NASA has finished building a redesigned space shuttle fuel tank that was reconfigured to eliminate the debris problem that doomed the shuttle Columbia and its seven astronauts, agency officials said on Tuesday. Project managers called the step a major advance in returning the US space program to manned flight after the shuttles were grounded when Columbia broke apart over Texas on Feb. 1, 2003. The first reconfigured tank is to be shipped by Friday from a NASA facility near New Orleans to the Kennedy Space Center in Florida as the space agency prepares for shuttle Discovery’s launch in May or early June.

“We are very close. We can taste victory here on shipping the tank,” said Sandy Coleman, external tank project manager at NASA’s Marshall Space Flight Center. The changes are aimed at preventing chunks of insulating foam from breaking off the tank during launch and damaging the shuttle.

A suitcase-sized chunk of foam broke off the tank and hit the edge of Columbia’s left wing when it was launched on Jan. 16, 2003. The damage went undetected during Columbia’s 16-day mission, but caused the spacecraft to break apart under the stress of re-entering the Earth’s atmosphere, killing the astronauts.

The insulating foam prevents ice from forming on the tank when it is filled with 500,000 gallons (1.9 million liters) of supercold liquid hydrogen and liquid oxygen before liftoff. On the new tank, NASA has reconfigured the struts and fittings where foam was prone to peeling off, and installed heaters to prevent ice from forming. The new tank has cameras that will allow ground workers to monitor for damage as the shuttle ascends.

Redesigned external tank

The space agency has also retrained the technicians who apply some of the insulating foam with spray guns, in hopes of reducing gaps in the foam. Those gaps can allow gases to seep in and expand as the tank heats up during launch, popping off chunks of the foam. Engineers have spent 18 months redesigning the external tank and incorporating the changes recommended by the Columbia Accident Investigation Board.

The external fuel tanks, comprised of a half-million pieces, are built by Lockheed Martin at NASA’s Michoud Assembly Facility near New Orleans. NASA had 11 of them ready for flight prior to the Columbia accident. The first of those to be rebuilt will be loaded onto a barge on Thursday or Friday for the trip to Florida, arriving at the Kennedy Space Center five or six days later. Workers there will attach the external tank and the booster rockets to Discovery, then test the tank in March by filling it with fuel and checking for ice formation.

Coleman said NASA could never completely eliminate the problem of foam breaking off the tank, but was confident the changes would prevent the type of damage that doomed Columbia “We’ve been working long and hard on this vehicle,” said Ron Wetmore, vice president of Lockheed Martin Space Systems external fuel tank project. “It’s going to be the safest, most reliable tank that we’ve ever delivered.”

Each tank cost about $ 40 million to build originally, but NASA could not provide a cost estimate for the post-Columbia modifications. Discovery is scheduled to take off in May or early June with a seven-member crew on a mission to the International Space Station. NASA’s shuttles have been grounded since the Columbia accident, and the crews aboard the Space Station have been resupplied by Russian Soyuz and Progress spacecraft. NASA hopes to fly three shuttle missions in 2005.

Jane SUTTON