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Comment by ajross | Hacker News Reader

It could be. But if it is, you seem to be arguing that flying a 360 mph missile around in the airspace above an active airport is... safe?

I'm shocked at the nerve I seem to have hit here. I'm not trying to take your model rockets away here, but this is not a harmless device. I think many people here lack an intuition of how fast "360 mph" is or the kind of energies that are involved. This is getting into the speeds seen for muzzel velocities of handguns, and that engine weight a hell of a lot more than a bullet.

Dangers like that require more care than just "it looks safe to me". Where are the people guarding the range and warning off intruders? Where is the posted notification of the testing schedule?

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First up, why the hell are you asking here? Ask the people in the video.

Second, you don't know that they don't have permission to do stuff at the airport for say an hour because its posted. Your whole argument amounts to fear uncertainty and danger.

> I'm not trying to take your model rockets away here...

But you'll spout off on an unrelated forum about dangers you don't even know are mitigated? Not to be too blunt, but grow up. These are professional rc modelers. They know the dangers better than you do. You don't design a launch system for a jet turbine rc model without keeping safety in mind.

I spent some time hanging out at an RC club in rural Connecticut that was co-located with a small airport. If you think they just flew their RC machines willy-nilly, you are dead wrong. There was strict coordination with flight control, and real airplanes would take precedence. Traffic was low enough that this worked out well in practice.

And I did in fact witness a jet-powered RC plane being flown there one weekend, which was quite impressive. At no time was a real airplane in danger of some kind of collision.

The point is, RC clubs like this one do think about this stuff, and they do take appropriate precautions.

> This is getting into the speeds seen for muzzel velocities of handguns, and that engine weight a hell of a lot more than a bullet.

No, actually; the average bullet travels at 2,500 feet per second (around 1,700 mph) [1].

Also, the pilot of a member of the Jets of Norway R/C club. These are probably some of the most experienced r/c jet pilots in the world. I'm sure they understand the risks involved better than any of us in this thread.

[1] http://www.mythbusterstheexhibition.com/science-content/dodg...

Handguns are far slower than rifles. .45 ACP usually goes about 1000 f/s. That jet, flying at half the speed of a .45 caliber bullet, weighs at least one hundred times as much. I think that's the point GP was trying to make.

The kinetic energy goes up by the velocity squared but then any damage done by the impact would be a function of the impulse and the cross sectional area of the impact. I certainly wouldn't like to get hit by this, but it is probably less lethal than those rubber rounds they use in crowd control.

edit - Boxer Rocky Marciano's punch was measured at 1028 joules, which is supposedly a greater kinetic energy than an armour piercing bullet. Direct kinetic energy comparisons are not as useful as you might think.

> I'm not trying to take your model rockets away here, but this is not a harmless device.

You're preaching to the choir. The hobbyists in the video are probably more aware of that than anyone in this thread.

I think you struck a nerve here because your entire argument is based on an assumption. Do you have any evidence he's endangering other people? Do you know something we don't, like there's a playground passed those trees, or he just pulled up in this public space and launched the jet without permission?

If not, then don't insult someone that appears to be extremely competent with years of experience, and call them irresponsible because you're jumping to conclusions.

People fly 360 mph missiles around in the air above active airports all the time. Even more dangerously, they often sit in the missile while doing it. Something should be done.

edit - this looks like there is the edge of an airfield on the other side of some pylons. If it is near an active airfield, or if there is any controlled airspace in the vicinity, then I would be incredibly surprised if air traffic control was not kept informed as per the existing regulations.

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