Tim Furniss
Boeing officials say the investigation into the failure of the guidance system on the first launched Delta III booster from Cape Canaveral on 26 August, will be completed by the end of September. The booster broke apart at about T+72s after launch.
"The control system recognised and tried to correct a slow oscillating roll which developed during the first minute of the flight-[but] thesystem contributed to the situation and in the end expended the hydraulic fluid used to gimbal the thrust vector controls[TVC] of the main engine and solid rocket boosters," Boeing says. The Delta III control system consists of an onboard computer which controls the main engine, two vernier engines and three solid rocket boosters with thrust vector assemblies.
OPERATING
Once the thrust vector control system was no longer operating, the oscillation had smoothed out but, at that point, the TVC assemblies were in a fixed position eventually causing the booster to pitch 35í, breaking apart under the extreme aerodynamic forces and triggering its self-destruct system.
The US Air Force, meanwhile, says that the loss of the final Lockheed Martin Titan IVA during its launch from Cape Canaveral on 12 August was caused by a sudden momentary battery power failure in the guidance system.
At T+39.4s into the flight, the flow of electricity from a battery in the guidance system was lost for a fraction of a second, which resulted in the system losing its horizon acquisition data.
As the power was restored almost immediately, the guidance system computer sent an attitude-correcting command that resulted in the booster pitching down and breaking up at T+41.3s, triggering the auto-destruct system.
Source: Flight Daily News