TIM FURNISS / LONDON
Space agency fears deeper metal fatigue problem as cracks found in liquid-hydrogen lines on all four orbiters
NASA is warning that the Space Shuttle fleet could be grounded for several months following the discovery last month of hairline fractures in the flow liners of liquid-hydrogen lines in the Space Shuttle Main Engine (SSME).
The agency fears that a small piece of flow liner could break off and be ingested into the SSME, shutting it down and causing an abort or an explosion (Flight International, 2-8 July).
On 10 July two cracks were found in the liners of hydrogen-fuel lines on Endeavour, the youngest orbiter in the fleet. Endeavour was the last of the orbiters to be inspected following its recent return from International Space Station (ISS) STS 111 mission. Further inspections were planned the following day.
Three cracks in one flow liner in a liquid-hydrogen line on one of the three SSMEs on the Space Shuttle orbiter Columbia have also been found during ultrasound inspections following the earlier discovery of similar 2.5-7.5mm cracks on Atlantis and Discovery.
Industry sources have suggested the cracks may be the result of a more serious, wide-ranging metal fatigue problem which would require a substantial inspection of the fleet. If new parts need to be manufactured, each orbiter could be grounded for a year. NASA hopes that it has enough spare parts to repair the fault, however, and that new procedures will reduce to a minimum the amount of disassembly required.
A lengthy grounding of the fleet would seriously affect the Space Shuttle schedule, particularly ISS assembly missions, and could necessitate the return of the Expedition Crew aboard a Soyuz TM ferry at the end of its shift in October. The next crew could have to be launched on a Soyuz. Supplies would have to ferried by Russian Progress tankers and continued assembly of the ISS put on hold.
The next scheduled Shuttle mission, the delayed STS 107 non-ISS science flight by Columbia, scheduled for 17 July will be pushed further down the priority list.
NASA has extended to May 2007 its six-and-a-half year, $2.4 billion contract with ATK Thiokol Propulsion for the production and refurbishment of 70 reusable solid rocket motors for the Space Shuttle at a cost of $429 million. The agency has also extended a 15-year Kennedy Space Center payload ground operations contract with Boeing, valued at $25.3 million.
Source: Flight International
