Shuttle countdown begins as test conductors prepare for launch

The countdown to Discovery's final flight got under way at 2 p.m. Sunday, after a two-day delay to fix a technical problem.

Clocks at Kennedy Space Center began ticking down from the T minus 43-hour mark, a process NASA hopes culminates in the 3:52 p.m. Wednesday blastoff of the shuttle and six astronauts to the International Space Station.

Orbiter Test Conductor Mark Taffet was among dozens of engineers who manned stations in Firing Room 4 in the Launch Control Center, passing by a message that read: "The greatest launch team in the world enters through these doors."

Beneath an angled two-story wall of reinforced windows 3.4 miles from the launch pad, Taffet donned a headset overlooking banks of wood-paneled consoles where experts would monitor shuttle systems around the clock for more than 70 hours until liftoff.

"There's an intensity, for sure, but a good intensity," said Taffet, a 50-year-old Rockledge, Fla., resident and United Space Alliance engineer, of the atmosphere during the three-day countdown. "Your senses are definitely heightened."

In the final hours before Discovery receives a "go" for a 39th flight, NASA and contractor test conductors like Taffet will make sure launch preparations stay on schedule and are performed safely.

The preparations include Monday's loading of fuel cells that will power Discovery in orbit, fueling of the external tank on Wednesday, setup of the crew module and the astronauts' entry into it.

With only a 10-minute window to launch the shuttle, there's little margin for delay if a challenging technical glitch arises or if rain showers approach at the wrong moment.
"If there's an issue going, there's definitely tension," Taffet said. "Sometimes countdowns are extremely smooth, and people are waiting for something to happen."

Unscripted, high-pressure moments that produce creative "work arounds" can become the most fun part of the job.

This countdown, Taffet is backing up United Space Alliance colleague John Kracsun, the lead orbiter test conductor.