Shuttle Dealt 5th Blow in Weeks as Firing of Engines Is Aborted : Launch Date for Discovery Slips Toward October

A crucial test-firing of space shuttle Discovery’s engines was aborted a fraction of a second before ignition today, dealing another setback to NASA’s 2 1/2-year effort to return to space.

Engineers had hoped to ready the shuttle for another attempt Sunday, officials said.

It was the fifth such postponement in two weeks. The test is considered crucial for qualifying Discovery for the first shuttle flight since the Challenger explosion on Jan. 28, 1986.

The flight is scheduled for late September, but even before today many officials believed that the launch would be delayed till October because of earlier delays in the engine test and an unresolved gas leak in a steering engine system that is separate from the main engines.

‘To Work the Bugs Out’

“That’s why we have flight readiness firings, to work the bugs out of equipment before we launch,” said NASA Administrator James C. Fletcher.

Discovery’s three main engines, generating total thrust of 1.1 million pounds, were to fire for 20 seconds in a test of the entire shuttle system. Steel bolts were to hold the spaceship firmly on the pad during the firing.

The engines were to have begun firing six seconds before the zero mark. The shutdown came just after the “go” for starting the engines was issued but before ignition actually began, launch control center commentator Hugh Harris said.

Harris said the shuttle’s master computer “did not see that the engine bleed valve had fully closed” and automatically sent a shutdown signal.

Engineers were trying to determine whether there was a faulty valve or the sensor had given an incorrect reading, he said. The bleed valve vents excess gases.

Tank Being Drained

If the problem is with the valve, the test will be delayed more than two days, said Boyce Mix, manager of shuttle main engine systems. If it is with a faulty sensor, he said, the turnaround could be 48 hours.

Immediately after the shutdown, the launch team began to make the vehicle safe by remote control as it sat on the pad, its 154-foot-tall tank loaded with 385,000 gallons of liquid hydrogen and 143,000 gallons of liquid oxygen. Harris said that the propellants will be drained from the tank and that the igniters in each engine will have to be replaced before another attempt.

Engine No. 2, where the problem occurred, is one of two brand-new engines on Discovery. Engine No. 1 has been flown on three shuttle missions.

Program managers have been grooming Discovery for the first shuttle flight since the loss 2 1/2 years ago of Challenger and its crew of seven in an explosion 73 seconds after liftoff.

Among the disappointed observers today were two of the five astronauts slated to fly Discovery on the first post-Challenger mission, Navy Capt. Rick Hauck and Marine Lt. Col. Dave Hilmers.