NASA Working Overtime to Understand Shuttle Pipe Cracks

These photos show a crack found on a metal liner used to direct flow in Space Shuttle Discovery’s main propulsion system propellant lines. The top photo is magnified 30 times and the bottom photo is magnified 100 times. Image: S | M | L |

Last week NASA announced that it was putting the launch of STS-107 – and future Shuttle missions – on hold after small cracks were discovered in the flowliners within the plumbing that feeds liquid hydrogen (LH2) to the Space Shuttle Main Engines (SSME).

Cracks a fraction of an inch in size were discovered in LH2 flowliners in Shuttle Orbiters Discovery (OV-103) and Atlantis (OV-104). [see links below for two NASA briefings on these cracks].

Cracks have also been found in a Shuttle propulsion test structure. Orbiters Columbia (OV-102) and Endeavour (OV-105) have yet to be examined.

NASA has decided to complete the inspections of the flowliners in all four Shuttle Orbiters before thought is given to taking more drastic actions – such as removing any hardware. Current activity is focused on trying to understand the environment these flowliners are exposed to, model the stresses and loads they’ve experienced, and to develop test and repair techniques. Some thought is also being given to how hardware would actually be removed if this ends up being the desired course of action.

In addition, NASA is looking back at the original data used during the initial qualification of the hardware and is also examining the MTPA (Main Propulsion Test Article or MPTA-098) which was used for the initial main propulsion tests during Shuttle development. Initial examinations (which have not yet been completed) of the MPTA’s flow liners revealed a crack on the Engine 1 liquid hydrogen flow liner. The flow liners in the MPTA use CRES 321 stainless steel as do the flow liners in Columbia. Orbiters Discovery, Atlantis, and Endeavour have liners made of Inconel, a nickel-chromium alloy. As such, it would seem that the cracks are not limited to a specific material since they have been found in both Inconel and stainless steel flow liners.

A “full test development” team met at Boeing’s Huntington Beach Facility on 28 June. Other teams are meeting as well. Work on this issue has been non-stop for the past week including weekends.

Doug Buford, with the Aft Engine shop, works at removing a heat shield on Columbia, in the Orbiter Processing Facility. After removal of the heat shields, the three main engines will be removed. Inspections of the flow liners will follow. Image: S | M | L

The STS-107 FRR (Flight Readiness Review) has been delayed with no new date set. NASA is now assuming that STS-107 will be launched no earlier than mid August in a best-case scenario. The launch dates for STS-112 and STS-113 are still not set.

STS-113 payload processing – and an early October 2002 launch – had already been affected due to the landing of Endeavour several days late. This was compounded by the need to then ferry Endeavour back from Edwards Air Force Base.

NASA has an assessment underway which will address the Space Shuttle’s launch manifest. The effect of the flowliner cracks on subsequent flights is still not known. Identifying the critical path for ISS assembly is driving this assessment process. Flights that do not support this critical path are being deferred as part of this evaluation exercise. One option under consideration is delaying the launch of Node 2 until March 2004.

At a time when NASA is attempting to demonstrate that it can fly the Space Shuttle safely, such caution on the part of the agency has received widespread support. However, keeping the Space Shuttle fleet on the ground – even if it is for only a few weeks – will have long term effects on the ability of the agency to assemble the ISS on schedule and within budget – a capability about which Congress and the White House already have expressed considerable doubt.

It is going to be a long, busy summer for NASA.

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