A critical shuttle test booster that was damaged when an O-ring joint was overpressurized last weekend apparently can be fixed with relatively minor repairs in time for a late August test firing, officials said Friday.

The rocket, called production verification motor No. 1, or PVM-1 for short, had been scheduled for a test firing around July 30 in which deliberate built-in flaws would allow hot gas to reach primary O-ring seals in the joints that hold the booster together.The space shuttle Challenger was destroyed in January 1986 by an O-ring joint failure, and since then NASA has redesigned the rockets, adding an extra "capture feature" O-ring along with other improvements.

But last Saturday, Morton Thiokol engineers conducting an O-ring leak test mistakenly overpressurized a cavity between the primary O-ring and the capture feature seal, applying 950 pounds per square inch instead of 100 psi.

As a result, the capture feature O-ring was pushed out of its groove toward the interior of the rocket.

Engineers spent the rest of the week disassembling the big rocket to get a close look at the suspect joint, and late Friday company officials said a preliminary inspection indicated the damage was minimal.