Aug 25 1985

From The Space Library

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Current revision

A computer failure 25 minutes before launch today forced postponement for at least two days of Space Shuttle mission 51-I, the NY Times reported. Launch crews planned to replace the malfunctioning computer, inspect the Space Shuttle's fuel plumbing, and try to launch Discovery on August 27 at 7:02 a.m. EDT.

At 7:15 the Space Shuttle crew and Johnson Space Center (JSC) flight controllers almost simultaneously noted warnings that a backup guidance and control computer was registering errors. This came as the backup computer was undergoing a final check to see that its programs agreed with those driving the Space Shuttle's four main computers.

NASA halted the launch countdown while engineers at Kennedy Space Center and JSC examined data retrieved from the malfunctioning computer and compared it with data from one of the regular computers. They concluded that the trouble was an apparent failure in the computer, which could not be remedied in time for a launch.

That the computer worked perfectly in tests before August 25 and worked in tests after the failure, although it showed signs of trouble, puzzled engineers. NASA was about 99% sure that it was a hardware failure, although only an inspection of the computer by JSC engineers would determine the exact nature of the problem.

It was the second postponement in two days for the Discovery and its crew of five, and NASA officials were growing concerned that Discovery might not reach orbit in time for repair of the crippled Leasat 3 satellite. Any delay beyond August 29 would cancel the repair effort, and the crew would have to confine themselves to deploying three communications satellites in the first three days of the mission. The flight would thus fall short of the eight days then planned.

Arnold Aldrich, manager of the Space Shuttle program at JSC, said NASA would not reschedule beyond August 29 any attempt to repair Leasat 3, as that would have too disruptive an effect on other flights scheduled in the next few months.

If it had been only a matter of replacing the computer, the delay would have been a day. However, the need to inspect insulated ducts that carried liquid-hydrogen to the Space Shuttle's three main engines necessitated the two-day postponement. After NASA had pumped the super-cooled fuel into the Space Shuttle system two consecutive mornings and drained it again, there was a chance that the contractions and expansions caused by the alternating freezing cold and Florida heat might have damaged the engines, which in extreme cases could cause them to explode in flight. (NYT, Aug 26/85, All)

NASA said that the GOES-6 weather satellite turned its eye toward space for about four and a half hours today before NASA personnel reversed it, the Washington Post reported. Located at a fixed point about 22,000 miles above earth, the satellite transmitted weather photos widely used by TV stations and newspapers across the nation.

NASA repositioned the satellite in a reprogramming effort that required transmission of 14 groups of 256 commands each, retiming the revolving satellite so that its instruments would come on when facing the earth.

Since August 1984 when GOES-5 lost its ability to transmit photos because a light in it failed, GOES-6 was the lone fixed-point satellite making transmissions. NASA had scheduled for launch in spring 1986 a replacement for GOES-5.

If a failure like the one that occurred on August 25 were to last longer, it could have a serious impact on the National Oceanographic and Atmospheric Administration's (NOAA) ability to monitor severe storms. (W Post, Aug 29/85, A8)

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