheat by having large feet and stiff ankles.
The period of a pendulum is 2pi sqrt(l/g) for small amplitudes. He’s most probably referring to the order of magnitude you need, not precisely that number.
If you take an inverted pendulum of length l in gravity g, and perturb it slightly from vertical the error grows like e^(t/sqrt(l/g)). So if you're off by 1 degree, you'll be off by 2.718 degrees sqrt(l/g) seconds later. (The real function involves hyperbolic cosines, but they grow like e^t).
If you can react 2x as fast the control problem is easy. If you can react 1x as fast, the control problem is feasible but requires accurate tuning.
For average-height humans on earth, the height of the center of mass is about 1.3m, so sqrt(l/g) is about 350 mS. Human response time, from the inner ear to the ankle muscles is about half of that. That gives some intuition for how hard it is to balance with 2x faster response. Balancing a yardstick on your finger is closer to 1x faster response.
If the toothpick was spinning around it's long axis it would be hell easy to balance it. Not only bigger things are stable, it depends on the dynamics of what you are trying to solve.
I was actually curious how cruise missiles were defined in itar. The definition of missiles is really broad and actually includes lots of UAVs.
> “Missiles”. (All) Rocket systems (including ballistic missiles, space launch vehicles, and sounding rockets) and unmanned aerial vehicle systems (including cruise missiles, target drones, and reconnaissance drones) “capable of” delivering at least 500 kilograms payload to a range of at least 300 kilometers.
> The definition of missiles is really broad...delivering at least 500 kilograms payload to a range of at least 300 kilometers.
Not as broad as I would have thought. You could do a lot of damage with 499 kg of TNT, and nuclear bombs weigh less. Little Boy was 64 kg of uranium according to [0].
The fissile core is a tiny part of the weight of a nuclear weapon, though. Little Boy weighed almost 10,000 lbs; it took a lot of explosive, metal, and circuitry to detonate it.
The Little Boy was seriously overbuilt. The W9, W19 and W33 warheads are examples of gun-type bombs similar to Little Boy with comparable cores and yields, but in much smaller packages.
A gun-type bomb doesn't require a very complex system to set it off. The complicated bomb was Fat Man, an implosion bomb, that required very precisely calculated explosive lenses and precise timing circuits.
On the bright side, 500kg and 300km seem to be quite a bit beyond what typical model rockets can do, so at least with that definition they might not be considered missiles?
As others have mentioned, the burn of the solid propellant used can't be controlled. However, you could look at things like gyros, thrust vectoring or servo controlled fins to give you more a more controlled ascent. That wouldn't help with the descent which is traditionally unpowered. Maybe a small charge to flip the rocket around and then use servo fins to control its glide direction on the way back down.
What do you mean by "practical?" Model rockets are for hobbyists. Practicality isn't a part of the equation. The only reason to fly a model rocket at all is that it's cool.
There's no "practical" reason to make it land vertically. Model rockets can land safely using parachutes.
Arduino hardware is barely capable of running a simple one-variable PID loop at a high sampling rate, say 1Khz. A rocket control software will require a full-blown MIMO model with complex transfer functions. You'll also need high ports speed; Arduino won't cut it. At the very least you'll need something like a Cortex-R5.
Copenhagen Suborbitals do thrust vectoring, and if I remember correctly the 4 jetvanes are controlled by an arduino .
The software is written by one guy in his freetime. Pretty amazing feat, considering how difficult it is, and that he has no way of testing it before the actual launch. It worked flawlessly the first time.
Here's a video of the Nexø 1 launch that uses the system to control the rocket on its ascent.
This video shows some technical data streamed live from the rocket that gives a good overview of what the jetvanes are doing. Notice the graphic in the lower left corner; The H in the middle is the floating launch platform (12x14 meters) and the moving red dot is the position of the rocket in the X-Y plane. On the whole trip it never moves more than a few meters from the center. Really impressive stuff...
This is a weird question. Model rockets aren't practical. Hobby's aren't practical. Hobby's are fun, and educational. A software controlled model rocket would be fun and educational and challenging. You should do it.
One of my hobbies is baking bread. I've seen professional bakers bake 100% whole wheat loaves with an open crumb. It's semi-magic and not practical. They literally spend years failing at it, learning every variable, sourcing different artisanal flours and setting up a professional workspace.
I do try it sometimes, and I always fail. It's interesting, but...
Sometimes I actually want to eat some nice bread. There are times when I say, just do a 33% whole wheat loaf Erik, it's fine. It is practical and it's still fun and it's a nice day doing my hobby. There's still plenty of sport in it and plenty to learn.
77 comments
[ 3.6 ms ] story [ 113 ms ] threadHobby rockets use simple solid fuel engines you’ll need to build an actual liquid rocket engine with controlled thrust that can be reignited the rocket it self also need to be large enough to be aerodynamically controlled and hobby rockets tend to be too light so they’ll simply tumble in the wind.
While you don’t need to build something the size of a falcon 9 for propulsive landing you’ll need something way larger than any hobbiest rocket I know of for sure.
If you just want the control part then simulating it is likely going to be a better use of your time, you can even build your own auto-pilot for something like Kerbal Space Program it won’t be the real thing but it would at least be achievable.
You might be able to do it with a hybrid rocket engine where the oxidizer is liquid or gaseous but the fuel is solid but I'm not sure.
As for the weight if you make it small but heavy then you are likely to lose aerodynamic control since it essentially will be a free falling brick.
You need something that is massive enough to resist the wind but have a large enough surface area to be aerodynamically stable and controllable, I'm not saying it's not possible I'm just saying that the time and money that you'll have to invest in it is going to be quite likely astronomical and while I don't doubt that there might be individuals that might be able to do it on their own this likely would require a pretty large team of dedicated people to solve.
If you are capable of building a rocket engine I would actually focus on simply building a hovering rocket rather than trying to land it, or at least you better off trying to build a hobbyist grasshopper https://en.wikipedia.org/wiki/Grasshopper_(rocket) than a Falcon 9.
But realistically even for something like this you should be better prepared to spend the better part of a decade building it and likely at least a few $100K's in funding since none of this is going to be cheap to produce.
Hybrid engines which use solid fuel and a liquid/gaseous oxidizer can be controlled better but these are often very hard to reignite.
So this means you'll have to have additional engines that are used just for the slam landing, technically possible but again might be harder to construct than a liquid engine since solid fuel engine ignition is also fairly inconsistent.
The Soyuz capsule uses rockets to soften the landing but these technically aren't propulsive landing and the landing forces tend to vary quite a bit between landings.
Overall when I think about this problem as a hobby the software isn't going to be the biggest blocker here especially considering the speeds/altitudes that we are talking about as well as the overall mass of the rocket, in fact since these rockets are going to be considerably smaller and would travel considerably slower you could absorb much more of their relative energy via hydraulics so the amount of precision needed for the slam/hover landing isn't as great.
If you go this route you might as well just use an EDF engine instead of a rocket engine for the landing.
Specifically:
https://www.youtube.com/watch?v=RMeEh5OUaDs
https://www.youtube.com/watch?v=_kd64VE3A1c
[0] https://www.youtube.com/watch?v=8_hJ48LCXWs
Test Launch: https://www.youtube.com/watch?v=QQt-9SSJ51c
Test Landing: https://www.youtube.com/watch?v=lXy-x6lkQvQ
This appears to be working with solid rocket motors, thrust vectoring, and a carefully timed ignition. How do they get accurate distance to ground? Is altitude just a constant for these tests?
I wonder what scale you would need to get the rocket into space/orbit? SpaceX should fund this guy to find out, could prove to be a valuable bootcamp for real SpaceX employees in the future?
There's a great "what if" xkcd about using solid fuel model rocket engines (the same type used in BPS.space's rockets) to get to space and orbit.
https://what-if.xkcd.com/24/
The summary is that you may be able to use a stupendously large number of them to get to space, but orbit is physically impossible. You'll need a different propulsion method.
The smallest rocket that has ever carried a payload to orbit is the SS-520. It's ~30 feet tall, ~2 feet in diameter and weighs ~5,700 pounds. It set the record in February 2018, so it's a pretty recent record.
This could theoretically be used to land vertically, though that hasn’t been achieved.
As others have been commenting, it's a completely different ballgame if you want to use propulsion engines and still be able to land it. At that point, you're just building a smaller version of the real SpaceX rockets, and that sounds much more difficult (not to discourage anyone from trying!).
[1] https://www.youtube.com/watch?v=ZsEBiAahAYM
But for all the model rockets I've seen, their mass ratios are quite small, and their motors don't allow for throttling. They blow their load as fast as they can and then drift down.
Software is not the biggest problem, you need a hobby quality throttling and gimbaling rocket motor, and I'm not sure if they even exist.
https://www.amazon.com/Rockets-Missiles-Men-Space-Definitive...
which is the story of a German rocket club which first got shut down by the Nazis because "somebody could get hurt" and then the Nazis thought it over...
Probably your best bet is a hypergolic monopropellant such as hydrogen peroxide.
For example (see J. Clark, Ignition!) nitric acid is hypergolic with turpentine, but not hypergolic with kerosene.
A bottle that large of TATP could blow up a plane but you'd be lucky to make it to the airport with it before it explodes.
The 90%+ stuff used in rocketry is hard to get because it is dangerous to handle.
But from previous research it sounds really simple to concentrate (up to 70%) if you can acquire enough low concentration hydrogen peroxide. So much so that it kinda scares me that I have a bottle of 3% hydrogen peroxide in my house.
Edit: Again, this is a bad idea, but here's the title of my source: Methods for Concentration of Hydrogen Peroxide To Obtain It in Anhydrous Form
No, but that is what people will tell you about every idea from Facebook to a pet rock.
If you want to do it, good luck. It will not be easy.
If you want a simple project- Add your arduino, get GPS, accelerometer and a noise maker. (Edit: if you are really ambitious, get it to communicate live)
See if you can optimize anything. I would guess your goal is to play in embedded C++ anyway.
Scale matters. Bigger things are more stable.
The same effect makes walking robots harder at small scale, unless they cheat by having large feet and stiff ankles.
If you can react 2x as fast the control problem is easy. If you can react 1x as fast, the control problem is feasible but requires accurate tuning.
For average-height humans on earth, the height of the center of mass is about 1.3m, so sqrt(l/g) is about 350 mS. Human response time, from the inner ear to the ankle muscles is about half of that. That gives some intuition for how hard it is to balance with 2x faster response. Balancing a yardstick on your finger is closer to 1x faster response.
https://duckduckgo.com/l/?kh=-1&uddg=http%3A%2F%2Fwww.engine... [PDF]
I don't know whether he got shut down by the authorities or not.
> “Missiles”. (All) Rocket systems (including ballistic missiles, space launch vehicles, and sounding rockets) and unmanned aerial vehicle systems (including cruise missiles, target drones, and reconnaissance drones) “capable of” delivering at least 500 kilograms payload to a range of at least 300 kilometers.
Not as broad as I would have thought. You could do a lot of damage with 499 kg of TNT, and nuclear bombs weigh less. Little Boy was 64 kg of uranium according to [0].
[0]https://en.m.wikipedia.org/wiki/Little_Boy
Or the W54 was reputedly much lighter, but with a larger diameter.
A gun-type bomb doesn't require a very complex system to set it off. The complicated bomb was Fat Man, an implosion bomb, that required very precisely calculated explosive lenses and precise timing circuits.
There's no "practical" reason to make it land vertically. Model rockets can land safely using parachutes.
The software is written by one guy in his freetime. Pretty amazing feat, considering how difficult it is, and that he has no way of testing it before the actual launch. It worked flawlessly the first time.
Here's a video of the Nexø 1 launch that uses the system to control the rocket on its ascent.
https://www.youtube.com/watch?v=8iTg55Ktkn4
This video shows some technical data streamed live from the rocket that gives a good overview of what the jetvanes are doing. Notice the graphic in the lower left corner; The H in the middle is the floating launch platform (12x14 meters) and the moving red dot is the position of the rocket in the X-Y plane. On the whole trip it never moves more than a few meters from the center. Really impressive stuff...
https://www.youtube.com/watch?v=Km7-2Ds6_Xs
I know it's not exactly what you're asking, but it's close, so I thought it might have some value.
One of my hobbies is baking bread. I've seen professional bakers bake 100% whole wheat loaves with an open crumb. It's semi-magic and not practical. They literally spend years failing at it, learning every variable, sourcing different artisanal flours and setting up a professional workspace.
I do try it sometimes, and I always fail. It's interesting, but...
Sometimes I actually want to eat some nice bread. There are times when I say, just do a 33% whole wheat loaf Erik, it's fine. It is practical and it's still fun and it's a nice day doing my hobby. There's still plenty of sport in it and plenty to learn.
http://www.argoniacup.com/