Human Thermal Vacuum Testing of International Space Station Extravehicular Activity Mechanisms

Successful construction and maintenance of the International Space Station (ISS) relies heavily on manual actuation of a variety of mechanisms during Extravehicular Activity (EVA). These items must perform within crew capability in orbital thermal and vacuum conditions [−150° F<T<200° F, 10⁻⁷ torr]. To verify that hardware is crew-compatible, NASA Johnson Space Center is conducting a series of Human Thermal Vacuum tests, 3-4 tests per calendar year, in which a suited astronaut enters a thermal vacuum chamber and actuates thermally conditioned space station hardware. To date nine such tests have been performed to evaluate common ISS hardware as well as unique mechanisms that will be launched prior to assembly flight 13A. Key findings include high fluid valve and hose forces, manageable electrical connector and line behavior, unexpectedly high launch bolt break torques, and smoothly deployable telescoping structural elements. This paper presents an overview of the test series including the process used to select hardware for testing, test chamber capabilities, typical test set up and conduct, and highlights of hardware performance to date.