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Alternatives to the Ares approach included the unofficial, yet highly public Direct team effort on a Jupiter Inline family of launchers and architectures, and an official \u2013 but behind the scenes \u2013 Sidemount effort, which became a larger team effort in late 2008.<\/p>\n
SSP manager John Shannon was able to publicly present the status of the preliminary Sidemount effort to the Augustine Committee\u2019s review into Human Space Flight in 2009, covering a variety of disciplines, even as engineers continued to add and refine the Sidemount system.<\/p>\n
In late 2009, Mr Shannon requested the Inline SD HLV to be included in the analysis to provide a comparison with the Sidemount system. Sources note the Inline systems were developed independently by Mr Shannon\u2019s team, as opposed to directly using the Jupiter vehicle blueprints, despite meetings between NASA officials and the Direct team members, and the great similarity between the architecture.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A92.jpg\" "\\"A92\\"")
NASA also requested for a trade study (HLLV Study) to be carried out on the HLV options, notably between the RP-1 booster, Sidemount and Inline systems. The SSP Assessment effort, however, ran independent of that study, but provided input.<\/p>\nRocket building kits
<\/path>Spaceflight <\/path>SpaceX <\/path>\n (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n
Work continued in earnest until President Obama\u2019s 2011 budget was unveiled in February, which proposed the cancellation of the Constellation Program (CxP), but also the use of Shuttle-derived systems, with SSP given notice to shut down their HLV study activities by completing the documentation of their findings.<\/p>\n
The documented effort on the SD HLV was completed this month, resulting in an impressive \u2013 and highly extensive \u2013 726 page presentation, which was acquired by L2.<\/p>\n
\u201cThis document describes the pre-Phase A concept definition, studies, and analysis results generated by the Space Shuttle Program on various Shuttle-derived Heavy-lift Launch Vehicle (HLV) concepts over a 15-month timeframe from December, 2008 through February, 2010,\u201d noted Mr Shannon in the foreword of the presentation, dated June 8.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A314.jpg\" "\\"A3\\"")
\u201cThe work was performed in response to questions from the 2008 Presidential Transition Team, the Augustine Committee\u2019s \u2018Review of United States Human Space Flight Plans,\u2019 and a 2009 internal NASA assessment of Heavy-lift Vehicles. Subsequent to the release of the President\u2019s proposed FY2011 budget in February 2010, HLV assessment activity was halted and effort began to document the preliminary results.<\/p>\n\u201cThis document reflects the hard work and dedication of individuals representing the Space Shuttle Program and its contractor community. The contributions of this team have contributed to the Agency\u2019s understanding of Heavy-lift Vehicles and are greatly appreciated.\u201d<\/p>\n
\u201cWhen the HLV assessment was stopped, some work was left unfinished, as noted by the inconsistency in detail found in the various sections. Results documented in this document should be considered similar to a Pre-Phase A collection of concept studies. A sound project formulation activity would be required to add necessary detail.\u201d<\/p>\n
\u201cThis document is under configuration control of the Space Shuttle Program\u2026 to preserve the knowledge developed by the subject activity.\u201d<\/p>\n
*Click here for NASASpaceflight.com HLV Articles*<\/p>\n
A Smooth Transition:<\/p>\n
The focus of the assessment \u2013 which concentrates on the Sidemount option \u2013 is based around a block transition of existing Shuttle hardware, for early flights using remaining assets left over after Shuttle, prior to the upgrading via new hardware and software.<\/p>\n
\u201cShuttle derived is the dominating factor that sets these studies apart from other similar assessments. This objective was to maximize the use of existing Space Shuttle skills and assets for developing and operating the HLV. This includes using the flight hardware, the flight software, the facilities, the processes and the skilled contractor and civil servant personnel that have been used successfully on the Space Shuttle,\u201d noted the Executive Summary.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A191.jpg\" "\\"A19\\"")
\u201cA block development approach was adopted to provide the earliest possible capability at the lowest cost and risk, and then evolve that capability over time. Block I uses the residual Shuttle flight hardware with little or no modifications, while Block II would replace the Shuttle subsystems and elements with new hardware and software when the existing assets ran out.\u201d<\/p>\nAs previously noted in memos on the ongoing studies, hardware availability allowed for the potential for around three flights of the Block I SD HLV. Extensive outlines on the actual stock count of SD hardware is provided later in the presentation.<\/p>\n
\u201cThe existing inventory of the certified flight hardware is sufficient to support three or more flights after the Shuttle\u2019s planned retirement. The only major new development for Block I would be the Payload Carrier (PLC) that replaces the Orbiter on the side of the External Tank (ET),\u201d the summary continued.<\/p>\n
\u201cBlock III upgrades could be done later to increase performance and reduce launch costs to support NASA\u2019s future needs.\u201d<\/p>\n
Also key to the findings, the proposed HLV is part of a larger mission architecture, one which could provide additional support for the International Space Station (ISS) if required, mainly via cargo capability, but also via crewed versions of the vehicle, and on to Lunar mission support and beyond.<\/p>\n
The presentation also noted that the crewed HLV version would utilize the Orion in its original role of transporting astronauts into orbit and back, as opposed to the FY2011 proposal of an interim role only as a Crew Rescue Vehicle (CRV) on the ISS.<\/p>\n
\u201cThe HLV is primarily for cargo and provides an excellent foundational capability for heavy-lift. It can deliver 80 metric tons (mt) of gross cargo to Low Earth Orbit (LEO), 45 mt to the International Space Station (ISS), 30 mt to Geosynchronous Orbit (GEO) and 8-10mt to the lunar surface.<\/p>\n
\u201cA capsule such as the Orion Crew Exploration Vehicle (CEV) can be added to the top of the PLC to carry crew to the ISS or do manned lunar or other crewed missions. A Launch Abort System (LAS) can be added to this crewed configuration which would significantly improve the estimated loss of crew (LOC) rate by a factor of 5 to 10 compared to the current Space Shuttle.\u201d<\/p>\n
\u201cThe goal was to have the HLV ready and tested prior to the planned Orion completion so it could be used as a crewed launch vehicle or as a backup for a commercial crewed launch vehicle.\u201d<\/p>\n
The Executive Summary also reported the findings that the Inline version of a SD HLV is at a disadvantage to the Sidemount, based on schedule and cost and degree of infrastructure changes. However, while the presentation focuses mainly on the Sidemount, due to the late start to the Inline study, both versions \u2013 along with the potential to start with Sidemount, before merging into an Inline vehicle \u2013 are deemed to be feasible.<\/p>\n
\u201cLate in the HLV concept definition studies, the HLV team was asked to evaluate an inline Shuttle derived HLV development with same approach and strategy to use existing Shuttle assets and compare those results to the side mount HLV,\u201d continued the Executive Study.<\/p>\n
\u201cThe in-line HLV performance results were very similar to the side mount HLV since using the same number of Solid Rocket Booster (SRB) segments, the same number of Space Shuttle Main Engines (SSME) and propellant loads were basically the same. Block I development would take about two years or longer than the side mount.<\/p>\n
\u201cBuilding the PLC for the side mount and adding a new thrust structure to house the SSME\u2019s on the bottom of the ET for the in-line core stage would be a wash. The largest difference would be that the launch pad and the mobile launch platform (MLP) would require a launch tower for the taller in-line vehicle and considerable changes to the MLP and the Tail Service Mast (TSM) configuration.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A20.jpg\" "\\"A20\\"")
\u201cThese additional changes for the in-line HLV could take longer and would cost more than the side mount. This document contains more information for the side mount than the in-line HLV due to the late start on the inline.\u201d<\/p>\n\u201cBoth are feasible and could provide a heavy-lift capability much sooner than a new heavy-lift launch vehicle. A viable option (no cost analysis yet) could be to start with the side mount first then evolve to an in-line HLV if and when needed.\u201d<\/p>\n
The summary also noted what is arguably the most attractive elements of a SD HLV-based transition; schedule, cost, and skillsets. Operational proficiency , a key aspect in flying safely and minimizing the gap in the current SSP operations team, is a critical driver and very perishable. Loosing the critical skills only to hire and train a new team seven years in the future could be very disruptive.<\/p>\n
\u201cThese studies identified some major advantages in pursuing a Shuttle derived HLV capability as soon as possible. First, it retains the Shuttle infrastructure and critical skills needed to fill the gap in our nation\u2019s human launch capability, and maintaining the United States\u2019 leadership in space exploration.<\/p>\n
\u201cSecond, it would provide a foundational heavy-lift launch capability that could support maintenance and growth for the ISS, it could be used to develop a propellant resupply depot in space, and it could be used to demonstrate critical subsystems and elements that would expand or raise the technology readiness level for future deep space operations. It could also support flexible path missions beyond LEO that would be building blocks and validate the systems needed to eventually go to Mars.\u201d<\/p>\n
\u201cThe primary advantage is that the Shuttle derived HLV provides a foundational heavy-lift capability soon, at affordable costs and relatively low risk, thus enabling meaningful development and space operations missions while providing the time and resources to develop the technologies and systems to meet our future space exploration needs.\u201d<\/p>\n
Interestingly, while the study team\u2019s primary goal is to document the findings of the extensive studies, as opposed to enacting an effort that is currently opposed by the FY2011 proposal, an element of hope is noted for the documentation to become the basis of a commercial proposal for a HLV that would fit into President Obama\u2019s outline for NASA\u2019s future.<\/p>\n
\u201cThe intent in documenting the results of these HLV concept definition studies and analyses is to make this wealth of information available to the Shuttle contractors and the commercial space systems development and operations community to meet our country\u2019s space exploration needs,\u201d the summary added.<\/p>\n
\u201cWe encourage the use of this data to support a commercial venture that would own and operate a Shuttle derived HLV system. Commercial ownership and operation of such a Shuttle derived HLV system may be a practical way to significantly reduce the operating costs to fly the current Space Shuttle while providing a near term, low risk heavy-lift capability for our national space program.\u201d<\/p>\n
Sidemount SD HLV:<\/p>\n
With history back as far as the Shuttle-C concept, the Sidemount HLV is the most natural of the transitions from the STS design.<\/p>\n
\u201cThe side mount HLV make extensive use of legacy Space Shuttle assets. The primary ascent elements of the SSP [ET, RSRB, SSME] are unchanged from their current configuration,\u201d outlined the presentation.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A413.jpg\" "\\"A4\\"")
\u201cThe main propulsion module is connected to the ET in the same manner as the Shuttle except there is no requirement for disconnects as the module remains attached to the ET after main engine cutoff. The avionics and software of the Orbiter will be virtually unchanged from their current configuration and functions, and are to be mounted in either the HLV aft propulsion module or distributed on the Payload Carrier (PLC).\u201d<\/p>\nThe first flight of the Sidemount HLV would have utilized the spare ET-94 tank, currently housed at the Michoud Assembly Facility (MAF) in New Orleans. This tank is a LWT (Light Weight Tank) as opposed to the SLWT (Super Light Weight Tanks) currently used by the Shuttle to achieve larger masses to be carried uphill.<\/p>\n
\u201cThe earliest flight configuration of the side mount HLV could use an existing Lightweight External Tank (ET-94) and a propulsion module boat tail based on the existing Shuttle design. Later versions of side mount HLV would use Super Lightweight Tanks (SLWT) and a new design boat tail housing the SSMEs.\u201d<\/p>\n
\u201cThe primary new element is the Payload Carrier with a payload envelope of 7.5-m x 30-m. The selection of a 7.5-m diameter was picked as the latest practical diameter that support future missions. Further analysis has shifted the focus to smaller lander designs for lunar orbit rendezvous missions and EDS designs based on a cluster of RL-10 class engines.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A73.jpg\" "\\"A7\\"")
\u201cWhile such later designs could be accommodated using a 6.5-m diameter Payload Carrier, it was decided to retain the larger diameter for future mission growth. Fairing elements of the Payload Carrier are jettisoned during the ascent to increase payload capabilities.\u201d<\/p>\nAnalysis of the use of a propulsion\/avionics module was also conducted to provide a future option to recover \u201chigh value assets\u201d following launch of the HLV \u2013 namely the SSME engine systems and avionics.<\/p>\n
\u201cBecause the staging point of the SSME propulsion is around Mach 17 for a J-2X upper stage or Mach 24 for an RL-10 upper stage, the module would reenter and land in the Atlantic Ocean.<\/p>\n
Inline SD HLV:<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A58.jpg\" "\\"A5\\"")
As referenced by the Direct Team\u2019s Jupiter Inline vehicle concepts, this design also has a history reaching back as far as the Marshall Space Flight Center (MSFC) studies (1990s) to design a shuttle-based heavy lift cargo vehicle to compliment the Space Shuttle. Known as the National Launch System (NLS), the concept was deemed to have significant merit \u2013 before being deleted due to budgetary concerns.<\/p>\n\u201cThe SSMEs and RSRBs are used unchanged. The propulsion module is positioned at the aft end of the in-line tank and the payload carrier is placed in-line above the tank,\u201d noted the presentation on both commonality and changes. \u201cBecause of the axial and bending loads the in-line tank requires strengthening beyond that of a standard External Tank design.<\/p>\n
\u201cIn addition the forward LOX tank is redesigned from the ogive shape of the External Tank to a cylindrical tank section with elliptical domes.<\/p>\n
\u201cThere are more extensive changes to the Mobile Launch Platform, Fixed and Rotating Service Structures, and tail service masts to accommodate the taller in-line configuration. There are also significant changes in the Vehicle Assembly Building (VAB) to assembly and servicing platforms. Payload fairings are jettisoned on the way to orbit to increase payload capabilities.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A8.jpg\" "\\"A8\\"")
A fascinating mitigation of numerous infrastructure challenges would be to place the SSMEs\/MPS on the side of the Inline vehicle, which would mirror the STS aft end on the current MLP and Pad.<\/p>\n\u201cAn alternative HLV configuration was also examined late in the study period. This hybrid concept uses an in-line mounting of the payload at the upper end of the in-line Shuttle derived tank, but retains the SSME engine placement in the side mount position as on the Shuttle.<\/p>\n
\u201cThe intent was to define a low-cost, interim flight demonstration vehicle that allowed use of an existing External Tank and minimized infrastructure changes especially at the MLP.<\/p>\n
However, this concept also has challenges of its own, such as offloading propellants during a pad abort, and axial and bending loads on the intertank region.<\/p>\n
\u201cA notional extensibility approach for operational vehicles using this hybrid concept is shown (in the graphic \u2013 left). The advantages include reducing the number of changes to the launch pad and also providing for easier detachment of the propulsion modules when used in conjunction with the recovery module concept presented (see reference in Sidemount overview).\u201d<\/p>\n
Upper Stages:<\/p>\n
Suborbital staging to increase payload capabilities is a charge that has sometimes been cited in opposition to the ESAS findings, which \u2013 mainly due to the restrictive timeline of the study \u2013 was deemed to have only made a cursory examination of the SD HLV options, notably Sidemount.<\/p>\n
The design of the Upper Stage is a key element to the ability of the HLV, to conduct the mission of interest.<\/p>\n
\u201cThe HLV has the capability of taking large cargo to an orbital or suborbital stage point. For a useful mission this cargo must contain the propulsion necessary to carry payloads to a final destination. This propulsion element may be integrated with the payload, but usually takes the form of an upper stage. Examples of upper stages include existing and new designs.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A118.jpg\" "\\"A11\\"")
\u201cEarly deployment of payloads to LEO or beyond LEO using Block I HLV could utilize existing stages such as the Delta IV or Atlas V upper stages. Such stages could support demonstration missions such as a lunar swing-by Orion test mission or GEO deployment of a Space-based Solar Power Satellite demonstrator.\u201d<\/p>\n\u201cBlock II and Block III HLV would also use new design upper stages based on various rocket engines including J-2X and the RL-10 family.\u201d<\/p>\n
Engineers went back further into the history of the program for the Upper Stage evaluations, referencing the engine used during the Apollo era.<\/p>\n
\u201cExisting systems were compared against mission needs and the original Apollo upper stage, the S-IVB, to highlight attributes of a successful configuration.<\/p>\n
\u201cBy taking this approach, the development of a fully integrated HLV flight system is possible that maximizes the application, with minimal redesign, of the Shuttle elements which remain in near-term production while replacing those elements \u2013 with the exception of the Payload Carrier \u2013 that are not in production with those derived from existing Evolved Expendable Launch Vehicle (EELV) systems.\u201d<\/p>\n
\u201cThis creates an overall vehicle capable of high performance, but with minimal development time and cost. A smaller and simpler upper stage derived from commercial experience also eliminates a large measure of the upper stage propulsion, avionics and systemic development efforts and refocuses those efforts on tailoring a stage uniquely suited to the requirements of a Shuttle derived Heavy-lift Launch Vehicle.\u201d<\/p>\n
The Block I, II, III approach:<\/p>\n
The three block approach would apply to both the Sidemount and Inline vehicles, a building block design approach that was determined as the best way to minimize cost and utilize Shuttle assets. There are three blocks in total, with Block I including a Proto Demo Test Flight for the in-line configuration.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A64.jpg\" "\\"A6\\"")
\u201cThe Block I HLV utilizes existing Shuttle assets wherever practical. The first flights are based on a large inventory of existing assets including RSRB, ET, SSMEs, avionics and software and other subsystems. The RSRBs are used unchanged,\u201d the presentation outlined.<\/p>\n\u201cFor side mount HLV the External Tank is unchanged except for minor modifications to ET bipod and thermal protection in targeted areas. Block I inline HLV will require a development effort for the in-line tank. Legacy SSMEs are housed in the propulsion module structure based on the existing Shuttle boat tail for the side mount HLV or on a new design for the in-line configurations.\u201d<\/p>\n
\u201cShuttle avionics and software and other applicable subsystems (e.g. APU, RCS) are modified or used unchanged. A new payload carrier with jettisonable fairings is developed. Existing upper stages may be used for various mission types.\u201d<\/p>\n
\u201cBlock II HLV: New production expendable SSMEs are used. These SSME are routinely run at 109 percent power level during ascent which will necessitate several minor modifications to the MPS (e.g. LH2 feedline flowliners, GO2\/GH2 flow control valve orifices, etc.). The side mount ET has further strengthening in localized ring frame areas. A new design side mount propulsion module replaces the Shuttle boat tail design.\u201d<\/p>\n
\u201cThe payload carrier design for cargo is modified for crew. Improved subsystems (non-toxic propellants, electromechanical actuators, etc) are used. Crew capability is provided using the Orion spacecraft with Launch Abort System. Provided are new avionics computers with emulation of current Shuttle computer architecture allowing current flight software to be used with little modification and low risk.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A131.jpg\" "\\"A13\\"")
\u201cFor larger payload flights beyond LEO a new Earth Departure Stage (EDS) is developed. Initially the J-2X engine from the Constellation program was baselined. However, later trade studies showed that an EDS based on RL-10 engines provided a lower mass and higher payload solution for missions beyond LEO.\u201d<\/p>\n\u201cBlock III HLV: To maximize payload to orbit, the Block III HLV uses four SSMEs housed in a reconfigured propulsion module design. These expendable SSMEs are routinely run at 111 percent power level during ascent. Significant modifications to the MPS will be needed to accommodate this configuration. The 4-segment RSRBs are replaced by 5-segment RSRBs for higher thrust.\u201d<\/p>\n
\u201cThe External Tank or in-line tanks are lengthened to accommodate a higher propellant load. The EDS from Block II also has increased propellant capacity tanks. This results in a 33 percent increase in payload capability over Block II.\u201d<\/p>\n
Available Assets from STS:<\/p>\n
A large effort was placed into inventory analysis of existing and required systems for \u2013 at the very least \u2013 the Block I flights, along with ground rules and associated costs and procedures on contract awards. Key areas \u2013 such as available ET, SSME and SRB hardware \u2013 provided an interesting status review of overflow STS assets.<\/p>\n
\u201cSSMEs: The SSME Project Office presented to the Shuttle derived Heavy-lift Launch Vehicle (SD HLV) team on two occasions. The Pratt & Whitney designation for the current configuration SSME is RS-25D,\u201d noted the presentation.\u201d<\/p>\n
\u201cThe first SSME Project Office presentation to the HLV team occurred on August 21, 2009. This briefing was in response to questions from the HLV team attempting to validate a cost analysis performed at the request of the HLV team. The SSME Project was asked to assess the reasonableness of the cost estimate as well as its associated assumptions.\u201d<\/p>\n
\u201cThe SSME Project determined the cost estimate to be reasonable with the following two exceptions: a. The estimate lacked sufficient funds to provide for tooling and infrastructure investments necessary to meet 15 engine per-year production goals. The SSME Project recommended adding 125 million dollars for capital investments. b. The estimate lacked sufficient funds to provide for design, development and certification costs. The SSME Project office recommended adding funds.\u201d<\/p>\n
\u201cThe SSME project recommended maintaining the current concept of operations for RS-25 fabrication, assembly, test and delivery. In this process, line replaceable units (LRUs) are completed by PWR and shipped to Kennedy Space Center (KSC) for engine assembly. Assembled engines are then shipped to Stennis Space Center (SSC) for acceptance testing, after which they are shipped back to KSC for installation and flight processing.\u201d<\/p>\n
A reference is also made to a decision that was noted by the all-powerful Program Requirements Control Board (PRCB) meeting in January of this year, where a proposal was put forward to delay the disposal of SSME assets, pending \u2018future launch vehicle architecture\u2019 decisions, which \u2013 as per the SD HLV presentation \u2013 now appears to have been an extension to the \u2018feasibility\u2019 of SSME production restart.<\/p>\n
\u201cAt the time of the briefing, SSME production restart was feasible. The assessment determined that in-house tooling and critical skills were still available to enable restart. Further, the majority of vendors were still available. However, some vendor restart funds would be required. It was determined that the Space Shuttle Transition and Retirement activity posed a significant risk to potential future RS-25 production,\u201d the SD HLV presentation added, before noting flight rate demands.\u201d<\/p>\n
\u201cTwo potential design changes were presented as necessary. The current RS-25 main combustion chamber would likely be replaced with a Hot Isostatic Pressing (Hip) Bonded MCC to help meet production rate goals. The current engine controller would be replaced after the current inventory was depleted. The current controller is made of electronic parts which are not currently available. Therefore a new design would be required.\u201d<\/p>\n
\u201cThe HLV team proposed a flight rate which would require up to 15 RS-25 engines per year. Heritage RS-25 production has not emphasized delivery schedule for many years. Rather, production was driven by funding and other resources demands. This brings into question the use of historical production actuals as the basis for estimates in a high-production rate environment. This further illustrates that caution should be used when doing so to ensure valid estimates.\u201d<\/p>\n
In total, 15 SSMEs are expected to be available at the end of the current Shuttle manifest, along with two development engines.<\/p>\n
\u201cProjections at the time of the briefing indicated that 15 current configuration (Block II) RS-25D flight engines would be available at the end of the current SSP manifest which included flights through STS-134. Additionally, 2 development engines would also be available. This projection included completion and acceptance testing of engine 2062 and 4 high-pressure turbopump recycles which were unfunded at the time of the briefing.\u201d<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2010\/06\/A9.jpg\" "\\"A9\\"")
A reference is also made to a new version of the SSME, called the RS-25E, which aids the HLV benefits via lower costs.<\/p>\n\u201cThe RS-25E design consists of design and process changes necessary to lower the per-unit cost as well as decrease the required production cycle time. An attempt was made to strike a balance between retaining current RS-25D reliability, while sufficiently improving cost and fabrication time with minimal design, development and certification requirements.\u201d<\/p>\n
\u201cThe previous end of program forecast indicated that 15 legacy flight RS-25Ds and 2 development RS-25Ds would be available. The recommendation to the HLV team was to assume 12 HLV flight ready RS-25D assets. This would provide 3 flight and 2 development engines for RS-25E development and certification testing, as well as stage\/main propulsion test article (MPTA) testing.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
The Shuttle Derived Heavy-Lift Launch Vehicle (SD HLV) Assessment has been completed, the result of applying years of historical expertise from members of the Space Shuttle Program (SSP) and others into a follow-on vehicle. The focused effort over 15 months to create a post-shuttle masterplan has fostered HLV options that could be completed to a […]<\/p>\n","protected":false},"author":1,"featured_media":29551,"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":[9034],"class_list":["post-40744","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-hlv"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40744"}],"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=40744"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/40744\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/29551"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=40744"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=40744"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=40744"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}