Preparation for Discovery's launch on the first post-Challenger shuttle mission heats up this week with an elaborate launch simulation and the "mating" of the shuttle's external fuel tank and boosters.

Hundreds of NASA and contractor engineers will practice launching a shuttle Tuesday in a major simulation to test new management procedures designed to improve the launch decision-making process.A major goal of the test, the most extensive such drill since Challenger's destruction, is to exercise NASA's "mission management team," a group of top agency and contractor managers under astronaut Robert Crippen charged with making the final launch decision.

Discovery is scheduled for blastoff in late August, 21/2 years after Challenger was destroyed in January 1986, and NASA managers want to make sure new procedures and lines of communication will work as advertised.

Launch processing, meanwhile, reaches another milestone this week with Discovery's giant external fuel tank scheduled to be attached, or "mated," to the ship's solid-fuel boosters on Wednesday.

The next step will be to attach the shuttle itself to the tank and boosters. Discovery is formally scheduled to be rolled from its hangar to the nearby Vehicle Assembly Building Thursday, although the move is expected to slip into next week because of unfinished work.

"Rollout" of the completed shuttle to the launch pad is planned for late this month.

Roy Lester, a member of the mission management team at the Kennedy Space Center, said the goal of the launch simulation Tuesday is to "bring the rest of the system into the simulation, primarily the mission management team."

"They, in the new scheme of things, are an integral part of the countdown and the launch decision process. This will be the first time we have involved both the mission management team along with the launch and flight teams in a simulation. It's going to be quite an exercise."

The so-called "super sim" also will involve an astronaut crew in a shuttle simulator in Houston, the entire launch team at the Kennedy Space Center and mission control personnel at the Johnson Space Center in Houston, all tied together by radio, satellite and telephone as they would be for a real launch.

"The super sim is designed to exercise the different lines of communications," said shuttle pilot James Wetherbee, who will join commander Loren Shriver and Franklin Chang-Diaz in the Houston simulator. "We'll strap in and do all the procedures as if we're in the real vehicle."

The test begins at 6:30 a.m. EDT Tuesday with "launch" planned for 9:50 a.m. The test will end around 10:40 a.m. with a simulated "return to launch site" abort, or RTLS.