spacetoday.net: Engine problem blamed for Ariane 5 failure

Posted: Wed, Aug 8, 2001, 10:33 AM ET (1433 GMT)
Ariane 5 liftoff on Flight 142

A combustion problem with an upper stage engine has been identified as the cause of a failed Ariane 5 launch last month according to a report released Tuesday. An inquiry board found that a "combustion instability" in the Aestus engine that powers the booster's upper stage degraded the engine's performance, lowering its thrust and causing it to use more of one propellant than planned. The engine ran out of that propellant and shut down earlier than planned, stranding its payload of two communications spacecraft in a lower than planned orbit. The combustion instability was traced to a dynamic hydraulic coupling between the propellant feed system and combustion chamber circuits. The inquiry board recommended a number of changes to the engine and upper stage that will keep the Ariane 5 grounded until late November. However, the problem with the Ariane 5 does not also affect the Ariane 4; its next launch is scheduled for late this month. One of the two spacecraft launched on that July 12 flight, ESA's Artemis communications technology satellite, is in the process of being gradually moved into geosynchronous orbit using the spacecraft's onboard ion thrusters. However, the other, the Japanese BSAT-2b direct TV spacecraft, likely cannot be salvaged.