Metal Guitarist Forums banner
1 - 20 of 28 Posts

·
NSLALP
Joined
·
13,286 Posts
Discussion Starter · #1 · (Edited)
Skydiver preparing for 120,000-foot supersonic fall - CNN.com

Anyone want to speculate on the physical effects of breaking the sound barrier on a human? I'm not entirely sure I understand what happens - the sound waves of your passing are in essence building up behind your axis of flight right? So isn't it dangerous to come back from supersonic? Depending on the altitude at which crossing that threshold occurs, there would be more or less pressure built up behind you, so I could see that wreaking havoc with his parachute or maybe tossing him around a bit extra?

Kudos to Red Bull too :yesway:
 

·
Read Only
Joined
·
1 Posts
This gives HALO Jumping a whole new meaning (High Altitude Low Opening)

I watched a documentary on the US Army Precision Paratroop unit. They basically do Demos at Airshows and such. Well one trick they do is 2 guys basically shoot past each other at like 350 MPH. One time the 2 guys actually hit each other. It severed one guys legs completely !
 

·
Banned
Joined
·
7,428 Posts
Wirelessly posted (A Destroyer of short people: Mozilla/5.0 (iPod; U; CPU like Mac OS X; en) AppleWebKit/420.1 (KHTML, like Gecko) Version/3.0 Mobile/4B1 Safari/419.3)

what a nutcase, that takes serious balls. :eek:
 

·
Bringer of, Satan Ants
Joined
·
3,384 Posts
This dude did not need red bull.
He weighed 150 pounds.
140 pounds of that were brass balls the size of your head. :metal:
19.5 mile freefall. :nuts:

 

·
Premium Member
Joined
·
9,388 Posts
I want to see the math on him hitting Mach 1 in free fall. Jumping 120,000 feet is nuts and all but I'm not sure the breaking the sound barrier claims might be hyperbole.
 

·
Premium Member
Joined
·
23,428 Posts
Hmm...

According to wikipedia, the speed of sound is 1,125 ft/s.

According to Terminal Velocity if the guy is 200lbs and about 2sqft in area, his terminal velocity is 2995 ft/s. I wonder how much force a parachute can handle...
 

·
Premium Member
Joined
·
9,388 Posts
1893 ft/s = 1290 mph. That's almost Mach 2 if he hits it. :eek:
 

·
Premium Member
Joined
·
9,388 Posts
What numbers are you plugging in? I'm not sure how to guesstimate his surface area, drag coefficent are the medium density. :lol:
 

·
I like turtles!
Joined
·
722 Posts
If I had to guess, I'd suggest he's breaking mach1 outside of the atmosphere. When he re-enters he'd slow down to terminal velocity, the parachute will be opening in the same conditions a regular parachute opens, won't it?
 

·
NSLALP
Joined
·
13,286 Posts
Discussion Starter · #13 ·
Without getting silly and actually trying to calculate this, I know there is a shape factor involved in the drag coefficient. We could probably assume he'll present a roughly circular cross-section, but hey, he could be a Canadian with a square body.

Won't the terminal velocity be higher if there isn't as much atmospheric pressure at the higher altitudes? I think we'd have to set up a system of equations to compare the pull of gravity increasing with the inverse square of his distance to the Earth's core vs. the increase of resistance from the atmosphere as he plummets toward sea level pressure. Plus there's water in the air.

But I'm wasting time at work as it is, so why would I try to do that when it's much harder than the work I'm avoiding...? :rofl:
 

·
NSLALP
Joined
·
13,286 Posts
Discussion Starter · #14 ·
If I had to guess, I'd suggest he's breaking mach1 outside of the atmosphere. When he re-enters he'd slow down to terminal velocity, the parachute will be opening in the same conditions a regular parachute opens, won't it?
Terminal velocity is the asymptotic maximum speed in a given set of conditions at which a body will travel - so when falling through the atmosphere, you assume a constant gravitational pull and a constant air medium etc. You wouldn't say he slowed down to terminal. So he will probably reach and maintain terminal velocity at some point, but the terminal velocity will change as he falls. And since I'm going to assume he'll be traveling faster than "ground terminal", he will slow down, but he may be going much faster than usual when he gets there.

Does anyone think returning from supersonic will cause him to get hit from above with the sound of his own passing?
 

·
Premium Member
Joined
·
32,765 Posts
According to Terminal Velocity if the guy is 200lbs and about 2sqft in area, his terminal velocity is 2995 ft/s. I wonder how much force a parachute can handle...
Forget the parachute, what about his body, when it opens?

I almost think you'd have to use a couple parachutes - the dude narrows himself into a pencil shape, breaks the sound barrier, then fans out a little, hits a small 'chute that applies a bit more drag, then follows up with a proper one.

Even then, it's risky as hell, because at the speed of sound he's traveling something like a quarter mile a second - if the world record is a 19.5 mile jump, then if we assume it takes maybe half of the distance to break the sound barrier, that gives him ten miles, at a mile every four seconds, to successfully break his speed to something where he won't get ripped apart by the force of his 'chute opening at almost 800 miles an hour.
 

·
Premium Member
Joined
·
9,388 Posts
Here's an interesting read on the guy who holds the record that is trying to be broken.

Speed of a Skydiver (Terminal Velocity)

On 16 August 1960, US Air Force Captain Joseph Kittinger entered the record books when he stepped from the gondola of a helium balloon floating at an altitude of 31,330 m (102,800 feet) and took the longest skydive in history. As of the writing of this supplement 39 years later, his record remains unbroken.

The air is so thin at this altitude that it would make for a moderate laboratory vacuum on the surface of the earth. With little atmosphere, the sky is essentially black and the sun's radiation is unusually intense despite polar temperatures.

Sitting in my gondola, which gently twisted with the balloon's slow turnings, I had begun to sweat lightly, though the temperature read 36 degrees below zero Fahrenheit. Sunlight burned in on me under the edge of an aluminized antiglare curtain and through the gondola's open door.

The density of air at 30 km is roughly 1.5 % that at sea level and thus drag is essentially negligible.

No wind whistles or billows my clothing. I have absolutely no sensation of the increasing speed with which I fall. [The clouds] rushed up so chillingly that I had to remind myself they were vapor and not solid.

This is not true for skydivers at ordinary altitudes, which is why they reach terminal velocity and cease to accelerate.

According to Captain Kittinger's 1960 report in National Geographic, he was in free fall from 102,800 to 96,000 feet and then experienced no noticeable change in acceleration for an additional 6,000 feet despite having deployed his stabilization chute. This gave him an unprecedented 3900 m (12,800 feet) over which to accelerate. At such extreme altitudes the acceleration due to gravity is not the standard 9.81 m/s2, but the slightly lower value of 9.72 m/s2. Using these numbers, it is possible to calculate the maximum theoretical velocity experienced during this record-setting jump. The result is amazingly close to the value recorded in National Geographic.


As one would expect the actual value is slightly less than the theoretical value. This agrees with the notion of a small, but still non-zero, amount of drag.

At nine-tenths the speed of sound, Captain Kittinger also holds the record for the greatest speed attained by a human without the use of an engine. The standard value of the speed of sound in air at 31,000 m is 300 m/s (670 mph).
 

·
Premium Member
Joined
·
32,450 Posts
A that height, he'll be able to see the curvature of the Earth. Absolutely insane. :eek:
 
1 - 20 of 28 Posts
Top