In 1997, NASA launched Columbia to study undercooled molten metals in microgravity; the STS-83 mission also carried experiments on sintering and fire behavior

Space missions do not always go as planned, and one flight from the 1990s is a good example. Space Shuttle Columbia launched on 4 April 1997 on STS-83, carrying seven crew members, five astronauts and two payload specialists, as part of NASA's first Microgravity Science Laboratory mission. The laboratory housed a range of experiments designed to study materials, combustion and other processes in microgravity.

Among them was an experiment called Thermophysical Properties of Undercooled Metallic Melts. It examined how far molten metal could be cooled below its normal freezing point before solidification began. The experiment used TEMPUS, a German electromagnetic levitation furnace that could hold metal samples without a physical container. This allowed researchers to study molten materials without the contact with a container that can influence when solidification begins. The results could help scientists better understand how the structure of metals develops as they solidify.

A mission cut short by a fuel-cell problem


STS-83 was intended to be a much longer mission. NASA's later account of the reflight says the original mission was expected to last 16 days, while the actual STS-83 mission lasted 3 days, 23 hours, 13 minutes and 38 seconds.

The problem involved one of Columbia's three fuel cells. These systems used liquid hydrogen and liquid oxygen to generate electricity and produce drinking water for the crew. Fuel cell No. 2 had shown some unusual readings before launch, but additional checks cleared it for flight. After Columbia reached orbit, however, the differential voltage in one of its substacks began trending upward.

Engineers tried purging the system to stop the increase, but the effort did not work. The fuel cell was eventually shut down, and further purges and other measures failed to correct the problem. Because shuttle flight rules required the three fuel cells to function properly enough to provide the necessary backup capability for reentry and landing, the Mission Management Team ordered the mission to end early on 6 April. Columbia landed on 8 April, after just under four days in orbit.

Even during the shortened flight, the crew managed to carry out some of the planned research. NASA records say work was performed with TEMPUS on the undercooled-metal experiment, along with the Liquid-Phase Sintering II investigation in the Large Isothermal Furnace. That experiment examined how a liquid component bonds with solid particles under heat and pressure without the entire mixture reaching its melting point.

Fire experiments and a second flight

The laboratory also contained experiments designed to examine combustion in microgravity. NASA records identify investigations involving soot processing and flame-ball behaviour. Without the buoyancy-driven flow that shapes flames on Earth, combustion can behave differently in orbit, allowing researchers to examine processes that are difficult to isolate under normal gravity.

The shortened mission meant that the full MSL-1 programme could not be completed. NASA subsequently decided to fly the same crew, spacecraft and payload again. The reflight, designated STS-94, launched Columbia on 1 July 1997 and lasted 15 days, 16 hours, 44 minutes and 34 seconds. NASA describes it as the first reflight of the same vehicle, crew and payload following a shortened shuttle mission.

The second flight allowed researchers to continue the microgravity investigations that had been interrupted in April. NASA says the 33 investigations conducted during STS-94 produced new knowledge in areas including combustion, biotechnology and materials processing. Among the combustion findings were observations of extremely weak flames and a new mechanism of flame extinction associated with soot radiation.