Skydiver Leaps From 18 Miles Up In 'Space Jump' Practice 192
wooferhound writes "A daredevil leapt from a balloon more than 18 miles above the Earth today, moving one step closer to a so-called 'space jump' that would set the record for the world's highest skydive. Austrian adventurer Felix Baumgartner stepped out of his custom-built capsule at an altitude of 96,640 feet (29,456 meters) above southeastern New Mexico, officials with Red Bull Stratos — the name of Baumgartner's mission — announced today. In today's jump, Baumgartner experienced freefall for three minutes and 48 seconds, reaching a top speed of 536 mph (863 kph), project officials said. Baumgartner then opened his parachute and glided to Earth safely about 10 minutes and 30 seconds after stepping into the void."
Re:air resistance (Score:5, Informative)
If you have very little air resistance, you're not going to be generating any heat (you get hot from the friction caused by the air resistance).
Asteroids, satellites, and space shuttles don't just fall out of the sky, they were already moving fast enough to stay in orbit. Their massive speed helps make them hot. The jumper will not be traveling at orbital speeds, thus the increasing air resistance will be enough to slow him down before the speed+air friction gets high enough to burn him.
Re:air resistance (Score:5, Informative)
3. I understand objects falling from that altitude tend to encounter very little air resistance, which means they pick up a lot of speed. The kind of speed that causes brilliant fireballs to appear in place of anything falling from that height, like asteroids, satellites, and space shuttles.
Not really. Most things that cause brilliant fireballs have a very high initial velocity (and kinetic energy) which must be dissipated when they first reach the atmosphere. This skydiver started with a vertical velocity of zero.
And since the density gradient of the atmosphere is low, a skydiver's air resistance will build up slowly bleeding off this energy gradually.
All that must be done is to bleed off the skydiver's potential energy. For a 115kg (person + gear. I'm pulling figures out of my *ss here) at 29,500m altitude, this is aprox. 32,700 Joules. Dissipated in 630 seconds, this is an average rate of 51 Watts. Warm, but not out of line with being wrapped in an electric blanket.
That same individual hitting the atmosphere at 7750 m/sec (Shuttle re-entry velocity) would have kinetic energy of 3.45E9 Joules. Over 630 seconds this would be 5.5 megawatts, although the 630 second figure does not represent the re-entry time anymore. That time would be less, giving a higher average dissipation rate. And nothing but a few ashes reaching the ground.
Not Really Freefall (Physics Lesson) (Score:3, Informative)
Freefall strictly speaking means 9.8m/s/s which, after 228 seconds, multiplies out to 5000mph. That's an order of magnitude more than Baumgartner's speed. Wikipedia explains:
"The example of a falling skydiver who has not yet deployed a parachute is not considered free fall from a physics perspective, since they experience a drag force which equals their weight once they have achieved terminal velocity (see below). However, the term "free fall skydiving" is commonly used to describe this case in everyday speech, and in the skydiving community."
Still, terminal velocity for a human at sea level is about 120mph which is 4.5 times slower than the quoted 536mph. Taking the square root gives an atmospheric pressure 2.1 times less than normal which translates to him popping the 'chute at about 25,000. Actually he had a pressure suit which would probably slow him down so it could have been higher than that.
Re:Not Really Freefall (Physics Lesson) (Score:5, Informative)
Re:Almost Craig Breedlove Speed! (Score:4, Informative)
Breedlove set world land speed records of 500 and 600 mph, and one of his cars got up to about 675 before crashing.
Its still short of the current land speed record [wikipedia.org] which is 763.035 mph, and slower than the current free fall speed record of 614 mph [wikipedia.org], which was set in 1960 by Joseph Kittinger.
Re:Almost Craig Breedlove Speed! (Score:4, Informative)
Kittinger is a consultant on this project, so I guess he's ok with losing his record :)
Re:Almost Craig Breedlove Speed! (Score:4, Informative)
Yes.
However, the reentry heat one normally thinks of comes from one of two additional vectors (sometimes both!) that make the effect larger than it would be from a simple drop from a balloon.
First, most objects fall from orbit. Depending on how high of an orbit they were in, they were deliberately put at a high lateral orbit speed somewhere below escape velocity.Which as it turns out is pretty damn fast when compared to the atmosphere, so objects returning from orbit "skid in" at high speed compared to the surface.
Some objects from from faster than escape velocity (space rocks, stuff coming back from orbiting the sun or to the moon) and have an additional "get there" velocity.
While a super-atmosphere sky diver might have to contend with speed related friction heat, it's not a large given like it is with other scenarios. With proper propulsion breaking it is possible to step out of a "stopped" capsule after coming in from a moon mission (for example) and drop to the earth in just a specialized suit.
It's not PRACTICAL to do so if you are running a space mission, but it's possible. Kittinger's missions were for investigating other things than reentry from orbit of humans though.
Re:air resistance (Score:5, Informative)
Re:New Extreme Sport (Score:5, Informative)
If you could run this as a business operation, I wonder how much you could charge people for "space jumps"?
I am a licensed skydiver, and I can tell you that the way "normal" jumps are priced is there is a boarding fee generally $10-13 USD and then you pay $1 per thousand feet of altitude. This is whether you get out at 3,000 feet or 13,000 feet. But this is out of an aircraft without needing supplemental oxygen or equipment.
Specialized jumps cost more:
Hot air balloon jumps are usually around $45 and you get out anywhere between 4-6k feet.
Anything above 15,000 feet requires supplemental oxygen, so these jumps can be more expensive.
A civilian HALO jump from 30,000 feet costs around $375.
However none of that applies in this case because of all the specialized equipment for the stratos mission.
For example, the bottom of the capsule is one-use-only. Upon landing, the capsule's bottom absorbs the force of impact and "crumples", so every flight requires a replacement. There is a pressure suit which needs to fit the jumper. There is a custom parachute rig made by Velocity.
Also, the time to altitude takes a very long time, and the winds need to be just right. So it is not uncommon for them to wait days or weeks to have a window to try. They also have a large ground team. So this whole production would need to spin up for each "jumper" meaning at best you could do one or two jumpers every few weeks, at worst, one every month or two.
Not to mention each jumper would need to have a base line skydiving skill set that exceeds what most sport jumpers possess. Figure you would need to have several thousands normal skydives, including HALO jumps, before you could even begin to train for a stratos jump. Training for stratos jump would include many jumps wearing the space suit and custom velocity rig, which is not a standard rig so it has different deployment and emergency procedures. This training would need to include wind tunnel time to work on falling in a stable belly to earth orientation. It would also need to include jumps from an aircraft.
As a business operation you would likely need to charge hundreds of thousands of dollars per jumper, if not millions, and only allow "customers" who meet the qualifications.
So really, you'd have to invest several years in skydiving and have a scrooge mcduck money pond waiting for you at the end of it.
OR, you use the red bull money from all the idiots who drink red bull and you have an awesome adventure on their dime ;)
USPA C-39657