How I landed a model rocket [video] | Hacker News Reader

How I landed a model rocket [video]

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127 pointsdonohoe29 comments

"I Landed A Rocket Like SpaceX - Scout F" - https://youtu.be/SH3lR2GLgT0

Was going to make the same comment. The entire BPS Space series of videos is excellent and goes into great detail on how it was done and the many challenges. To me, the BPS solution is also more interesting because it allows "throttling" (really variable deflection) of the solid rocket motor.

How did the guys in the OP do it? They used liquid fuel? I didn't know that was possible for model rockets

Looks like two separate motors to me. The second one is staged after apogee and is only powerful enough to slow the rocket down.

He described it in the video - he uses two motors. The launch motor is held in place by friction and is ejected by the ignition of the landing motor.

There's always Joe B's rocket but this one takes the cake. It lands much smoother than Joey's ever did and with probably less budget. I applaud the creator!

"for the past 4 years" is some dedication. kudos for not giving up

Hopefully it wasn't "I just kept trying various ones until one happened to work"

Aka. the Soviet development process.

Aka, a way to compete with a vastly richer and more resourced opponent.

Pretty much what SpaceX does too, so he’s in good company. History is full of stories like that. Edison’s “I didn’t fail 999 times, I just found 999 ways not to make a light bulb”

I was thinking more of the equivalent of p-hacking; my design only has a 1% chance of working, but instead of improving it I just launched to 100+ times until the 1% hit.

unless you didn't watch the video or were multitasking while it played, he definitely showed how he iterated through design ideas. so i'm really not sure what you're on about with the whole comment anyways

What do you think he meant by "I'm not going to show you the full code, for safety reasons"?

A hobbyist thinking their design is so advanced that a terrorist could never make a guided missile on their own.

Well a hobbyist that took 4 years to develop his design so not just some dude who built something over a weekend. And by that logic a lot of countries could make ICBM nukes on their own - why don't we open source that technology since there's no reason not to share it since they already could probably figure it out.

So then what are the obvious reasons?

Hi, Im the creator of the video, Not that - the main reason was to prevent people with little experience blindly copying code onto a rocket without understanding what it does and then getting hurt/breaking their rocket and then blaming me. I did say you could contact me for the code, so this doesn't make much sense. Also, this is nothing close to a guided missile...

In those model rocket circles, there's a strongly held belief that any code you write that includes a PID controller to steer a rocket is sensitive information / ITAR restricted.

Maybe I am missing something but since when are PID controllers "restricted/secret?" I think I get what you mean, and I guess my question is: is that a falsely held belief by amateurs or?

If you paste a link to your full source code for a thrust vectoring rocket in the BPS Space discord, it'll get removed.

And yeah a PID by itself is not restricted. They are more worried about that in combination with other circuitry and software that may be used maliciously.

I think it's an over reaction

Llast time I checked guidance systems for model rockets fall into a regulatory space normally applied to guided missiles.

You cannot legally make (sell/distribute?) a guided missile in the USA without the appropriate manufacturer’s licensing. The guidance system itself triggers this regulatory wall.

Thrust vectoring for landing is fundamentally different in application, but it is still technically guiding a “missile” to a specific point of impact.

People working on this as hobbyists are wise to make sure their projects are not seen as presenting an enforcement target, since they could easily be technically crossing the letter if not the intent of the regulations.

Amateur rocketry exists in a little space between regulated “destructive devices” and unregulated “fireworks” and they try hard not to tempt regulators to further constrain their activities.

It’s almost funny how little amateur rocketry is legally regulated, you can pretty much do anything you want to legally because practically people in charge of launch sites, etc. will not let you do dangerous shit, but for example without any certification you can buy 1 L1 motor at a time from HPR sites, with an L1 motor you can acquire 1 L2 motor at a time, and with an L2 you can acquire 1 L3 motor at a time so in effect an L2 will let you buy the highest power rocket motors as long as you do so one at a time. Of course no one will let you launch a rocket with 5 L3 motors as an L2 but in theory you could.

Also yes code that lets you arbitrarily steer a rocket in any direction is software for a missile and goes under ITAR. I don’t think there’s anything that actually legally prevents you from doing it, but once you make something classified under ITAR it is now an ITAR product and there are limits to what you can publicly say about it, You can legally perform TVC +/- 5 degrees without it being under ITAR from what I’ve heard and a think publishing code for that would be fine, but in practice people probably don’t want to risk it and honestly it’s not that hard to implement yourself if you’re capable of building a TVC rocket anyways

The regulation says "active controls", which is pretty broad.

https://www.ecfr.gov/current/title-22/chapter-I/subchapter-M...

Can’t wait till ITAR gets ruled unconstitutional

Assuming he's in the US, he doesn't want his door kicked in by the FBI. No kidding.

https://www.google.com/search?client=firefox-b-d&q=MTCR+miss...

MTCR, ITAR, commerce control list related.

amateur model rocket people who fly stuff in the black rock desert go out of their way to NOT incorporate active guidance systems, lest they run afoul of this.

Hi - Im the creator of the video,

I put the ITAR there, but the main reason for not showing code was to prevent people with little experience from blindly using code which could be unsafe. There are a lot of young kids or folks with no prior knowledge about rockets trying to get into the hobby, which is great, but can be dangerous if they are using software without understanding what it does. I did say you can email if you want to learn more about it!

Thanks, that's interesting!

Very nice engineering.

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