The crew of the shuttle Discovery, running through the final flight simulation before the first post-Challenger mission, was prevented by a mock malfunction from launching a satellite.

The primary goal of Discovery's long-awaited mission is the launch of a $100 million NASA communications satellite identical to one destroyed aboard the shuttle Challenger on Jan. 28, 1986. The satellite was installed in Discovery's payload bay Monday.A mock malfunction in a tilt table prevented deployment of the satellite Tuesday, prompting the crew to plan a pretend space walk for the second day of the simulation Wednesday.

"They encountered a problem with the tilt table in the payload bay. It has to be raised to 50-degree elevation to deploy the satellite. It only went up to 24 degrees. Using the remote control, they couldn't get it to go up any higher," NASA spokesman Jerry Berg said.

Commander Frederick Hauck, co-pilot Richard Covey, John "Mike" Lounge, George "Pinky" Nelson and David Hilmers "blasted off" in the Johnson Space Center shuttle simulator at 9:04 a.m. Tuesday, about an hour late because of technical glitches.

Nelson and Lounge planned to go into the underwater weightless trainer, a large swimming pool, early Tuesday to simulate going outside the shuttle for a manual raising of the tilt table, Berg said.

The 56-hour simulation, the longest of three long-duration tests to date, marked a final chance for the astronauts and flight controllers to practice procedures in detail before Discovery is launched from the Kennedy Space Center in the last week of September.

A firm launch date for the first post-Challenger mission will not be announced until a flight readiness review Sept. 13 and 14, but NASA hopes to get Discovery off the ground between Sept. 26 and Sept. 29.

Before the tilt table problem Tuesday, the crew fought off a make-believe engine failure and other deliberate malfunctions.

Strapped into a highly realistic, computer-controlled mockup of the shuttle's flight deck, Hauck's crew quickly ran into problems to test their ability to get out of jams.

"Five minutes into the launch, the left space shuttle main engine shut down," said NASA spokesman Brian Welch. "The center and right engines continued burning at 104 percent (power)."

As a result, Hauck and company had to fly an "abort to orbit," which left their imaginary shuttle at a lower-than-planned altitude. Compounding their problems, one of two maneuvering rockets used to circularize the ship's orbit shut down prematurely, and problems developed with the satellite payload.

"In terms of this simulation, everything is going normally and according to plan, which is to say a great many systems are experiencing problems," Welch said. "This allows us to challenge the flight controllers. It allows the system to be tested.

"We would expect to have a long list of systems failures and malfunctions aboard the orbiter before this simulation is over."

The flight simulation is scheduled to end Thursday, setting the stage for a dress rehearsal countdown demonstration, one of the last major milestones on the road to resuming shuttle flights.

Hauck and his crew mates plan to fly to Florida next Tuesday to participate in the three-hour test Sept. 8 at launch pad 39B.

Pending resolution of a handful of open issues, including a small hydrogen leak and two sluggish gas valves, NASA plans to announce a formal launch date at some point during the flight readiness review Sept. 13-14.