NASA investigators said today that the failure of a Delta rocket over the Atlantic Saturday night apparently was caused by two powerful surges of electricity that drained power from the battery in the first-stage engine, choking off the rocket's fuel supply 71 seconds after liftoff.
Although investigators said they cannot yet pinpoint the cause of the electrical malfunction, they are sufficiently concerned about the Delta's engine system to advise postponing the upcoming launch of an Atlas Centaur rocket, the nation's only large launch vehicle not grounded by a recent failure. The Atlas Centaur has a similar engine system made by the same company, Rockwell International's Rocketdyne division in Canoga Park, Cal.
Lawrence J. Ross, chairman of the National Aeronautics and Space Administration's eight-member board investigating the Delta accident, said there are "strong resemblances" between the two engines and he has spoken to the Air Force about delaying the Atlas Centaur launch of a Navy communications satellite.
"There's a fair probability it will be delayed, unless we stumble on an answer very, very quickly," said Ross at a news briefing here.
The discovery of the electrical failure, and its potential relationship to the Atlas Centaur, was described by aerospace experts as virtually the crowning blow to a national space program devastated by the Jan. 28 Challenger shuttle disaster and the April 18 explosion of an Air Force Titan 34D rocket.
Even temporarily grounding the Atlas Centaur will leave the country with no means of orbiting heavy military and commercial satellites since the shuttle, the Titan and the Delta rockets are officially grounded pending accident investigations.
"This puts us right out of the space business," said Gary Flandro, a prominent rocket expert at Georgia Tech University. "It's a terrible disaster . . . . We can't do any military payloads, we can't do any SDI experiments, we can't do anything."
Flandro also noted that the Delta and Atlas Centaur engines were "really tried and proven, and tremendously reliable."
"This is just not a mode of failure that's been observed before," he said. "I'm amazed they [NASA] would be caught by this sort of difficulty . . . . It's a very peculiar situation."
The latest crisis was triggered Saturday when the normally reliable Delta, carrying a $57.5 million weather satellite, suddenly veered out of control and broke apart shortly after launch, forcing Air Force range officers to destroy it from the ground with onboard explosives.
William Russell, NASA's Delta project manager, said investigators reviewing telemetry data discovered that there had been two "spikes," or sharp electrical surges, through the engine's main power lines starting at 70 seconds into the flight, just before the engine lost power.
The first surge lasted 6 or 8 milliseconds and pulled power from the engine's main battery down to an abnormally low 10 or 11 volts, he said. The surge quickly abated, but nine-tenths of a second later there was another electrical surge, lasting 14 or 15 milliseconds, that measured about 150 amperes -- at least 12 times higher than the normal current, Russell said.
This second surge again drained the battery, cutting power to the valves that hold open the first-stage engine's fuel lines. The abrupt cutoff of fuel to the rocket's first stage appears to have caused the sharp break in engine power that Russell said Saturday resembled "a commanded shutdown."
But while Russell called the telemetry showing the two electrical surges "quite a significant find," investigators remain stumped as to what caused the malfunction. Russell said that faulty wiring, mishandling or improper construction of the engine are possibilities.
"We're still going back and looking at all the prelaunch processing of the vehicle to make sure we didn't do something that may have caused it," he said.
The Delta engine, known as a RS27 engine, has been used throughout the 26 years of the Delta project without any history of problems, said Joyce Lincoln, a spokeswoman for the Rocketdyne division.
"I don't think there's any question about this not being a design flaw," she said.
Rocketdyne is the manufacturer of the shuttle orbiter's main engines, a longstanding source of difficulty in development of the shuttle program.
Investigators, responding to continued speculation of possible sabotage, said today they cannot rule it out, but it is "highly unlikely" that any ground signals triggered the rocket engine's shutdown.
"There is absolutely no indication" of this, the investigators said.