Disastrous debut

The inaugural launch of the Delta III from Canaveral on 26 August 1998 failed. The vehicle broke up at T + 72 seconds, destroying Galaxy 10, which was an HS-601 satellite for PanAmSat.74 When a slow oscillating roll developed in the first minute of the flight, the control system tried to correct it by vectoring the RS-27A and the three strap-ons that had active nozzles, but the system overcompensated and the remedial

The RL-10-B-2 engine of the second stage of the Delta III introduced a 'crank down' extension to its nozzle bell.

action contributed to the instability. Ironically, once the hydraulic fluid for the thrust-vectoring system was expended the oscillation smoothed out, but then the disabled gimbals pitched the vehicle over, causing the self-destruct system to intervene. The investigation found that the roll oscillation was due to unpredicted solid rocket motor dynamics. "It took us four days to confirm the guidance problem," said Joseph Palsulich, the programme's senior manager for business development. Boeing attributed the loss to "improper analytical assumptions in the dynamic models, and poor communication between two design engineering groups''.75 The control system software was revised to compensate for this effect.76,77

0 0

Post a comment