The maiden flight of the Lockheed Martin/NASA X-33 sub-orbital technology demonstrator for future single-stage-to-orbit vehicles is likely to be delayed from next July until early 2001.

The hold-up is due to damage to the demonstrator's liquid hydrogen (LH) tanks.

The outer wall of one of the X-33's two 8.8m (28.8ft)-long, 2,100kg lightweight graphite epoxy LH tanks was damaged during a pressure and loading test at NASA's Marshall Space Flight Center, Alabama.

The damage was found after the fifth in a series of pressure tests which used 110,000 litres of LH.

A structural test simulated the force the tank would encounter from a liquid oxygen tank on top of it in flight configuration.

The outer skin of one of the tank's four metal-composite panels peeled away from its inner surface. The incident was similar to one last December in which one of the metal panels came off while it was being bonded.

The damaged tank was to have been the X-33's right-hand one. The LH and LOX tanks are the largest composite cryogenic tanks ever built.

Source: Flight International