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Shuttle Narrowly Misses Ocean Ditching During Launch

July 30, 1985

SPACE CENTER, Houston (AP) _ Space shuttle Challenger, with one engine off and an on-board computer set to shut down another, ″would have been in the water″ without the quick action of Mission Control, which ordered the crew to override the computer, the flight director said.

Cleon Lacefield said Monday’s launch was the most dangerous moment yet of the space shuttle program. Asked if he was frightened, he said, ″Oh, yes.″

But Challenger’s rockets fired long enough for the $1.2 billion craft and its seven-man crew to reach orbit safely and officials believe the shuttle will be able to complete its weeklong mission.

Here is a blow-by-blow account of what happened:

Powered by two solid rocket boosters and the thrust of its three main engines, Challenger lifted away from the Kennedy Space Center in Florida at 5 p.m., 97 minutes later than planned.

Two minutes later, the spent solid rocket engines fell away to the ocean and Challenger continued to climb on the boost of its main engines.

Three minutes, 40 seconds after launch, a temperature sensor on the fuel pump turbine of main engine No. 1 rose to 1,960 degrees and turned off. A back-up sensor came on and also began show overheating. The sensor rose to 1,850 degrees and caused Challenger’s computers to shut down No. 1.

″We show a center engine failure,″ said mission commander Gordon Fullerton.

″Roger,″ said Mission Control. ″We copy. Stand by.″

Moments later, the astronauts were told: ″Abort ATO (abort to orbit). Abort ATO.″

This told the astronauts that Challenger was going fast enough by then to reach orbit if both of the remaining engines continued to fire at maximum thrust. It also told the astronauts to fire another rocket system, the Orbital Manuevering System, to lighten the spacecraft. The OMS dumped 4,400 pounds of propellant by burning it off.

Lacefield said the spacecraft already had passed the point where it could have aborted to an emergency landing site in Spain, a maneuver called Transatlantic Abort Landing, or TAL.

″We were 33 seconds past a TAL abort,″ he said, but the spacecraft was not yet moving fast enough to reach orbit.

At 8 minutes, 12 seconds after launch, with Challenger still below orbital speed instruct the computer to ignore the temperature sensors.

″Main engines limits to inhibit,″ said ground control.

″OK. Inhibit,″ responded Fullerton. He touched a switch that told the computers to leave the engine on.

If this had not been done, and if the single remaining sensor on the right engine had reached its limits, Lacefield said, the computer automatically would have shut down the second engine, causing Challenger to fall toward the Earth.

″If the right engine failed . . . we would have been in the water,″ he said in a talk with reporters after a formal briefing. ″The transducer (sensor) never got to its limit, but it sure scared us.″

There was a chance that Challenger would have been able to land on a runway on the Greek island of Crete, Lacefield said.

Both engines fired for another 17 seconds, 86 seconds longer than normal, and Challenger reached the speed necessary for orbit, although it was 46 miles lower than planned.

″As soon as we knew the other engines were OK, then we felt better because we knew we could press uphill,″ Lacefield said in the briefing. ″It’s always a relief to get into orbit.″

The shuttle’s orbit, ranging from 124 miles to 165 miles above the Earth, will be increased gradually to 194 miles, using the OMS rockets. The planned orbit had been 241 miles, but officials said Challenger would be high enough to complete its seven-day mission.

But the expenditure of more than 5,000 pounds of OMS fuel, including 750 pounds used to steer the ship into its new orbit, means some scientific experiments will have to be abbreviated.

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