Boeing is investigating why its Delta IV Heavy expendable launch vehicle placed its dummy payload into a lower-than-planned orbit on its 21 December maiden flight from Cape Canaveral, Florida. The Boeing Rocketdyne RS-68 engines on the three first-stage core boosters shut down 8s early on the mission to deliver the 6t DemoSat direct to geosynchronous orbit (GEO).

The premature shutdown of the 663,000lb-thrust (2,950kN) RS-68s forced the Pratt & Whitney RL10B-2-powered upper stage to compensate and it ran out of fuel before the payload reached its planned 36,340km-circular, 10¡-inclination orbit. The extended 5.14h coast, third upper-stage burn and payload separation were achieved, but the DemoSat has been left in a 36,400 x 19,030km elliptical orbit inclined 13.5¡.

Rather than risk a real satellite on the first launch, the test mission was funded by Boeing and the US Air Force Evolved Expendable Launch Vehicle (EELV) programme. "While the demonstration satellite did not reach its intended orbit, we now have enough information and confidence in the Delta IV Heavy to move forward with preparations for the upcoming Defence Support Programme [DSP] launch," says Dan Collins, vice-president, Boeing Expendable Launch Systems. The DSP-23 launch of an USAF early-warning satellite is planned for mid-2005.

Boeing is currently barred from receiving new Delta IV Heavy launch contracts under the EELV programme, but is working on growth designs to support NASA's space exploration initiative.



Source: Flight International