After another set of evaluations, engineers have documented all of the damage that was suffered by orbiter Atlantis, her External Tank and Solid Rocket Boosters, following Monday night’s freak hail storm, outlined in two expansive presentations acquired by this site.
Atlantis – currently having her payload removed overnight – will rollback to the Vehicle Assembly Building (VAB) this weekend, where further evaluations will take place.
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Related Notes and Presentations on L2, including: The NASA and Lockheed Martin e-mails and memos on the ET damage (VAST), plus new images and serveral presentations. ET Manifest (Lockheed Martin) ET-117 Production Milestone Presentations, plus more, available to download on L2.
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The presentations (all available to download on L2), written by NASA, United Space Alliance, Lockheed Martin, Boeing and ATK, gave a comprehensive overview of the damage sustained by the storm, which gives hope that Atlantis herself will only require cosmetic work.
The SRBs did suffer some damage, but nothing near to the level that would require serious engineering work. However, the External Tank (ET-124) remains a major concern, with over 7,000 areas of damage, which engineers will attempt to repair in the VAB.
The storm hit a very localised area over the launch pad complex, lasting from 22:05 to 22:22 (GMT), with a peak wind strength of 62 knots.
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‘Space Shuttle Vehicle (SSV) Hail Damage: Due to the extensive hail damage that the External Tank suffered, the STS-117 SSV will rollback to the VAB to repair the damage. Payload transfer from the Orbiter to the PCR is scheduled to start after S0024 hazardous operations are complete. Preparations for rollback will pick-up after the payload work is complete,’ noted the Feb 28 NASA Launch Operations report.
‘The external tank, solid rocket boosters, and orbiter were inspected for hail damage yesterday; TPE took new IPR to document the damage: The external tank experienced approximately 7000 areas of foam damage from hail. The Left SRB RSS antenna and ETA ring show some damage. The orbiter sustained 27 hits to the tile; all appear repairable at this point.’
‘Additional areas to be inspected: Minus Z side of RH SRB (Access available in VAB -Requires manlift at pad),’ noted the extensive presentation on damage evaluations. ‘Additional Data Required: SRB hold down post data. Wind Load concern.’
Atlantis herself suffered 27 areas of tile damage, but not to any of her RCC panels. Repairs to the tiles will be lesser than those carried out on post flight processing operations – and can be carried out in the verticle position she’ll be in once back inside the VAB.
’27 tile damages total: 8 locations on L/H wing tip and Left Outboard Elevon (possible slurry repair). 1 location on Lower surface (possible putty or slurry MR repair). Port side 10-15Â¡Â¯ fwd of LMLG door. ~ 18 on L/H chine FWD of RCC (Combination of putty and slurry repairs).
The process in carrying out repairs on the damage will be conducted by erecting a special platform inside the VAB, where engineerings can carry out ‘slurry repairs’ with the aid of a applicator on the end of an extension aid.
While the damage was caused by a freak weather situation, the Weather Protection System at the pad did protect Atlantis from serious damage, alongside the obvious protection from the giant Rotation Service Structure (RSS).
‘Based on the wind heading at the time of the event and weather protection arrangement, threat was identified to the port wing panels 17-22,’ noted another presentation from Wednesday. Nose Cap and Starboard WLE were protected from hail impacts.’
However, as expected, the ET is the major concern, with large scale damage observed. The worst case scenario would involve a demate and swapout with Endeavour’s ET (ET-117), due for STS-118, which won’t even be completed at the Michoud Assembly Facility (MAF) in New Orleans until April.
Currently, the plan is to repair the tank, in the vertical, without the need to demate the orbiter and boosters from the ET. That process will take weeks, which led to the delaying of the launch of STS-117 to at least the end of April.
‘TPS Impacts 360 degrees with heaviest concentration on +Z side (>1200 hits in quadrant). Numerous areas of damaged foam (LO2 Acreage). Heaviest damage in +Z / -Y quadrant,’ noted an expansive evaluation presentation.’
Another worry is the IFRs (Ice Frost Ramps) which are a major area of concern for potential foam liberation on ascent. With ET-124’s damage now upgraded from one IFR, to all inboard IFRs, repairs will need to pass a stringent level of approval before the tank is cleared to fly.
‘LO2 Ice Frost Ramps: Minor damage on inboard side of all Ice Frost ramps (could not inspect fwd of XT-634). XT-634 and Xt-676 have crushed foam,’ was listed on one of the presentations. ‘LH2 Ice Frost Ramps: Possible damage sites on lower LH2 ice frost ramps forward face.
‘Intertank: Numerous areas of damaged foam. Heaviest damage in -Z / -Y quadrant (see map). Foam damage on intertank flange in -CY / -Z quadrant. LH2 Acreage. ~12 small hits on -CY quadrant. Aft Interface Hardware: Foam damage on -CY ET/SRB ramp, aft fairing and cable tray.’
The repairs on the ET can be carried out in the VAB with the addition of special platforms and scaffolding, with previous experience drawn from the repairs that were carried out on STS-70’s tank, after that tank saw some of its foam pecked away by woodpeckers, which had wrongfully assumed the ET was a giant tree.
‘VAB Integration Cell: Will require special access and scaffolding comparable to what was performed for STS-70 woodpecker damage. VAB Checkout Cell: Access is better in the checkout cell but special access would still be required.’
The level of information that was gained within a few days of the event is staggering, even to the point of the weather itself. One presentation noted the actual size and speed the hail impacted the vehicle, as NASA showed that they are prepared to evaluate any occurrence – however rare – in the launch flow.
‘Diameter ranges from 0.5”- 2”(0.017 lbs to 0.138 lbs). Reports of ‘golf ball’ size hail. Density assumed to 57 lb/ft3. 61.8 knot (104 fps) maximum gust combined with terminal velocity of 90 mph (132 fps). Maximum impact velocity is 219 fps. Assumes a partial downward wind component of 45 degrees from wind gust (74 fps).’
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