Tim Furniss/LONDON

Orbital Sciences' (OSC) Pegasus XL air-launched satellite booster failed in its mission on 4 November for the third time in six flights. The vehicle's satellite payload - Argentina's first spacecraft, the Satelite de Aplicaciones Cientificas (SAC-B), and NASA's High Energy Transient Experiment (HETE) - failed to separate from the XL's third stage after the planned orbit had been achieved.

Four of the five instruments on the joint Argentine/NASA SAC-B solar-flare and gamma-ray research satellite may return some data, but the HETE, which was unable to deploy its solar arrays, ran out of battery power rapidly.

The XL had been deployed from OSC's Lockheed L-1011 TriStar carrier aircraft at 39,000ft (11,900m), 160km (85nm) east of NASA's launch base at Wallops Island, Virginia. The launch had been halted on 30 October, when a locking pin on the XL's rudder failed to disengage.

The original Pegasus model, first flown in 1990, has a record of six successes and two partial failures. The XL was first flown unsuccessfully in 1994, followed by a failure on its second flight. There is a backlog of 17 launches for government and private customers.

NASA, which has already suffered delays following earlier failures, may be forced to transfer to other small launchers, following OSC's poor performance.

Lockheed Martin has its Launch Vehicle waiting in the wings, but this, too, failed on its maiden flight. Several Russian small satellite launchers are available on the commercial market, promoted by Western companies. These include the Cosmos, Rokot and Start.

Source: Flight International