Countdown Begins for Shuttle Discovery's Last Flight

Following a two-day delay to repair shuttle Discovery Orbital Maneuvering System leaks, NASA picked up the start of the STS-133 countdown on Oct. 31, aiming for liftoff at 3:52 p.m. EDT Nov. 3.

“Work is currently on schedule,” NASA test director Steve Payne told reporters.

A helium leak in the right-side OMS system has been repaired and the tanks repressurized for flight. A second minor leak with the OMS nitrogen system also was resolved.

The repairs ate two of the seven days in the STS-133 November launch window. Sun-heating issues and other activities at the International Space Station will bump Discovery’s 11-day mission to December if it is not off the launch pad by Nov. 7.

NASA will have four possible attempts over the five-day period for launch. Meteorologists forecast generally good conditions, with a slight chance of rain in the area at launch time on Nov. 3 and scattered clouds. Overall, the chance of a weather-related delay was 30 percent on Nov. 3 and 40 percent on Nov. 4 due to an approaching front, said Kathy Winters, with the 45th Space Wing’s Weather Office.

On its 39th and final flight, Discovery will be heading to the space station to deliver the last U.S. pressurized module, spare parts, supplies and a prototype humanoid robot flying as a technology demonstration.  The Leonardo logistics module has been modified for permanent installation on the station, where it will serve primarily as a storage depot.

“She’s been an incredible vehicle and she’ll cap a long and distinguished career with this flight,” Payne said.

If Discovery launches before Nov. 7, an extra day likely will be added to the mission. In addition to installing the Permanent Multipurpose Module Leonardo, which has been outfitted with extra shielding, stripped of its internal thermal control system and had its avionics racks modified to allow crew easier access, the Discovery astronauts will be attaching the third of four planned ExPRESS Logistics Carriers to the station’s truss.

Two spacewalks are planned to prepare the station’s broken ammonia pump module for possible return to Earth and other maintenance tasks. The pump, which was replaced by the station crew in August, would be returned on the proposed STS-135 mission next summer, if Congress funds the flight. Shuttle program manager John Shannon said the extra cost would be about $600 million.

Tags: NASA, Shuttle, os99