For anyone with an interest in the starry skies and around 42 million dollars to spare, NASA may have an interesting proposition.

The US space agency has announced it is selling three used space shuttles when they are retired in 2010, after 30 years of service.

Sadly for enthusiasts planning their own voyage of discovery, the orbiters will only be made available for display in museums and other educational institutes.

And potential buyers may have to move quickly.

One of the three craft -- the most complex aircraft ever built which launches into space like a rocket before gliding back to Earth like a plane -- has already been earmarked for the Smithsonian's National Air and Space Museum in Washington.

There the shuttle will join a wealth of exhibits held by the museum which mark the history of flight and space exploration, including a first successful motorized plane produced by the Wright brothers in 1903.

The two remaining craft, which were generally used to transport equipment into space, will be cleaned, decontaminated and stored in the Kennedy Space Center in Florida while new homes are found.

The 42-million dollar cost includes six million dollars to fly the shuttle to its new home piggybacked on a special Boeing 747, but not the costs of the final road transport.

For those with a smaller budget, NASA is also selling engines found at the rear of the shuttles and which run on a mixture of liquid hydrogen and liquid oxygen. They will cost around 400,000-800,000 dollars each, not including delivery.

The 37-metre long shuttle has carved a place into space history, helping to construct the orbiting International Space Station and to repair the Hubble space telescope.

It must be kept in a covered and temperature-controlled area, NASA said.

Only six space shuttles were ever built. The prototype Enterprise never flew in space.

Two were destroyed. Challenger exploded 73 seconds after its lift-off in 1986 killing seven astronauts on board. Columbia disintegrated as it returned to the Earth's atmosphere in 2003 also with seven astronauts on board.

Only three shuttles remain -- Discovery, Atlantis and Endeavour. They are due to make eight more flights to the ISS to finish construction and carry out the last maintenance mission on the Hubble.

According to the British daily The Guardian, the Science Museum in London has voiced interest in buying Endeavour, but reportedly only American organizations are being considered.