Decompression sickness, Space suits -- Testing, Space flight -- Human factors
Aviation Decompression Sickness (DCS) is a well-known and well documented phenomenon in which a spectrum of physiological and cognitive symptoms result from aircrew exposures to altitudes greater than roughly 10,000 feet, where atmospheric pressures and the partial pressure of oxygen are significantly lower than the mean pressures in which the human body has evolved. The main factors involved in the likelihood of DCS are (a) exposure altitude, (b) exposure time at altitude, (c) preoxygenation / denitrogenization duration and procedure and (d) exercise at the exposure altitude. Mitigation of DCS is largely achieved by (a) preoxygenation / denitrogenization before flight, (b) use of 100% Aviator's Breathing Oxygen during flight, (c) limiting time at exposure altitude, (d) limiting exercise at altitude, (e) use of pressurized cabin and/or garment to offset low ambient pressure and (f) postflight transition-tolower-altitude procedures. I review experimental and review literature on DCS factors and mitigations and present a draft pressure schedule for the Pacific Spaceflight / Copenhagen Suborbitals balloon flight planned to reach 65,000 feet MSL (19,812m) in 2015. The pressure schedule is maintainable with current performance of the Pacific Spaceflight Mark I Pressure Garment (model Gagarin) in terms of pressure maintenance, but a Mark II garment must be built for use with 100% Aviator's Breathing Oxygen and to increase mobility while pressurized, which will decrease exercise at exposure altitude, the most important factor involved in DCS onset after prebreathing protocol. The draft pressure schedule requires the balloon pilot to alter suit pressure 13 times during flight, with important implications for placement and operation of the suit pressure controller, the suit pressure display, and backup suit pressure controllers.
Smith, C. (2013). Review of High Altitude Aviation Preoxygenation / Denitrogenization Procedures and Draft Pressure Schedule for Open-Cockpit Balloon Flight to 65,000 Feet. Pacific Spaceflight Research Brief #2013-2 Review