A last-minute glitch forced a NASA contractor to call off the first test firing Aug. 27 of the Ares 1 rocket’s five-segment solid rocket booster.

The $75 million test by Alliant Techsystems (ATK) in Promotory, Utah, was scrubbed when a power unit required to point the booster’s engine nozzle properly failed with just 20 seconds remaining in the test countdown.

Engineers said it appeared a fuel valve in an auxiliary power unit that drives the rocket’s booster nozzle hydraulics may have failed, but they are not sure why.

NASA and ATK are targeting no earlier than Sept. 1 to make another test attempt.

“By choosing to scrub today, we have not compromised any of the components and preserved the ability to execute a successful test and capture all of the data,” ATK spokeswoman Trina Patterson said in an Aug. 27 statement.

“[Sept. 1] gives us enough to determine root cause and prepare the motor for test.”