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<\/p>\nIn the latest of a series of Request For Information (RFI) filings, NASA has called for alternative options to the RS-25 engine that will power the core stage of the Space Launch System (SLS). The RFI appears to be aimed at engines to be used after the RS-25Ds left over from the Space Shuttle era \u2013 and some already purchased RS-25Es \u2013 have been used up, although the requirements section all-but ensures new RS-25s \u2013 the expendable version that is already being worked on \u2013 will remain the engine of choice.<\/p>\n
The Space Launch System (SLS) is a \u201cShuttle Derived Heavy Lift Launch Vehicle\u201d \u2013 or SD HLV, as requested via the 2010 Authorization Act that gave birth to the vehicle design as NASA moved away from the failing Constellation Program (CxP) and its Ares rockets.<\/p>\n
While the design of SLS went through a number of rigorous reviews \u2013 via the RAC (Requirements Analysis Cycle) effort \u2013 which allowed alternative rockets to be considered as NASA\u2019s next HLV, the political direction heavily weighted the decision-making process towards using existing technology from the Shuttle era.<\/p>\n
<\/p>\n
Slide used during the RAC to show many rockets were considered to become SLS \u2013 NASA\/L2<\/p>\n
Although that continues to be referenced by detractors, the plus side is the rocket will be making use of proven technology that has a rich heritage from the Shuttle era, not least the final salvo of flights that saw flawless performance from the final iterations of the RS-25 and Solid Rocket Boosters (SRBs).<\/p>\n
However, that heritage also includes the large costs associated with the Shuttle program, which have \u2013 despite some streamlining \u2013 fed into the SLS program.<\/p>\n
With NASA having large amounts of success in utilizing commercial companies that compete against each other for NASA contracts, the RFI and RFP (Request For Proposals) route has become increasingly popular in trying to create a competitive environment with SLS contracts, with the aim of reducing overall costs to the NASA budget line.<\/p>\n
However, with SLS locked into a very specific design, that has proven almost impossible with the rocket. The latest RFI provides another example that one person involved with SLS told NSF was \u201clike the Russian Presidential election. You have to have one, but there\u2019s only going to be one winner.\u201d<\/p>\n
SLS\u2019 first four flights have engine assignments based on the stock of RS-25s, most of which were handed over from the Shuttle program. The RFI is looking for an additional 18 engines to cover flights in the second half of the 2020s.<\/p>\n
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<\/p>\n
The current stock of RS-25Ds \u2013 via NASA<\/p>\n
The LEO (Liquid Engine Office) at the Marshall Space Flight Center (MSFC) is seeking potential sources to provide the Core Stage Engines (CSEs) in support of the flight manifest,\u201d noted the RFI.<\/p>\n
(adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n
\u201cThe SLS vehicle architecture is documented and it is expected that the first four CSEs (from this next contract) will be required to be delivered by July 2025. The CSE currently in this architecture is the RS-25 engine (derived from the Space Shuttle Main Engine). The early SLS flights will utilize RS-25 engines.\u201d<\/p>\n
However, those sources must conform to numerous requirements that rule out most \u2013 if not all \u2013 of the more obvious contenders to the RS-25.<\/p>\n
\u201cNASA is seeking CSE design sustainability, manufacturing, assembly, test, analysis, certification, and flight support capabilities that can meet its technical and programmatic constraints. The engines must meet or exceed the performance, interface, and reliability requirements of the current RS-25 engine to avoid costly impacts to the vehicle and core stage design.<\/p>\n
\u201cAs such, the engines must be certified to meet the current RS-25 functional,human-rating and performance requirements, match interface conditions and design configurations, and operate within all natural and induced environmental constraints.\u201d<\/p>\n
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<\/p>\n
The specific requirements on the RFI<\/p>\n
The general requirements refine the request down to a near-match of the RS-25.<\/p>\n
The RFI and its timing are strange, given it\u2019s been no secret SLS wants the RS-25 to be the engine of choice for the long-term.<\/p>\n
Back in 2015, NASA awarded Aerojet Rocketdyne over a billion dollars to restart production capability for the RS-25, focusing on the RS-25E \u2013 the expendable version of the engine. This also included an order for six additional engines, for a total cost of around $1.5 billion. A decision to move away from the RS-25 in the second half of the 2020s would effectively mean NASA paid $1.5 billion for six engines.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2018\/04\/2018-04-11-192818.jpg\")
<\/p>\n
RS-25\u2019s firing on the core stage of SLS \u2013 as envisioned by Nathan Koga for NSF\/L2<\/p>\n
NASA issued a \u201cJustification for Other Than Full and Open Competition (JOFOC)\u201d in accordance with the Federal Acquisition Regulation (FAR) as a result of the sole-source nature of the deal.<\/p>\n
The JOFOC literally ruled out any other engine for SLS\u2019 core, which would likely be used in future reasoning if a company somehow managed to propose an alternative to the RS-25 via the latest RFI.<\/p>\n
The total engine stock, based on Shuttle\u2019s \u201chand-me-down\u201d engines, an additional stock created from spare parts, and the six engines ordered via Aerojet Rocketdyne would support SLS\u2019 first five missions, taking into account the need for flight spares, etc.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2018\/04\/2018-04-11-185035.jpg\")
<\/p>\n
The four RS-25s \u2013 all Shuttle veterans \u2013 that will launch the EM-1 SLS mission<\/p>\n
As such, the RFI is focused on at least the sixth SLS flight onwards, but only a re-order from Aerojet Rocketdyne makes sense per the requirements and the money already invested in the re-start of production facilities.<\/p>\n
A huge amount of work has already taken place on refining the engines for their next role, with numerous test firings at the Stennis Space Center already conducted \u2013 with more to come. The engines have also gained additional upgrades via the use of 3D printed parts and upgraded engine controllers.<\/p>\n
The engines are preparing for the upcoming milestone of the Green Run test, which will be conducted on the modified B-2 test stand at Stennis. This will be the first time four RS-25 engines \u2013 on the first Core Stage \u2013 will be fired for a full mission duration of approximately 500 seconds.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the latest of a series of Request For Information (RFI) filings, NASA has called for alternative options to the RS-25 engine that will power the core stage of the Space Launch System (SLS). The RFI appears to be aimed at engines to be used after the RS-25Ds left over from the Space Shuttle era […]<\/p>\n","protected":false},"author":1,"featured_media":38478,"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":[2363,624,8116],"class_list":["post-38476","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-rs-25","tag-sls","tag-ssme"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/38476"}],"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=38476"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/38476\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media\/38478"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=38476"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=38476"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=38476"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}