Space: Those Balky Computers Again

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After a splendid voyage, Columbia returns tardily to earth

Only seconds after the space shuttle touched down on the California desert last week, a playful voice crackled from the radio at Mission Control in Houston. "Columbia," it said, "we've got some good news and bad news for you. The good news is, we've had lots of beer waiting for you. The bad news is, we drank it eight hours ago."

NASA, of course, does not permit alcohol aboard its spacecraft or on its facilities, but last week, after Columbia's harrowing, computer-plagued final day in orbit, the space agency had good reason to splash everyone with champagne. Sweeping out of the skies in the fading glow of a setting sun, the space shuttle settled gently onto Edwards Air Force Base's Runway 17 in the California desert with the "right on the numbers" precision only a master pilot like John Young, 53, America's premier astronaut, can muster. For seven hours and 50 minutes before that landing, however, flight controllers worked frantically hi Houston to get Young, his five crewmates and their prize scientific cargo, the European-built $1 billion Spacelab, safely back to earth. During the unscheduled extension of the 166-orbit flight, the shuttle's longest, some California radio stations had even begun speculating ominously that the ship might become marooned in space.

The electronic glitches that led to those fears began on Columbia 's ninth day in orbit as it circled 155 miles above the earth. The flight had already been lengthened by 24 hours to give ground scientists more experiment time. This was made possible by the shuttle's unexpectedly low use of its "consumables" (oxygen, fuel, electric power). But when Columbia, in preparation for its descent, fired the small maneuvering rockets, or thrusters, hi its nose, the jolt rocked the ship. The usually laconic Young said that it sounded like a "howitzer blast going off in your backyard."

At that instant, the spacecraft's No. 1 computer, responsible for directing the orbiter's navigational and guidance systems, as well as general housekeeping duties, "crashed," or shut down. To the relief of Houston controllers, the No. 2 computer promptly took over. Indeed, under NASA's suspenders-and-belt philosophy, the orbiter is equipped with four electronically linked computers, plus an independently operating backup. Any one of these machines can take charge of the shuttle. About four minutes later, however, after the thrusters fired again to slow the ship, the second computer also stopped.

For three or four minutes, there was no computer at all steering the orbiter. The failure was an echo of earlier difficulties with the IBM-built machines, including a breakdown that caused a last-minute postponement of the first shuttle flight in 1981.

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