h a l f b a k e r y"My only concern is that it wouldn't work, which I see as a problem."
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Streaming smoke, the daredevil would be jumping from
a
plane into a bay or
lake that's
deep enough that he wouldn't hit the bottom.
You need to increase the time of deceleration, that
is, the time between when the guy hits the water and
when he stops. So as counter intuitive as it sounds,
you
need to put very heavy weights on the underside of him.
He'd have to be heavily armored and the weights would
have to be attached to that armor or else they'd rip him
apart when they hit the water, but they'd lengthen that
time of deceleration that he'd need to survive.
He wouldn't fall any faster through the air and hit
any harder, he'd just decelerate much more slowly once
he hit the water because the additional mass would push
through the water more effectively and the water would
take longer to stop him. I'm guessing maybe 300 pounds
of weights located on his underside might do it but
whatever it takes. 500 pounds, 1000?
Of course he'd have to have a quick release mechanism
that dropped the weight package as soon as he stopped.
Televise it and you could probably generate some real
ratings and real money.
After he hit the water, would he pop up victorious with
his fist pumping
in the air of float up face down? It would be the
textbook breath
holding moment. For the audience and him.
A 30 second job with immediate retirement one way or
another.
(NOTE: This post has been changed from the original
idea which was just to have a shock absorber of some
kind.)
belly flop
http://www.bbc.co.u...rld-europe-12773427
[pocmloc, Mar 19 2011]
(?) This one's a little higher.
http://www.youtube....watch?v=C_tvMhzM7GM
Sorry about posting a tubby guy in a Speedo, but it's for science. [doctorremulac3, Mar 19 2011]
Higher still
http://www.youtube....BDo&feature=related
Featuring the worst video edit in history [doctorremulac3, Mar 19 2011]
Speed_20Demonstrati...bit_20For_20Museums
[spidermother, Dec 24 2012]
Here's the old net version actually being done.
https://www.youtube...watch?v=aPC_h9Vmlxw
[doctorremulac3, Feb 16 2023]
And a not at all what I'm talking about water landing with a wing suit.
https://www.youtube...watch?v=o2xmAWS4akE
Don't even bother watching, he skims along the water and stops. Not even a stunt in my eyes. [doctorremulac3, Feb 16 2023]
[link]
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I've always wondered what sort of apparatus would allow a
water-landing at freefall speeds. A cone (or maybe
something exponential) would seem most suitable. |
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On the other hand, such a cone (plus the fact that one would
be falling upright, not face-to-earth) means that the
terminal velocity would be well above 120mph. |
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Yea, I thought about that. Maybe the cone could have slots in it that catch the air but still push the water out of the way. Sort of like a cone shaped sieve. |
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It would certainly be an interesting engineering challenge. |
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The seive idea is interesting. |
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Maybe no cone needed. Just a horizontal disc of seivish
material, on the end of a long pole, with the jumper
strapped securely to the top of the pole. |
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The seive would hit and enter the water, and would
decelerate rapidly (due to drag) but not instantaneously,
perhaps slowing the jumper from 120mph to 0 by the time
they touched the water. With a 10ft pole, this would
mean a deceleration of around 50G, which should be a
doddle. |
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Great idea [MB], but deceleration to zero is excessive (and also stops [DrE]’s showbiz cliffhanger). What’s the terminal velocity of the highest highdivers? |
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The limit of competitive high-diving seems to be
around 50m. Assuming air resistance won't really have much
effect from that height, that would give a fairly meagre
terminal velocity of 10m/s, or 20mph. That doesn't seem
very terminal to me. |
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Your calculations don't seem to match mine. A fall of 50 meters in a vacuum should give a velocity of not 10 m/s, but 31 m/s which translates to about 70 m.p.h. |
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Highest olympic platform is only 10m. I find some reference to 15m platforms, but nothing approaching 50m. |
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You're right [NOYK] - my numbers are broken. 70mph seems
much more manly! |
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MechE - google "highest high dive" or similar. |
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I was refering to competition high diving, not saying nothing goes higher. |
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F(drag)=1/2rho v^2 Cd A -Form drag equation |
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v=sqrt (m a 1/2 rho Cd A) -solving above for v |
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a max ~= 50g -upper limit of surviving accel. |
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v=sqrt 2g h -equation for v from a fall |
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2gh=m 50g 1/2 rho Cd A -combine the above |
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h(max)= m*12.5*g*rho*Cd*A -solve for h |
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This is the solution for where deceleration due to being in water becomes lethal. This ignores skin drag, and any surface tension effects from the water. It also ignores air resistance on the way down. I don't know what the Coeffecient of drag is for water, and 50g is the "it will kill you" limit rather than the safe limit, but it seems like this should be a start. |
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So what's the minimum distance you need to go
from
terminal velocity, say 120 mph (?) to a dead stop
without getting killed? |
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2.93m minumum at 50g. It's inverse with acceleration, so if you want to hit a safer 10g, it's 14.7m. distance=v^2/(2*a) |
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The cone itself may increase the terminal velocity to even more dangerous proportions. What an absolutely necessary stunt, however. + |
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//heavy weights on the underside of him// As long as the armour is effectively one-piece it shouldn't matter where the weight is concentrated, as long as the structure that integrates it is what hits the water. |
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The combination of a child, a wingsuit, and a waterfall ought to work every time. |
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//on the end of a long pole// |
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//slowing the jumper from 120mph to 0 by the time they touched the water//
It would be a real anticlimax if they slowed to zero before they hit the water wouldn't it!
"Ooh look, mum! 'E's just stopped in mid-air!"
"Yeah, what a let down! It's a bloomin' cheat!"
"Just 'angin' there, 'e is! I want my money back!"
"Boo! Boo!"
[riot ensues] |
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//Water pogo.// Aha! (Off to write...) |
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With an explosive and exceptional timing, a lovely column of water could be made come up and cushion you to less impact prone situation. |
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Didn't Mythbusters do something along those lines? |
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If not, it's right up their alley. They've got a website where you can post ideas, but the best way to get them to do it would be to simulate it on the web, get 5 million hits and goad them into investigating it. |
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It should work, it's pretty much just a water version of an airbag. |
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I think having the dude swathed in armor makes it less appealling. He should have ntohing but a Speedo, a bathing cap, and moustachios flapping in the wind. |
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I think the answer is in the water. By having a bubble source deep underneath the target one can decrease the density of the water column such as to gently decelerate the diver over 60 or 70 feet. It may be more practical for the diver to continue down rather than up, meeting up with scuba-equipped helpers at the bottom so that he can remain there a while. This would also allow increased suspense as his cap floats ominously to the surface alone, then his suit, then his moustachios. Then the diver himself emerges triumphantly! |
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Considering this further, bubbling the water with a mix of oxygen and hydrogen would allow ignition, so that the water could unexpectedly explode into flames just as the diver made contact. Such an event is always welcome at displays of this sort. These would be relatively cool flames, with a lot of spray so it would all be ok. |
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I love the idea of a bubble / explosion hybrid. |
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The neat thing about a stunt like this, nobody
would want to be the one who didn't see it. Even
people who thought such a display represented
the low point of human civilization would want to
see it just to be able to make derisive comments
on "...that idiot with the speedo and the massive
flapping mustache plunging to his possible
death..." |
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If people will watch a fat guy dance badly to
"gingham style" or whatever that thing is called
they'd certainly watch this. |
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There would no doubt be some company wanting
to get in on this as a sponsor. Farmer's Insurance?
Speedo? Rentisham's Traditional Flenting Wax? |
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What if the diver was headed for a pool of lighter
material? Like jet fuel? Also He could have 2 stage
weights on him, one breaks away immediately. The
other, 2 seconds later. |
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I'm thinking keeping it simple it would be less prone to failure. |
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I just saw the Mythbusters exhibit yesterday at our local science museum and it occurred to me this would be perfect for their show. They do the accelerometer on the crash test dummy thing all the time. |
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It's got the two things you need for a good Mythbusters test: controversy and danger. |
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