The space shuttle simulator will get a workout today as the crew of Discovery performs its final integrated launch simulation at NASA’s Johnson Space Center in Houston. The center, which is the training base for astronauts and the home of mission control, has mock shuttle flight decks that are correct to the last detail. With a lot of help from computers, the astronauts sitting in the simulator “fly” the cockpit arrangement through the launch profile as mission controllers practice their own routines for liftoff. Discovery is targeted to launch for real Aug. 24 on a mission to the International Space Station.