MIT had key roles on Spacelab


MIT scientists and alumni/ae were deeply involved in STS-83, the first Microgravity Science Laboratory (MSL-1) Spacelab mission, which was launched on Friday from the Kennedy Space Center and returned yesterday afternoon, 12 days early, after fuel cell troubles developed.

The planned 16-day mission aboard space shuttle Columbia was intended to serve as a scientific test bed for a series of microgravity experiments under development for the International Space Station.

On Sunday, problems developed with a fuel cell which combines hydrogen and oxygen to produce electrical power aboard the space shuttle. Following mission rules and safety guidelines, the decision was made to power down the fuel cell, institute a series of energy management steps using the remaining two fuel cells, and develop plans for an early end to the mission. It is only the third time in space shuttle history that a mission has been cut short due to equipment failure.

Shuttle program manager Tommy Holloway said NASA would consider reflying the Microgravity Science Laboratory on a shuttle mission later this year.

Two materials science experiments planned for this mission were developed at MIT. Both utilize the Electromagnetic Containerless Processing Facility, which allows containerless processing of metallic samples in the microgravity environment of space. Electromagnetic coils are used to levitate samples in Earth-based experiments, but they require the use of strong magnetic fields to overcome the Earth's gravity.

In the microgravity environment, the samples can be positioned far more accurately under much lower magnetic fields, resulting in significantly lower fluid flows within the samples. Because of the lower power required for positioning of the sample, the temperature of the sample can be controlled precisely, resulting in a well-defined heat balance. Also, the samples can be processed without use of cooling gases, greatly improving the purity of the processing environment.

Professor Merton Flemings and postdoctoral associate Douglas Matson, both of the Department of Materials Science and Engineering, developed the Alloy Undercooling Experiment, which is designed to measure the solidification velocity in samples of steel alloys which are melted and then cooled below their equilibrium melting point while still in a liquid state. This process is known as undercooling.

Researchers expect that this work will have direct applications in the design of steel strip casting facilities, the casting of high-performance alloys used in jet engine turbine blades, and the welding of stainless steel alloys where rapid solidification occurs.

The undercooling experiment is designed to produce data on phase selection and growth kinetics within the limited melt convection environment that is possible in the microgravity environment of space.

The Measurement of Surface Tension and Viscosity of Undercooled Liquid Metals Experiment was originally developed by the late Professor Julian Szekely of materials science and engineering and was previously flown on the STS-65 International Microgravity Laboratory mission in July 1994.

In a tribute to Professor Szekely, who died in December 1995, his students and colleagues, Dr. Gerardo Trapaga and Robert Hyers, decided to continue this investigation into measuring the viscosity and surface tension of reactive and undercooled liquid metals such as zirconium, gold, a gold-copper alloy, a palladium-silicon alloy and stainless steel alloys.

Researchers expect that the combination of electromagnetic levitation and the microgravity environment in space would minimize internal fluid flows in the samples, preventing transition to turbulence and allowing measurement of the fluid's molecular viscosity.

In this experiment, metallic samples are positioned using electromagnetic levitation coils and melted by induced currents. The sample is then deformed by a pulsed magnetic force, creating surface oscillations. Using high-speed digital image analysis, the deformation of the sample over time can be analyzed using Fourier spectrum analysis to determine the frequency of these oscillations, which allows the surface tension and viscosity of the samples to be determined.

Two of the seven crew members of STS-83 have close ties to MIT. Dr. Janice Voss (SM '77 in electrical engineering, ScD '87 in aeronautics and astronautics) is the payload commander for the mission. She became a NASA astronaut in July 1991 and has flown two previous space shuttle missions: STS-57, the first Spacehab mission (a separate mission from Spacelab) in June 1993, and STS-63, the first shuttle rendezvous mission with the Mir space station in February 1995.

Dr. Roger K. Crouch, the mission's payload specialist, was a visiting scientist at MIT from 1979 to 1980 and is now chief scientist of NASA's Microgravity Space and Applications Division.

Two backup crew members who trained for the STS-83 mission are MIT alumni/ae: NASA astronaut Catherine G. Coleman (SB '83 in chemistry), trained as a backup mission specialist, and Dr. Paul D. Ronney (ScD '83 in aeronautics and astronautics), trained as an alternate payload specialist.

(John Tylko, SB '79 in aeronautics and astronautics, is a special correspondent for MIT Tech Talk).

A version of this article appeared in MIT Tech Talk on April 9, 1997.


Topics: Aeronautical and astronautical engineering

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