Space shuttles may fly till 2040

The X-33 project is "over budget and behind time"

Nasa's announcement that its fleet of space shuttles have been grounded due to wiring problems comes just shortly after Dana Rohrabacher, Chairman of the US House of Representatives Science Committee, stated that "Nasa officials were planning to upgrade and operate a government-owned Space Shuttle for another 40 years."

A US General Accounting Office report says the shuttle's prototype replacement, the X-33, will not meet its "original cost, schedule, and performance objectives".

The current shuttles, operated by the US Government, are supposed to be replaced by cheaper, commercial spaceplanes based on the X-33, starting in 2006. Nasa hope this will cut the cost of delivering objects to space from $44,000 per kilogram (2.2 pounds) using the Space Shuttle to $2,200.

The X-33 project is primarily for suborbital flights. The X-34 will test engines and structures and the X-37 will be used for final spaceflight tests.

Plan "is not working"

However, Mr Rohrabacher said: "The GAO's report confirms what we've suspected for some time: that this administration's approach to developing next-generation reusable launch vehicles (RLV) isn't working.

"Instead of building on the Defense Department's successful strategy of 'build a little, test a little', the administration put all its technology eggs in one fragile basket and then told it to start flying."

He blamed President Bill Clinton for moving the RLV development from the US Defense Department, "which had successfully developed the DC-X", to Nasa. The DC-X was later abandoned.

He also said that Nasa's efforts were then underfunded "by paying for only one copy of one experimental design that was supposed to knock down all the technology barriers to building a highly-challenging, single-stage-to-orbit RLV."

Mr Rohrabacher pointed out that no successful X-program has involved only one aircraft design but instead relied on early and frequent flights of multiple copies of competing designs which incrementally "expand the envelope."

The trouble with the X-33 means the shuttle programme may fly for longer, but the shuttles have their own immediate difficulties to overcome.

Short circuits

Wiring problems mean they will not carry out further missions until mid-October at the earliest, Nasa said on Saturday. Inspectors are now painstakingly checking the problematic wiring on each orbiter.

The last shuttle to fly was Columbia in July and it came within one short-circuit of a first-ever, emergency abort. The close call resulted from power failures to two of the computers controlling Columbia's three main engines.

The Columbia launch in July encountered numerous delays

That led to electrical inspections on the entire shuttle fleet, and technicians have discovered enough problems, including faulty insulation and frayed wires, that mission managers have decided not to schedule any more flights until the work is complete.

Nasa said damage had been found inside each orbiter, something unexpected until Columbia's troublesome lift-off. So far, inspectors have found 38 electrical defects on shuttle Endeavour and 26 aboard shuttle Discovery. Comprehensive inspections of Columbia, the oldest shuttle in the fleet, and Atlantis will begin later this month.

Fuel leaks added to the problems caused by faulty wiring

"Our focus is to be absolutely certain that we do our very best to find, fix and prevent any recurrence of this problem," said Ron Dittemore, Nasa's shuttle programme manager.

Nasa said many of the electrical defects were caused over the years as technicians worked inside the shuttles, often stepping on wires or inadvertently nicking them.

The US space agency said it was revising service procedures in light of the discoveries.