Rocket Men

theodp writes "Slate reports on the guys who really, really want to fly, who got together the other week at the Niagara Aerospace Museum for the First International Rocketbelt Convention. To date, only 11 men in history have free-flown a rocketbelt (aka JetPack). More men have walked on the moon. Why? 'It's not a matter of if you get hurt, it's when,' says Eric Scott, an ex-stuntman who's in the exclusive club."

Comments

Re:Gyroscopic stabilizers

[evanbd]

And while we're at it, that's a *hell* of a lot easier said than done. You can't do it on cheap gyros (read: you're probably spending $5-10k per axis), and they're not particularly light weight (a couple pounds each may not seem like much, but it eats into your fuel budget quite quickly). And you need a *good* control program, which isn't easy to write. Getting it mostly right wouldn't be too hard, but would you trust your safety to "mostly right"? To date, only one VTVL rocket vehicle has demonstrated fully autonomous takeoff, hover, and landing (John Carmack's vehicle over at Armadillo Aerospace). It ain't easy.

Also, don't forget you have to build the rocket motors and feed system and such. Most belts so far are peroxide monopropellants -- a good choice IMHO, but peroxide is hard to get and takes a lot of care to handle safely. And building any size rocket motor and ensuring it's safe enough to stand next to is a bit of work.

What I'm saying is, if you're a single amateur, or a small group, then building just the rockets is a big project unto itself. It shouldn't surprise you that no one has the time, money, and skills to do that, *plus* build and test the IMU, *plus* write fly-by-wire control software for it. If a modest sized startup company decided to pursue the matter, with a bit of financial backing, I would expect they could get it all built without too much hassle (provided they had the appropriate expertise in all areas, obviously). Oh, and don't forget that your software has to handle a non-fixed CG if the person moves about much at all.

What about women?

[Dan East]

To date, only 11 men in history have free-flown a rocketbelt (aka JetPack).

According to the Wikipedia article, at least one woman (Isabel Lozano) has flown one as well (happened almost a month ago).

As to why haven't more people flown the device, take a look at Isabel's pictures, and you'll see that had to make a custom cast of her body for the mounting hardware the device uses. Also, for some reason many people may not feel very comfortable with jets of gas at 740 C venting at supersonic velocities mere inches from their body.

Dan East

Re:Sounds like a job for real-time computers

[GeeksHaveFeelings]

The Wright Brothers achievement was ''not'' building an aeroplane that could get off the ground; it was building an aeroplane that they ''and others'' could get (relatively!) ''safely'' off the ground.

What? Their first airplanes were insanely unstable. It was harder to control than a F/A-22 now, except the F/A-22 has a powerful computer to keep it stable. It had next to no dihedral and its horizontal stabilizer was in front of the plane, while the vertical stab had next to no moment (so it was pretty useless, though better than nothing). They could pilot it because they had practised on equally unstable unpowered gliders for years. What they achieved was a new, working model of aerodynamics (as nothing had existed at the time for propeller design and the existing knowledge about wings were wrong), a light, high-powered gasoline engine, and an airplane that could get off the ground and was cheap. It was however, not at all safe or even remotely pilotable by modern standards.

Re:rocket "belt"

[westlake]

Why is it called a rocket "Belt", when it's typically something the size of a surfboard with a pair of propane tanks that you strap on your back?

The rocket belt made its first appearance in comic strips like Flash Gordon around 1934. It is everyone's evokes dream of someday flying like a bird, without the need for magic.

Re:Gyroscopic stabilizers

[evanbd]

Not entirely true. I have spoken with multiple people directly involved in the area -- gyro-based IMUs for rocket vehicles -- and the FOGs are clearly superior. AIUI, some of the recent MEMS gyros *might* be good enough for low-accuracy use, depending on the application details, and how much other sensor data is available to correct with.

I do know that at least until recently, inexpensive gyros were completely unusable. Modern ones appear better, but my sources suggest that they aren't all the way there yet. It's possible there are good gyros out there that haven't been tried in this application and that I haven't heard about; I'm not averse to admitting my knowledge could be out of date or incomplete. I am, however, quite confident that the problem is not so easy as the OP implied.

And for reference, IAARS, and I have read detailed discussions by people doing actual investigation with real hardware testing of exactly this problem -- and I'd say that makes me better qualified to comment than the vast majority of posters. But, like I said, not infallible -- so please don't jump on me for admitting my fallibility.

Re:Gyroscopic stabilizers

[wjsteele]

To date, only one VTVL rocket vehicle has demonstrated fully autonomous takeoff, hover, and landing (John Carmack's vehicle over at Armadillo Aerospace).

I'm not sure they've actually conducted a fullly autonomous test. According to their web site, they've only done very limited tethered tests.

However, I know the Delta Clipper (DC-X) and it's follow on (DC-XA) had several sucuessful tests, fully autonomous. But even they had a bunch of development issues that eventually lead to the programs cancellation.

Bill