TEMPUS facility - MSL - Spacelab operations and future design

TEMPUS is an electromagnetic levitator for containerless processing of metals and alloys in a high-purity atmosphere and under reduced gravity. TEMPUS allows the investigation on nucleation kinetics by statistical analysis of achieved undercooling temperatures. Solidification speeds can be recorded dependant on the amount of undercooling. Thermophysical properties of even highly reactive metals and alloys can be measured above the melting point and below in the undercooled state. This includes the measurement of specific heat, heat of fusion, thermal conductivity, surface tension, viscosity, thermal expansion and electrical conductivity. TEMPUS was used for experiments during the Spacelab missions IML-2 and MSL-1 on the US Space Shuttle in 1994 and 1997, respectively. A technical description and technical data of the facility are presented. Performance data on vacuum level and temperature measurement accuracy are given. The experimental techniques on studying solidification and thermophysical properties are explained. The success of the Spacelab experiments initiated studies on the design of a TEMPUS facility for the International Space Station. The experiments shall be executed in an experiment container which is used for a sealed transport of the samples up and down. Pyrometers, cameras, vacuum and gas system and other infrastructure would stay on the station. Coil system, process chamber walls and other components which might be affected by evaporated sample material will be part of the experiment container and thus be refreshed with every exchange. By and during the exchange of the experiment container the facility i.e. the diagnostic and stimulus systems can be reconfigured for the specific needs of the next sample charge.