Leaking Fuel Again Scrubs Shuttle Columbia Launch

For the fourth time in four attempts since May, NASA engineers Monday evening detected a leak of potentially explosive hydrogen while fueling a space shuttle, forcing them to scrub the launch of the shuttle Columbia with the Astro observatory for at least two months.

It was the third time the mission has been aborted because of a hydrogen leak discovered only hours before the scheduled launch time.

In a press conference shortly after the scrubbed launch, space shuttle director Robert Crippen said: “The next vehicle up will be Ulysses”--the shuttle Discovery carrying the Ulysses probe that will be sent into a polar orbit around the sun. It is now scheduled for an Oct. 5 launch.

After the Columbia launch was scrubbed at 3:35 p.m. PDT, seven hours before the scheduled liftoff, NASA engineers continued loading hydrogen fuel aboard the shuttle in hopes that trouble-shooting might allow them to identify an obvious source of the leak. By late evening, however, it was clear that that prayer was not going to be answered, and Crippen decided to scrub the launch so that more extensive studies could be conducted.

Crippen also said the agency was considering performing a fueling test on Discovery to ensure that it does not have a leak that would imperil the high-priority Ulysses mission. Discovery must be launched by Oct. 28 so that Ulysses can perform a slingshot maneuver around Jupiter to enter its polar orbit around the sun. If it is not launched by that date, NASA must wait another 13 months before the planets are once again in the proper alignment.

Performing a tanking test would add at least five days to pre-launch preparations for Discovery even if no leak were found. That would eat into the agency’s 18-day window for the launch.

Crippen said, however, that he believes the leak is unique to Columbia and that “there is no reason I know of to suspect a leak in Discovery.”

He emphasized that there would be no danger in attempting to launch discovery without performing a fueling test first. “The only risk . . . is that it will be unsuccessful,” he said.

NASA has twice thought it had the hydrogen leak in Columbia corrected. After the first scrubbed launch in May, technicians found a large leak in a valve, called a 17-inch disconnect, that connects the external fuel tank to the shuttle orbiter. A similar leak was subsequently found on Atlantis, which was scheduled to carry a Department of Defense spy satellite into orbit in July.

In both cases, the leak was traced to microscopic glass beads that contaminated the 17-inch valve, preventing gaskets from sealing properly. That valve did not leak Monday evening, officials said.

After another launch attempt was scrubbed 1 1/2 weeks ago because of another hydrogen leak, engineers suspected a leak in a recirculating pump that forces liquid hydrogen through the three shuttle engines to cool them before launch. The recirculating pump was changed, but technicians could find no leak in it when it was tested.

During the testing associated with the pump changeover, however, engineers found a crushed seal in a valve that normally permits hydrogen to enter engine No. 3. Earlier Monday, before the launch attempt, Crippen said that technicians had determined that the crushed seal could account for the volume of leakage that was observed last time.

NASA officials were obviously distressed and just as obviously mystified when the leak reappeared Monday. In their attempt to isolate the leak, they were pumping liquid hydrogen through the engines and opening and closing various valves in order to narrow down the area that must be searched.