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These two tasks \u2013 fluid line connections to the new ATA and the retrieval of now-unnecessary MMOD (Micro-Meteoroid Orbiting Debris) shields for the Quest Airlock \u2013 although there have been notes of a problem with a valve on the new ATA that requires evaluation.<\/p>\n
Under standard mission timelines, Rick Mastracchio and Clay Anderson\u2019s spacesuits (or EMUs as they are known within NASA) underwent pre-EVA purges just under two hours prior to the start of EVA-3.<\/p>\n
EVA crews tend to work ahead of the planned timeline, as was the case with this spacewalk, which beat the scheduled start time of 3:16a.m., by 45 minutes.<\/p>\n
Pre-mission timelines indicate that four (4) tasks scheduled for EVA-3 are classified as Cat-3 objectives, the lowest EVA Category for the STS-131 mission.<\/p>\n
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![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A311.jpg\" "\\"A3\\"")
As such, the CP13 ETVCG light, SPDM (Special Purpose Dexterous Manipulator) CLPA1 installation, EP1 cover removal, S1 radiator GF beam installation, and\/or WIFEX release tasks could be deferred to a stage (ISS crew) EVA or to one of the next two Space Shuttle missions in order to accomplish the fluid line connections to the new ATA and retrieval of the MMOD shield objectives.<\/p>\nRegardless, the primary activities (in order of performance) were the stowage of the AGB, preparation of the LMC (Lightweight Multi-purpose support structure Carrier) for old ATA berthing, installation of the old ATA onto the LMC for return to Earth in Discovery\u2019s Payload Bay, FGB removal and stowage, setup of the SSRMS (Space Station Remote Manipulator System) for LWAPA (Light Weight Adapter Plate Assembly) retrieval, LWAPA retrieval, SSRMS cleanup, and Airlock ingress.<\/p>\n
Due to more trouble with a bolt during ATA installation into the LMC, the LWAPA tasks were deleted from the EVA. Instead, get-ahead work was carried out on work for a space-to-ground antenna, which will arrive on STS-132.<\/p>\n
The entire EVA lasted approximately 6.5 hours and wrapping up around 8:38a.m. EDT \u2013 with mission controllers calling the due \u201cEVA superheroes\u201d for their work during the three spacewalks.<\/p>\n
With the completion of EVA-3, the two EMUs will be de-serviced and prepared for transfer back to orbiter Discovery on FD-10. The Discovery crew will then head to bed at 3:21p.m. EDT.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A411.jpg\" "\\"A4\\"")
Meanwhile, ground controllers have reviewed Comm (Communications) issues experienced during the first EVA for the STS-131 mission.<\/p>\n\u201cEVA-1 Intermittent Loss of Left Ear Audio: At the very end of EVA1, EV1 (CM Mastracchio) experienced intermittent audio drop out in left ear when he turned his head,\u201d notes a status update from the Mission Management Team (MMT).<\/p>\n
Following the EVA, the CCA was inspected for any moisture and MBED integrity.<\/p>\n
The presentation notes that moisture could lead to potential failure modes of the CCA because of \u201cwiring problems in the CCEM crossover cable.\u201d<\/p>\n
A backup CCA was used for EVA-2 and will most likely be used for EVA-3 as well.<\/p>\n
STS-131 Specific Articles: http:\/\/www.nasaspaceflight.com\/tag\/sts-131\/<\/p>\n
TPS DAT Cleared for Reentry:<\/p>\n
Meanwhile, while Discovery\u2019s Flight Crew worked tirelessly in orbit, the Damage Assessment Team (DAT) completed their task of reviewing all imagery assets associated with Discovery\u2019s Thermal Protection System (TPS).<\/p>\n
Following additional thermal and trajectory analyses surrounding three of the four damaged areas on Discovery, the team reached the unanimous conclusion that Discovery\u2019s TPS could be officially cleared for reentry.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A58.jpg\" "\\"A5\\"")
The first area of Discovery\u2019s TPS to gain note in the final and comprehensive DAT presentation were three (3) small areas of tile damage clustered together on the vehicle\u2019s Left Hand (LH) OMS Pod.<\/p>\n\u201cOMS Pod Damages 550-001, -002, and -003: Tile substrate is exposed and AFD photos identified damage depths to be shallow,\u201d notes the final DAT analysis \u2013 available for download on L2.<\/p>\n
Further assessment of the area revealed that all safety margins are maintained in that area of the vehicle despite the cosmetic damage to the OMS pod tiles.<\/p>\n
The second region of discussion in the DAT presentation was the Rudder Speed Brake (RSB) trailing edge tile liberation.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A74.jpg\" "\\"A7\\"")
As expected, this area has been cleared of any concern due in large part to the fact that this area of the vehicle experiences higher temperatures during ascent than it does during reentry.<\/p>\n\u201cStructure Maximum Temperatures Ascent: Aft closeout structural temperatures exceed the RTV, aluminum and structural adhesive limits,\u201d notes the DAT presentation.<\/p>\n
No temperature or structural exceedances were identified underneath the undamaged TPS areas in the region.<\/p>\n
Moreover, \u201cStructure Maximum Temperatures Entry: No Structural or TPS temperature exceedances were identified during entry.\u201d<\/p>\n
Further aiding the positive results for the RSB\u2019s trailing edge is the fact that the RSB remains in the closed position from the De-orbit Burn (at Mach 25) until the Mach 10 region, creating a \u201clow heating\u201d environment during the plasma stage of reentry.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A68.jpg\" "\\"A6\\"")
Additionally, the RSB trailing edge is \u201ca lightly loaded structure that is the end of the cantilever aero surface and is not part of the load path of the RSB main torque box \u2013 i.e., it is structurally isolated.\u201d<\/p>\nTherefore, the RSB trailing edge does not take the brunt of the RSB structural loads, only local aero loads.<\/p>\n
\u201cDisbond of closeout does not reduce trailing edge panel capability and propagation of disbonding (during reentry) is not credible,\u201d notes the DAT presentation.<\/p>\n
Furthermore, the surrounding TPS as well as the intact portion of the partially liberated TPS tile will remain intact during reentry.<\/p>\n
The presentation also notes that \u201cEntry RTV bondline temperatures are below certification.\u201d Thus, the partially liberated RSB tile is not a concern for reentry.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A83.jpg\" "\\"A8\\"")
Lastly, the final area of Discovery\u2019s TPS to gain mention in the comprehensive DAT report is a protruding AMES gap filler (G\/F) on the left hand side of the orbiter\u2019s FRCS (Forward Reaction Control System) \u2013 specifically, its potential liberation properties during reentry.<\/p>\n\u201cWindow Summary \u2013 Window PRT Assessment: Potential for G\/F to liberate during entry,\u201d notes the DAT summary.<\/p>\n
While Discovery\u2019s reentry attitude precludes the possibility of the G\/F impacting windows #1 and #2 (the two windows to the Commander\u2019s left) should the G\/F liberate while Discovery is travelling below Mach 2.5, the G\/F does hold the potential to impact the windows during a liberation event between Mach 6 and 2.5.<\/p>\n
\u201cThermal panes protect for descent temperatures which subside ~Mach 8. Panes start experiencing burst loads after Mach 4,\u201d notes the DAT presentation.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/04\/A93.jpg\" "\\"A9\\"")
\u201cBased on previous window impact tests, it is possible the G\/F could create damage to the pane exceeding maximum flaw depth allowable for descent.\u201d<\/p>\nWhile the likelihood of a G\/F impact creating a \u201cthrough hole\u201d is classed as \u201cunlikely,\u201d a shallow angle (~10 deg) low mass (0.0008 lbm) impact at a velocity of ~1,050 ft\/sec at or above Mach 4 could cause damage to the outer thermal pane that could propagate during Mach 4 flight burst loads.<\/p>\n
\u201cIn the event damage occurs at any of the Mach #\u2019s and flaw propagation occurs, it would manifest itself in the form of cracks radiating from the impact site, when subjected to burst loads,\u201d notes the presentation.<\/p>\n
In the event that this was to happen, the thermal pane is expected to remain intact and retained in place with a fairly nominal view across the window.<\/p>\n
Therefore, the event would be \u201cnon-catastrophic\u201d and is thus deemed an \u201cacceptable risk for entry.\u201d<\/p>\n
Likewise, should the G\/F liberate and strike the LH OMS pod, WLE RCC (Wing Leading Edge Reinforced Carbon-Carbon) panels, or the RSB, \u201cNo structural damage (is) predicted.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
On the 29th anniversary of the first Space Shuttle mission (April 12), Discovery continues to perform well, as her crew completed the third and final EVA of the mission \u2013 including replacement tasks associated with the ATA (Ammonia Tank Assembly). Meanwhile, the Damage Assessment Team (DAT) have presented their final overview of the orbiter\u2019s Thermal […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[567,9184],"class_list":["post-40818","post","type-post","status-publish","format-standard","hentry","category-news","tag-eva","tag-sts-131"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40818"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=40818"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40818\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=40818"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=40818"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=40818"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}