The Revolutionary Tempus

With four times as much time aloft as had been possible on STS-83, the scientific teams associated with both LIF and TEMPUS were gathering so much data that many were confidently expecting to spend at least a year analysing it all. The unique TEMPUS electromagnetic-levitation facility yielded the first measurements of specific heat and thermal expansion of glass-forming metallic alloys and, in so doing, obtained the highest temperature (2,000 Celsius) and largest undercooling ever achieved in a space-borne furnace. Moreover, significant progress was made in learning how to control and position liquid drops, using electromagnetic means.

So revolutionary was the facility, which flew first on IML-2 in July 1994, that NASA guaranteed its German manufacturers a free-of-charge flight on board the Shuttle in exchange for American participation in using it. In total, 20 investigations were conducted and almost a quarter of a million commands transmitted during the 16-day mission. On 10 July, materials scientist Robert Bayuzick of Vanderbilt University expressed delight at how well his zirconium samples - found in ceramic and refractory compounds - turned out. ''We're doing fundamental science, so like always it's a long stretch between the fundamental science and the applications.''

The shortened flight in April had actually proved beneficial to several investigators using TEMPUS, since they were able to examine the characteristics of the facility and their samples and make adjustments and improvements where necessary. On the whole, it performed admirably, with the exception of a problem with one of its television cameras, although a few experiments had to be terminated when their samples inadvertently came into contact with the side of the container. ''Before the sample stuck to the coils, we were able to get some good data,'' said Principal Investigator Hans Fecht of the Technical University in Berlin.

Other studies of the heat capacity, thermal conductivity, nucleation rates, surface tension, viscosity and thermal expansion of a variety of glass-forming alloys proved enormously successful. During one experiment run, Thomas measured the heat of undercooled liquid metals to determine the ability of certain zirconium-based alloys to form glass. ''This is the first time that these particular alloys could be prepared and measured in this way,'' said Fecht. ''Undercooling to 200 Celsius is a lot! We have excellent and very important data.''

Such fundamental discoveries and measurements of these alloys, some of which were being observed for the first time, could, said Project Scientist Jan Rogers, be used to improve sporting goods, including golf clubs, due to their excellent elastic properties. Mixtures of gold-coated aluminium-copper-iron and aluminium-copper-cobalt, in balls the size of blobs of chewing gum, were also extensively undercooled in TEMPUS. ''The gold is protecting the sample from oxidation,'' explained D.M. Herlach of the German Aerospace Research Establishment in Cologne. ''If the sample were to oxidise, it could not be undercooled.''

Throughout the high-temperature heating and undercooling processes, electromagnetic 'pulses' were imparted by TEMPUS to squeeze, then release, the samples. ''By measuring the [resulting] oscillations,'' researcher Bob Myers of Massachusetts Institute of Technology said on 10 July, after watching Linteris work with a specimen of palladium-silicon, ''we can determine the surface tension and viscosity, or resistance to flow. We're using a new technique which is allowing us to measure the viscosity of these samples for the first time, measurements which can't be obtained on Earth. And even some of the surface tension measurements are a first. Preliminary results look very promising.''

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