Endeavour’s initial TPS assessment encouraging

by Chris Bergin

Endeavour’s opening Thermal Protection System (TPS) assessment shows a major reduction in the amount of ‘hits’ on her tiles and RCC panels, compared to Atlantis’ flight – STS-117.

A full assessment is currently being conducted inside Endeavour’s OPF-2 (Orbiter Processing Facility), to be compiled into a report after August 26. So far, Endeavour appears to be one of the “cleanest” post flight orbiter in recent history.

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The report was based on a runway assessment at the Shuttle Landing Facility (SLF) – shortly after she landed at the end of her two week mission to the International Space Station (ISS). The data was used to collate a map of ‘hits’ on the orbiter into presentations (available on L2).

While the number of ‘major dimension’ hits was slightly higher than seen on Atlantis after STS-117 – mainly relating to the multiple areas of tile damaged near the starboard Landing Gear Door – the total amount of ‘lower surface’ hits was much lower than observed on previous flights with parallel assessment charts.

‘The Orbiter TPS sustained a total of 174 lower surface hits of which 30 had a major dimension of one inch or larger,’ noted an assessment report. ‘This number will change when we are able to do a close up hands on inspection. The hits on the windows and OMS pod tiles will be added for the final report.’

This is much lower than the 247 hits – rounded up to 292 hits – noted at the same time period after Atlantis had landed after STS-117 – a flight that was praised as another example of reduced lower TPS damage on a post flight orbiter.

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Some of the hits can occur as the orbiter is rolling out on the runway, picking up any small pieces of debris on the strip, after touching down at around 200 miles per hour. While the runway at the SLF is thoroughly checked before the orbiter lands, a post landing walkdown is also conducted.

‘A post landing walk-down of the runway was performed. The only flight hardware found was a TCS strap. All components of the drag chute were recovered. The drag chute hardware and components appeared to have functioned normally.

‘Both reefing and line cutter pyrotechnic devices were expended,’ added the report, before highlighting what may have been a minor issue with the drag chute.

‘Both reefing lines were still attached to the main chute. One line had been tied off to a ring and did not separate. The other line did not fully cut even though the pyro cutter had fired,’ the report noted, before confirming that, ‘the remaining drag chute components and hardware appeared to have functioned nominally.’

Every other element of post landing on the orbiter appears to have worked as planned, confirming the visually successful landing of Endeavour on Tuesday afternoon.

‘Tire material loss on the main landing gear and nose landing gear tires was nominal,’ the report added. ‘The main landing gear door corner tiles did not have any chips. The RH (Right Hand) nose landing gear door had a 2” x 0.5” chip off the side of a tile.

‘The LH (Left Hand) and RH ET/Orbiter umbilical pyros appeared nominal. There did not appear to be any umbilical plate warping. The orbiter nose cap, LH RCC (Reinforced Carbon Carbon), and RH RCC panels all appeared to be in nominal condition.

The SSME DMHS (Dome Mounted Heat Shield) blankets all appeared to be in excellent condition, with a very low amount of fraying. The base heat shield tiles had very little damage between the engines, especially as compared to STS-117.

‘There were small damages to two of the tiles on the underside of the vertical stabilizer. This is most likely drag chute induced tile damage. The rudder speed brake trailing edge did not appear to have any tile damage. Windows 3, 4, and 5 appeared to have some hazing on them. Windows 4 and 5 each appeared to have a small streak on the surface.’

Endeavour – now back inside OPF-2 and undergoing a level of post flight deservicing – has an extended processing flow ahead of STS-123 in February 2007.

Worst case fears that up to 12 weeks of that flow would be on repairing her structure under the gouge in her TPS have been completely dismissed, after engineers took a close look at the cavity last night.

The red filler bar, made of Nomex felt, appears to be untouched by the heat of re-entry, with one engineer noting that it appears to have ‘a bit of soot’ on it, requiring a ‘wipe down with a cloth’ – a far cry from the extensive processing repairs that were noted as one scenario of not carrying out an EVA repair during STS-118. A full evaluation will take place once TPS engineers remove all the tiles from the area.


Post flight processing will continue inside the OPF for a few days, which includes initial preparations for Aft access via vent plug installations, SSME (Space Shuttle Main Engine) bearing purge, potable water sampling, PRSD (Power Reactant Storage and Distribution) cryogenic offload and the continued post flight inspections.

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.


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