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.

NASA engineers continued loading hydrogen fuel aboard the shuttle after the launch was scrubbed at 3:35 p.m. PDT, seven hours before the scheduled liftoff, in hopes that trouble-shooting would allow them to detect the source of the leak. By mid-evening, however, it appeared unlikely that the leak would be easily detected and repaired for another attempt at a launch this evening or Wednesday.

NASA associate administrator William Lenoir said Monday that if Columbia could not be launched in that time frame, its mission most likely would be delayed until after the scheduled Oct. 5 launch of the shuttle Discovery, and possibly even longer.

“We would go fly the other two birds (Discovery and Atlantis) while we fix this one,” he said.

Regarding a possible second launch attempt this week, Keith L. Hudkins, director of NASA’s shuttle orbiter division, said: “I don’t think we can solve it in that length of time.”

The space agency has only until the middle of this week for another launch attempt because of a self-imposed three-week gap that must occur between shuttle launches.

The constraint on this launch is the planned Oct. 5 launch of Discovery carrying the high-priority Ulysses probe that will slingshot around Jupiter to achieve a polar orbit around the sun.

If Discovery is not launched by Oct. 28, NASA officials will have to wait for 13 months before the planets are in the proper alignment once again.

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 number three. Space shuttle director Robert Crippen said Monday 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.

But Hudkins said that even if they find a likely source of the leak, it will take at least 15 hours to get into the aft compartment, meaning that another launch attempt could not be made until Wednesday at the earliest.

Astro is a $150-million package of four telescopes designed to view the hottest and most violent objects in the universe at ultraviolet and X-ray wavelengths that are inaccessible to Earth-bound telescopes because of atmospheric interference.

Crippen said that the best chance of finding the leak will require installing lights and television compartments in the aft compartment and conducting a visual search during another fueling. He said that, because of the size of the leak, more than 20,000 standard cubic inches per minute, it should be readily visible.

Crippen said he now believes the most likely cause of the leak is a through inspection of the engine assembly that was conducted after Columbia’s last flight. After the flight, engineers had found traces of Carborundum--particulate matter used in very fine sanding paper--in the shuttle fuel system. The Carborundum paper was apparently left on top of the mobile launch platform, which carries the shuttle from the vehicle assembly building to the launch pad, when the platform was refurbished before Columbia’s last mission.

The paper evidently got sucked into the fuel system, apparently during fueling. Engineers found no trace of the Carborundum in the engine assembly when they inspected it, but apparently they created one or more leaks during the inspection process. “Obviously, it’s a leak that we cannot pick up by our normal method of assessing leaks with liquid helium,” which is not as cold as liquid hydrogen, he said.

They will thus have to find the leak while Columbia is on the launch pad because they have no capability for pumping liquid hydrogen through the system anywhere else.

Astro is a $150-million package of four telescopes designed to view the hottest and most violent objects in the universe at ultraviolet and X-ray wavelengths that are inaccessible to Earth-bound telescopes because of atmospheric interference.