Discovery launch moved to July

by Chris Bergin

The long-awaited Return to Flight of NASA’s Space Shuttle fleet has been delayed until at least July – following a review of the Engine Cut Out (ECO) sensor fault and Debris Verification Review (DVR).

The SCO fault was found during the Tanking Test – which evaluated the redesigned External Tank (ET), which also may require work on installing new heaters to allay concerns noted in DVR. Roll-back from the pad will occur next week.

New NASA administrator Mike Griffin made the internal call to Shuttle workers late on Thursday, informing that Discovery will be rolled-back to the VAB and have her launch delayed until at least July. An official announcement will be made on Friday.

NASA appeared set on launching Discovery on a window that stretched from May 15 to June 3. However, problems with completing paperwork on time started to become apparent when the Stafford-Covey Return to Flight Task Group cancelled their meeting and press conference two weeks ago – a meeting that was planned to rubber stamp their approval on NASA’s mission of complying with all 15 recommendations insisted on by the Columbia Accident Investigation Board (CAIB). The Task Group was set to reconvene on May 6.
Delaying once again to May 22 – again for reasons of paperwork demands – failed to dampen Shuttle managers Wayne Hale and Bill Parsons’ enthusiasm and optimism that Discovery would make the window. However, behind the scenes, engineers started to raise concerns on several issues that would eventually lead to the major delay to the opening of what was set to be Atlantis’ window, beginning July 14. Atlantis is now set for launch in September.
The list of issues was headed by the recently completed DVR analysis, showing around 170 potential debris sources on the new ET, which holds over 500,000 gallons of supercold propellant for the Orbiter’s three main engines. This review is still being undertaken by experts who are tasked with avoiding the same debris strike that eventually downed NASA’s flagship, Columbia – along with her crew of seven in 2003.

The largest concern noted by the DVR is the 70-foot long liquid oxygen propellant line that runs along the outside of the fuel reservoir. A small ramp of foam – aimed at diverting drops of water away from areas where it could freeze – was added, but failed to satisfy experts who are claiming ice is still building up when the ET is exposed to high humidity.
This problem is already being dealt with for the Discovery’s second launch since the loss of Columbia – the third in total as the Discovery and her sistership Atlantis play tag while the youngest Orbiter, Endeavour, remains out of action until mid-2006 – with a heater running along the line to alleviate icing. This heater may now be added to both Discovery and Atlantis’ ETs for STS-114 and STS-121 (300) respectively. This work has to be carried out in the VAB.

The double ECO (Engine Cut Out) sensor fault, which suffered failure during – and after – the Tanking Test, will also require additional work to be undertaken by engineers. A replacement of the avionics box on Discovery failed to show why the sensors failed. All four sensors need to be in full working order, as they are designed to shut down the shuttle’s three liquid-fuelled main engines if they sense the tank is out of fuel. A malfunctioning sensor could trigger a premature engine shutdown in flight, leading to an abort. Testing is still being actioned to determine the fault.

The previously noted hydraulic fluid leak that dripped on launch pad equipment – and subsequently blew on to the left OMS Pod of Discovery when winds gusted during launch preps – has also been a note of concern. The Orbiter’s thermal protection blankets could have temporarily set on fire during assent, due to the heat generated by the adjacent Solid Rocket Booster (SRB) on launch. While the fire itself was deemed to be no risk to Discovery, the blankets may now be replaced in the VAB.
Although demoralising to all associated with the Shuttle Program, Griffin’s decision to roll-back Discovery to the VAB will have the backing of all concerned. The safety and protection of NASA’s three remaining Shuttles is paramount above all time constraints and public perceptions.

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