- \n
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Engineers also noted there was a question about \u201cloctite\u201d on five closeout screws on the star tracker door, noticed when the coupon screws \u2013 used to verify if the loctite worked correctly \u2013 showed the screws were breaking free at too low a torque. These screws have since been changed out.<\/p>\n
The Fuel Cell (F\/C) flow-through purge has also completed without issue, followed by their activation around 10pm local time on Sunday.<\/p>\n
The STS-125 crew \u2013 led by Commander Scott Altman \u2013 departed from the Operations and Checkout Building for the pad at around 10:16 am, entering Atlantis around 30 minutes later. Closeouts of Atlantis\u2019 crew hatch \u2013 now the crew are onboard \u2013 will take place shortly.<\/p>\n
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\u201cSTS-125 S0007 Launch Countdown operations: CTS (Call To Stations) was completed Friday at 1530L. Countdown operations continue to progress per the Barchart and on-time,\u201d noted Monday morning processing information via L2.<\/p>\n
\u201cAir to GN2 changeover was completed last night at 2114 EDT. ET tanking began at 0442 EDT and should be complete by 0742 EDT. Launch window opens at 1341 EDT. Preferred time is 1401 EDT.<\/p>\n
\u201cWeather forecast 90 percent Go for launch.\u201d However, TAL (TransAtlantic Abort Landing) sites are questionable at this time and the biggest threat to launch at this time. Update: Observed TAL weather has improved and is currently green.<\/p>\n
Engineers are also keeping an eye on a formation of ice on the LH2 ET Umbilical \u2013 located at the aft of the orbiter. Currently, the estimated mass of the ice is not enough to threaten a scrub, although it will continue to be observed via pad cameras, while the ice inspection team are sent back out to the pad for a closer look. Following discussions, a wavier was issued.<\/p>\n
Tanking:<\/p>\n
The loading of LOX and LH2 into Atlantis\u2019 External Tank has now completed to the stage of stable replenish. The Engine Cut Off (ECO) sensors were checked out during slow fill and deemed to be operating as required, with good voltages.<\/p>\n
As always, engineers will be keeping a close eye on the entire tanking process, though special attention will be paid to the Ground Umbilical Carrier Plate (GUCP) \u2013 following the leak during STS-119\u2019s opening launch attempt.<\/p>\n
![\"a37\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/05\/a37.jpg\" "\\"a37\\"")
\u201cSTS-119 \/ ET-127 Performance Summary: Pre-launch: 1st loading resulted in scrub\/LCC (Launch Commit Criteria) violation due to GH2 leakage at GUCA (>40,000 ppm. Flight seal\/QD (Quick Disconnect) replaced,\u201d noted a post mission IFA (In Flight Anomaly) review presentation on L2, written by the MAF (Michoud Assembly Facility).<\/p>\n\u201cLeakage occurred during transition from fast fill to topping. Vent valve opened when 98 percent level sensor indicated wet. Detected by leak detectors (LD 23 & 25) located in ground umbilical shroud. Isolates leak to either ground side quick disconnect (QD) or interface with flight seal.<\/p>\n
\u201cContingency plans (vent valve cycling) unsuccessful in controlling leakage within acceptable limits. Launch scrubbed, flight seal\/disconnect replaced. No GH2 leakage observed during subsequent loading. No other anomalous performance observed during loading.\u201d<\/p>\n
Following unmating and realignment work, the second launch attempt for Discovery was issue-free. However, an investigation was initiated, in order to ensure STS-125 would not suffer from the same problem.<\/p>\n
The mating of the GUCP to Endeavour\u2019s ET-131 \u2013 for the STS-400 LON (Launch On Need) requirement on Pad 39B \u2013 was also used to aid checks into mating procedures.<\/p>\n
The investigation found that the most probable cause identified a momentary breach in flexible flight-seal to bellows probe due to \u2018thermal shock\u2019 of GH2\/LH2 with vent valve in open position. Tape has also been applied to areas of the GUCP, in order to monitor any change to the alignment since initial mating.<\/p>\n
Sunday\u2019s L-1 Engineering Meeting:<\/p>\n
A meeting between the crew and engineers overviewed specific flow items, such as the subsystem work on Atlantis during her time in OPF-1 (Orbiter Processing Facility).<\/p>\n
\u201cThe purpose of this briefing is to provide the Atlantis Flight Crew with a summary of significant vehicle and payload issues that have occurred since the STS-125 TCDT L-1 Day briefing that was presented on 9\/23\/08,\u201d outlined an expansive L-1 presentation, acquired by L2.<\/p>\n
\u201cThis includes problems or issues that have occurred following the decision to rollback from PAD A, remove Atlantis from the integrated stack in the VAB and return to the OPF.<\/p>\n
![\"a28\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/05\/a28.jpg\" "\\"a28\\"")
Critical subsystems that will be utilized during Atlantis launch include the Space Shuttle Main Engines (SSMEs), Fuel Cells (FCs) and Auxiliary Power Units (APUs).<\/p>\nThe APU is a hydrazine-fuelled, turbine-driven power unit that generates mechanical shaft power to drive a hydraulic pump that produces pressure for the orbiter\u2019s hydraulic system. There are three separate APUs, three hydraulic pumps and three hydraulic systems.<\/p>\n
As with every flow, lessons learned from the previous flight of both the program and the orbiter herself are factored into modifications and improvements of the systems. As with STS-125, work on the APUs was outlined.<\/p>\n
\u201cUpon return to the OPF, the APU 3 QD (Quick Disconnect) Heater mod was implemented (APU 1&2 circuits modified earlier): This modification replaced the existing fuel fill line heater with a longer heater that provides protection to the previously unheated system 3 GN2 service QD,\u201d outlined the engineering presentation.<\/p>\n
\u201cPurpose of mod is to lessen chance of developing on-orbit GN2 QD leakage with resultant fuel tank pressure decay, which has occurred on two recent Shuttle flights (STS-121\/OV-103 and STS-123\/OV-105). Also, Tempilabels have been affixed to QD flight caps in order to provide post-flight data on heater performance.<\/p>\n
\u201cBecause of the launch delay, an APU confidence run was performed after return of stack to PAD A. All three APUs performed nominally.\u201d<\/p>\n
Also vital to the orbiter power system are the three Fuel Cells, which are located under the payload bay area in the forward portion of the orbiter\u2019s midfuselage. The Fuel Cells operate as independent electrical power sources \u2013 each supplying its own isolated, simultaneously operating 28-volt dc bus.<\/p>\n
\u201cSTS-125: Fuel Cell Total runtime: F\/C1, 2036 hours. F\/C2, 434 hours (Replaced since last flight F\/C operational life: 2600 hours). F\/C3, 1130 hours,\u201d listed the presentation.<\/p>\n
Atlantis\u2019 three SSMEs, the main engine that can boast an impressive track record, will help power the vehicle\u2019s ride uphill. The reusable power plants flying with Atlantis are engines: 2059 (Main Engine 1), 2044 (Main Engine 2), and 2057 (Main Engine 3).<\/p>\n
Debuting on Atlantis\u2019 engines is a software modification, which followed observations of \u2018erroneous alarms\u2019 sounding during Return To Landing Site (RTLS) abort simulations.<\/p>\n
\u201cDSP Memory Dump Sequence Change: Eliminates erroneous Shuttle Orbiter Cockpit Alarms during RTLS aborts. Discovered during Shuttle Avionics Integration Lab (SAIL) RTLS abort testing,\u201d noted the SSME presentation to the STS-125 SSP (Space Shuttle Program) Flight Readiness Review (FRR) on L2.<\/p>\n
\u201cResult of the Shuttle Primary Avionics Software System (PASS) SSME Subsystem Operating Program being active during RTLS and detecting unsolicited SSME Controller \u2018Command Accepts\u2019.<\/p>\n
\u201cSSME Controller software issues \u201cCommand Accepts\u201d for the duration of the post MECO digital signal processor power spectral density (PSD) data memory dump for each SSMEC internal generated command.<\/p>\n
\u201cSoftware Version AD08 changes the DSP Memory Dump to report \u2018No Command Received\u2019 for each SSMEC internally generated command and makes the first six words standard in all VDTs. DSP memory dump sequence terminated if vehicle command received. No vehicle command expected during memory dump sequence.\u201d<\/p>\n
![\"a42\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/05\/a42.jpg\" "\\"a42\\"")
The nozzles on Atlantis\u2019 SSMEs also required cleaning, after contamination \u2013 caused by their extended stay out on the coastal launch pad \u2013 was observed by engineers.<\/p>\n\u201cDeposits of green and brown contamination on the tubes of STS-125 nozzles,\u201d added the presentation. \u201cBackground: Pre rollout inspection noted green contamination on the tubes of all three nozzles. Green contamination is nickel corrosion products.<\/p>\n
\u201cCaused by chlorides in sea salt deposition. Superficial corrosion of tube nickel plating. Isolated brown spots contain iron products and are likely A-286 corrosion products. Affected areas on hotwall and coldwall correspond to onshore wind direction when orbiter is on pad.<\/p>\n
\u201cNozzles cleaned to remove chloride deposits. Post clean leak tests confirmed superficial nature of corrosion. No change from prior leak test results. No pitting through EDNi plating on exposed tube surfaces observed. Reapplication of sodium chromate inhibitor to cold wall aft manifold crevices maintains in-family condition<\/p>\n
\u201cCleaning assumed to have diluted existing protection. STS-125 nozzle cumulative pad time well within family. No abnormal corrosion expected. Large margins to leakage which would result in unacceptable engine performance.\u201d<\/p>\n
More will follow during the count.<\/p>\n
L2 members<\/em><\/em>: Documentation \u2013 from which most of the above article has quoted snippets \u2013 is available in full in the related L2 sections, now over 4000 gbs in size.<\/em><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"
Shuttle Atlantis has launched on her flagship mission to the Hubble Space Telescope, as STS-125 completed smooth S0007 (Launch Countdown) operations on Monday. Atlantis\u2019 External Tank (ET-130) enjoyed an issue-free tanking, bar the need for the Orbiter Project Office to issue a waiver for a small amount of ice that built up on the LH2 […]<\/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":[9122,8290],"class_list":["post-41108","post","type-post","status-publish","format-standard","hentry","category-news","tag-gucp","tag-sts-125"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41108"}],"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=41108"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41108\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41108"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41108"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41108"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}