Dr Jon Clark is an Associate Professor of Neurology and Space Medicine at Baylor College of Medicine in Texas. He has been the Space Shuttle crew surgeon six times and serves as the space medicine advisor for the National Space Biomedical Research Institute (NSBRI). He was an advisor to both Felix Baumgartner’s Red Bull Stratos and Alan Eustace’s StratEx record-breaking stratospheric skydives. Adventure Medic Editor Matt Wilkes caught up with him to talk about the differences between the two projects and some of the physiological challenges involved in skydiving from the edge of space. Click to see videos of Felix Baumgartner’s jump from 127,852 ft and Alan Eustace’s from 135,890 ft.
How did you become involved with the Red Bull Stratos and the StratEx missions?
I joined Red Bull Stratos in 2009 when the program was starting to spool up. I was approached by Art Thompson, the program manager at Sage Cheshire Aerospace. I had a background as a military high-altitude parachutist and sport parachutist, and had studied crew escape systems and space suits while at NASA from 1997-2005. I was also on the Columbia Survival Investigation Team from 2004-2008, and wrote an article on crew survival lessons from the 2003 Columbia mishap. I started on the StratEx project in 2012 at the conclusion of the final Stratos jump. I have always been interested in parachuting, high-altitude protection, and crew escape.
To the outsider, the StratEx setup appeared much simpler than Stratos. What were the important differences from your point of view?
The wonderful thing about both Stratos and StratEx is that they were both civilian programs that were successful. They used entirely different space suits and concepts of operation. Red Bull, a commercial company, funded Stratos for Felix Baumgartner, who was one of their top athletes, while StratEx was privately funded by Alan Eustace, who paid the bills and made the jump himself. Red Bull sponsors extreme sports events and often has extensive media coverage of events in real time. Stratos also had a major scientific and educational mission. Alan Eustace of StratEx also wanted to forge scientific and technical advances, but didn’t want the media coverage, so we all operated under a non-disclosure agreement throughout the mission.
Red Bull Stratos opted for a capsule system on ascent to have a backup pressure system in addition to the suit and to provide a more thermally-protected environment for the jumper. The capsule added complexity and cost. Red Bull Stratos used the David Clark company for the pressure suit, which was based on the Air Force U2 and NASA advanced crew escape suits. It had a self-contained life-support system that could only cover the freefall period.
StratEx, however, opted for a fully self-contained life-support system and pressure suit for the ascent, float and freefall phase. This was a less complex system. Pressure protection was afforded by an ample supply of pressure and oxygen that could feed any leaks while in the upper atmosphere. The StratEx concept was more like the spacewalks conducted on the International Space Station. ILC Dover was the pressure suit manufacturer and Paragon Space Development Corp built the self-contained life-support system and avionics.
It took 52 years for Joe Kittinger’s altitude record to be broken by Felix Baumgartner, who became the first person to break the sound barrier without an aircraft. Two years and ten days later, Alan Eustace broke the altitude record, but not the speed record, although he also broke the sound barrier. I think this really shows how much things have progressed from government and military programs that started stratospheric freefall, which is now largely done by commercial and private groups.
What was your role as medic on the project?
These were our main medical objectives:
- To assure the health of test parachutist during all segments of the mission.
- To provide medical, safety, and health expertise in planning and implementing procedures, training, and integrated testing of support systems.
- To provide medical expertise, treatment, and planning for pre-flight, in-flight, and post-flight phases.
- To evaluate physiological, scientific, and medical data.
- To coordinate with and assist EMS support at landing sites.
What did you see as the main physiological challenges of the attempts? How were they overcome?
Medical risks included decompression sickness – we reduced the risk for this by breathing 100% oxygen prior to the flight to wash out nitrogen from the blood. We also developed protocols in case of a stratospheric bailout. These included an ebullism treatment protocol for exposure to a vacuum following suit depressurization and a medical protocol for a flat spin with negative Gz acceleration.
We also faced problems with anxiety and claustrophobia from the confines in the suit with Felix. Cognitive behavioural therapy was helpful for this.
The effects of negative G from a flat spin must have been a concern. What could have been done to recover the situation had it occurred?
In a negative G flat spin, the body spins laterally around the centre forcing blood outwards into the upper torso and skull and causing a rise in intracranial and intraocular pressures (toe-head acceleration). It is poorly tolerated and can lead to unconscious and eye damage including permanent blindness.
We knew that a flat spin was a serious threat based on the dummy drops done by the Air Force, and also from the dummy drops of Stratos and StratEx. Joe Kittinger went into a flat spin on his first jump. The solution is to use a drogue chute in the proper configuration. For Red Bull Stratos, Felix wanted to go as fast as possible so he only had a drogue as a backup.
After Stratos, Joe Kittinger suggested future jumps should include a drogue as primary means for stability, which is what we did on Alan Eustace’s StratEx. StratEx conducted multiple dummy drops with a variety of drogue configurations and developed a drogue that would not foul or wrap around the jumper during the unstable period. This is perhaps the biggest technical accomplishment besides the fully self-contained life-support system that was developed. For Alan’s final jump the drogue was so stable he didn’t even rotate at all, which is an amazing accomplishment.
Can you tell us about ebullism?
Ebullism is the physiological response the body undergoes when it is exposed to a pressure below the vapour pressure of water, resulting in body fluids turning to a gas. The blood effectively boils. A major technical advance made during the Stratos program was the development of a field treatment protocol for ebullism using high frequency percussive ventilation. This system was carried by all the medical teams in the field for both Stratos and StratEx.
Despite ebullism being responsible for deaths in spacecraft mishaps, these missions were the first to have a specific field treatment protocol for ebullism.
With Stratos, there was some speculation that breaking the sound barrier in a space suit could be hazardous. Did you have any specific worries? Or was it just that this was uncharted territory?
Analysis of high altitude breakup (SR-71 and space shuttle) revealed the potential for shock wave impingement (shock-shock interaction) that had the potential for serious trauma. Demonstrating that a pressure suit would protect against this at the altitude and airspeeds we encountered was a major objective of the programme. We had aerodynamic experts and modelling programs analyse the threat, which was felt to be unlikely, but we still had to put Alan and Felix out there to demonstrate we could do it.
We read that Alan Eustace didn’t have a cooling system for the ascent – was this of particular concern to you?
Alan’s life support system had a liquid cooling and heating garment (torso, abdomen and legs) very similar to the cooling garment used by NASA. On the ground, heat build-up was the problem, so a cart on the ground cooled the vest. During flight we were facing cold so it ran in the heated mode.
It has been reported that an aim of these skydives was to test out spacesuit technology. What in particular was being tested? And have they indeed advanced our knowledge?
Stratos and StratEx demonstrated that both the thermally-enhanced David Clark S1034 suit (operating at 3.5 psi) and the ILC Dover advanced spacesuit (5.4 psi), could operate in the extreme stratosphere during the aerodynamic loads of supersonic freefall. Both pressure systems had to be integrated with the life support systems, avionics, communication, navigation-location and the parachute systems. This was an incredible accomplishment by both teams. The advances made will be applied to future crew escape systems that are in development.
Photo: Dr Jon Clark / JG Mitter / Red Bull Content Pool
