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However, that position has been reevaluated now that Endeavour is tracking a rather pro-longed stay inside OPF-2 for a newly realigned launch date of February 2011 for the STS-134\/ULF-6 mission.<\/p>\n
As outlined by a PRCB (Program Requirements Control Board) presentation (available for download on L2), \u201cThe 4th & 5th Orbiter BLT DTO [flights] will attempt to gather flight-derived data regarding the effects of Mach 19.5 transition due to a 0.50\u2033 protuberance on the Space Shuttle Orbiter during the re-entry trajectory.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/a25.jpg\" "\\"a25\\"")
In all, for STS-133, CR approval will see Discovery fly with a 0.5\u2033 protuberance tile and a total of 10 thermocouples located on the protuberance tile as well as downstream TPS tiles. These thermocouples will record the valuable data sought by the DTO team.<\/p>\nAdditionally, Discovery will fly with the 2nd re-flight (3rd total flight) of the Catalytic Coating DTO. This will involve coating one TPS tile with a catalytic coating material and installing two thermocouples to measure both the heating effects of the catalytic coating as well as the \u201cfully-turbulent heating\u201d from the BLT DTO tile.<\/p>\n
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Furthermore, while the BLT DTO experiment on STS-134\/Endeavour would be tasked with gathering more data on the effects of 0.5\u2033 protuberance, Endeavour will only be affixed with three (3) thermocouples instead of 10 and will not carry a TPS tile coated with the catalytic coating.<\/p>\n
Benefits and Significance of a 0.5\u2033 BLT DTO Tile:<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A313.jpg\" "\\"A3\\"")
As noted by the PRCB presentation, there are several benefits to flying two 0.5\u2033 BLT DTO protuberance flights that will trip the Boundary Layer at ~Mach 19, not the least of which being the benefit to future spacecraft returning to Earth from \u201ctrajectories beyond LEO (Low Earth Orbit).\u201d<\/p>\n\u201cBLT FE Flight Test Objectives planned to include three primary areas of entry data: Boundary Layer Transition, Turbulent Heating, Turbulent\/Catalytic Heating.\u201d<\/p>\n
In all, Boundary Layer transition data has been collected on three previous Discovery flights: STS-119, STS-128, and STS-131.<\/p>\n
However, the presentation notes that the data collected for \u201cturbulent heating\u201d on STS-128 and STS-131 was \u201ccompromised.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A412.jpg\" "\\"A4\\"")
Likewise, the two flights (STS-128 and STS-131) designed to provide data on Turbulent\/Catalytic Heating both produced \u201ccompromised\u201d data beginning at the first roll maneuver during entry.<\/p>\nEngineers have determined that the BLT DTO data is being compromised by a \u201csurface thermocouple measurement anomaly;\u201d however, the root cause for this anomaly has not yet been determined.<\/p>\n
The presentation notes that Orbiter flight testing to \u201cdisprove some legs of root cause\u201d are possible, as is the addition of alternate measurements for the BLT DTO flight on Endeavour that could lead to \u201cfuture design changes for entry instrumentation.\u201d<\/p>\n
However, since BLT onset data is extremely limited in controlled environments, and obtaining \u201cfully turbulent data at higher Mach numbers will provide more relevant data for re-entry trajectories beyond LEO,\u201d an increase of the BLT DTO protuberance tile from 0.35\u2033 to 0.5\u2033 was requested for STS-133.<\/p>\n
Moreover, the addition of a second 0.5\u2033 BLT DTO on Endeavour\/STS-134 was requested to help \u201creduce uncertainty from 1.06 to 0.90 times the standard deviation of the flight data,\u201d notes the PRCB document.<\/p>\n
\u201cAdding BLT FE flight will allow the technical community to rigorously evaluate ground\/flight scaling because the flight uncertainty will no longer be dominated by the number of flights.\u201d<\/p>\n
STS-134 Specific Articles: http:\/\/www.nasaspaceflight.com\/tag\/sts-134\/<\/p>\n
Furthermore, highlighting the multi-faceted potential of the Space Shuttle Orbiter is its ability to gather this BLT data, a fact noted in the PRCB presentation.<\/p>\n
\u201cDecreasing the Uncertainty of BLT prediction with Orbiter flight data is one of the primary benefits being accomplished by the BLT Flight Experiment.\u201d<\/p>\n
Currently, there is a +\/- Mach 2.5 uncertainty factor in all BLT onset prediction tools.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A57.jpg\" "\\"A5\\"")
As part of the BLT DTO process, engineering teams were tasked with determining the BLT Mach increment increase from the previous flight for the progressive BLT DTO. Their analysis showed that a Mach increment of >1.0 in \u201cfree stream Mach number would provide a unique data point of magnitude similar or greater to the 1-sigma uncertainty of the current state of the art empirical BLT prediction capability.\u201d<\/p>\nA BLT protuberance height of 0.5\u2033 would translate to a trip of boundary layer at ~Mach 19, an increment increase of ~1.5 from STS-131\u2019s Mach 17.5 trip of the boundary layer.<\/p>\n
In all previous Boundary Layer trips during flight, no trips exceed the Mach 17.9 limit. Thus, STS-133 will be the first occurrence of a break in the BLT flight history.<\/p>\n
BLT DTO Predictions for 0.5\u2033 Protuberance:<\/p>\n
A benefit of the previous BLT DTO flights in regard to STS-133 and STS-134 is the understanding that the unadjusted aeroheating analysis tools \u201cover-predict\u201d heating flux.<\/p>\n
In fact, the analysis tools over-predicted the STS-119 heating environment by ~900-degrees F compared to the actual flight data.<\/p>\n
Following this understanding, a \u201cunique method [was] developed to account for the discrepancy between analysis and flight data.\u201d This allowed the teams to analyze potential temperature problems downstream of the TPS protuberance on STS-128 and STS-131 while still maintaining a high degree of conservatism.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A63.jpg\" "\\"A6\\"")
Furthermore, these \u201clessons learned\u201d were applied to the pre-decisional analysis of the 0.5\u2033 BLT protuberance.<\/p>\nIn all, an extremely conservative Orbiter weight was assumed for each mission. (STS-133\u2019s Nominal End Of Mission [NEOM] weight is ~204,000 lbs v. the 233,000 lbs analysis weight. Likewise, STS-134\u2019s NEOM weight is ~203,000 lbs v. the 233,000 lbs analysis weight.)<\/p>\n
A Mach 14.6 BLT for all areas upstream of the protuberance was used \u2013 a measurement that includes all but nine (9) recorded Orbiter flights in the history of the Space Shuttle Program. These non-included flights are believed to be a result of upstream gap fillers that would be seen and accounted for under current program on-orbit imagery inspections.<\/p>\n
Furthermore, \u201cAnalysis for STS-133\/134 used conservative & generic wing heating limits. Less-conservative location & configuration specific limits could have been used, but were not,\u201d notes the PRCB document.<\/p>\n
Moreover, the document notes that \u201ctrends in heating adjustments\u201d were required to match flight data and that additional reductions in heating are required as the height of the protuberance increases, reductions that were made to properly predicted the 0.5\u2033 protuberance heating environment.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A72.jpg\" "\\"A7\\"")
Engineers further utilized the Arc Jet facility to understand the potential heating environment induced by the protuberance.<\/p>\nA protuberance height of 0.35\u2033 (the height flown on STS-128 and STS-131) was used and the heating capacity of the Arc Jet facility was increased by \u201cutilizing a 14-heater pack configuration.\u201d<\/p>\n
The document notes that during the highest temperature run the protuberance temperature reached 3,000-degrees F \u2013 at which point, 180-seconds into the test, all temperature measurements were lost \u201cpresumably due to thermocouple wire exposure to hot gas flow.\u201d<\/p>\n
Post-test inspection showed a change to the shape of the protuberance and a reduction to its height \u2013 which correlated to a decrease in the upstream and downstream temperatures.<\/p>\n
According to the document, \u201cThis provides some level of validation that a protuberance that experiences over-temperature conditions and changes shape will result in a progressively more benign environment downstream of the protuberance.\u201d<\/p>\n
Therefore, \u201cAnalysis and results have been reviewed and approved by the Entry Aeroheating Panel, Orbiter Thermal Panel, BLT IPT, TPS PRT and members of the SLD Panel,\u201d notes the PRCB document<\/p>\n","protected":false},"excerpt":{"rendered":"
As NASA and Space Shuttle Program Managers continue to narrow down options for the final two missions on the flight manifest, preparations and modifications for\/to Orbiters Discovery and Endeavour are continuing in their respective Orbiter Processing Facilities (OPFs) at the Kennedy Space Center \u2013 most notably the process to approve a new Boundary Layer Transition […]<\/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":[9196,9051,3366],"class_list":["post-40746","post","type-post","status-publish","format-standard","hentry","category-news","tag-blt","tag-sts-133","tag-sts-134"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40746"}],"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=40746"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40746\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=40746"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=40746"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=40746"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}