Third Tanking Test not required – NASA

by Chris Bergin

NASA managers have decided to rule out a third Tanking Test ahead of Shuttle Discovery’s Return to Flight mission – STS-114 – leaving only the Debris Verification Review as the remaining issue.

Tests carried out at the weekend by Marshall Space Flight Center on ET-120’s LH2 Diffuser appears to have pin-pointed the cause of over-cycling of the LH2 pressurization relief valve – which was noted on the previous two Tanking Tests.

ET-121 – which will fly with Discovery – has the old single mesh Diffuser, thus procedure in the flow is currently back on for launch on July 13 – in a window that extends to July 31.

Five days of contingency time is available in the flow for any unexpected issues that may arise.

A third tanking test would have seen a few days taken out of the launch window – but with this issue now resolved only the Debris concerns remain. Ice and Frost have been reported at length, although concerns of slush (possibly from melted ice from the new heaters on the ET) are gaining attention.

Slush has enough density to cause small cracks – should there be impact at supersonic velocity – in the Orbiter’s Thermal Protection System, cracks which would prove to be highly dangerous to the Orbiter on re-entry.

Stafford-Covey’s Return to Flight Task Group – meeting on Wednesday – may touch on this subject.

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