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The next earliest launch opportunity is 16 July, per the current plan, which can be \u2013 if required \u2013 negotiated with the the United Launch Alliance (ULA) to potentially juggle the range priority back to Atlantis.<\/p>\n
With Atlantis\u2019 Main Propulsion System (MPS) and Hyper pressurization tasks completed at the end of last week, S1287 operations were finalized, relating to orbiter aft closeouts. This resulted in the installation of the aft flight door and post closeout aft completion.<\/p>\n
The APU (Auxiliary Power Unit) post-door aft confidence test has also been completed, with nominal results, as the orbiter was buttoned up for her big day. Also listed was the completion of the ODS (Orbiter Docking System) confidence tests, along with final preps on the MPS ahead of launch day.<\/p>\n
NASA mission updates
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STS-135 Specific Articles: http:\/\/www.nasaspaceflight.com\/tag\/sts-135\/<\/p>\n
Only two issues required a level of engineering discussion, namely final clearance for a waiver to be issued on the Interim Problem Report (IPR-55) relating to a slight breach of limitations during pressurization tasks on the Left Orbiter Manuevering System (LOMS), in addition to work on a problematic ground TACAN unit.<\/p>\n
\u201cIPR 135V-0055, helium regulator locked up above desired limit, update: An ERB (Engineering Review Board) will be held today (Monday) to discuss waiver rationale. This will be followed by a noon board,\u201d noted the NASA Test Director (NTD) report (L2), with the waiver expected to be confirmed later in the day.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2011\/07\/TACAN.jpg\" "\\"TACAN\\"")
\u201cOn Friday, a problem with the ground TACAN station Transfer Control Unit (TCU) was detected. Weekend troubleshooting identified the power supply to the primary TCU as the root cause. Repair and retest is scheduled Monday upon completion of STA (Shuttle Trainer Aircraft) operations.\u201d<\/p>\nThe ground-based TACAN and VHF omnirange TACAN stations constitute a global navigation system for military and civilian aircraft operating at L-band frequencies (1 gigahertz). The orbiter is equipped with three TACAN sets that operate redundantly. Each TACAN has two antennas: one on the orbiter\u2019s lower forward fuselage and one on the orbiter\u2019s upper forward fuselage.<\/p>\n
The onboard TACAN sets are used for external navigation and for the orbiter during the entry phase and return-to-launch-site abort. Normally, several ground stations will be used after leaving L-band communications blackout and during the terminal area energy management phases. TACAN\u2019s maximum range is 400 nautical miles (460 statute miles).<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2011\/07\/A64.jpg\" "\\"A6\\"")
With the crew arriving at the Shuttle Landing Facility (SLF) in their T-38 jets on Monday, the latest on the weather for Friday\u2019s launch attempt remains pessimistic, as much as the ever-changable Florida weather may improve matters as the week progresses.<\/p>\n\u201cSynoptic Discussion: The Bermuda high pressure ridge is slightly north of the area, and weak, east winds will cause showers and thunderstorms to develop along the sea breeze inland today,\u201d noted the latest weather briefing by the 35th Weather Squadron (L2).<\/p>\n
\u201cOn Wednesday, a tropical wave in the vicinity of the Turks and Caicos Islands is moving west-northwest and will impact Florida on Thursday, increasing moisture and bringing scattered showers and isolated thunderstorms by Thursday afternoon and evening.<\/p>\n
\u201c
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2011\/07\/A313.jpg\" "\\"A3\\"")
By Friday, the wave will move off to the northwest, but the residual moisture will provide the ingredients necessary for showers and thunderstorms to develop as the sea breeze forms Friday late morning. Our primary concerns for launch are showers and thunderstorms within 20 nautical miles of the Shuttle Landing Facility and cumulus clouds near the flight path.\u201d<\/p>\nAs such, officials are currently forecasting a 60 percent chance of a weather violation at launch time, a probability which improves for later launch attempts.<\/p>\n
\u201cThe same concerns exist for the following two days, but due to the launch time moving earlier and a slightly dryer atmosphere on Sunday, the threat of sea breeze development during the launch window decreases each day; therefore, the probability of KSC weather prohibiting launch decreases as well.\u201d<\/p>\n
Ideally, STS-135 will want to launch at the first attempt after a nominal countdown, which would result in a Flight Day 3 rendezvous and docking, something which would also aid the potential for managers to opt to extend the mission by one extra day.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2011\/07\/A73.jpg\" "\\"A7\\"")
STS-135, also designated ISS Utilization and Logistics Flight-7 (ULF-7), is launching with a full set of mission objectives, but the situation is complicated by the combination of the widely-discussed smaller crew size with the shorter mission duration, since the available Shuttle orbiter for this mission is the one that can\u2019t receive power from the ISS.<\/p>\nA complicated set of circumstances meant that while Atlantis remained available to fly STS-135 rather than being retired a few years ago, the orbiter didn\u2019t receive the modifications necessary to use the Station-to-Shuttle Power Transfer System (SSPTS) for an extended stay at the Station.<\/p>\n
One of the other consequences is that this will be the only time that Atlantis carries an MPLM to the Station and back, even though she\u2019s been manifested to do so on at least two previous occasions.<\/p>\n
The timeline remains very tight during the docked part of the mission and there remains a desire to return as much equipment and trash from Station back to the ground as possible; close to launch, with most details of the mission now finalized, mission planners took another look at Atlantis\u2019 consumables situation to see how far away they are from being able to squeeze another day in, docked to ISS. <\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2011\/07\/A331.jpg\" "\\"A331\\"")
During the preflight briefings, STS-135 Lead Flight Director Kwatsi Alibaruho explained that while they\u2019re still a little short, there are a few ways to make up the deficit \u2013 if Atlantis launches on-time:<\/p>\n\u201cWe are flying full cryogenic tanks; our cryogenic oxygen and hydrogen tanks are used to generate electrical power, which is the limiting consumable that drives how long we can stay on orbit,\u201d he explained. \u201cBased on our analysis and based on our power requirements for this mission, we are approximately 80 kilowatt-hours away from having sufficient margin to extend from twelve days to thirteen days.<\/p>\n
\u201cWe assessed some options for making up that deficit; one option we\u2019ve discussed with the ISS program and that we\u2019ve agreed to, is that if we do launch on time, we will not power the heaters that are used to keep the MPLM warm in the payload bay. We won\u2019t power them between flight day one and flight day four, where we install the MPLM, and we won\u2019t power them after we unberth the MPLM and bring it home.\u201d<\/p>\n
Confirmed at the Flight Readiness Review (FRR), the mitigation of not powering the MPLM heaters via the orbiter\u2019s consumables will buy additional margin to aid a positive decision on the mission extension evaluations.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2011\/07\/A5511.jpg\" "\\"A5511\\"")
\u201cWe\u2019ve done analysis which suggests that the temperatures can be maintained within acceptable limits without those heaters \u2013 those heaters really provided additional capability and redundancy \u2013 so by not powering those heaters, we\u2019re going to save most of the power that we need to save in order to make up that extra day,\u201d added Mr Alibaruho.<\/p>\n\u201cThe remaining deficit \u2013 which is to the tune of right around 25 kilowatt-hours \u2013 we think we can make that up with what we call a cryo \u2018overload.\u2019<\/p>\n
\u201cWhen we\u2019re loading the cryogenics, the oxygen and hydrogen into Atlantis just prior to launch, (and) typically when we top it off and fill it up there\u2019s just that little bit extra that we\u2019re able to get in the tanks above and beyond the spec\u2019d volume of the tanks. We call that our sort-of \u2018cryo overload\u2019 and historically we\u2019ve seen a consistent trend of how much additional\u2026cryogenic oxygen and hydrogen we can get.<\/p>\n
\u201cIf we get what we\u2019ve seen typically, our analysis says that will make up the remaining deficit, so (with) the combination of cryo overload and not powering the MPLM heaters, we think that\u2019s going to get us there \u2013 if we launch on-time.\u201d<\/p>\n
Should this procedure fail to buy the expected margins, other elements of mitigation are available to the talented engineering teams on the ground.<\/p>\n
\u201cIf we don\u2019t get the cryo overload that we expect, we might be able to make up that deficit with some very modest additional powerdowns, again nothing that\u2019s critical that we would need during our travel to and from the Space Station, (for example) turning down the lights when we don\u2019t need them, that sort of thing,\u201d the Flight Director noted.<\/p>\n
\u201cThe sort of power-saving measures you might use in your own home. So we think we are actually very close to getting it if we get off on-time.\u201d<\/p>\n
(Images: Via Brian Papke (Lead and VAB) and Larry Sullivan (T-38 and crew) MaxQ Entertainment\/NASASpaceflight.com and L2 content. Further articles on STS-135\u2032s status in work, driven by L2\u2032s fast expanding STS-135 Special Section which is already into the FRR content and live flow coverage, plus more.<\/p>\n
(As with all recent missions, L2 is providing full exclusive level flow and mission coverage, available no where else on the internet. To join L2, click here: http:\/\/www.nasaspaceflight.com\/l2\/)<\/p>\n","protected":false},"excerpt":{"rendered":"
Atlantis and her engineers are now working through the complex set of tasks relating to S0007 \u2013 better known as the launch countdown \u2013 with no major issues currently under evaluation. However, Friday\u2019s countdown does have at least one challenge to overcome, related to the stormy weather which is expected to roll in over the […]<\/p>\n","protected":false},"author":1,"featured_media":29959,"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":[3659],"class_list":["post-40405","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-sts-135"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40405"}],"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=40405"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40405\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/29959"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=40405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=40405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=40405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}