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Comment by centimeter | Hacker News Reader

I looked into building a vectored guided rocket several years back and remember discovering that it would land me in hot water with the ATF or some similar TLA. At what point does rocket guidance step into legally questionable territory?

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“Stability, not guidance” — its sort of like “tax avoidance, not tax evasion”.

I’m not sure what the defined red lines are in the US, but most people building rockets big enough for the feds to worry about are following the model rocketry code and associated with NAR/Tripoli, so at least have access to more expertise to help follow the rules.

Getting the big motors requires multiple certs from those orgs, so the system tends to be self regulating to some extent, since you can’t test your code without the hardware.

I know Joe Barnard of BPS has mentioned a few times that he doesn’t release his code because the laws are unclear, and lawyers familiar with them are expensive.

Stability and guidance are both covered, specifically "gyrostabilizers or automatic pilots and integration software therefor" per ITAR. The MCTR has similar language bit I'm too lazy to find it. This is why most rocketry hobbyists won't release airfoil designs, propellant formulas, or advanced flight control systems.

The issue isn't you building a rocket big enough for the feds to care about, but the people who can build (and use) big rockets using your designs. Iran for example relies heavily on open source for its drone program.

It seems that sharing plans would be fine after verifying citizenship of the recipient.

I'm sure there are plenty of citizens of $YourCountry who are either (a) loyal to $CountryYouThinkIsBad or (b) not discerning about passing on some designs they got from an internet stranger.

Sure, but the legal problems go to them.

Only if you got them to sign an ITAR End User Certificate and you have a reasonable belief that it was completed truthfully.

HP for example is still heavily involved in the investigation of Huawei's export of HP hardware to Iran. They didn't get to just point and say "go talk to them."

I don't think that's how legal problems work.

Careful, citizenship can still hide double allegiances [0]

[0] https://www.justice.gov/usao-az/pr/former-raytheon-engineer-...

My desire to do same has barely gotten its shoes laced, but it’s attractive to me because it combines so many interesting technologies and concepts.

I think I’ve made the emotional pivot to UAVs instead because swarming and autonomous guidance & control is one of the more interesting parts to me and even if it weren’t likely to draw ’attention’, the development process for rocket is stymied by the characteristics of rocket propulsion.

Yeah and UAV's last longer and it doesn't cost $15 a pop for a 3 second burn time.

Are there any promising hybrid engines or are we stuck with solid fuel for the time being?

For model rocket stuff of this size, yeah all we got is solid motors. I've seen some larger amateur rockets that use liquid fuel though but at that point, that leaves "amateur single person" territory and it's more for larger institutions or clubs.

I flew high-power rockets under a Tripoli certification back in the late 90s. The Aerotech hybrid system looked really attractive to me at the time. I wasn't in a financial position to take the plunge, though.

I've thought about getting back into the hobby and it looks like all the hybrid systems have disappeared. The ATF permitting for solid fuel motors seemed pretty onerous back in the late 90s (I always flew at launches where I could purchase reloads for my Aerotech RMS on-site so I didn't have to deal with transporting motors) and I assume it got worse after 9/11.

Anybody know what ever happened to the hybrid systems? Aerotech's website looks like it stopped being updated about the time I left the hobby. Same goes w/ their competitor Hypertek (which I thought had a ridiculous ground-support system).

I've noticed the same. Maybe all of this YouTube tinkering will help revitalize the hobby.

Many many orders of magnitude longer and thousands of km further on hydrocarbon fuels ;)

https://en.m.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm

> My desire to [...] has barely gotten its shoes laced

This is such a hilarious phrasing but it nicely captures the feeling!

At the point where you start telling the rocket to go anywhere but upwards I'd assume. As long as it's active stabilization and not active guidance I'm assuming.

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