After two previous postponements, Commander Eileen Collins, Pilot Jeff Ashby and Mission Specialists Cady Coleman, Steve Hawley and Michel Tognini lit up the skies at Kennedy Space Center at 11:31 p.m. Central time Thursday (12:31 a.m. Eastern time Friday), to kick off the 95th mission in shuttle program history. It was the 20th nighttime launch. About 5 seconds after liftoff, flight controllers noted a voltage drop on one of the shuttle's electrical buses. Because of this voltage drop, one of two redundant main engine controllers on two of the three engines shut down. The redundant controllers on those two engines -- the center and right main engines -- functioned normally, allowing the engines to fully support Columbia's climb to orbit. The left engine was unaffected. Main engine controllers receive commands from the shuttle's general purpose computers, and send commands to main engine components. Flight controllers and the crew continue to work to identify more precisely the cause of the voltage drop. Less than nine minutes after liftoff, the first female shuttle commander and her crew were in orbit, ready to begin a full night of work to prepare Chandra for its deployment as the third of NASA's Great Observatories. It will study the invisible, and often violent mysteries of x-ray astronomy. After the astronauts open their cargo bay doors, they will conduct health checks on the Chandra telescope and its two-stage solid-fuel Inertial Upper Stage booster. If all goes as planned, the astronauts will send commands later this morning to elevate the 56-foot long spacecraft to its deployment position behind Columbia's crew cabin. After a critical "go-no go" decision by flight controllers in Houston and at the Chandra Operations Control Center in Cambridge, Mass., cables routing electrical power to Chandra from Columbia will be disconnected; Chandra will be on internal battery power until its solar arrays are deployed. The schedule calls for Coleman and Tognini to command Chandra to be spring-ejected from its cradle at 6:48 a.m. Central time. Collins and Ashby then will maneuver Columbia to a "window protection" orientation with the belly of the shuttle pointed toward the Inertial Upper Stage booster nozzle. One hour after deployment, with Columbia about 30 nautical miles behind Chandra, the telescope's booster is scheduled to ignite in two stages, sending Chandra to its preliminary elliptical orbit. The telescope eventually will reach an oval orbit one-third of the distance to the Moon to conduct its astronomical observations. Chandra's solar arrays are to unfurl just prior to the separation of the Inertial Upper Stage's second stage, at which point telescope controllers in Massachusetts will begin several weeks of activation procedures before Chandra officially begins its astronomical investigations. Columbia's astronauts are in excellent shape, with the shuttle currently orbiting the Earth at an altitude of 178 by 175 miles.