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Wednesday also marks the arrival of the three FCVs from the manufacturer Vacco, several days ahead of the \u201cdeadline\u201d to make the February 12 launch date \u2013 though the main constraint remains flight rationale.<\/p>\n
\u201cGH2 flow control valves are expected to arrive to KSC today. The team is awaiting OPO (Orbiter Project Office) approval to install the vales into the orbiter (expected to start Monday),\u201d added Wednesday processing information.<\/p>\n
\u201cAre in position now to pick up with Flow Control Valves (FCVs) once decision is made to install that hardware. Need date for the FCV is nine days prior to launch (February 3); that\u2019s in-hand, installing.\u201d<\/p>\n
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As previous reported, the issue with the FCVs relates to an incident with one of Endeavour\u2019s valves during STS-126\u2019s ascent last year.<\/p>\n
While the shuttle was not in any danger, post flight reviews evaluated the worst case scenario relating to a more severe issue with the valves, which included the \u201cpotential\u201d of the failure causing the External Tank to vent beyond limits \u2013 deemed a Crit. 1 failure, or a LOV\/C (Loss Of Vehicle\/Crew) threat.<\/p>\n
The role of the three FCV\u2019s relates to the Main Propulsion System (MPS) and the SSMEs (Space Shuttle Main Engines) during thrusting periods. In each SSME, gaseous hydrogen from the low-pressure fuel turbopump is directed through two check valves to two orifices and a flow control valve for each engine.<\/p>\n
During the main engine thrusting period, the liquid hydrogen tank\u2019s pressure is maintained between 32 and 34 psia by the orifices and the action of the flow control valve from each SSME. The flow control valve is controlled by one of three liquid hydrogen pressure transducers. When tank pressure decreases below 32 psia, the valve opens; and when tank pressure increases to 33 psia, the valve closes.<\/p>\n
If the tank pressure is greater than 35 psia, the pressure is relieved through the liquid hydrogen tank\u2019s vent and relief valve. If the pressure falls below 32 psia, the LH 2 ullage press switch on panel R2 is positioned from auto to open , which will cause all three flow control valves to go to full open and remain in the full-open position.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/01\/a55.jpg\")
During STS-126\u2019s second stage flight, engineers noticed an uncommanded drop in SSME #2 hydrogen outlet pressure. The data indicated FCV #2 opened without removal of close command, which was an anomaly. Endeavour\u2019s performance was not compromised thanks to Valves #1 and #3 compensating, and she achieved a nominal MECO (Main Engine Cut Off).<\/p>\nAs soon as Endeavour returned back to KSC \u2013 following a ferry trip back from her Californian landing \u2013 engineers removed the FCVs from the vehicle as a priority processing item, and sent them off to Vacco for examination.<\/p>\n
USA Logistics added that the three valves arriving at KSC today \u2013 a day ahead of their schedule \u2013 will be a mix of three reassembled valves that have come directly from Vacco.<\/p>\n
\u201cOn the FCVs, Vacco has completed reassembly of three. These are not the three removed from OV-103 (Discovery), but a mix from OV-104 (Atlantis) and OV-105 (Endeavour). Are doing paper review and closeout this week. Which ones they install is still to be worked out by OPO.\u201d<\/p>\n
With the FCV issue likely to be removed as the single constraint to launch for STS-119, the Orbiter Project praised the extensive amount of teamwork undertaken by the NASA and contractor teams in working the problem \u2013 and gave an indication as to exactly how much work has been involved.<\/p>\n
\u201cOn FCV, have many activities ongoing. Have been very sensitive to team in terms of workload; tried to give people rest where think may have overtaxed people. Most work now is ongoing at Vacco in terms of getting valves reassembled and with the MSFC (Marshall Space Flight Center) Engineering team in terms of analysis\/modal analysis.<\/p>\n
\u201cHave also pulled in research centers at Ames and Glenn to help with analysis to try and not overload MSFC team. Have outstanding support from other centers in resolving this. White Sands has worked toward restoring their capability to do FCV testing. Think they may be able to get into a test as early as next week.<\/p>\n
\u201cWill take the valves they assembled and downselect based on the analysis later this week. Understand Ground Ops need date to have valves in hand is February 2, to start installing on February 3. Will accelerate that if can without taking undo risk.\u201d<\/p>\n
Other pre-launch resolution work taking place includes the completion of modifications to the SRB (Solid Rocket Booster) Holddown Post Debris Containment System (DCS) and work on the T-0 Umbilical Plates in the TSM (Tail Service Mast) on Pad 39A to mitigate ice build up on the vehicle. Articles will follow over the next few days.<\/p>\n
L2 members<\/em><\/em>: All documentation \u2013 from which 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":"
Discovery remains on track for her February 12 launch, pending the successful replacement, testing and flight rationale for the spare three Flow Control Valves (FCVs), due to arrive at the Kennedy Space Center on Wednesday. Discovery is ready to accept the valves, as the vehicle continues the process of closeouts for flight. The pad flow […]<\/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":[9191,9123,9219],"class_list":["post-41204","post","type-post","status-publish","format-standard","hentry","category-news","tag-fcv","tag-sts-119","tag-sts-126"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41204"}],"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=41204"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41204\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41204"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41204"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41204"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}