NASA to Try Shuttle Launch Despite Fuel Cell Problem

NASA officials will try again today to send off the space shuttle Atlantis on a long-delayed mission to resume construction of the international space station.

Space shuttle program manager N. Wayne Hale Jr. said late yesterday that a glitch in the shuttle's internal fuel cell system appeared to be limited and random, leaving the vehicle safe to fly. If weather cooperates and no other mechanical problems arise, the shuttle will launch around 11:40 this morning.

NASA managers had weighed the risk of losing the 30-year-old fuel cell while the shuttle was in space -- which could force them to shorten the mission -- against the fact that the orbiter has two other fuel cells and additional backup capacity. A decision to replace the fuel cell would have required returning the orbiter to the hangar and a delay of at least several weeks.

"After a very extensive review over the last 48 hours now, the team came to the conclusion that the cloud we saw over fuel cell number one" does not pose an unacceptable risk to the mission or the crew, Hale said. He said, however, that "there is some risk; that's undeniable."

The flight, which will carry a 17-ton truss for the solar energy system of the space station, has been held up for more than three years. It was first grounded by the 2003 Columbia disaster and continuing problems with foam shedding from the shuttles' big external fuel tanks. Since the current launch window opened Aug. 27, it was delayed again by a lightning strike, stormy weather and now the fuel cell problem.

If the shuttle does not launch today, NASA officials said they may be able to try again tomorrow, although that would require shortening the mission by one day.

NASA is very eager to launch this week because the next opportunity under NASA rules will not come until the end of October. That potentially long wait is due to the upcoming flight of a Russian Soyuz vehicle carrying a new crew to the space station and to an agency requirement that Atlantis lift off in daylight so the shuttle's external fuel tank can be photographed for signs of foam loss.

The fuel cells, weighing 255 pounds each, are under the orbiter's cargo bay floor and are very difficult to reach. They combine oxygen and hydrogen in a process that generates electricity and, as a byproduct, water.

The fuel cell problem was first noticed Tuesday night when technicians saw a spike in the voltage in the motor of the fuel cell's No. 1 coolant pump. The pump sends Freon through the fuel cells to prevent them from overheating.

Hale said a major factor in deciding to go ahead was that there is substantial risk to the spacecraft in replacing a fuel cell. He said the manufacturer, UTC Fuel Cell, had recommended that the cell be replaced but the NASA team concluded there were compelling reasons to fly with the current cell.