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Comment by spiritplumber | Hacker News Reader

Legally, if I bring it down, can I keep it? What if I call the CIA and tell them "Hey, I spent $5K bringing it down, but I'll gladly sell you it for $10K"?

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Shooting down an unmanned aircraft in skies where the FAA has jurisdiction (just about all in the US) is a felony equal to shooting a manned aircraft, even hobby drones. You might not want to alert them.

If you can get something to above 65k feet and conduct some sort of kinetic action against a small moving target for only 5k dollars I'm sure lots of us defense contractor UAV manufacturers would like to hire you or license your technology.

In the High power rocketry hobby, properly certified, $5k will get you high enough. Guidance is something else, I think you could do it, the knowledge is there and available. It would take many $5k test flights to get it working however.

There's a recent Veritasium video, where they were trying to demonstrate tungsten "rods from gods" space weapons by dropping heavy weights from a helicopter.

When they asked an expert about the aiming issue, the response was basically laughter and "I'm not going to solve the precision guided munitions problem for you because of legal reasons, and you're not going to be able to figure it out."

I expect precision guided rocketry is going to be a lot harder than a chunk of steel barely high enough to reach terminal velocity.

That Veritasium video is probably the worst video he ever produced. It was full of the most obvious mistakes possible along with a pointless hype. He probably felt forced to release it because he spent so much money on the failure.

AFAIK, in the US, precision guidance to a specific orientation on a amateur rocket is legal (i.e. active stabilization), but precision guidance to a specific location on a amateur rocket is indeed illegal.

Interesting. This was my take as well. I’ve been a fan of rods from god stuff for years, but his whole attempt to “recreate” was really lame. He explains physics stuff all the time, and then struggle with some simple engineering, just so they could create “suspense” around a helicopter drop. It was kinda surreal. I’m still scratching my head.

I'd go with the worst ones being one of the straight up commercials like the self driving cars one

It’s not really that hard to figure out, unfortunately. It gets trickier for moving targets… but it’s still not that hard. These days, the easiest way is just to use a neural network trained in a simulator. You don’t even have to understand the math or even fully grep the sensor/image processing. The methods used for conventional targeting systems are actually pretty well documented.

Hobbiests are already making self landing (spacex-style) model rockets. That is a much harder problem.

Entertainingly, mark Robert posted a video of him solving the precision guided missile problem, and realizing on talking to an expert in the field that that's what he'd been building

I think you're thinking of Mark Rober's recent 'egg drop from space' video?

https://www.youtube.com/watch?v=BYVZh5kqaFg&t=660s

Ah, I think you're right.

Sufficiently advanced hobby grade model rocketry with guidance system and kinetic effect payload might start to resemble an ITAR controlled missile technology item (and/or something the ATF would be interested in for USA domestic destructive device and munitions laws).

There are people building missiles as a hobby? Sounds fun.

Guidance is a big no no because it’s bad for the whole hobby. We basically self govern so not to cause problems. People work on active vertical stabilization systems which is basically guidance for going straight up. No one attempts guidance to a specific destination because it’s a good way to put the whole hobby at risk. However, the skill and know how is there. People are putting passive stabilized rockets to 280k feet in black rock. A guy in Austin have active stabilization working above mach 1. It can be done within the hobby but no one wants to do it.

There are GPS guided model airplanes which are absolutely nothing like cruise missiles because they fly so much slower.

There are ducted fan model airplanes which are absolutely nothing like cruise missiles because they aren't GPS guided.

What's the best online venue/forum for one to read & learn more about this hobbyist scene?

An example of high altitude amateur flights. Granted this guy is more or less a legend in the hobby, definitely not the run of the mill.

https://www.rocketryforum.com/threads/project-mesos-a-two-st...

The rocketry forum. Dot com.

That is really sad.

You can go see the most impressive ones launch at the annual BALLS event [1] in Blackrock desert several weeks after Burning Man.

The FAA closes off the airspace around the desert which allows the really powerful rockets to fly.

[1] http://www.tripolimn.org/events/balls/

This makes me wonder what else of interest occurs in that desert throughout the year? Is there anything preventing someone from just camping there year-round to enjoy the spectacles?

It's not that desert, but instead in a near by desert in Arizona: https://bigsandyshoot.com/

https://www.youtube.com/watch?v=_h3HAv9ra9Q

It's where all the private individual owners of the biggest military equipment you can buy in the US go to shoot their equipment that would be basically illegal to shoot anywhere else.

https://www.youtube.com/watch?v=R02emks3BoQ

I like this one where they shoot a ball turret from a bomber from a different year: https://www.youtube.com/watch?v=7_TaK0WZj2k

There are limits to how long you can camp in a single spot on public land, but no law against travelling around and camping in different areas as long as you want.

BLM will kick you off public land when pay to play permit holders show up.

You might be able to bring it down with a powerful enough laser, so a cheap weather balloon and a 50w laser plus a raspberry pi with adequate connectivity, four propellers for course correction, and some servos ought to do the trick for under 1000$.

I am no expert on the upper atmosphere but I think the wind speeds at those altitudes vastly outstrip the ability of anything with batteries and electric motors to adjust its course. The only way to change directions is to rise or fall into a differently moving stream of air current. This is how the Google project loon things were supposed to navigate?

Presumably both balloons are affected by the same air currents, right? So as long as you lift it up from the right spot it should be able to get within a few kilometers of the target, no?

Doubtful. It's more like trying to steer a ship. There are currents, but also a lot of noise/turbulence.

That's true, but it only needs to get within a few kilometers.

Didn’t some guy freefall from something like 100k ft or something to a specific landing zone. Remember seeing a red bull video of the event. How did he manage to avoid high altitude winds blowing him off course?

Think the name was Baumgartner or something like it.

your laser doesn't need to do anything to the balloon and can be as weak as a laser pointer. just aim at the cameras and zap the sensors. assuming the ability to aim and hold would be achievable at this level. who cares if it's just floating there if it is blind?

“Just aim” seems to be understating the challenge of hitting a tiny target through multiple miles of atmosphere and holding the same position long enough to damage the sensor. The laser alone seems like it would blow that $5k budget by a handy margin — not much economy of scale at that power level.

With a portable generator, you can literally spend days aiming at the balloon. Eventually you're going to make contact with the sensors.

Yes, but damage is a function of power and time. If you can’t keep it on that a precise position you need to deliver far more power — there are links here to some research and they tend to be measured in seconds, which is a very aggressive target for something this far away through moving air.

https://www.ilda.com/camera-sensor-damage.htm

i said assuming with caveat of "at this level"

edit, however, lasing a camera sensor doesn't need a lot of holding time. so just keep bouncing it around and hopefully, eventually you'll cover enough to render useless.

Remember, I’m not saying it’s impossible - just a lot more expensive. I’m sure the U.S. military budget could include powerful lasers, precision sensors, and the software to keep focused on a small target at a long distance but I’d be surprised if it wasn’t at least two orders of magnitude more expensive.

And you power the laser with…?

A battery. A 50Wh battery should only weigh around 100g and would be able to power the laser for a good while.

No, you'll get arrested. Even if it's Chinese, you're not allowed to mess with it, only the gov is.

How about if it mysteriously, spontaneously fell down and you just retrieved it?

Normal private property like someone's quadcopter, I would assume the owner still has rights to it (and possibly liability depending on how/where it fell). But foreign government property that's not supposed to be there in the first place?

https://xkcd.com/1523/

> How about if it mysteriously, spontaneously fell down and you just retrieved it?

Judges aren’t obligated to believe your bullshit.

except, the unbelievable thing would be that someone on the ground would have the ability to cause it spontaneously fall down. i'd hope the judge would put the larger burden of proof on the prosecutors here.

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