Col. Kittinger's jump: Terminal velocity?

According to wiki article, Col. Kittinger achieved a maximum speed of 614 mph. It’s not clear at what point in the fall that was, but I would assume that after that point he would have started slowing down. The article as written implies that he was traveling at maximum speed when he opened the chute, but I suspect that that’s just bad editing.

So. . . .

How would the velocity curve on this look? Would he have slown down at roughly the same rate that he accelerated, more quickly or faster? I would guess that his terminal velocity would have been a good bit higher than most skydivers, as he opened his chute in much thinner air quite a bit higher than most skydivers.

Also, 18, 000 feet seems a bit high to open the chute. Was that because he was in freefall at a higher speed that most skydiving, unless it was because the ground in Northern New Mexico was probably 4000ft or so above sea level. It’s not obvious from the article whether the 18000 is above ground level or sea level.

(Also, but unrelated to the question, I suspect some wise guy made the comment about “rope torture made an impression on him.”:dubious:

Terminal velocity was reached, as I recall, at approximately 90,000 feet altitude. He was trailing a small (6 foot diameter?) drogue chute because they weren’t positive whether he could hold a stable position for the duration of the jump.

Main canopy deployment was at 18,000 feet as you noted. At that altitude (in the much denser atmosphere) he would have slowed down to a relatively normal terminal velocity for skydiving - in a normal arch, at slightly lower altitude and without a drogue that would be around 120mph. If he actually kept the drogue down to main deployment altitude (possibly using it as the pilot chute for his main) I’d guess he was going something on the order of 100mph (that’s totally off the top of my head).

I do remember that my old USPA skydiver’s manual had a section on high altitude jumps and there were some big warnings about inadvertent openings at high altitudes where terminal velocity is much faster. The delta V can be large enough to injure or kill people. This was well up above 30,000 feet (normal skydiving operations are limited to about 15000 feet).

ETA:

Not positive why main deployment was at 18,000 but I can think of a few possibilities:

  1. To give more descent time so the recovery crew would be closer when he landed. With an exit altitude of 102,800 feet the potential landing zone was pretty huge.
  2. When it comes to dealing with any kind of problems like malfunctioning gear the skydiver’s saying is “Altitude is your friend” - these were experimental high-altitude jumps and they may have been working with a big safety factor just in case. Kittinger was wearing a pressure suit and plenty of cameras and other gear so he wouldn’t have had the mobility of a sport skydiver.

At 18,000’, air density is about half that of a sea-level atmosphere. A skydiver configured to do 120mph in freefall at sea level would thus be doing around 165 mph at 18,000’.

No idea about these jumps, but generally, skydivers only care about their altitude above ground level, unless your LZ happens to be at sea level, it’s irrelevant.

The question recently came up elsewhere because a new guy is looking to skydive from an even higher altitude, hoping to break the sound barrier during his freefall.

The article provided some useful data: during “freefall” in a vertical windtunnel, the skydiver (in his pressure suit) sustained a terminal velocity (in sea-level density air) of 130 MPH. I did an Excel simulation of his freefall from 123,000 feet, incorporating that bit of data to estimate his drag profile. The results are here. I’ve forgotten a lot about compressible flow, so his speed profile above the speed of sound may not be accurate, but that’s a relatively short portion of the whole freefall. OTOH, if he goes into a head-first dive, he might go even faster.

Kittinger jumped from about 100,000 feet; his velocity profile would be expected to look similar to this (although achieving a lower peak speed due to starting from four miles lower).

OK, I just reran the same simulation, using a jump altitude of 100,000 feet to simulate Kittinger’s jump. Came up with a peak speed of 625 MPH, which is pretty darn close to his actual reported peak speed of 614 MPH. Happened at t=43 seconds, when his altitude was about 75,000 feet. Plots here.

The parachute can be engineered to open/unfold at a particular rate. BASE jumpers want one that goes from “pull the cord” to “full-open canopy” extremely fast, but for Kittinger they probably made a main chute that took several seconds to open, providing a more gentle transition from high terminal velocity to safe touchdown velocity. Likewise with larger objects, e.g. the manned space capsules used for reentry during the Apollo program.

You can become a fan of Col. Kittinger on Facebook!

Well, I’m not on Facebook, but I’m certainly a fan. The picture says it all: http://upload.wikimedia.org/wikipedia/commons/8/81/Kittinger-jump.jpg

You gotta figure Kittenger’s gigantic brass balls must have increased his terminal velocity by a bit.