On August 27, 1960, Joseph Kittinger, Jr. parachuted out of a balloon at an altitude of 102,800 feet. He free-fell for more than four-and-a-half minutes through temperatures of -94 degrees fahrenheit, reaching a speed of more than 600 miles per hour — almost the speed of sound — before deploying his parachute at about 18,000 feet and floating safely to earth.
Two questions:
(1) Why didn’t he burn up in the atmosphere? Or at the very least, explode? I’ve seen documentaries about Mach-speed flight, and part of what made it possible was meticulous attention to the shape of the aircraft. Models without proper shapes spontaneously blew up.
(2) Why didn’t his parachute yank his torso from his hips when it deployed? Or, why didn’t the parachute itself just disintegrate from the sort of friction that a wide sheet would encounter at such a speed in full atmosphere?
Afterthought bonus question:
(3) He says that his right glove had a tear in it, but that he told no one so that his mission would not be aborted. Given that a man’s blood will boil at 60,000 feet (according to him), why didn’t he die with blood rushing to his hand and building up enough pressure to push right through his skin?
(4) Kittinger’s camera showed, and he attests to the fact, that the sky around him was pitch black, and that the roundness of the earth and the haze of its atmosphere could be seen below him. Well, if he was above the atomosphere, how did his lighter-than-air ballon get him there? It wasn’t lighter-than-space, was it?
Likely the highest velocity the guy achieved was in the thinnest portion of the atmosphere. Since there is less air, there’s less drag and a higher terminal velocity is possible. Also since there is less friction there would be less heating of the guy’s body.
This leads to answer number two which is that he slowed dramatically to a normal terminal velocity closer to the ground. Hence the lack of free falling shoulders.
As for skin, at most a 1 atmosphere pressure difference between the outside and inside of the skin will not cause it to rupture or the blood to boil. It might lead to sweat or saliva to boil off, but it’s a cold boil caused by atmospheric pressure.
Finally at 20 miles you’re above the majority of the atmosphere’s mass. The balloon was simply less dense than its surroundings. Must have been a damn big balloon though.
At the altitude he jumped the air is very, very thin; as he plummeted down the amount of air particles he encountered was, compared to sea-level, very small, so it was less air to push through, that´s why he accelerated to 600 MPH, that was the terminal velocity his body had on those conditions (rarified air at high altitude), simply there wasn´t enough air to slow him down; think of the difference walking on a pool floor and walking against a heavy rain.
The aerodynamic forces were tha same as if he was on a normal sky-dive, he reached terminal velocity, the two factors involved in that are his weight and the density of the air surronding him; as he fell down the air density increased so he actually slowed down as he fell. So I think that it would have felt pretty much the same as falling from a Cessna.
So… there wasn´t much air rushing around him, that´s why he didn´t burn up, in any case 600 MPH, even at sea-level, wouldn´t generate that much friction heat.
As I said, as he fell through and ever increasing density of air he slowed down, by he time he opened his parachute he probably was doing much less than 200 MPH, besides if I were the man in charge of designing his parachte I´d use one that wouldn´t open instantly, or a smaller drag chute to stabilize and further reduce speed.
Perhaps his air supply was able to keep up with the loss of air through a small tear; I remember reading how the Apollo lunar module was designed so that it´s air supply would keep a constant pressure inside for several minutes even with a hole a few inched wide on the hull.
As for the last question, there´s still some air at that altitude, the volume of that air displaced by the balloon was still lighter that the same volume of air.
Capt. Kittinger’s peak speed was less than 700 mph. Spacecraft re-entering the atmosphere from orbit are traveling at something like 17,000 to 18,000 mph.
One small nit-pick. The heat generated by a vehicle re-entering the earth’s atmosphere is not due to friction but from increased pressure. Boyle’s law says as the pressure increases (and volume remains the same), the temperature increases. Effectively, the leading edges of the spacecraft are pushing the molecules in the air into a small space (before the molecules can slip around the edge) creating a localized high pressure area.
So the answer to why he did not burn up is that the higher pressure areas created by his body did not increase in temperature enough to cause him to combust.
Using the standard atmosphere calculator available on line and assuming he reached max velocity of 880 ft/sec (600 mph) at 70000 ft altitude the stagnation pressure only turns out to be about 1.6 times ambient. This would give a temperature of 176[sup]o[/sup]F. In an insulated space suit with cool oxygen being provided this would be survivable as long as the oxygen lasted. And this figure is admittedly pretty rough. The temperature might not be that high because he might have reached max velocity at a higher altitude which would reduce the stagnation pressure and thus the temperature.
And of course he slows down after reaching max speed and the stagnation pressure falls off as the square of the velocity, although it does rise with increasing density.
This is only rough but it does show that the temperatures reached are no where near the “burn up” level and the fact that he didn’t burn up sort of proves that. At least we now have a ballpark figure.
Ok, so this discussion raised an obvious question in my mind: For safe reentry why don’t they slow down reentering spacecraft to a speed which doesn’t involve the danger of burning up?? Goodbye ceramic tiles. I can imagine any number of ways this could be done, and it seems a more obvious solution than hurtling through the upper atmosphere at 17000 miles per hour.
I was always under the mistaken impression that the acceleration due to gravity is enough to heat you to a crisp. Hearing about an (relatively) unprotected human being falling safely to earth is kind of heartening and fascinating… What if you’re an astronaut jumping off a spaceship in fixed orbit… with a parachute…would you fall to earth in the same manner?
A 10 ton spacecraft in orbit 150 mi above the surface has a kinetic energy of about 1.510[sup]11[/sup] ft lb and a potential energy of about 1.610[sup]10[/sup] ft lb. In order to slow it down you need to carry enough fuel to get rid of the kinetic energy and that is about 90% of the total. So you would have to carry a lot more than twice as much fuel than is the case using the present scheme.
Please name one of the ways. the Shuttle, for example, glides in from orbit. It has to slow from orbital speed, more than 17000 mph, to a speed condusive to landing on a runway, a bit more than 200mph. It does that mostly using atmospheric drag. To get it to slow down to a speed that wouldn’t cause the heating, you would have to use a lot of fuel, which you would have to carry into orbit, and taking a pound of fuel into orbit means a few more pounds of fuel you have to use to get into orbit.
When the shuttle takes off, it weighs more than two million kilograms, but the landing weight is about a hundred thousand kilos. The remaining 1.9 million kilos is mostly fuel that is used to get it into orbit.
Rutan’s SpaceShipOne didn’t need heavy shielding because it didn’t go into orbit, it just went up and down, like the balloonist.
An astronaut in orbit would be in orbit, and would decelerate the same way as the space shuttle, and would require shields.
Kittinger reached his highest speed at about 90,000 feet (even higher than the 70,000 feet that David Simmons reckoned on).
He was stabilized during freefall by a small (about 6 foot diameter) drogue chute, deployed soon after he left the gondola. The fear was that he wouldn’t be able to hold a stable body position and would spin out of control (not really an issue as it turns out).
Main canopy was deployed at about 18,000 feet. I don’t know if it was actually pulled out by releasing the drogue as a pilot chute but that seems likely. That’s much higher than a sport jumper would deploy, but by that point he’d slowed down to a more reasonable velocity and if the drogue was still deployed he was probably not going much faster than normal terminal velocity. In the USPA Basic Safety Regulations discussing high altitude jumps they do warn of the dangers of inadvertant openings at very high altitudes (we’re talking 8-10 miles up) - suddenly slowing from 400 to 100mph is much worse than going from 120mph to 10mph.
Balloons can go that high (and higher, Nick Piantanida went up to 123,000 feet on his unsuccesful, and fatal, attempt to break Kittinger’s record) because there is still some atmosphere left for them to be lighter than. At 100,000 feet you’re above something like 99% of the atmosphere but a balloon is extremely large and filled with helium so there’s a lot of bouyancy. We did some figuring on this a few months back using basic atmospheric density/altitude equations and known weights of envelope material (mylar) and you can go surprisingly high in a balloon.
The glove leak wouldn’t necessarily be fatal - his hand hurt like hell as I recall, but if the opening didn’t bleed off all the oxygen from the suit damage would be limited to his hand.
What killed Nick Piantanida was that his helmet seal was breached at 123,000 feet. They’re not positive how it happened but even though ground station was alerted immediately and remotely cut the gondola free (it freefell down and deployed a cargo chute automatically) his air supply was gone very quickly and he suffered pretty severe damage and died shortly thereafter.
blood does not “boil” in space. in fact there have been animal tests that prove blood does not boil, and there was even a human skin exposure to space and the guy’s blood didn’t boil.
The speed needed to achieve low earth orbit starts around 9.4 km/s(about 21,000MpH). Imagine firing a bullet at such a velocity that it reaches the horizon before it can fall to the ground. That is orbit; falling around the earth. Felix Baumgartner and Colonel Kittinger both went (basically)straight up and staight down. A rocket must reach a horizontal speed that will keep it from falling to the earth but not so fast that it continues to climb in altitude. Once achieved, no additional energy is required and the object will fall toward the earth indefinitely. To re-enter from orbit requires a loss of speed(energy) equal to the that required to reach that speed. The atmosphere provides that breaking; a delicate balance between friction(heat) and g-forces(human tolerance) limit that breaking. A motion-less body aka skydiver would accelerate in the near vacuum at 32ftper sec. etc. until encountering drag from air and then would decelerate to about 120MpH. If a person were to enter the earth’s atmosphere from orbital speed; poof!!