Extreme high altitude diving (sky) & bubble issues

[detroit diver]

Dr. Deco,

Just read an interesting article on a couple of people about to attempt the world's high skydiving record. They going to jump from 130,000 ft from a ballon with modified space suits, reaching 1000 mph and blowing right thru the sound barrier.

Obviously, deco stops wouldn't quite work here! What do these folks do for decompression/recompression traveling at these speeds of even 125 mph when they slow down? What other issues do they run up against that are pertainent to scuba?

 

[Dr Deco]

Dear Detroit diver:

This is an adventuresome task. That is a very high altitude with a very low external pressure. In fact, it will require a pressure suit. With an external pressure of 0.0424 psi at 130,000 feet, even breathing pure oxygen, there would be too few gas molecules to support respiration. Thus, the pressure suit is necessary.

Depending on the pressure in the suit, it may be necessary to breathe oxygen for a while to purge the body tissue of dissolved nitrogen. With out some type of a countermeasure, decompression sickness could result. It is also possible that the pressure in the gondola of the balloon is at the about the same pressure as the suit and thus no prebreathe is necessary since the external pressure and dissolved gas pressures are equal.

Pressure suits are worn by aviators at high altitude and the EVA suits of astronauts are simply extreme examples of this. The first pressure suit was made for Wiley Post by engineers at the BF Goodrich company (I believe). A race around the globe prompted all of this, since Post found out that at very high altitudes the winds would give him a tail wind boost. He would need to reach 40,000 feet to do this, however. I do not recall if he actually used the device, but the technology was used in later pressure suits.

Dr Deco

 

[scubadoc]

Hello Detroit Diver;

Along these same lines we reported in our newsletterThe Ten Foot Stop for August 22, 2001[/url], on a study sent to me by Dr. Richard Vann at Duke University, "Parachuting and Free Fall after diving?"

"Dr. Richard Vann, DAN researcher, has provided us with some answers to the question of how long to wait to parachute after diving. Not many of us will be doing this but we actually had a question recently from an ardent sky diver as to his length of wait before doing a free fall. If you're interested in a recent study of Military
Free-Fall Parachuting After Diving. http://www.scuba-doc.com/MFFAD.pdf

Best regards for safe diving!
scubadoc
Diving Medicine Online
http://www/scuba-doc.com

 

[Liquid]

DCS suposed to happen when DECREASING pressure. from my understanding than, the DCS risk is on the ascent upward, not on the jump itself, if they go up it shouldnt be a problem (DCS, not lack of enough PFO2 to suport life) as long as they do it slow enough (hm... they go up with a reverse dive computer? RGBM? Haldanian? hm...)untill the suits jump in. The sky dive itself, shouldnt be a problem-like in touch and go dives, where you descent as fast as you can, no deco stops on the way down.

(please correct me if i'm wrong doctors, or if i misunderstood the subject).

 

[Dr Deco]

Dear Liquid:

As I mentioned on several occasions in this forum, decompression that is “off gasing”does not end when you reach the surface. After diving, you are still losing inert nitrogen and are exposed to the risk of decompression sickness. DCS can be brought on by (a) strenuous musculoskeletal activity while onboard ship or (b) by reexposure to decreased pressure.

The most common occurrence for exposure to decreased pressure for the scuba diver is flying home after the dive trip. There are multiple dive scenarios and no hard and fast rule is possible.

If one is in the military, and planning to jump with a parachute, several scenarios are possible but there dive expose can generally be bracketed within some boundary. The first possibility is an underwater swim followed by transport in a pressurized cabin of a plane. When arriving at the jump location, the aircraft cabin is depressurized, the doors open, and the jumpers exit. During the descent, jumpers are at risk of DCS.

Another scenario is when the parachutists are transported to the jump site by unpressurized aircraft. During the transport, they are exposed to reduced pressure, and are at risk for DCS during the plane flight. Anytime oxygen is breathed, the risk of DCS is reduced. Upon arrival, the jump phase is also at reduced pressure and DCS can again appear.

Dr Deco

 

[blacknet]

Dr Deco,

Any comment on the usn flying after diving tables?

Ed

 

[Dr Deco]

Dear Ed:

Other then the standard post-dive waiting times, I was not aware that the USN had a flying after diving table.

Dr Deco

 

[Liquid]

Dr Deco,

Maibe I misunderstood the original post, but I think it didn't mention anything about diving before the jump, and it said that the jumpers are using modified space-suits, so there will not be a "cruiscial" pressure decrease while jumping. so DCS, in THIS case, I do not belive possible.
However-Its the first time I hear about specially pressurized airplanes, for use after diving-before jumping.
It sounds interesting, and I would really like to learn some more about this.

 

[blacknet]

Hello,

I'll move the flying after diving to it's own thread.

Ed