New shuttle tank ready for lift-off

By Irene Mona Klotz
at the Kennedy Space Center

Filling and testing the huge external tank was a major step for Nasa

Set against the sparkling Atlantic Ocean, shuttle Discovery emerged on Thursday from a cocoon of protective metal gantries to undergo a final test, stemming from the 2003 Columbia accident.

The object of inquiry was the same item that failed on Columbia: the massive, bullet-shaped fuel tank.

Newly remodelled since the fatal accident, the US space agency (Nasa) is painfully aware that the tank will never again be looked upon as the passive backbone of the shuttle system, which also includes the winged orbiter and a pair of solid fuel rocket boosters.

The accident showed that the tank's foam insulation, necessary to keep the shuttle's exotic rocket propellants as cold as minus 217 Celsius (-423 Fahrenheit), was as great a hazard as the explosive solid rocket boosters, which claimed the shuttle Challenger and killed seven astronauts 20 years ago.

Colombia disaster

Columbia was destroyed and its crew killed because a 623g (1.67lb) wedge of foam insulation broke off the tank during launch and hit the ship's left wing.

When the shuttle flew through the atmosphere 16 days later for landing, superheated gases blasted inside the wing, dooming the ship and crew.

Nasa is eager to put that day behind it and has been labouring diligently for more than two years to make the tank, as well as the entire shuttle system, safer.

After a long period of preparation, we're beginning to see our operations come to fruition Wayne Hale, Nasa

During Thursday's test, which took place at the shuttle's launch pad, Discovery's fuel tank was pumped full with 1,900,000 litres (500,000 US gallons) of cryogenic propellants, then thoroughly inspected for ice build-ups.

Icicles pose a far greater risk than lightweight pieces of foam, because chunks can break off and smash into the shuttle during launch.

At the end of the six-hour hour exercise, shuttle managers were glowing. The new tank passed with flying colours.

"We had an outstanding day today," said deputy shuttle programme manager Wayne Hale. "After a long period of preparation, we're beginning to see our operations come to fruition."

The orbiter will deliver Raffaello, the Italian-built supplies module, to the ISS

Of particular interest was the area where the tank is connected to the forward part of the shuttle by pairs of rods.

All the shuttle fuel tanks before Discovery's had wedges of foam to protect the area from ice formations, and provide aerodynamic surfaces for smoother flight.

But it was one of those custom-made ramps that downed Columbia and Nasa decided to eliminate the problem areas entirely.

Replacing the foam wedges are new electric heaters to prevent ice, but there are still plenty of other potential problem areas.

The tanking test was intended to check how well the insulation withstands the frigid temperatures of the propellants, as well as an opportunity to test new tanking equipment and inspection procedures.

"One of the things we were very interested to look at was the performance of the tank and ice growth on the tank," Mr Hale said. "It performed very well - that is heartening news - but that is not all the story."

Ice debris

Engineers are continuing tests to understand the potential hazards of ice debris, particularly on the leading edges of the wing and the shuttle's nose. Both areas experience tremendously high heat during the shuttle's re-entry through the atmosphere.

As Nasa completed the tanking test, another rocket was being fuelled halfway around the world to carry a new crew to the International Space Station.

The station crew plans to help with the extensive in-flight inspections Nasa is planning for shuttle Discovery.

Also on Thursday, Nasa's new administrator, Michael Griffin, told employees the only thing on his schedule that was not flexible were reviews and meetings critical to returning the fleet to flight.

With the tanking test complete, the shuttle processing team is squarely back on familiar terrain, as everything left to do before flight is standard procedure.

"Today's test was a major milestone," shuttle launch director Mike Leinbach said. "The next one is launch, and I'm really looking forward to that one."

Nasa hopes to launch the shuttle between 15 May and 3 June.

A final launch date will be selected after an extensive design review and flight readiness evaluation.