NASA may delay space shuttle Atlantis launch

CAPE CANAVERAL, Fla, Sep 6 (Reuters) NASA managers delayed filling the space shuttle Atlantis' fuel tank today to give technicians time to trouble-shoot a problem with one of the ship's three onboard fuel cells, a spokeswoman with the US space agency said.

NASA had planned to begin pumping 500,000 gallons of cryogenic propellants into the shuttle's tank in preparation for launch at 2159 hrs on a mission to resume International Space Station construction.

However, when managers met today to review Atlantis' launch preparations, they learned one of the ship's fuel cells, which combine liquid hydrogen and liquid oxygen during the flight to produce electricity, had a problem as it was powered for flight.

All three of the fuel cells must be working for the shuttle to be cleared for launch.

NASA can postpone filling the shuttle's external fuel tank until 1330 hrs and still make today's launch window, said NASA spokeswoman Kim Newton.

NASA had planned to launch Atlantis and its six-member crew last week, but a lightning strike and a storm triggered a series of postponements. The mission already has been delayed more than three years while NASA recovered from the 2003 Columbia disaster.

Since the accident, which claimed the lives of seven astronauts, NASA has flown two test missions to check safety improvements. The accident was traced to a piece of foam insulation that fell off shuttle Columbia's fuel tank during launch and smashed into the ship's wing, damaging its heat shield. The shuttle broke apart as it flew through the atmosphere toward landing.

Despite two redesigns of the fuel tank, managers still expect foam to fly off during launch. The debris, however, is expected to be small enough and detach late enough so that it does not pose a threat to the shuttle.

A third redesign is under way to reduce the risk of foam falling off metal brackets near the top of the tank. The modifications were not ready in time to be tested on shuttle Discovery's flight in July, but NASA approved that mission, as well as Atlantis', because even under the worst-case scenario, the crew would not be at risk.

If the shuttle was too damaged to safely return home, the astronauts would stay aboard the space station until a rescue mission could be launched. That option was not available to the Columbia crew, which was not even aware that their ship had been damaged.

NASA now requires its crews to conduct extensive in-flight inspections to assure the heat shield is safe for reentry.

Shuttle program manager Wayne Hale said he expects the next tank modification to be made early next year.

The agency plans one more station assembly mission this year. The station needs to be finished by 2010 when the shuttle fleet is scheduled for retirement.

Reuters KR RS1315