Full-scale propellant injector and thrust-chamber tests of the first-stage engine of the McDonnell Douglas (MDC) Evolved Expendable Launch Vehicle (EELV) candidate vehicle have been completed at NASA's Marshall Space Flight Center, Alabama, marking a major milestone in the programme.

The 2,850kN (640,500lb)-thrust RS-68 liquid-oxygen/liquid-hydrogen (LOX/LH) cryogenic main engine from Boeing's Rocketdyne division, has 90% fewer parts than the Spac e Shuttle engine from which it is derived. The powerplant, to be fully tested late this year, would power the common first stage of a standard fleet of Delta 4 boosters. It is the most powerful LOX/LH engine yet to be developed.

The Delta 4 will be in competition with a family of Lockheed Martin boosters, based on the Atlas, for the final $1.4 billion EELV contract to be awarded by the US Air Force in 1998.

MDC and Lockheed Martin were awarded $60 million final design contracts on 20 December, with Boeing and Alliant TechSystems being eliminated (Flight International, 1-7 January).

The first medium-class version of the EELV is scheduled to fly in 2001, to be followed by the first heavy- class vehicle in 2005.

The EELV family - which will also feature a small-class model not scheduled for a flight test - will replace the current Titan, Delta and Atlas fleets, achieving a reduction of 25-50% in launch costs.

About 200 EELV missions will be required from 2001-20, says the USAF, with at least 15 of them using the heaviest EELV version.

Payload range of the EELV will be 1,135-20,410kg into equatorial and polar orbits from Cape Canaveral, Florida and Vandenberg AFB, California. The top figure compares with the best Titan 4 capability to polar orbit of 17,690kg.

The EELV will also have commercial potential for the winning company, particularly as it has to be able to place payloads weighing up to 6,125kg into geostationary orbit, a capability far exceeding those of current models.

Source: Flight International