I've been watching for the Red Bull Stratos jump; last time I'd heard, it had been stuck on some legal stuff.
Still, I created a skydiver model and then ran a simulation in Mathematica (not Matlab). I tuned the model to the Kittinger jump, although it's pretty close to his maximum speed and altitude/velocity without it. The Stratos jump was compared to the Kittinger jump and jumps at 200,000 ft and 105 Km.
Kittinger reach a maximum velocity of 614 mph; based upon my simulation, I expect the Stratos jumper to reach a top speed of 763 mph. The top speed also breaks the sound barrier, which I think is a first for a human not in a vehicle. The G-forces experienced on the Stratos skydive are about 1.6 G, well within human tolerance. Note that skydivers from higher altitudes can get well over 2,000 mph.
I expect the simulation of the Stratos jump to match reality reasonably well, as its 's close in altitude to the Kittinger jump. I expect the higher jumps are still a reasonably good match, although not as close as the Stratos jump. Even at Kittinger's altitude, you run into issues with estimating air density, which can vary quite a bit depending upon solar activity (space weather).
At a typical skydive height off maybe 13,000 feet, height differences don't mean much and the skydiving experience is essentially the same. At higher altitudes, there is little atmosphere and the jumper picks up a very high velocity. Entering the thicker atmosphere results in significantly higher g-forces imparted to the jumper as drag begins to slow the skydiver down. You can see that at an altitude of 105 Km, the jumper can reach well over 2,000 mph.
Note from the velocity graph that at about 40,000 ft, all high-altitude jumpers end up with about the same velocity. That means that jumpers from higher altitudes have to shave off a lot more velocity. The acceleration curves shows the peak acceleration versus times, with a 105 Km jumper experiencing almost 6 G's.
A question was raised on the podcast regarding spin. The first though might be to consider aircraft spin, but people aren't aircraft, so a lot of the basic assumptions are wrong. Any aerodynamically unstable body will start to spin even in minimal atmosphere, people are about as uneven, ungainly and floppy as projectiles can be. As one reader points out, angular momentum is conserved, so jumping out at altitude with even the slightest uneven torque will cause spin and tumble that's hard to correct. Add to that the limited atmosphere at altitude to push against, and most of the time not even a basic knowledge of what torque it would take to stop the spin, and it can get messy fast. At lower altitudes, there's more chance for uneven drag to start a spin, but there's also more drag to correct it with.
