OBSS reaches new heights – and depths – for tile evaluations

by Chris Bergin

The ability of the Orbiter Boom Sensor System (OBSS) has once again proved its worth, providing NASA with a huge array of data on the tile damage suffered by Endeavour.

Managers and engineers are in the midst of evaluations on whether to repair the area – or leave ‘as-is’ – aided by high resolution imagery and even a stunning 3D movie showing every possible angle of the damage.

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Caused by a liberated piece of foam that came off a bracket on the 17 inch LOX feedline, before unluckily bouncing off an External Tank strut on to the orbiter, the tile damage is still historically less than that suffered by orbiters that have previously arrived home safely.

However, NASA isn’t leaving anything to chance, as they file through hundreds of images and data on the gouge. Options include the repair of the area, which could be conducted on an EVA later in the mission, or clearing the area for re-entry.

‘Focused inspection determined depth of damage is 1.14 inches – full tile depth at tile edge. Damage cavity is complex configuration,’ noted one of several NASA presentations to be presented to the Mission Management Team on Monday. ‘Large damage site does not fit within our standard cavity definition base (due to multiple features).’

**UPDATED: Ride home through the fire, sparks and plasma of re-entry with Atlantis, Discovery and Endeavour. FOUR Stunning high quality 2hr, 355-400mb Camcorder and HUD videos – from payload bay closure to post landing – several more videos showing landing from 90,000 ft also available**

The main basis of evaluations – required due to the complexity of the damaged area – refer to the ability of the area to withstand the thermal environments of re-entry.

These evaluations are being based on the new data acquired by Flight Day 5’s Focused Inspection, which utilized the OBSS suite of cameras and lasers.

The OBSS instrumentation package – which rides on the end of the 50 foot boom – consists of visual imaging equipment, the Laser Dynamic Range Imager (LDRI), and the Laser Camera System (LCS). The post-Columbia modification has sensors that can resolve at a resolution of few millimeters, and can scan at a rate of about 2.5 inches per second.

Thanks to Neptec’s Laser Camera System (LCS), NASA now have an array of detailed high resolution images and even a 3D model – made into an amazing movie within a day (available on L2) – to provide additional data for their thermal modelling and requirements.

‘Re-entry Assessments have been initiated to simulate the complicated shape of the Tile Damage,’ added a presentation, which noted that the results are expected on Tuesday. ‘Prioritization: Mach numbers 20.3, 24.9, 16.5, 22.9.’

The data has also aided the creation of test articles of the tiles with mirrored damage, for testing at the Arcjet facility at the Johnson Space Center. Several 24×24 inch test articles are already at NASA’s disposal, with another 6×6 inch test article being built at the Kennedy Space Center.

NASA’s evaluations have also included the impact on the processing flow, once Endeavour returns to KSC, with the ‘worst case’ OPF (Orbiter Processing Facility) flow scenario still easily fitting inside the timeline for Endeavour’s next flight – STS-123 next year.

‘Timeline of 12 weeks total: TPS removal to expose damage site (1 week). Structure assessment, repair development, parts fabrication (4-5 weeks),’ noted the information. ‘Structural repair (2 weeks). TPS closeouts (approx 4 weeks).’

A special MMT will be conducted around 5pm (Central time) to discuss the latest evaluations.

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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