Expedition 18 Commander Michael Fincke, Flight Engineer and Soyuz TMA-13 Commander Yury Lonchakov and space tourist Charles Simonyi have returned home safely, following their landing in Kazakhstan this morning. The safe return backs up the findings presented in an expansive NASA and Russian document that outlined the off-nominal ballistic re-entries of Soyuz TMA-10 and 11, and the subsiquent mitigation proceedures undertaken.<\/p>\n<\/p>\n
The landing took place near the town of Dzhezkazgan, which is west of Karaganda and southeast of the usual landing zone near Arkalyk. Fincke and Lonchakov have been aboard the orbiting laboratory since October 2008, following their ride to the ISS on the same Soyuz they landed with.<\/p>\n
The Expedition 18 crew members undocked their Soyuz from the station at 10:55 pm CDT April 7. The deorbit burn to slow the Soyuz and begin its descent toward Earth began at 1:24 am this morning. The landing was moved to a more southerly landing site because of poor landing conditions at the original site.<\/p>\n
Off-Nominal re-entries investigation:<\/p>\n
The nominal re-entry and landing follows an issue-free return for Soyuz TMA-12. However, Soyuz TMA-11 and TMA-10 both suffered from what is called a ballistic re-entry \u2013 a degraded mode for landing, which initiates a steep trajectory, resulting in a much shorter than planned re-entry, exposing the crew to up to 10G.<\/p>\n
![\"a34\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/04\/a34.jpg\" "\\"a34\\"")
The Soyuz Vehicle consists of three modules: the Orbital Module, the Descent Module (DM), and the Instrumentation\/Propulsion Module (IPM). All three modules nominally separate simultaneously, shortly after the deorbit burn is completed \u2013 at around 140 km altitude.<\/p>\n
The two \u201coff nominal\u201d re-entries in 2007 and 2008 were the cause of separation failures on the modules, thus initiating the ballistic return for their three person crews.<\/p>\n
Aerospace industry analysis (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n \u201cIn October 2007, Soyuz 14S (TMA 10) undocked from ISS and landed in Kazakhstan. The Instrument and Propulsion Module and the Descent Module failed to separate when commanded,\u201d the large investigation document, available on L2, outlined. \u201cVehicle trims in a hatch-forward configuration when modules fail to separate. The modules eventually separated at approximately 80 km.<\/p>\n \u201cSubsequently the \u201cBallistic Mode\u201d was entered (steeper trajectory, higher G-loads) and the vehicle successfully landed at the ballistic landing site. A special commission was formed to investigate these events.<\/p>\n \u201cIn April 2008, Soyuz 15S (TMA 11) undocked from ISS and landed in Kazakhstan. The Instrument and Propulsion module and the Descent Module again failed to separate when commanded. Vehicle trims in a hatch-forward configuration when modules fail to separate. The modules eventually separated at approximately 60 \u2013 66 km.<\/p>\n \u201cThe \u201cBallistic Mode\u201d was entered and the vehicle successfully landed at the ballistic landing site. Two commissions were formed to investigate these events: External Commission headed by Koroteev from the Keldish Institute. RSC-E internal Commission headed by Lapota.\u201d<\/p>\n On both occasions, the failure of one or more pyro bolts \u2013 which initiate separation \u2013 was deemed to be the root cause of the modules remaining together, prior to the eventual release of the DM due to aerodynamic drag and mainly heating loads.<\/p>\n However, this came only after a prolonged period of the vehicle diving through re-entry \u201chatch first\u201d.<\/p>\n \u201cThe DM \/ IPM interfaces consists of 5 \u2018locks\u2019 and 5 pusher springs,\u201d the document explained. \u201cEach lock has 2 pyro bolts that are commanded simultaneously. 1 of 2 is required to successfully open the lock and allow separation. The pusher springs provide the force to separate the DM \/ IPM modules after the locks release.<\/p>\n \u201cKoroteev Commission conducted an extensive investigation. 26 Branch Fault Tree that encompassed failures: Electrical firing circuits for separation. Failure of the pyro bolts. Mechanical failure of the lock.\u201d<\/p>\n \u201cWorst Case Assumption for Mechanism Penetration Insulation,\u201d explained one slide on the presentation. \u201cHatch failure assumed when temperature of hatch aluminum structure reaches point where internal pressure causes failure, around 750 degrees F.\u201d<\/p>\n However, a Russian slide (see left) added to the investigation document appears to show the period of time Soyuz TMA-12 was in the \u201chatch forward\u201d position was relatively short, with post landing photography backing up the slide, showing most of the vehicle\u2019s TPS (Thermal Protection System) was in reasonably good shape, with only the antenna melted away.<\/p>\n Findings:<\/p>\n Following the investigation, the Commission found that the most likely cause of the failure to open the latch located at \u201cPlane I\u201d of the interface, \u201cwas a failure of the 8 X 55 explosive bolt, caused by combined long-term exposure, under space flight conditions, to electrical discharges resulting from the difference in potential between the station hull and the surrounding plasma, which increased in magnitude after the electrical power capacity of the ISS was augmented.\u201d<\/p>\n The findings relating to the long-term exposure to electromagnetic emissions on-orbit, and their potential to cause issues with the pyro bolts, came after an extensive investigation that included the removal and return of one pyro bolt from Soyuz TMA-12.<\/p>\n The removal came via EVA 20A, a special Russian spacewalk which was conducted by Sergei Volkov and Oleg Kononenko. Their task was to remove one of 10 pyrotechnic bolts from the docked Soyuz, and place it in the blast-proof canister, which was subsequently returned to Russian engineers on the ground.<\/p>\n \u201cSoyuz commissions (one independent and one internal to Energia) were discussed at SORR (Stage Operations Readiness Review),\u2019 noted a memo to senior managers, during the investigation. \u2018According to the Russian report, the most likely cause of pyro bolt issue was long-term exposure to the space environment and electromagnetic emissions.\u201d<\/p>\n Soyuz TMA-12 \u2013 minus one of its pyro bolts \u2013 returned to Earth on a nominal re-entry, landing on October 24, 2008. This vehicle also debuted a software patch, to aid the nominal chain of events during the separation of the modules, and cause the acceleration of a heating load forced separation in the event of a pyro bolt failure \u2013 by positioning the vehicle sideways on to the re-entry path.<\/p>\n \u201c16S vehicle (TMA 12) had pyro lock at Plane 1 released via EVA by removing 1 of 2 pyrotechnic bolts. Bolt returned to ground to support root cause investigation,\u201d noted the presentation. \u201cVehicle had new software patch installed. 16S re-entry nominal.<\/p>\n \u201cTelemetry was obtained that verified software patch was functional (although did not affect re-entry since nominal separation occurred). Only received 30 sec of telemetry from separated IPM, but showed software was being executed up to that point. Note: Russians have flown a receiver with the capability of recovering telemetry from IPM for future re-entries.<\/p>\n The Commission used the findings to work on changes to the Soyuz TMA-13, which Expedition 18 crew members returned on without issue.<\/p>\n \u201cChanges made to 17S (TMA 13) vehicle in response to Commission findings: Based on the Russian Commission findings, several changes were made to the 17S vehicle currently on-orbit,\u201d added the document.<\/p>\n Replaced the pyro bolts with a more robust design that is less susceptible to the electromagnetic environment.<\/p>\n \u201cInstituted a software change that will use IPM thrusters to force the vehicle to re-enter \u201csideways,\u201d increasing heat loading on the truss, helping lead to truss failure and earlier separation.<\/p>\n \u201cTo be implemented on all future Soyuz re-entries. Software acts on IPM thrusters whether separation occurs or not.<\/p>\n \u201cPerformed a significant number of vehicle system checks to verify quality of TMA-13.\u201d<\/p>\n US Assessment:<\/p>\n NASA \u2013 with an obvious stake in both the safe return of their ISS crewmembers, and future interest in the utilization of the Russian vehicle during the gap between shuttle retirement and Orion\u2019s debut \u2013 held their own investigation into the Russian findings.<\/p>\n No specific conclusions were formed via the NASA overview, bar a specific understanding of both the anomalies and the consequences, and a level of concurance with the Russian findings.<\/p>\n \u201cNASA formed a team to perform analysis Included members from Engineering, Operations, Crew, Safety, NESC, and the ISSP,\u201d noted the NASA section of the presentation.<\/p>\n \u201cGoal was to perform analysis based on the best information available to better understand Soyuz re-entry dynamics, and to better understand the Russian Commission report when it became available.<\/p>\n \u201cAnalysis based on: Basic vehicle data provided by RSC-E. Discussion between RS and US specialists. Soyuz 14S and 15S crew comments. Training for US crew members. Best Engineering judgment of our engineers based on similar materials and design practices.\u201d<\/p>\n \u201cObjectives: Assess truss failure and generate 15S notional trajectory. Compare with telemetry data provided by Russians. Implement software patch via analysis and assess effectiveness in accelerating truss failure. Compare with analysis data provided by Russians. Suppress DM-IPM separation and assess survivability of the hatch and chute covers.<\/p>\n \u201cCompare with photographs from 15S re-entry. Note \u2013 analysis assumes that all 5 pyro locks fail to release. Since failure occurs due to heating, at a time when aero forces are relatively low, separation time should be similar no matter how many locks fail to release.\u201d<\/p>\n Included in the findings are notes that the crew on Soyuz TMA-11 suffered from almost 8.5G during part of their re-entry, and that there is a serious risk \u2013 albeit under worst case scenarios \u2013 that the hatch could fail, or the parachute cover could incur damage \u2013 both hold the serious threat of LOV\/C (Loss Of Vehicle\/Crew).<\/p>\n \u201cAnalysis Summary: Notional trajectory (15S) had truss failure at 67.85 km altitude. Max g = 8.42 gees, consistent with crew experience. Comparable trends with Russian telemetry data. Software patch is effective in accelerating truss failure,\u201d noted the presentation.<\/p>\n \u201cNotional truss failure at 70.44 km (conservative), an acceleration of 2.6 km in altitude or 12.91 sec. Russians\u2019 range of separation altitudes with software patch is within the bounds of our calculations. Russians\u2019 range is 77 \u2013 83 km. Our range is 68 \u2013 89 km<\/p>\n \u201cIf separation did not occur and the spacecraft continued in the hatch-forward orientation. With worst case assumptions, the hatch would fail: Failure altitude = 55.95 km (11.9 km from notional truss failure). Failure time = 400 sec (59.49 sec from notional truss failure)<\/p>\n \u201cWith more realistic design assumptions, the hatch frame survives with a margin of around 100 degrees F from burst temperature. With conservative assumptions, the chute cover would fail: Failure altitude = 35.9 km (31.95 km from notional truss failure). Failure time = 487 sec (146.5 sec from notional truss failure).\u201d<\/p>\n \u201cISS environments team does not feel that plasma environment caused electrical potential issue, BUT, with improperly grounded system, failure of the type predicted is possible. Pyrotechnic experts have evaluated \u201cdud-ing\u201d condition of pyros. Dud-ing phenomenon is possible, but low probability<\/p>\n \u201cNOTE: Results from Russian testing of returned pyro bolt have shown no anomalous behavior. NDE (Non Destructive Evaluation) inspections. Destructively fired at minimum \u201cAll Fire\u201d current.\u201d<\/p>\n Overall, NASA appear to be satisfied with the Russian Commission\u2019s findings, and the actions taken to mitigate the threat of future issues during Soyuz re-entries.<\/p>\n \u201cConclusions From Analysis Team: Russian developed Fault Tree is very thorough, nothing to add from our side. IF the \u201cmost probable root cause,\u201d as identified by the Russians is correct, all of the implemented changes are consistent with actions we would have taken.<\/p>\n \u201cIf another pyro failure occurs, the software patch is likely to help facilitate an earlier separation than without it, and should not make the situation worse.<\/p>\n \u201cOur independent analysis agreed well with Russian provided data. Pyrotechnic and environments experts believe the stated most probable cause is possible, however unlikely in our experience.<\/p>\n \u201cDetailed analysis of the hatch and parachute compartment indicate that truss section is likely to fail, leading to successful separation, prior to failure of either the hatch or parachute compartment. However, this analysis is based on multiple assumptions and an incomplete knowledge of the entire system and other potential failure modes.\u201d<\/p>\n Backing up both the NASA and Russian findings has been the safe return of Soyuz TMA-13, which was the focus of the presentation \u2013 created at the end of February for evaluation by the STS-119 Flight Readiness Review (FRR) \u2013 due to the requirement for flight rationale with the immediate downstream plan relating to STS-119, and Soyuz TMA-13.<\/p>\n \u201c17S vehicle has several modifications to address the identified most likely root cause: Replaced pyros (8X55 with 15X571) with a design less susceptible to EMI (similar to those used in the APAS).<\/p>\n \u201cImproved bonding in Plane 1 pyro lock area with the used of Aluminized tape. Replaced explosive bolt power cables with new cables having enhanced shielding. Routed the cables attached to the explosive bolts along two independent paths. Introduced lockwiring of pyro bolt electrical connections.<\/p>\n \u201cThe software patch is available and planned for use, analysis indicates that it will help ensure separation. Independent re-entry analysis indicates truss will likely fail due to thermal heating prior to hatch or parachute compartment failure, leading to successful re-entry.\u201d<\/p>\n As expected, the experts were proven right, early on Wednesday morning.<\/p>\n L2 members<\/em><\/em>: 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":" Expedition 18 Commander Michael Fincke, Flight Engineer and Soyuz TMA-13 Commander Yury Lonchakov and space tourist Charles Simonyi have returned home safely, following their landing in Kazakhstan this morning. The safe return backs up the findings presented in an expansive NASA and Russian document that outlined the off-nominal ballistic re-entries of Soyuz TMA-10 and 11, […]<\/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":[233,1302],"class_list":["post-41137","post","type-post","status-publish","format-standard","hentry","category-news","tag-iss","tag-soyuz"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41137"}],"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=41137"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/41137\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=41137"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=41137"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=41137"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}See Also<\/h4>\n
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![\"a25\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/04\/a25.jpg\" "\\"a25\\"")
\u201cHatch forward\u201d is undesirable for long periods of time during re-entry, due to the obvious risk of excessive heating causing a breach, which would result in the loss of the Soyuz crew.<\/p>\n![\"a51\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/04\/a51.jpg\" "\\"a51\\"")
\u201cCorrected the grounding issues at the Plane 1 pyro lock location. Physical separation of the pyro firing cables. Lockwiring the pyro connectors.<\/p>\n![\"a42\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/04\/a42.jpg\" "\\"a42\\"")
NASA\u2019s highly regarded thermal modelling capability, used mainly on shuttle analysis, is put to work on several slides relating to heating loads on the Soyuz \u2013 mainly used on working out when the separation of the modules would occur, in the event of a nominal separation failure.<\/p>\n![\"a61\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/04\/a61.jpg\" "\\"a61\\"")
Also included in the presentation is one slide titled \u201cAlternative Engineering Evaluations,\u201d noting dissenting opinion on the Russian findings on the root cause of the pyro bolt issues, although it is conceded that the alternative explanation has a low probability.<\/p>\n![\"a72\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2009\/04\/a72.jpg\" "\\"a72\\"")
\u201c17S Return Flight Rationale: Separation failures are still Unexplained Anomalies, however, 17S\/TMA 13 vehicle highly scrutinized and tested due to anomaly,\u201d added the presentation, which also summarized the actions taken with Soyuz TMA-13.<\/p>\n