I have two skydiving questions that Unca CeCe doesnt find fitting enough to answer… or… gasp… can’t. Even I dont beleive that.
First I saw on tv (dont tune out yet) that in the late 50’s or 60’s (?) a man in a spacetype suit and an upper athmosphere balloon jumped out and was able to break the sound barrier skydiving. I beleive they said he is still alive today. Would a falling body (literally this time) be able to take the stress? or were early planes that broke up when approaching the barrier of just bad design?
Second… in a separate show it was said that a skydiver doesnt need to breath when in freefall because his body will absorb enough oxygen through the skin. It was also stated that this is the reason that people dont skydive through clouds as the condensation could cause them to suffocate. Sounds way far-fetched to me.
Any takers? any dopers actually skydive?
The wisest man I ever knew taught me something I never forgot. And although I never forgot
it, I never quite memorized it either. So what I’m left with is the memory of having learned
something very wise that I can’t quite remember. -George Carlin
Yes, a falling human can, in fact, exceed the speed of sound without falling apart. This is because humans have much less wing surface area than airplanes.
Humans do not need to breathe while falling. This is because as a falling man approaches the speed of sound, time dilation makes the man’s fall seem subjectively much shorter than it actually is. Once he is on the ground, however, he will discover his twin brother is now an old man.
It should be noted, however, this has never been tested with feminine pronouns.
That would have to be quite an aerodynamic suit, to allow a free-falling human to multiply his ‘normal’ terminal velocity by five.
I saw that claim on Ushuaia and it’s bunk. Cecil and others have debunked the “Goldfinger” myth and this is directly related.
I’ve jumped through rain clouds and I know others who have done so. We all complain about how painfull it is to be pelted by raindrops at 120 mph and joke about hitting the ‘pointy’ end, but none of us felt short of breath.
The reason you’re not supposed to jump through a cloud, is that you’re supposed to have a clear view of the ground below when you jump. It would suck to lose your bearings in a cloud and be forced to land somewhere you could get killed.
Besides, the claim seems to imply jumping naked and discounts the fact that a skydiver naturally continues breathing during the jump. I don’t know of anyone stupid enough to think, “Hey, I can breath through my skin, I think I’ll hold my breath for the next few minutes!”
I suspect the person who gathered that little factoid spent a good deal of time searching the jump site for a “Hammerfor”.
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The show you saw was on TLC. I also saw it. The man was a military jumper testing the limits of HALO (High Altitude Low Opening) jumping. IIRC he jumped from about 60000ft. Thinner air = greater speed.
However, I believe the terminal velocity was somewhat slower.
according to this site: http://www.skyranch.com/faq.htm#howfast
record freefall terminal velocity is 321mph.
I must admit I thought the premise of both questions ridiculous when I read them; and the second most assuredly is. I skydived some many years ago and learned 120 mph as terminal velocity for a human (in the spread eagle free fall position).
Well, anyway… according to my September 1999 issue of National Geographic, on August 16, 1960 U.S. Army Capt. Joe Kittinger jumped from a balloon at a still record altitude of 102,800 feet. According to the magazine he was in freefall for thirteen minutes and reached a speed of “more than 600 miles an hour,…” which, while not breaking the sound barrier, is close enought to say he approached it. The speed of sound in air near the earth’s surface is ~680 m.p.h.
The longest delayed drop and the greatest altitude for any parachute descent was achieved by U.S. Air Force Captain Joseph Kittinger over Tularosa, New Mexico, on August 16, 1960. He stepped out of a balloon at 102,200 feet for a free fall of 84,700 feet (16.04 miles) lasting 4 minutes 38 seconds, during which he reached a speed of 614 mph, despite a stabilizing drogue.
I’m not sure what the speed of sound is at that temperature (-94 F.) and atmospheric pressure (very little, I imagine).
Dangit, beatle! Scooped by 8 minutes.
At least I have a nit to pick; the National Geographic didn’t quote that speed for sound, did they? Mach 1 is 760 mph at sea level at 1 atmosphere.
There seems to be quite a bit of confusion concerning Kittinger’s record. An excerpt from TIME quotes him as saying “Within 9/10ths of the speed of sound for my altitude.” (which seems to agree with Guiness). While a bio claims he was the first man to break the sound barrier without an aircraft at 714 mph. The NG article mentioned 13 minutes freefall, while others mention ~4.5 minutes.
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No, NG didn’t give that number, and I knew it was going to be a little wrong. In my daily life we use 1000’/s for sound in air, while it’s actually closer to 1086’/s. I just multiplied it out. I have a physics reference here that gives it 3.31*10^4 m/s at 1 atmosphere and 0º C, which works out to 740 m.p.h.
13 minutes has got to be wrong; if you just took a near earth terminal velocity of 120 m.p.h., or 176’/s and the near surface gravitational acceleration of 32’/s a 13 minute freefall (assuming that, although the atmospheric pressure up there is significantly lower allowing a much higher than near surface terminal velocity, the gravitational attraction between man and earth would be just barely less than near surface conditions) would consume 5.5 seconds to reach terminal velocity and would have the man travel 25.8 miles. Impossible! The earth would induce significant drag about 6 miles before the end of that journey.
Even using the 4’30" freefall and assuming a terminal velocity of 600 mph is too long w/a linear calculation. But the atmospheric pressure is constantly increasing around this fellow, so he would, I guess, possibly start to slow down before he (or the altimeter/timer) opened the 'chute. I’m not going any deeper tonight, but will say the Guiness number sounds more credible.
Not really knowing, then, how fast he was going when the 'chute opened, I still hope they put some thought into that harness.
So is the speed of sound higher or lower at less air pressure? Of course, I should know, but I don’t; though I guess it would always be slower in a less dense material.
It did really happen. He rode up in a customized Weather balloon, and wore a very heavy pressurized suit and life support system.
He jumped from 102,800 feet. (19.47 miles)
He opened his chute at 17500 feet (3.314 miles)
He free fell for 4 minutes 38 seconds
Landed after 13 minutes 45 seconds
He reached a top speed of 614 mph (9/10ths the speed of sound at atlitude) at 90,000 feet (17 miles).
at 90,000 ft the speed of sound is ~300 m/s (671 mph)
If anyone wants to do the math to fix the silly mistakes above here are your important numbers from the CRC. g(102800ft)=9.7117m/ss g(90000ft)=9.7208m/ss Temp(o-f)=227K-224.5K. a(o-f)=302.37-300.4 m/s
The second premise is too silly to comment on.
I read somewhere online that a Russian Cosmonaut has surpassed these records for altitude and speed, I’ll look on line and get back to you.
About the speed of sound and the aerodynamics about it…
It is very possible to reach the speed of sound (in air) as a human projectile and it is all owed to the aerodynamics of a swept-back wing design. Although most sky divers cannot attain this speed at normal dive altitudes, it is possible and it is a principle that helped to design the World’s fastest planes.
Sweeping back the wing (for those of you who know nothing about aerodynamics, but I guess I probably shouldn’t have mentioned this on here :-)) helps reduce drag enabling the plane to engage higher speeds. (Take a look at an F-14 and its design. It has a lever to sweep back the wing for super-sonic flight). Anyway… back to the show.
Reguar skydivers who drop form 12K or so ft. can push the 200 mph envelope with special suits and techniques. Source: just browse… you can’t miss it.
A swept wing is not required for supersonic flight. The X-1 did not have swept wings. Swept wings certainly help a lot, as does a fuselage shape like a coke bottle.
I believe that sweeping the wings back is needed to alter the center of force relative to the center of mass, so that the plane can continue to produce lift with the appropriate center of force as the air flow characteristics alter drastically going supersonic creating significant bow waves.