Jun 16 1980
From The Space Library
MSFC reported that the last of the three main engines scheduled for flight on the Columbia had successfully completed its second flight acceptance test with an 8-minute 40-second test run that exceeded the time required to put a Shuttle into orbit. Engine no. 2007 underwent throttling and gimbaling during the test to show its ability to change speed and direction after liftoff. The other two engines (2005 and 2006) had completed their second acceptance tests June 2 and 5, respectively. Although the engines had undergone acceptance test firings last year, modifications made since that time had led NASA to retest them. Successful retest also demonstrated the on-line component replacement that would be required in repeated reuse. Testing of associated main propulsion equipment would continue at NSTL. (MSFC Release 80-86)
The Washington Post reported that heat-resistant tiles on Columbia had survived without damage a critical test June 14 simulating separation of the giant fuel tank. Engineers scanned the tiles for 10 hours and were "all pretty ecstatic," said a NASA spokesman, adding that they would spend the next few days evaluating results of the "pyrotechnic shock test" before pronouncing it a complete success. Dr. Robert Gray, project office manager, said previous simulations had damaged Shuttle tiles; "if there are no major problems, we could launch our first flight in February," he added. (W Post, June 16/80, A-11)
NASA reported that its five-year-old Landsat-2 spacecraft, after nearly six months of inaction, was restored to service through "intensive efforts" by engineers at GSFC. Problems had developed November 5, 1979, when the yaw-attitude flywheel in the Landsat's Earth-pointing system stopped functioning, probably because of a lubrication breakdown. The attitude-control system could not keep the spacecraft sufficiently stabilized to acquire pictures of Earth, or keep the solar panels facing the Sun to collect enough energy for operation.
The spacecraft was "retired" on its fifth birthday, January 22, 1980, but GSFC engineers began trying to use magnetic compensation operating without either the flywheel or the control-system gas, which had been depleted. Magnetic control required defining the spacecraft's magnetic characteristics in order to plot interaction with Earth's magnetic field. As the spacecraft had no system for direct measurement of yaw attitude, engineers had to find a way to use the solar-array output, which varied with the spacecraft's attitude and its latitude position relative to Earth.
On May 5, 1980, apparently as a result of redistribution of the lubricant, the flywheel responded to an ON command and started running again, and the attitude-control system was once more able to keep the spacecraft pointed properly toward the Earth and Sun. However, lack of gas required use of the magnetic system to keep roll and yaw flywheels in a safe range.
Experience gained in magnetic control of attitude was applied to controlling wheel speeds without delays in development. The GSFC engineers believed that this new procedure would let Landsat-2 operate almost at previous capacity, although this would be limited to readout since the tape recorders were not functioning. The return to operational status was important because the multispectral scanner, principal Earth-imaging device, would again provide data to three U.S. and nine foreign sites, supplementing operations of Landsat 3. (NASA Release 80-94)
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