Just before a series of leaks and flukes made a shambles of Discovery`s launch schedule, George Sasseen, the space shuttle`s engineering director, made this observation:
Despite a $2 billion reconditioning, the spacecraft is still a used and aging vehicle.
”It doesn`t get safer by aging,” said Sasseen in his office at the Kennedy Space Center, where Discovery is sitting on the launch pad. ”It doesn`t grow anything or develop anything by aging. It just gets old.”
Like other experts at the National Aeronautics and Space Administration, Sasseen believes that the shuttle is safe to fly and that it won`t blow up as its predecessor, the Challenger, did 31 months ago. But, he said, there will be problems.
In the past few months there have been lots of them.
Last week, leaks in a liquid hydrogen line and a sensor-valve problem delayed the fueling of the shuttle, postponing a test firing until late this week at the earliest. On Saturday, engine crews entered the crowded aft section of the craft and removed the malfunctioning valve-sensor combination. Once the main engine test is finally concluded, other obstacles to launch remain. There is a test in Utah of the solid-fuel rocket boosters, set for Aug. 20, and a leak in the ship`s steering engine system that NASA hopes it can fix without taking the craft back to its hangar for massive repairs.
These are just the latest of several delays since January that have caused NASA`s launch timetable to slip from early summer into October.
People at NASA are nervous, not so much that Discovery will repeat the Challenger disaster, but more because they are under the closest public scrutiny since the agency was founded in response to the Soviet`s Sputnik satellite launch in 1957.
Even the first Apollo manned moon landing 19 years ago didn`t attract the media attention of the coming shuttle flight. These continuing delays could make it seem as if NASA will never get its manned space flight act together. The specter of incompetence has people edgy.
”NASA isn`t an `embattled agency.` I`m tired of hearing that,” said Sasseen. But if anything major goes wrong with this flight, it could be the end of the space agency.
”They understand they are really under the gun on this one,” said retired Air Force Gen. Alton Slay, chairman of one National Research Council committee that oversaw NASA`s new safety planning.
People inside NASA and others, like Slay, who were designated by the federal government as official second-guessers after the Challenger disaster, make two points about the upcoming shuttle flight: first, this rocketship is as safe as any the U.S. has ever flown, and second, there are no guarantees because the technology necessary to fly the shuttle is still largely new and experimental.
H. Guyford Stever, chairman of the National Research Council committee that oversaw redesign of the shuttle`s booster rockets, said the upcoming Utah test is vital to assure that the rockets are ”reasonably safe, if assembled correctly.”
”Absolute safety you aren`t going to have,” said Stever.
Even Sasseen, an unabashed booster of America`s space program, says that flying the shuttle is risky business.
”Will we lose another one?” Sasseen asks. ”Well, the probability is pretty good. Hopefully, not for the next 10 or 15 years. You lose airplanes periodically. You lose a lot of cars.”
To assure that it won`t lose Discovery on its next flight, NASA has made more than 400 changes in the shuttle`s hardware, computer programs and ground support systems. All are intended to make the craft safer than it was before its sister ship blew up.
Because it was a solid rocket booster burn-through that caused the Challenger explosion, NASA ordered a virtual total redesign of the two 149-foot long Roman candles that give the shuttle additional thrust during the first two minutes and seven seconds of liftoff.
The booster rocket`s O-rings, nozzles and insulation have all been changed and augmented.
External heaters will keep the booster rockets from getting too cold while sitting on the launch pad, protecting safety components from becoming stiff and brittle, a likely factor in the Challenger failure.
These changes should have been made three flights into the shuttle program, Sasseen said, because engineers could see evidence that burning fuel was not being contained as well as the design intended.
Hundreds of other changes unrelated to the Challenger explosion were also made during the last 2 1/2 years, while the shuttle fleet has been grounded. Because of pre-Challenger pressures to keep the shuttles flying, NASA officials now say, many needed modifications were postponed.
Downtime for redesign of the booster rockets gave NASA a chance to fix up the rest of the ship as well. An escape system has been added, including a hatch that can be blown off in emergencies and a pole that would keep the astronauts from hitting a wing or other part of the ship when parachuted out. This system, though, wouldn`t have helped the seven Challenger astronauts, including teacher Christa McAuliffe, who plunged nine miles into the Atlantic Ocean when that shuttle blew up 73 seconds after liftoff. Once the solid rockets are ignited, there is no way to shut them off until they have completed their 127-second burn, and by then the shuttle is going too fast and is too far from Earth for a bailout.
The new system is good only for escaping the shuttle in the landing process. Pre-Challenger shuttle flight plans included an abort routine in which the craft was ditched in the ocean. But after seeing what happened when the Challenger`s cabin hit the ocean, NASA engineers concluded that such a maneuver likely would kill the crew on impact. The new escape system should get the crew out of the ship before ditching, engineers say.
Besides the two booster rockets, the shuttle is lifted by three main engines that burn liquid oxygen and hydrogen, and about 30 hardware changes have been made in these engines. This includes modifications to strengthen turbine blades in the engines and prevent cracking.
These blades run at 36,000 revolutions per minute, shoveling supercold fuel into 1,400 degree combustion chambers under high pressure. In past flights, the blades have developed cracks. If a blade broke during liftoff, an explosion would probably result.
The structure of the shuttle itself and of the 154-foot long expendable external fuel tank that holds the liquid hydrogen and oxygen have been strengthened with more than 200 modifications.
These costly modifications, made after experience from 25 shuttle flights, have definitely improved shuttle safety, NASA experts and outsiders agree, but these spaceships still are nowhere near perfectly safe.
And as NASA`s Sasseen observed and recent events attest, the maze of complex machinery that makes up the space shuttle doesn`t get better with age. It just gets older.
