United Space Alliance workers at the Kennedy Space Center have begun the mating of Discovery to ET-121 and its twin Solid Rocket Boosters this morning. <\/p>\n
Meanwhile, Marshall Space Flight Center have been testing a LH2 Diffuser to evaluate whether a third Tanking Test will be required to determine the cause of over-cycling issues. The LH2 pressurization relief valve that cycled nearly twice as many times than normal during the two tanking tests. Discovery will be rolled back out of the Vehicle Assembly Building in mid-June, following the mating with ET-121 \u2013 which was to have flown with Atlantis on the second Return to Flight launch. <\/font><\/p>\n The External Tank swap has a slightly ironic twist given the issues that have arisen over the previous two Tanking Tests. <\/font><\/p>\n Officially slated to be sent back to its manufacturer \u2013 NASA\u2019s Michoud Assembly Facility in New Orleans \u2013 to have its propellant line fitted with new heaters in order to help elevate concerns of icing on the ET, sources have noted an issue with the Liquid Hydrogen Diffuser, which is receiving its fair share of attention as a possible cause of liquid hydrogen pressurization relief valve over-cycling nearly twice as many times during the Tanking Tests than is normal. <\/font><\/p>\n Only recently revealed by a USA source \u2013 the Diffuser on ET-120 is a new design, a \u2018Double Weaved\u2019 Diffuser, compared to the single mesh Diffuser that has flown on previous Shuttle launches. <\/font><\/p>\n The new Diffuser was tested this weekend at Marshal Space Flight Center (MSFC) in Alabama \u2013 as they press for a third Tanking Test in order to try and pinpoint the cause of the over-cycling. <\/font><\/p>\n \u201cIn the case of the diffuser; the double mesh was not per the drawing configuration,\u201d said a source. \u201cMSFC did not notice that the diffuser was not per drawing (specification). <\/font><\/p>\n \u201cThe double mesh was never tested for flight; it was never integrated into the STS (Space Transportation System). Reports that the double mesh was a modification were not correct. The double mesh was a bad part from the vendor which was not recognized by the MSFC inspection prior to installation. <\/font><\/p>\n NASA mission patches (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n \u201cIn my opinion the vendor made a mistake and did not realize the mistake. The MSFC inspectors missed it as well. It will be interesting to get the test details on Monday.\u201d <\/font><\/p>\n The details of MSFC\u2019s evaluations is still to be made known, although NASA\u2019s Systems Engineering and Integration (SE&I) have \u2013 on Monday \u2013 noted their take on the situation. <\/font><\/p>\n Their key points noted that the: \u201cDiffuser test results obtained late last week and over the weekend have significant impact on the anomaly investigation. Data review from these tests has not yet been completed. Analyses which simulate these component test results and characterize the actual diffuser flow field and associated heat transfer in the ET ullage need to be completed. \u201cAlthough the technical community agrees that the test results are significant, there is disagreement over whether the results warrant conclusions without completion of the analysis. Not possible to achieve consensus of technical community regarding further program action until analysis is complete. Data analysis will be completed this week. CFD analysis of diffuser flow field will be completed this week. <\/font><\/p>\n \u201cConsequently, SE&I is bringing forward recommendations for program action without the endorsement of the entire community <\/p>\n The report added confirmation that the Diffuser is likely to be the cause of the issues \u2013 which would help the case against the requirement for a third Tanking Test, given ET-121 \u2013 which will fly with Discovery in the July window \u2013 has the old Diffuser which has not raised the issues noted.<\/p>\n \u201cMost probable cause of tanking test pressurization anomaly is Diffuser in Improper Configuration,\u201d the report from NASA\u2019s SE&I continued. \u201c(The) Program should attempt to complete chain of engineering that links changes in diffuser flow to increased heat transfer from ullage gas. <\/font><\/p>\n \u201cDue to uncertainties in analysis, (the) program should not expect a perfect match between heat transfer characterized by CFD\/mixing analysis and heat transfer required to create anomaly as predicted by system model. The only possible test objective for additional tanking test would be to identify any remaining effects of RTF redesign on heat transfer\/pressurization of external tank once the diffuser is returned to proper configuration. Fault tree analysis has indicated a minimum potential for additional causes of pressurization anomaly.\u201d <\/font><\/p>\n Most importantly, NASA\u2019s SE&I has backed United Space Alliance against the MSFC recommendation, and noted their position as \u201cnot conduct an additional tanking test but to proceed to flight. With the obvious issue of not wanting to launch with what is classed as an Unexplained Anomaly (UA), the report also listed the concerns that have been raised by some quarters of the NASA engineering community.<\/p>\n \u201cJSC engineering is concerned that reoccurrence of ET ullage high temperature value would indicate an error in our failure identification methodology and that unknown phenomena would be present. JSC engineering is concerned that in-flight analysis might not bound the unknown phenomena. JSC engineering recommends that if elimination of the ET ullage temperature anomaly is not verified by tanking test that an RTF-only ullage temperature LCC be instituted to detect reoccurrence of the anomaly. Anomaly can only be detected under T-1min 57 secs. <\/font><\/p>\n \u201cKSC Chief Engineer is concerned that we should complete demonstration of our working hypothesis of pressurization anomaly by full scale tanking demonstration. ET project is concerned about making a decision prior to completion of analysis and recommends continuing preparation to test. Analysis completion will be after start of tanking test preps for most tanking test opportunities, so a decision to start planning in parallel with analysis really is a decision to execute.\u201d <\/font><\/p>\n This leaves the requirement of a third Tanking Test still very much under review \u2013 a review that will still take a number of days. <\/font><\/p>\n <\/p>\n Should another tanking test be required, the impact on the launch schedule should only be minimal, with the ability to still make the mid-to-end of July window very much open.<\/p>\n <\/font><\/p>\n","protected":false},"excerpt":{"rendered":" United Space Alliance workers at the Kennedy Space Center have begun the mating of Discovery to ET-121 and its twin Solid Rocket Boosters this morning. Meanwhile, Marshall Space Flight Center have been testing a LH2 Diffuser to evaluate whether a third Tanking Test will be required to determine the cause of over-cycling issues. 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":[],"class_list":["post-42380","post","type-post","status-publish","format-standard","hentry","category-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/42380"}],"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=42380"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/42380\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=42380"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=42380"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=42380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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It went on to note that they are \u201cconfident that will be able to characterize gas\/heat transport, (but) less confident in capability of analysis to accurately quantify heat transfer from gas to structure and to liquid hydrogen.<\/font><\/p>\n
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\u201cPressurization anomalies that can pass existing LCC have been assessed and determined to meet normal certification criteria nominal ascent, RTLS and nominal ascent with 1 flow control valve failed closed protects ET ullage pressure and NPSP constraints. If mixing\/heat transfer analysis shows an small effect rather than the anticipated larger effect, then this recommendation would require re-evaluation.\u201d <\/font><\/p>\n