robie@umbc1.umbc.edu (Mr. William Robie; POSI (GRAD)) (03/04/91)
Ok...I'm not an aeronautical engineer (and I dont play one on tv) but I AM a pilot and skydiver. Frankly, some of the discussion that has been passed around about bungee jumping from an airplane sort of amazed me. More than a little appears to be plain ole BS. First of all, the key seems to me to have the bungee attached at or very near the plane's CG. Since the cord is flexible, not rigid; and since the force of the body falling against it HAS to be, basically DOWN, and a bit aft; and since the force of the falling body can't possible exert many Gs (or bungee jumpers would die), I fail to see why this would be such a big deal?!?? All the talk about C-130s is a bit of nonsense. General aviation planes can handle their entire weight at four, or more, Gs (positive) - actually much more. The force of a bungee jumper would be MUCH less, and would not have near the dead-fall pull of a static line entanglement stopping abruptly at the end of the "dope rope." If I were flying such a plane, I would want some form of bridling system to suspend the bungee from a central point beneath the plane (like is used on water ski boats to centralized the forces of the tow rope), and of course a cutaway system to let the bungee go would be a swell precaution (as is used in glider tows), but the rest of this stuff is nonsensical. Other than rigging, the only big factors would be keeping the weight of the plane's load down, and having a way to get rid of the cord (it would probably be a real pain to retrieve). With proper planning, and enough $$$ to pull it off, the thing sounds quite "do-able." As for asking BJ Worth, good idea! Tell him I said Ptttbbtt! from the hairlips of Louisburg.
bleck@ai.mit.edu (Olaf Bleck) (03/05/91)
|> With proper planning, and enough |> $$$ to pull it off, the thing sounds quite "do-able." Yes, it does, but the key word is "sounds"--wouldn't you rather be sure before you took off? It still would be interesting to get some back-of-the-envelope numbers in the problem. I do a lot of things by feel and they work, but usually there's little immediate risk of life, limb, or $$$! Also, you're deaing with a somewhat complicated dynamic system here, and they can do things which you might not expect at all, but might reveal themselves quite easily by twidling a few numbers. (BTW, none of the numbers that I've seen posted, including my own, I would consider correct. I'll work on it when I get some time...) Or, I'll just sit back with a cocktail and watch you go for first...! -Olaf