Discovery, scheduled to make the first post-Challenger space shuttle flight, is beset by persistent technical problems which could delay its scheduled Aug. 4 liftoff.

In recent weeks, there have been troubles with fuel and oxidizer pumps, engine controllers and booster rocket insulation."We've always said Aug. 4 is the target, and like most targets, it's the bull's eye," said Thomas Utsman, deputy director of the Kennedy Space Center. But the technical troubles "certainly are going to make that target a small bull's eye."

"I still think from where we are today, an August launch is achievable," he said.

The problems have forced NASA to delay the rollout of the shuttle to the launch pad by a week, from May 24 to June 1. Also delayed a week, until June 22, is a 20-second firing of Discovery's three main engines with the vehicle locked onto the pad.

Hugh Harris, a NASA spokesman, said there are several days of contingency time built into the launch preparation after June 22, and "although there are problems, we haven't given up on early August."

A decision on whether to postpone could be made April 14 when senior NASA managers meet at the Johnson Space Center in Houston. However, officials said a launch date assessment might not be made until after technicians finish assembling the two solid fuel booster rockets in late May.

The newest problem cropped up Tuesday: a faulty controller in one of Discovery's in-flight maneuvering engines. Replacement is expected to take two or three days.

Workers also are removing and checking the high-pressure oxidizer turbopumps from each of the three main engines, a procedure that is taking several days.

Earlier, the hydrogen fuel turbopumps in all three main engines had to be replaced after a defective weld was found in a non-flight pump.

Technicians also are repairing several small areas on a segment of a solid fuel booster rocket. In these areas, insulation separated, or debonded, from the steel rocket casing either before or during shipment here from the Morton Thiokol plant in Utah.

Failure of a joint on one of Challenger's two solid fuel boosters caused the shuttle's explosion and loss of its seven crew members in January 1986.