NASA-LLIS-0877

Abstract

<strong>Description of Driving Event:</strong> <br>On May 28, 1993, a NASA astronaut suffered frostbite on eight fingers during manned thermal-vacuum (MTV) testing in Chamber B, Building 32, at JSC. This test was the second portion of a two-part test designed to evaluate the extravehicular activity (EVA) hand tool functionality and flight crew operations for the Hubble Space Telescope First Servicing Mission. The actual test lasted 6 hours in the thermal-vacuum chamber with the suited astronaut repeatedly operating a large number of hand tools and hardware at temperatures as low as 140&#176; F. At the conclusion of the test, upon removal of his extravehicular mobility unit (EMU) gloves, the astronaut noted to the test director that his hands appeared frostbitten. <br>During this test, the astronaut had reported that his hands were cold and that he was experiencing pain. This report was not made in a way that indicated any concern or alarm, and it went undetected by the test team. Astronauts routinely note experiencing cold during MTV and some hand pain is also a normally experienced due to the effort required to function in the pressurized suit gloves. The astronaut never again indicated during the run that he was experiencing pain or cold in his hands. As the test continued, the astronaut operated virtually all of the flight tools, most of them repeatedly. Temperature of the tools and other items was consistently measured via thermocouples at between -113&#176;F and -131&#176;F. Furthermore, these tools required hand & finger intensive manipulation to operate, and were in some instances operated repeatedly for functional verification. <br>The MTV test team as a whole shared an apparently universal perception that the EMU provides sufficient protection to an astronaut in extreme environmental conditions. Failure modes and effects analysis (FMEA) and hazards analysis were accomplished on the test; however, they concentrated on hardware malfunctions and did not thoroughly assess hazards associated with the unique human factors in this test run, nor adequately consider operational hazards. The EMU-specific hazard analysis also did not adequately address hazards associated with exposure to extreme cold. It was also noted during the investigation that certain of the tools did not operate properly, or had not undergone any type of thermal of vacuum testing prior to the MTV tests. Additionally, the thermal effects of these tools on the astronaut's hands were not a design consideration. Nothing had been done to reduce thermal conductivity of the hand tools, and most had bare metal surfaces. There was also a lack of specific test data on thermal effects within the EMU gloves. Tests had been done on maximum allowable temperatures for short/light exposure, and on warmer temperatures for longer exposures; but it is difficult to extrapolate from these to actual temperatures, grasp pressures, length (of time) of grasp and cumulative effects. These factors are also affected by a number of variables in EMU sizing and individual astronaut options.