Tim Furniss/LONDON

The first flight of the $1.2 billion Lockheed Martin X-33 spaceplane technology demonstrator has been delayed again. The latest setback, caused by a hydrogen tank problem, pushes the maiden flight back seven months, to July 2000 at the earliest.

The programme - which was started in July 1996 - has already been delayed beyond its original March 1999 first launch date by technical problems. These include the development of the craft's linear aerospike engine, which had pushed the flight date back to next December.

The graphite epoxy resin inner wall of one of the hydrogen tanks separated while being bonded last December, it has been revealed by Lockheed Martin, which is investing $941 million in the NASA project, but has had to spend much more on funding the delays.

The X-33 is expected to make a series of suborbital flight demonstrations from Edwards AFB, California, reaching a maximum speed of Mach 13.8. The first five flights will take the craft to Mach 11 at a maximum altitude of 165,000ft (50,293m), followed by two more flights, reaching the Mach 13.8 ceiling at an altitude of 300,000ft. Fifteen flights were originally planned as part of the NASA/Lockheed agreement.

Even when the X-33 does eventually fly, many industry observers expect that it may become another DC-X-type programme, providing more technology data rather than leading directly to the fully fledged, but still unfunded, proposed $5 billion VentureStar.

This larger and orbital version of the X-33, seen as a replacement for the Space Shuttle, could be launched in "late 2004", says Lockheed Martin - an ambitious, almost unrealistic, target, given the experience of the X-33.

Source: Flight International