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Skydiving from 25 Miles Up
chisox writes "The Observer has a story about a retired French army colonel who is soon to make a free fall parachute jump from 25 miles up. In the process he will break the sound barrier, reaching a top speed of mach 1.68 before he opens his parachute 1,000 metres above the Earth. Of course, if the chute doesn't open, the hole he'll make will be about 1,000 metres deep." Well, actually his max speed will be high up and near the earth the atmosphere will have slowed him down to terminal velocity.
I don't think his ears will be in the area which could experience the sonic boom. The sonic boom is actually a cone-shaped are where the sound becomes concentrated (because you are moving faster than it).
I am more interested in how much his suit would heat up if his chute doesn't open due to air resistance and decreasing terminal velocity.`
LedgerSMB: Open source Accounting/ERP
Nope, not at all. Terminal velocity is the max velocity you can travel at a certain point in the atmosphere. You hit it really quickly. By the time he pulls his shoot he won't be travelling any faster than someone who jumped from 15000ft. He'll be going fast when hes REALLY high up and the atmostphere is thin and terminal velocity is higher.
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"it does make you wonder why something like this has not been undertaken by any government agency."
y di vin.shtml
/. injects a space in that URL.
This has been done. I'm not sure why we forget. In 1960, Joe Kittenger jumped from ~20 miles, breaking the sound barrier. See:
http://www.dropzone.com/news/SpaceParachutingSk
A.
ps: I'm sorry that
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If the cute doesn't open, the crater he makes will be the same size if jumps from 25 miles or 10,000 feet. That's how terminal velocity works. Sure he'll break Mach 1 in the thin air aloft, but as he gets to into progressivly thicker air he'll be slowed to the same 55 m/s as any other skydiver. As long as he doesn't tuck into a ball or go head first, that is.
ISTR that the speed of sound changes with air pressure and it's faster when the pressure is lower. The speed of sound at sea level is around 300 m/sec so mach 1.68 at sea level would be around 500 m/sec.
But at 100,000 feet, the speed of sound in that thin air might be 1000 m/sec. So if the guy is falling at 500 m/sec at that altitude, that's really just half the speed of sound there. If he's falling at 1700 m/sec, that sounds awful, sonic booms and all that kind of thing.
So what's the deal?
The force on the parachute when it opens is due to air resistance, which is (roughly) proportional to speed, not acceleration.
The OP's thoughts were probably something along the lines of "Since he's falling for much longer, won't he be going much faster, and hence won't the force on the 'chute be huge?"
The answer is almost certainly "no" though - as he falls, air density increases, creating an extra drag force on the parachutist, slowing him down. So when he pulled the ripcord, he'd only be falling at about the terminal velocity of a skydiver at 1000m. Therefore the 'chute would be subject to similar forces to those of a normal skydiver.
http://www2.tsixroads.com/Corinth_MLSANDY/jk004
including an amazing shot of him taken from the gondola from which he jumped:
http://www2.tsixroads.com/Corinth_MLSANDY/corin
I use Friend/Foe + mod-point modifiers as a karma/reputation system.
Speed of sound is significantly lower higher in the atmosphere, and since there is less air resistance, he can fall faster.
The last attempt, five miles lower, got pretty close to the speed of sound, this should do it. Not sure how safe it would be, but he should break it.
Of course, if his chute doesn't open, he becomes his own airbrake and bursts into flames.
I am a science fantasy fan
Disclaimer: I am a skydiver, has slightly more than 300 jumps, so I am not really that experienced.
I have been doing a jump from 22000 ft = 6700 meters. And I also experienced the thin air, making it more difficult to turn, and my speed max was around 300 km/h, where it normally tops at 200 km/h on a normal skydive.
At deployment time (1000 meters / 3500 ft), the thick air near the planet had slowed me to below 180 km/h.
4) Everyone in Slashdot knows the story and knows that it is an urban legend (U) for untrue.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Will he really experience a sonic boom? If so wouldn't that destroy his ear drums.
Actually, no. The sonic boom is never heard by the body traveling at supersonic speeds, wether it be plane, rocket, or person. Concorde passengers are unaffected by the boom.
The conical shock waves never touch. At least they aren't supposed to. Now, since a person is thin like a rocket, I am sure he won't have to worry about shock waves.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
check out his home page:
e s/ gb_accueil.html
http://www.legrandsaut.org/
or straight to the english version:
http://www.legrandsaut.org/ressources/gb/gb_pag
He has some movies and facts and explanations and interviews....etc
few on land.
Just because several (I know of at least half a dozen) sites have that sound-barrier quote, that doesn't make it true.
;)
I consider the several links on that page as a good cross-section of sources, and from what I read, I agree with Kittenger himself that the most reliable information is that he achieved 90% of the speed of sound at his altitude. The most credible information was that his top speed was 614mph, and that somebody somewhere made a typo of 714, hence many sources believed he broke the speed of sound. It turned into one of those urban myths. There was no evidence at all that he broke the sound barrier, and reasonably solid data that he didn't, and the man himself agreed with the 614mph data. Also, the math agrees with this, showing that another 1300m or so of altitude is needed to break the sound barrier.
It's not like everybody was out there with their own altitude radar taking measurements. I'll side with Kittenger's own opinion, that the radar reading was the most reliable, and that the man himself is more likely to be correct than a few sensationalist storytellers.
So when the data and the people involved say he didn't break the sound barrier, I'd say that's the closest to definitive that we have.
Disclaimer: No, I don't believe anything simply because it's posted on a website. But I remain happy to disagree with you. Enjoy!
GE once designed a device called the MOOSE, to allow astronauts to bail out from orbit and re-enter the Earth's atmosphere with little more than a space suit and plastic cocoon (remember that early heat shields where basically a big slab of high-temperature plastic that would flake off during re-entry).Here's one link about the MOOSE: http://www.boggsspace.com/strange_but_true.htm
There's a 100ft bridge where I live that people jump off of into the river below. People do it all the time, and it would be perfectly safe if people didn't have a disturbing tendancy to go straight through the 8 feet of water and get stuck in the mud at the bottom, and drown because they can't free themselves. Oops. They also have their arms stuck out when they hit the water, so they get the belly-flop effect on their under-arms only 30 times as bad. Big blood-blisters and stuff. Nasty.
They have a section on how to survive if your parachute doesn't open; part of what they tell you to do is signal to other jumpers in the air that your parachute won't open, dock on them, and hold on to them until landing. First of all, everybody else will have deployed by the time you realize you're in trouble,
Why would that be? You pull your cord, and nothing happens. You pull you reserve cord, and nothing happens. That takes all of ten seconds. What says everyone is going to pull at once?
and even if there were people with you, you wouldn't have time to dock onto them, get a good grip on them, and let them pull.
Why not? It seems to me that some dives have minutes in the air, which is probably time enough.
It would take a VERY good grip on them too -- the deceleration of them pulling with the added weight of you hanging on would make holding on a bit difficult.
The WCSSH says that, and recommends that you put your arms through their straps.
It's a good story so I don't want to Lone Gunman it. Suffice it to say, no one gets killed and those involved weren't QUITE that stupid. There is a true story that gave birth to the urban legend. What REALLY happened isn't quite like the parent quoted Legend.
. ht ml
http://www.wagoneers.com/pages/RocketCar/rockit
However, you're absolutely right in that it's not that hard to safely dive from much greater heights. I've personally seen people do 30 metre dives at acquatic shows.
Any sufficiently advanced technology is indistinguishable from a rigged demo
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