NASA Administrator Mike Griffin is soon to make an “informed decision” on whether Shuttle Discovery will launch in July – amid a major implementation task currently underway regarding ice debris concerns – relevant to the External Tank’s LOX Feedline Brackets.
Griffin noted – in reaction to the Stafford-Covey findings on NASA progress in implementing the recommendations of the Columbia Accident Investigation Board (CAIB) findings – that the agency “will not be rushed” to launch, while admitting the Shuttle will never be risk free.
While sources noted that Iron Contamination – found in a spare Space Shuttle Main Engine (SSME) and noted in the last Shuttle Standup Summary – proved not to be a concern with other SSMEs, following a bore scope inspection of in-use engines on Discovery and Atlantis, a Program Management Council (PMC) report dated June 10 has thrown the spotlight back onto Ice Debris concerns.
The report, titled Lox Feedline Bracket Ice Mitigation – Tiger Team – opened with the seriousness in which NASA and its departments are taking the issue of Ice.
“LOX Feedline Bracket Ice is likely to constrain launch of STS-114,” before noting the risk mitigation that is in-works is “promising.” The absolute aim of the modification is “reduce the risk of bracket ice damage to the Orbiter RCC and Tiles – (Thermal Protection System).” It was foam debris from the External Tank that caused a breach in Columbia’s left wing during the launch of the ill-fated STS-107.
The report focuses on a self-proclaimed “simple” approach, based on a proof of concept of testing a “No-Purge Bag” and “Inflatable Surrounds” – which requires no significant new structure for implementation, with removal of the modification being carried out by “Special Red Team” activity prior to launch, using lanyards.
The Mitigation Tiger Team consists of people from both the Kennedy Space Centre (KSC) and Marshall Space Flight Center (MSFC) with liaisons from both the External Tank and Solid Rocket Boosters departments. The objectives note the development, certification and implementation of an existing bag concept that had previously been developed by the Ice Storming Team.
With a launch window still being set for July 13-31, the time allowed for verification and qualification may be the main concern – with an on-pad test noted as a requirement for the modification. The Inventions and Contributions Board (ICB) and the Program Requirements Control Board (PRCB) will join the PMC for approval of the modification, with coordination on hand with NASA’s Engineering and Safety Center at the Langley Research Center in Virginia.
The No-Purge bags will go onto the External Tank in six locations – as high as the intertank area, all the way down the feedline. The purpose of the bags – as an inflatable enclosure – is to inhibit airflow to the bracket, eliminating moisture, which in turn eliminates condensation which could turn to frost and/or ice. With the modification coming off the External Tank prior to launch, a small amount of frost growth has been classed as acceptable.
A test article was put under the spotlight at the MSFC Hot Gas Facility in Alabama – which will also serve as the testing facility during the verification process. However, the test article lacked the ability for condensation simulations, the cold box was filled with LN2 – rather than LH2 and there was no articulation during the testing. The No Purge Bag was tested at the MSFC on May 16.
An update, recieved today, noted that very recent testing has shown that low density ice poses a more serious risk to the Shuttle wing RCC than previously thought.
Such concerns regarding ice debris is now classed as the largest potential “show-stopper” to STS-114 launching in the July window.
Further updates and follow-ups are pending.