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Shuttle managers meet to debate Atlantis problem BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: September 7, 2006 Engineers continue to assess the health of an electrical generator aboard the shuttle Atlantis today to develop a rationale for either pressing ahead toward launch Friday, the end of the current launch window, or standing down to replace the powerpack. NASA's Mission Management Team will meet at 2 p.m. to make a decision one way or the other. At issue is whether a short inside fuel cell No. 1 that is preventing one of three phases of AC power from reaching the pump motor could worsen during the vibration of launch or later, shutting down the pump and forcing the crew to turn off the fuel cell to prevent over heating. By pulling a circuit breaker, the crew can isolate the phase A circuit to prevent any short-related transients that might affect two of six main engine controllers during ascent. Otherwise, the Freon pump can operate normally on two-phase power. But a subsequent problem could knock out the coolant pump, forcing shut down of fuel cell No. 1. That, in turn, would force the astronauts to carry out a so-called minimum-duration mission that could prevent them from accomplishing all of their space station assembly work. During an MMT meeting Wednesday, the engineering community was split on whether to proceed with flight or replace the fuel cell. As of this writing, it's unclear whether data collected overnight will provide enough additional insight to permit a definitive resolution. If NASA managers ultimately decide to swap out the pump - either before or after a Friday launch try - engineers believe the work could be accomplished at the pad in 11 days, setting up a launch attempt two weeks after the replacement work was ordered. That assumes NASA managers relax a launch constraint that currently requires takeoff in daylight for photo documentation of the shuttle's heat shield and external tank. Even if the lighting constraint is eliminated, Atlantis would not be able to take off until after the Sept. 28 landing of a Russian Soyuz spacecraft carrying the international space station's outgoing crew back to Earth. Assuming a shuttle launch Sept. 30, for example, launch would be targeted for around 2:50 a.m. If Atlantis fails to get off the ground Friday, and if the lighting constraint remains in force, launch would be delayed to Oct. 26. If engineers decide to forego good lighting for post tank separation in orbit, the launch window could open as early as Oct. 20.
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STS-115 patch The official crew patch for the STS-115 mission of space shuttle Atlantis to resume orbital construction of the International Space Station. Choose your store:U.S. - U.K. - E.U. - Worldwide  |
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VIDEO:
BRIEFING ON FUEL CELL DELAY 