Orbital Flight Preparations of Get Away Special Payload G-572: Design and Testing of Electrical Systems

University of Utah

Orbital measurements of the cardiac function of Space Shuttle crew members have shown an initial increase in cardiac stroke volume upon entry into weightlessness followed by a gradual reduction in stroke volume. In an effort to explain this response, it was postulated that gravity plays a role in cardiac filling. A mock circulation system was designed to investigate this effect. Preliminary studies carried out on the NASA KC-135 aircraft, which provides brief periods of weightlessness, showed a strong correlation between cardiac filling, stroke volume, and the presence or absence of gravity. The need for extended periods of high quality zero gravity was identified to verify this observation. To accomplish this, the aircraft version of the experiment was reduced in size and fully automated for eventual integration into a Get-Away-Special canister for the orbital version of the experiment. Three nonlinearities, that govern the ability of the apparatus to regulate to a mean cardiac outflow pressure of 95 mm Hg, were identified and minimized. In preparation for an anticipated 1997 shuttle flight, the automated system was again flown aboard the KC-135. The control algorithm was successful in carrying out the experimental protocol, including regulation of mean outflow pressure.