US investigates space bomber

The US Pentagon is reportedly exploring the possibility of developing a "space bomber", which could streak to the other side of the world in 90 minutes and drop bombs from 60 miles (97 km) away.

Defence Secretary Donald Rumsfeld has asked the Pentagon to investigate a sub-orbital military space plane, which could be used for "rapid global strikes", according to the Los Angeles Times.

There are already concerns over the US missile defence programme

A senior Pentagon spokesman, Rear Admiral Craig Quigley, said the Pentagon was interested in the concept because in a crisis, "the military couldn't get anything (to a war zone) faster than this... It could be useful in any number of scenarios".

The concept is likely to worry foreign governments as the plane could be adapted to strike enemies' satellites, and would inflame international concern about the militarisation of space.

But Pentagon officials insist that the plane would only be used for targets on the ground.

Necessary protection

Mr Rumsfeld raises the prospect of the Buck Rogers-style bomber, which could be manned, in a paper called Guidance and Terms of Reference for the 2001 Quadrennial Defence Review.

The document says that a military space plane "would be valuable".

A US military base was targeted in Saudi Arabia in 1996

John E Pike, director of independent research organisation GlobalSecurity.org, told the Los Angeles Times that the direct expression of interest in a paper which is largely conceptual indicates that it is a serious proposal.

The plane would help the US tackle one of its most severe military challenges: the difficulty of destroying distant targets when its foreign bases are dwindling and proving increasingly vulnerable.

It would be possible for the Pentagon to adapt a reusable spacecraft, which was under development by Nasa for five years before it was shelved due to technical problems and cost concerns.

The US air force has expressed an interest in taking over the X-33 Venture Star programme.

Engineering challenges

Industry experts say such a bomber could soften up key targets in the first minutes of a war, making the area safe for conventional aircraft.

Weapons dropped from such a height would be so powerful that they would not need to encompass explosive warheads.

One of the major engineering challenges would be developing sufficient thermal protection to withstand the incredible temperatures - rising to thousands of degrees - incurred by the friction of re-entering the Earth's atmosphere.

Analysts also say cost is a major hurdle, although Mr Pike speculated that the craft might only run to a few billion dollars, rather than tens of billions.