By Corinne Podger BBC science reporter

The American space agency (Nasa) has begun trawling the internet for spare parts for its shuttles, according to United Space Alliance, the company that runs the shuttle fleet.

The shuttles, first launched in 1981, often rely on computer components that are so out of date, they are no longer made.

The orbiters even use a type of computer disk drive that was outmoded by the end of the 1970s.

Astronauts could be using old parts until 2020

Nasa is hunting internet sale and auction sites like Yahoo and e-Bay for shuttle parts that are so antiquated, they would be unrecognisable to the average computer user today.

The agency is particularly short of a type of Intel computer chip known as the 8086.

A chip similar to this was used to power the first personal computers made by IBM in 1981 - the same year as the first shuttle launch.

'Scavenger hunt'

The shuttle operators also need eight-inch floppy disk drives that went out of fashion nearly 20 years ago, and have long since been replaced by much smaller disk drives and CD-Roms.

Nasa is looking for stockpiles of old parts it can buy in bulk to repair old machinery, as well as keeping some spare for future use.

The internet search has been described as ''a scavenger hunt'' by Jeff Carr, spokesman for the Houston-based United Space Alliance.

However, the parts will be needed for at least the next 10 years, with the shuttle due to remain in service until 2012 - and there is a possibility of that being extended to 2020.