**The most comprehensive collection of Shuttle, Ares, Orion and ISS related presentations and mission documentation, plus expansive daily processing documentation and updates are <\/em>available to download on L2<\/em><\/font> **<\/em><\/font><\/p>\n <\/font>**STS-123 Special: MOD Flight Readiness Review (FRR) Presentations, Baselines and Mission Overviews. <\/font><\/em><\/font><\/p>\n <\/font><\/em>Over 35 Checklists and Handbooks, plus STS-123 Flight Plan and Detailed Mission Timeline Overviews. LIVE MMT Level Flight Day coverage (Memos, Info, Images, Videos and Presentations). APU 1 Evaluations:<\/u><\/em> <\/p>\n The evaluations were called after Endeavour\u2019s APU 1 Fuel Tank was observed to be suffering from decaying tank pressure (tank outlet pressure transducers) at a rate of around 4 psi\/day. <\/p>\n This was deemed \u2018Out of Family\u2019 with Endeavour\u2019s APUs 2 and 3 and historical APU on-orbit profile \u2013 with a typical in-flight decay from thermal affects being around 1.0 psi per day.<\/p>\n Due to the lack of available system instrumentation that provide means to distinguish between fuel (hydrazine) or GN2 (gaseous nitrogen) leakage \u2013 engineers created documentation to prove it was not a hydrazine related leak.<\/p>\n That\u2019s where the main element of evaluation was centered, due to the associated risk with a hydrazine leak \u2013 specifically a fire risk during the latter stages of landing. <\/p>\n \u2018Criticality and Consequence: If leakage is GN2, no impact to mission. Leak rate is minor and will not affect APU operations,\u2019 opened one of the three presentation \u2013 available on L2. \u2018If leakage is fuel, possible fire in aft fuselage during landing. During on-orbit operations aft environment does not support combustion.\u2019<\/p>\n Upon noticing the decaying pressure readings, engineers first cleared any immediate risk on orbit \u2013 mainly through experience that a leak of fuel would freeze in the environment of space. With the leak rate unlikely to increase while Endeavour remained on orbit, along with the lack of a combustion risk, the system was \u2013 and is \u2013 deemed to be \u2018stable\u2019.<\/p>\n Checking their extensive flight history, engineers used the most recent example of decaying tank pressure on an APU \u2013 seen during STS-121 with Discovery, with a decay rate of around 3 psi per day \u2013 in order to find the potential cause of the issue.<\/p>\n \u2018Post STS-121 Inspections: Fuel System. No evidence of fuel leakage noted on the APU 1 fuel system. Point-to-point Drager checks with resolution to 0.1 ppm showed no evidence of external hydrazine at aft compartment lines, fuel tank, or service QD (Quick Disconnect). Conclusion was no fuel leakage occurred during STS-121 event,\u2019 added the presentation.<\/p>\n \u2018Insulation inspections. No insulation anomalies were noted on either the fuel or GN2 system. Discredits theory that pressure decay was actually thermally induced anomaly.\u2019 <\/p>\n Flight history also included the pulling of post flight documentation from Endeavour\u2019s previous flight \u2013 STS-118 \u2013 and processing work ahead of STS-123, including pre-flight pad preparations for launch.<\/p>\n \u2018No Disturbance to Fuel Tank Region Except Insulation Repair on Fuel Side of Tank. Insulation was found during surveillance inspections to not be installed per drawing (inadequate amount of batting previously installed),\u2019 noted the findings. <\/p>\n \u2018Reinsulated the Bottom of the Tank Area Where Line Exits the Tank. Insulation work was non-intrusive to fuel system fluid lines and tank. Very low likelihood any collateral damage occurred during this rework. Fuel and GN2 QD actuated during fuel servicing. Only Fuel Components Disturbed During Flow. New\/Refurbished Cap Installed.<\/p>\n \u2018No QD Leakage Noted Post Loading Operations: Post 400 psi Pressurization for Flight on 2\/29\/08. Both Fuel and GN2 QDs Passed Leak Check Prior to Cap Installation. Caps are inspected prior to installation. QD Cap Was Leak Checked Prior to Vehicle Install. No Pressure Decreases Noted post pressurization (11+ days).<\/i> Conclusions: No Indication of Fuel or GN2 Side Leaks Prior to Flight.\u2019<\/p>\n In fact, documentation over the life of the shuttle program shows engineers have a very good record for screening for any issues associated with leakage on the orbiter\u2019s hardware, with only a handful of incidents documented in addition to STS-121.<\/p>\n and most notably STS-9 \u2013 which is documented as an \u201cEntry\/Landing Fire\u201d after injector stem leaks on Columbia caught fire during landing, only discovered in post flight processing.<\/p>\n As part of the evaluations, physics based analysis was needed to help differentiate between a Hydrazine Leak and a GN2 Leak, due to the limited ability to distinguish between the two leakage media. <\/p>\n This brought out the NASA big guns from JSC Thermal and Fluids Analyst department and NESC (NASA Engineering and Safety Center) Technical Fellow for Life Support and Thermal Control, who assessed whether STS-123 data indicates a hydrazine leak or a nitrogen leak. Leak physics were investigated and scoping analyses were performed to assess the leak.<\/p>\n The findings work on several theories associated with the gained data from STS-123\u2019s decaying pressure readings and flight history \u2013 along with expected results on various scenarios. <\/p>\n \u201cIf there were a hydrazine leak in a line or at the QD, we would expect that it would be freeze over and stop flow, stabilizing the tank pressure,\u201d noted the summary of their findings. \u201cIf there were a hydrazine leak in the tank, we would expect that it would be either be detectable in the temperature measurements or would freeze over and stop flow, stabilizing the tank pressure.<\/p>\n \u201cThese are not consistent with the temperature data and the persistent pressure decay seen on STS-123. STS-123 data signature is analogous to that of the nitrogen leak that occurred on STS-121. It is highly unlikely that there is a hydrazine leak on STS-123.\u201d<\/u><\/p>\n <\/u>In conclusion, the engineering community concluded that STS-123\u2019s APU 1 has a GN2 leak \u2013 which holds no risk for continued on orbit operations and landing.<\/p>\n \u201cPhysics Based Analysis Concludes a GN2 Leak is More Likely based on Data. Confirmed by Independent Analysis Performed by Boeing, WSTF (White Stands Test Facility) and USA (United Space Alliance). General Experience from Test Facilities and the Orbiter Show Many More Problems with Gas Leaks than Liquid,\u201d added the conclusion pages. <\/p>\n \u201cSeveral Fuel Leakage Scenarios Would be Detectable with Available Flight Data: Leakage Near Thermostat or Temperature Sensor, Vacuum Induced Freezing causing Blockage to Stop Leak, takes a Smart Leak (coupled with large area of insulation missing) to be Fuel.<\/p>\n \u201cBased on the results of this investigation, the APU community has a high degree of confidence that the decay observed in the APU 1 fuel supply system is a GN2 leak and not a fuel leak. The APU recommendation is to run the APU \u201cOps Nominal\u201d for both FCS (Flight Control Surface) check-out and entry.\u201d <\/p>\n A full roundup of the latest mission status will be added to the next article \u2013 to be published in-between Flight Day 10 and 11.<\/p>\n","protected":false},"excerpt":{"rendered":" As the STS-123 crew enjoy a well deserved period of off duty on Flight Day 10, documentation has confirmed Endeavour\u2019s Auxiliary Power Unit (APU 1) pressure decay is no cause for concern \u2013 as initially thought. More telling is the large scale effort that went into the evaluations, which involved several NASA and contractor teams […]<\/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":[],"class_list":["post-41455","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41455"}],"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=41455"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41455\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41455"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41455"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41455"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/em><\/font>**Click here for sample of L2 menu and content**<\/font><\/em><\/p>\n
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**STS-123 L2 Special: Includes 16 SSP Flight Readiness Review (FRR) Presentations (1500 pages). Live FD Notes and Presentations (MMT).
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<\/font>**LIVE news updates on Endeavour STS-123 Flight Day Specific**<\/font><\/em><\/p>\nEach orbiter has three APUs \u2013 which produces pressure for the orbiter\u2019s hydraulic system that controls the vehicle\u2019s wing flaps, rudder, body flap and landing gear, among other elements of the vehicle. <\/p>\n
Those are listed as STS-65\u2019s processing flow, STS-72 post flight \u2013 though not officially a leak, even though the QD cavity was observed to be \u2018wetted\u2019, and STS-3 \u2013 which required a pre-flight waiver.<\/p>\n
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