By Dr David Whitehouse BBC News Online science editor

US space agency (Nasa) officials say there was probably nothing that could have been done to save the crew of Columbia, even if mission control had fully realised the jeopardy the astronauts were in.

A report to be handed to the Columbia Accident Investigation Board next week will say the crew were almost certainly doomed from the moment a chunk of foam from the external fuel tank struck the left wing shortly after launch.

Damage to the wing's leading edge that resulted in a "thermal breach" is the most likely candidate for the cause of the shuttle disaster.

Plans for carrying out in-orbit repairs to the shuttles during future flights are now being developed.

Throw it overboard

Next week's report looked into emergency actions that could have been taken had it been realised the shuttle could not re-enter the atmosphere safely.

These included jettisoning as much mass as possible, including the Spacehab experimental module in the payload bay, radiators, internal components and excess fuel.

By reducing Columbia's weight and adjusting the re-entry trajectory it would have been possible to lower the temperature stress on the vehicle as it raced into the upper atmosphere.

But it would probably have made no difference; the temperatures would not have been reduced enough.

There were no "Apollo 13-like" solutions that could be devised, the report concludes.

Repair job

Questions were asked very early on in the investigation concerning the lack of a capability to examine the shuttle for damage whilst in orbit, and the inability to repair damage to the heat-resistant tiles in space.

When the space shuttle was being developed there were ideas for in-orbit repair, but they were not carried forward. Now it seems they may be.

Rescue missions for the future are being considered

In recent weeks, a panel of experts has met to see what could be done to inspect and patch up the orbiter whilst on a mission.

One suggestion is to use the International Space Station (ISS) as a photographic platform to image the shuttle when it is in its vicinity, and then use the ISS's arm to position astronauts in the right place for a repair job, if needed.

A report on "in-orbit repair" will be ready during the summer and hardware tests could be carried out in space next year.

Even if it had been recognised that Columbia was damaged, it would not have been possible for the vehicle to get to and dock with the ISS. Columbia was in a different orbit and did not have sufficient fuel to make it to the space platform.

How long?

One survival strategy is to keep the shuttle aloft until some sort of rescue mission can be raised.

In Columbia's case, experts doubt the next shuttle due for launch, Atlantis, could have been prepared in time.

Nothing could have been done to reduce the heating sufficiently

But for how long could any shuttle limp along in space waiting for a rescue?

Engineers say one crucial limiting factor would be the CO2 scrubbers that remove this poisonous gas from an orbiter's atmosphere.

No Russian craft could have reached Columbia's orbit but an unmanned rocket from Cape Canaveral or Europe's spaceport at Kourou in South America might be designed to deliver supplies and equipment that would enable future shuttle missions to hang on until a rescue bid could reach them.

Many things about the space shuttle system that were once considered but discarded as the vehicle became operational are now being re-examined (perhaps along with the question as to why they were abandoned in the first place).