CAPE CANAVERAL — The three-day countdown for launch of space shuttle Discovery on its 39th and final mission is under way, with T-0 targeted for 4:50 p.m. EST on Feb. 24.
The countdown began at 3 p.m. on Feb. 21 for the mission, designated STS-133, which has been on hold since Nov. 5 to resolve problems that led to cracking in the shuttle’s external fuel tank. The shuttle will carry a logistics module, an external spare parts stowage platform and supplies to the International Space Station (ISS).
“It’s been an interesting and exciting and probably challenging few months for us,” NASA Test Director Jeff Spaulding told reporters. “This will be the second-longest vertical flow [which began when the shuttle rolled out of the Orbiter Processing Facility]. The longest was STS-35, which was 183 days, and this one will be 170 if we make our launch date on Thursday, which we’re certainly planning on doing.”
Weather
Meteorologists with the 45th Space Wing are predicting good conditions for launch, with an 80% chance of suitable weather at Kennedy Space Center (KSC).
So far, just one technical issue has surfaced: a slight internal leak on a reaction control system regulator. “We’ve seen this condition before. It is well within acceptable limits and we’re going to accept it for flight,” said Test Director Steve Payne.
The countdown began amid budget uncertainties affecting not only follow-on programs to the shuttle, but also the orbiter’s remaining manifest. Following the STS-133 flight, NASA plans to launch Endeavour with the Alpha Magnetic Spectrometer particle detector in April on STS-134. The so-called Launch-On-Need rescue mission to back up STS-134 has been renumbered as STS-135, an ISS cargo run managers want to fly as late as possible before the end of the current fiscal year. The mission, staged on Atlantis, would buy about a year’s worth of time for Space Exploration Technologies (SpaceX) and Orbital Sciences Corp. to prepare their vehicles for hauling cargo to the space station under delivery services contracts with NASA, a business model the Obama administration wants to extend to crew transport as well.
Docking
If Discovery launches on time, it will reach the station’s forward docking port at 2:16 p.m. on Feb. 26, beginning a week-long stay that includes two spacewalks and installation of the Permanent Multi-Purpose Module. An extra day for docked operations may be added to support a Soyuz fly-around of the station for photographic and video surveys. If approved, the extra day would keep Discovery at the station until March 6, with landing slated for March 8 at KSC.
“We’re back here for another attempt at this,” commander Steven Lindsey told reporters. He and the other five Discovery astronauts arrived at KSC on Feb. 20 for final flight preparations. “We’re pretty confident about this one.”
The launch delay cost the crew its lead for extra-vehicular activities (EVAs). Timothy Kopra was replaced by Stephen Bowen after Kopra was injured in a bicycle accident on Jan. 15. The crew also includes pilot Eric Boe and mission specialists Michael Barratt, Nicole Stott and Alvin Drew.
“We’re all disappointed he’s not going to be here,” Lindsey said of Kopra. “If it wasn’t for Tim developing our EVAs as the lead spacewalker ... we couldn’t have pulled this off in four weeks of training.
“Steve Bowen has jumped into the crew and just done a fantastic job,” Lindsey added. “We’re ready to fly.”
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