Tim Furniss/LONDON
The failure of Boeing's Delta III launcher to place the Orion 3 satellite into a correct orbit in May was probably caused by an explosion in the combustion chamber of the second stage engine, says Boeing. The stage was powered by a Pratt & Whitney RL-10 Centaur-class cryogenic engine.
Two unexplained "shocks" or "jolts" occurred 4.2s after the first burn of the second stage. A larger one was recorded 3.5s after the second burn had begun. The engine stopped and the stage and its payload tumbled in orbit.
At the time of the incident, sensors detected a sudden increase in temperature, possibly as hot gas exploded in the combustion chamber. Later, a sudden drop in temperature was observed as the cryogenic liquid hydrogen and liquid oxygen vented from the stage.
Investigators want to determine whether the failure was caused by a structural flaw in the combustion chamber, or a rupture, or whether external forces were to blame. The May failure was the second unsuccessful Delta III launch. The first rocket exploded last August.
Before the end of the year, Boeing hopes to launch another Delta III, which is most likely to carry a dummy satellite payload instead of the ICO Global Communications satellite scheduled for the next launch. The Delta III has 16 firm launch orders from Hughes and Space Systems/Loral.
The launches of Lockheed Martin Atlas II and III boosters are on hold while the probe continues into the Delta III failure, because they carry upper stages with similar RL-10-class powerplants. Atlas payloads awaiting launch are two earth observation satellites and a US Navy communications spacecraft. One earth observation craft, the Terra, will mark the debut launch of an Atlas Centaur-class vehicle - the Atlas 2AS - from Vandenberg AFB, California.
Lockheed Martin may also be forced to carry a dummy satellite on the first Atlas IIIA, which also has a new first stage engine, the Russian-US RD-180. The designated payload for the first launch in August is the Loral Telstar 7. This may be switched to an Ariane, according to sources, provided that Arianespace has room for a launch this year.
• A Boeing Delta II was launched from Pad 17 at Cape Canaveral, Florida, on 24 June, carrying NASA's 1,360kg (3,000lb) Far Ultraviolet Spectroscopic Explorer satellite (FUSE) into a 768km circular orbit.
The satellite will "increase astronomers' abilities to test basic theories about the evolution of galaxies and the formation of the universe", says NASA.
The FUSE was built by Orbital Sciences for Baltimore's Johns Hopkins University and incorporates "pioneer" command and control ground and flight operations software provided by Interface & Control Systems of Maryland.
Source: Flight International
