spacetoday.net: Air Force, Boeing determine Delta 4 fix

Posted: Sat, Apr 9, 2005, 11:42 AM ET (1542 GMT)
Delta 4 Heavy liftoff on first flight (Boeing)

The Air Force and Boeing announced Friday that they have closed their investigation into a problem with the inaugural launch of the Delta 4 Heavy late last year and determined a solution that should not delay the next launch of the vehicle. As reported earlier, investigators concluded that cavitation in the liquid oxygen propellant line created bubbles that caused a sensor to erroneously conclude that the engine had run out of liquid oxygen, shutting it down prematurely. That shutdown stranded the test payload on the vehicle into an orbit thousands of kilometers lower than planned. Boeing has agreed to make a number of hardware and software fixes to the vehicle to prevent the problem from reoccurring. The fixes will be implemented on all Delta 4 vehicles, not just the heavy variant, although they will not be incorporated on the Medium-Plus version scheduled to launch a weather satellite early next month. The next Delta 4 Heavy, carrying the last DSP missile warning satellite, is scheduled for launch in late October.