Endeavour will be fueled Wednesday to test repairs
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: June 30, 2009
Engineers at the Kennedy Space Center are preparing to load the shuttle Endeavour's external tank with liquid oxygen and hydrogen rocket fuel early Wednesday in a critical test that could either pave the way to launch July 11 or trigger another lengthy delay.
If the line is leak free Wednesday, or at least tight enough to prevent concentrations higher than 4 percent near the vent line umbilical plate, NASA will press ahead with plans to launch Endeavour on a 16-day space station assembly mission July 11.
But if higher-than-allowable leakage is detected, shuttle managers could be forced to move Endeavour to a different external tank, a move that would delay launch up to two months or more in a worse-case scenario.
Engineers believe they understand the problem - the rectangular vent port housing in the side of the tank was riveted into place slightly out of alignment - and they are hopeful the alternate seal and shims will, in fact, keep the vent line quick-disconnect fitting from leaking.
Complicating the issue for troubleshooters, the leaks only show up when the hydrogen section of the tank is nearing a full load and the hardware in the vent line is subjected to ultra-low cryogenic temperatures. Shuttle Program Manager John Shannon ordered Wednesday's fueling test to assess the performance of the vent line fixes before committing to a full-up launch countdown.
As of Tuesday evening, there were no technical problems of any significance at launch pad 39A, but forecasters say morning showers and thunderstorms may develop near the space center. For fueling, the probability of thunderstorms near the pad must be 20 percent or less.
NASA will provide television coverage of the fueling test starting at 7 a.m. A news briefing with Mission Management Team Chairman Mike Moses and launch director Pete Nickolenko is planned for 1 p.m. to discuss the results of the test.
Here is a timeline of major countdown events:
EDT...........EVENT Wednesday, July 1 01:00 AM...Final preparations for fuel loading 03:00 AM...Personnel clear launch pad 06:00 AM...Countdown enters a one-hour hold at the T-minus six-hour mark 06:30 AM...External tank ready to load 06:30 AM...Mission Management Team meets to assess readiness for fueling 07:00 AM...NASA television coverage begins 07:00 AM...Main propulsion system transfer line chill down 07:45 AM...Liquid hydrogen low-level engine cutoff sensors are submerged 08:00 AM...Fast fill begins 09:15 AM...Liquid hydrogen tank 98 percent full 09:45 AM...Liquid hydrogen topping begins; hydrogen vent valve cycling 10:00 AM...External tank in stable replenish mode 10:00 AM...Final Inspection Team (FIT) launch pad walkdown 12:00 PM...Test team 'go' for tank drain (duration approximately 2.5 hours) 01:00 PM...NASA TV: Post-tanking test press briefing with MMT Chairman ...........Mike Moses and Launch Director Pete Nickolenko 01:30 PM...LH2 boil off (duration approximately 19 hours) 04:00 PM...Pad opened for limited access
In a bit of good news for NASA, engineers successfully extracted an astronaut work light attachment knob that was jammed between one of the shuttle Atlantis' cockpit windows and an instrument panel housing after the ship's just-completed mission to repair the Hubble Space Telescope.
The knob, apparently lost by the crew during the mission, was pressing against window No. 5's critical internal pressure pane. It apparently got lodged in place during re-entry when the pressurized crew module contracted slightly.
The knob had to be removed to allow engineers to assess what, if any, damage had been done to the pressure pane when the knob got stuck. Engineers initially tried to cool it with dry ice, but the knob refused to budge. They then attempted to reverse the effects of the shuttle's descent by pressurizing the crew module. That worked, and engineers were able to retrieve the troublesome knob without having to resort to more invasive measures.
The issue was potentially significant because replacement of a pressure pane would require engineers to remove or disconnect cockpit instrumentation and other structures, work that could take four to six months to complete. NASA managers are hopeful the knob caused no significant damage to the window, but inspections are not yet complete.