Orbital ATK managers have finalized their procedures related to the newly upgraded Antares launch vehicle in readiness for upcoming missions to help deliver their Cygnus spacecraft on resupply runs to the International Space Station (ISS). The new Antares required a reworking of how to prepare the rocket for launch, such as moving away from sub-cooled liquid oxygen through to changes to the vehicle avionics and software.\n<\/p>\n
New Antares:<\/p>\n
After the CRS-3 mishap at Wallops in October 2014, Orbital ATK decided to re-engine the first stage of the launch vehicle with RD-181 engines from NPO Energomash.<\/p>\n
The two RD-181 engines replaced Aerojet AJ-26 engines that were used in the first Antares launches in 2013 and 2014. The new vehicle configuration is designated as the Antares 200 series.<\/p>\n
Cygnus flights to the ISS will use the new first stage coupled with Orbital ATK\u2019s CASTOR 30XL solid motor as a second stage in the Antares 230 configuration.<\/p>\n
![\"2016-01-02-041423\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-02-041423-350x232.jpg\")
The RD-181 engines are similar in design to the single RD-180 engine that is used on the Atlas V first stage. The two RD-181 engines will give Antares about 13 percent more thrust than the AJ-26 engines, according to Kurt Eberly, Orbital ATK Antares Deputy Program Manager.<\/p>\n
\u201cWe\u2019re using the same amount of propellant and we\u2019ll get through it quicker because of that higher thrust,\u201d Mr. Eberly noted to NASASpaceFlight.com. \u201cThe 130 (configuration) was about 234 seconds (in duration); this is going to be about 214, that\u2019s the predicted cutoff.\u201d<\/p>\n
Mr. Eberly noted another significant change, where moving away from the AJ-26 meant the Antares would no longer use sub-cooled liquid oxygen.<\/p>\n
Space Shuttle models (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n The change from sub-cooled liquid oxygen to boiling point liquid oxygen also drove changes to the Antares pad at Wallops, Pad 0A. The original plan was to remove the sub-cooler needed for the AJ-26.<\/p>\n \u201cWe were going to take the sub-cooler out, but then we started looking back at the data for cross-country LOX temperature rise from the storage tank across an uninsulated line to the launch mount and we scared ourselves that on a worst-case day we could be too warm,\u201d Mr. Eberly explained.<\/p>\n \u201cWe have a bypass line that goes through the sub-cooler so we can chill some of the LOX and mix it back into the main LOX. We\u2019ve been testing that with them and so far it\u2019s been working pretty well. It gives us fine temperature control of the LOX that is going into the vehicle.\u201d<\/p>\n In addition to hardware changes to the first-stage propellant feedlines and thrust frame required by changing the engines, there were some significant changes to the vehicle avionics and software.<\/p>\n \u201cNow we\u2019re closing the loop within our avionics, so Orbital ATK avionics are doing more of the job for the RD-181 configuration \u2013 and it\u2019s just different, so we\u2019ve had to adapt our avionics to interface with the engines.<\/p>\n \u201cThat lower level code is new and we\u2019ve got a whole \u201cbench-top\u201d set up in Chandler, Arizona; that\u2019s where we do most of our manufacturing for avionics and harnessing and the upper stack structures. So we\u2019ve got non-flight valves set up \u2018on the table,\u2019 (and) we\u2019re just running through all the different control algorithms and making sure they\u2019re working right.<\/p>\n \u201cEverything is going really well. We\u2019re in a software validation phase, (where) we go down all the different logical paths at the code level, (doing) unit level testing, and then we\u2019ll do systems level testing at Wallops when we get that code released.<\/p>\n \u201cThen we\u2019ll go through mission simulations where we (are) practicing with the rocket flying the mission.\u201d<\/p>\n \u201cThis is a Cardian joint on these engines, whereas with the AJ-26 there was a gimbal joint that gimballed the whole engine and you had to put a whole lot of flexibility in our feedlines,\u201d Mr. Eberly continued. \u201c(On) these, the thrust chamber and the turbopumps are all fixed and then there\u2019s this Cardian joint, which is a basically a metal bellows that rotates the nozzle. The same joint is used on the RD-180.\u201d<\/p>\n Another major difference is in engine operation and control.<\/p>\n \u201cIt\u2019s a different design and so there\u2019s a different sequence \u2013 we\u2019ve worked through that with Energomash. We have a detailed document that prescribes all of that. After ignition there\u2019s a health check; we already had the structure for that for the AJ-26, and one of the key parameters is pump speed.<\/p>\n \u201cWe\u2019re going to mechanize that and practice it and then the hot-fire test \u2013 the stage test \u2013 will be the real verification of that. And then the shutdown sequence is similar, there\u2019s a series of valves that have to be operated to shut down the engines and put on purges that are required after engine cut off.\u201d<\/p>\n The Antares 230 vehicle will be able to lift a Cygnus spacecraft loaded with as much as 3200 kg of cargo. However, depending on NASA\u2019s needs for a given mission, some of that performance could be allocated in other ways besides cargo upmass.<\/p>\n \u201cWe can go to an instantaneous launch window, that would then mean we can devote more performance to Cygnus, but we try to strike a balance (with the length of the window),\u201d Mr. Eberly added.<\/p>\n \u201cLet\u2019s say there\u2019s a boat (on the range) \u2013 (it\u2019s useful) if they (have time to) get a spotter plane so he can get his eyes on something to meet their probabilistic risk assessment. So there is some benefit to having a five or fifteen-minute launch window.<\/p>\n \u201cSo we try to balance the use of the excess performance \u2013 we could launch them to a higher orbit, we could have a longer launch window \u2013 it\u2019s just a matter of how you spend the performance on the mission design.\u201d<\/p>\n For the OA-5 mission on Antares, the current plan has a fifteen-minute long launch window. However, that remains subject to change until more details for the mission are finalized.<\/p>\n \u201cIf they came back with even less cargo, we may re-evaluate this approach to give us a bigger window. Typically, we finalize that manifest at about four months prior to launch with the customer \u2013 we have a cargo integration review, we call it.\u201d<\/p>\n The launch day countdown will also be a little different for Antares. Mr. Eberly noted that Orbital ATK is restructuring the countdown and pre-countdown timeline.<\/p>\n \u201cA lot of that (time) is spent in preparing the ground systems for the (propellant) loading. We start loading at about an hour and a half, we start with liquid oxygen and then about 30 minutes later we start with the RP (RP-1 refined kerosene fuel) and then we do them simultaneously from there on.<\/p>\n \u201cIt\u2019s all automated process control with human intervention.\u201d<\/p>\n \u201cAt three minutes we handover to the flight computer onboard the vehicle, but we can still stop (the sequence) from ground intervention.<\/p>\n \u201cFrom three minutes, we pressurize the tanks, we switch the navigation to free inertial, and then inside three minutes we start the ignition sequence \u2013 there\u2019s a purge of the main chamber and the turbopumps with heated nitrogen and then there\u2019s a whole sequence that starts the engine. It\u2019s similar to the RD-180.\u201d<\/p>\n As noted earlier, the countdown culminates in the ignition sequence of the RD-181 engines, which involves the engines coming to life, but no vehicle movement for a few seconds.<\/p>\n \u201cAt T-0 (we) start the ignition process, and we won\u2019t lift off for over three seconds. There\u2019s a number of automated health checks on a number of parameters on each engine. The main one being when we get up and running we check the turbopump speed, that\u2019s the main indicator and that means everything is healthy if those speeds are in the right range.<\/p>\n \u201cI think it is fifty-five percent is what we ignite to and (if) we pass the health check we throttle up the engines, which takes about a second, we release the hold-down mechanisms, and we rock back the transporter erector launcher (TEL) which serves as our umbilical mast. As thrust exceeds mass, we\u2019re cutting commodity lines, which are pyro-released.\u201d<\/p>\n \u201cThat\u2019s to save that transporter erector launcher and reduce the amount of impingement from the plume on that because we want to turn that around pretty quickly,\u201d Mr. Eberly added.<\/p>\n There will also continue to be a relatively long coast period between the first-stage and second-stage burns when Antares returns to flight.<\/p>\n \u201cWe start closed-loop guidance during that coast phase and we figure out where we are, where we want to be, and we\u2019ve got a whole algorithm. We use PEG, Powered Explicit Guidance, it was developed by NASA a while back,\u201d Eberly explained.<\/p>\n Cygnus still has one more ride atop the ULA Atlas V before the spacecraft joins forces with her intended ride to orbit.<\/p>\n Per the recent CRS2 contract award, Cygnus can now ride with either the Antares or Atlas V for future missions, with NASA\u2019s focus on the upmass, as opposed to the launch vehicle tasked with lofting the spacecraft.<\/p>\n (Images via Orbital ATK, NASA and via L2\u2019s Antares\/Cygnus Section \u2013 Containing presentations, videos, a vast set of unreleased hi-res images, interactive high level updates and more).<\/p>\n (Click here: http:\/\/www.nasaspaceflight.com\/l2\/ \u2013 to view how you can support NSF and access the best space flight content on the entire internet).<\/p>\n","protected":false},"excerpt":{"rendered":" Orbital ATK managers have finalized their procedures related to the newly upgraded Antares launch vehicle in readiness for upcoming missions to help deliver their Cygnus spacecraft on resupply runs to the International Space Station (ISS). The new Antares required a reworking of how to prepare the rocket for launch, such as moving away from sub-cooled […]<\/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":[1871,2304,639,233],"class_list":["post-39147","post","type-post","status-publish","format-standard","hentry","category-news","tag-antares","tag-crs","tag-cygnus","tag-iss"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39147"}],"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=39147"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/39147\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=39147"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=39147"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=39147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Hot](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2013\/03\/Z32.jpg\")
\u201cThat was consistent with the design of the NK-33, to use sub-cooled LOX \u2013 here we use normal boiling point LOX, but the temperature constraints that we\u2019ve been given from Energomash are fairly strict because they don\u2019t have a lot of test history at different temperatures.\u201d<\/p>\n![\"2016-01-21-124214\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-124214-350x243.jpg\")
\u201cSo we traded off installing vacuum-jacketed line all across there which is very expensive and hard to implement and we made the decision with MARS (Mid-Atlantic Regional Spaceport) to add the sub-cooler back in, but implemented in such a way that it\u2019s (only) there when we need it.<\/p>\n![\"2016-01-21-124310\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-124310-350x237.jpg\")
\u201cThere are a bunch of new interfaces,\u201d Mr. Eberly added. \u201cWe had a Moog TVC (Thrust Vector Control) box that we communicated with digitally and then it closed the loop when we wanted to steer the AJ-26 engines.<\/p>\n![\"2016-01-21-124414\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-124414-350x252.jpg\")
The way the RD-181 engines are gimballed is also different from the AJ-26.These engines can be gimbaled up to plus or minus five degrees.<\/p>\n![\"2016-01-21-124908\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-124908-350x256.jpg\")
\u201cThe ignition sequence for the RD-181 is very different from the AJ-26,\u201d Mr. Eberly noted. \u201cThere\u2019s a series of solenoid valves that have to open in a certain sequence when compared to the AJ-26 which had a lot of pyro valves.<\/p>\n![\"2016-01-21-125002\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-125002-350x263.jpg\")
Currently, the hot-fire of an Antares first stage at Pad 0A is planned for mid-March.<\/p>\nSee Also<\/h4>\n
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![\"2016-01-21-125109\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-125109-350x235.jpg\")
\u201cRight now we\u2019re protecting against loading 3200 kilograms of cargo, but we\u2019re going through the process of what NASA intends to fly,\u201d noted Dave Hastman, Orbital ATK CRS Deputy Program Director. \u201c(But) they might not take advantage of that full 3200.<\/p>\n![\"2016-01-21-125208\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-125208-350x226.jpg\")
\u201cWe had a long countdown for the 130 (original configuration) \u2013 we\u2019re going to shorten that up (and) put a lot of stuff in the pre-count, things like filling the sub-cooler with liquid nitrogen,\u201d he explained. \u201cSo we\u2019re going to shorten that to around five hours.<\/p>\n![\"2016-01-21-153523\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-153523-350x216.jpg\")
Mr. Eberly also outlined the terminal countdown automatic sequence that will be employed with the new Antares.<\/p>\n![\"2016-01-21-153640\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-153640-350x251.jpg\")
\u201cIt sits on the ground for a while, this ignition sequence. It\u2019s more of a heart attack situation for everybody involved where you see the flames come out but nothing really happens.<\/p>\n![\"2016-01-21-153753\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-153753-350x250.jpg\")
As before, Antares will perform the \u201cBaumgartner Maneuver\u201d shortly after liftoff. Named after Antares Guidance Navigation and Control (GNC) lead Paul Baumgartner, the vehicle pitches slightly away from the TEL.<\/p>\n![\"2016-01-21-154201\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2016\/01\/2016-01-21-154201-350x251.jpg\")
\u201cThat\u2019s really useful for when your last stage is a solid rocket motor. Basically, it divides up the burn of the solid rocket motor into a first half and second half \u2013 so you\u2019re continuing to correct your guidance based on even the performance of the first half of the solid rocket motor burn and feed that into how you fly the second half.\u201d<\/p>\n