Image: Discovery crew
Charles W. Luzier  /  Reuters
The shuttle Discovery's crew members leave their quarters for the launch pad Wednesday during a simulated launch exercise at NASA's Kennedy Space Center in Florida as a SWAT team member stands guard.
By Alan Boyle Science editor
msnbc.com
updated 5/4/2005 3:27:05 PM ET 2005-05-04T19:27:05

Astronauts suited up and strapped themselves into a space shuttle on its launch pad Wednesday for the first time in more than two years, going through a simulated countdown that marked a milestone in NASA’s return to flight.

Wednesday’s dress rehearsal at Kennedy Space Center was aimed at ironing out the procedures for the shuttle Discovery’s real launch, now scheduled for July 13 or later. Discovery’s 12-day mission to the international space station would be the first shuttle flight since Columbia’s catastrophic breakup in February 2003, which killed all seven crew members and caused NASA to ground the shuttle fleet.

Discovery commander Eileen Collins said she was thinking about the crew of the Columbia mission, also known as STS-107, as she went through the rehearsal.

"Strapping in today, the thought did go through my mind that the last crew that strapped in on the pad was the 107 crew," she told reporters.

Gun-toting guards
The mock countdown, known as the terminal countdown demonstration test or TCDT, boasted many of the features of a real-life launch, including gun-toting guards looking out for the crew from the ground and from a helicopter circling overhead. The seven astronauts walked from the crew quarters, waved for the cameras and piled into NASA’s silver “AstroVan.” Then the caravan headed out to Launch Pad 39B, and the astronauts took their seats in Discovery’s crew cabin, assisted by white-clad workers.

Other aspects of the countdown were purely pretend: For example, the hatch was never closed, and the shuttle's auxiliary power units were never started.  

Because it had been more than two years since shuttle managers went through a countdown, they fully expected to encounter glitches during the rehearsal – and it didn’t take long for them to turn up: Just after the astronauts were strapped in, ground controllers found that they couldn’t communicate with crew members on the shuttle’s middeck, behind the cockpit. After about 10 minutes, engineers found the source of the problem: “I inadvertently turned the power switch off,” one worker reported.

“This is one of the reasons we do the terminal countdown demonstration test, to flush out these launch configurations,” NASA commentator George Diller said.

There were also problems communicating with Air Force range safety officials, but NASA managers decided not to troubleshoot that glitch on Wednesday. "On launch day, that would be a requirement," Diller said.

The crew and controllers checked their computers and control systems as they counted all the way down to a main engine cutoff at T-minus-4 seconds. For the purposes of the simulation, the scenario involved the shuttle's computers detecting a problem with the engine's startup sequence that required aborting the launch. Of course, the problem was merely make-believe — there was no actual attempt to start the engine.

The astronauts reviewed the procedures for making an emergency escape from the launch pad — without actually riding the slide -- wire baskets down to the ground. Then they returned to their quarters and prepared for the jet plane trip back to their home base in Texas.

Weather at Cape Canaveral was overcast, and forecasters said that if this had been a real countdown, the launch would have been called off due to low clouds. In fact, the crew's departure from Florida was delayed because of an afternoon storm.

Looking ahead
Collins said the crew had a "very successful" rehearsal on the launch pad. "It felt to me like it was a real launch day," she told reporters.

Usually, the TCDT is followed by a weeks-long buildup to the launch itself. But there will be a longer-than-normal lull between the dress rehearsal and the real thing this time around. Last week, shuttle managers postponed liftoff from mid-May to July, due to safety concerns about Discovery’s external fuel tank.

NASA safety officials were particularly worried about the potential for ice to form around the tank's liquid-oxygen line. The space agency wants to minimize the risk of ice or foam insulation coming off the fuel tank, because investigators believe that a flying piece of foam debris damaged Columbia's left wing shortly after launch and set the stage for the catastrophe during atmospheric re-entry 16 days later.

To address the latest concerns, engineers plan to install another heater for the liquid-oxygen line and also troubleshoot some sensor problems they had seen during a recent test, Collins said. Sometime in the next week or so, Discovery is to be rolled back from its launch pad into the 52-story Vehicle Assembly Building so that workers can begin the tank modifications.

When NASA decided on the launch postponement, Discovery’s crew had the option of putting off the TCDT, but Collins said they wanted to go ahead with the rehearsal for its motivational value. "It helps keep us moving," she said.

She also said completing the TCDT would free up the crew's time so that they could deal with unexpected problems later — or perhaps even take a short vacation. "If something else comes up that needs to be worked on, this test is done, it's behind us," she said.

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