{"id":899147,"date":"2026-04-14T13:21:31","date_gmt":"2026-04-14T18:21:31","guid":{"rendered":"https:\/\/newsycanuse.com\/index.php\/2026\/04\/14\/nasa-selects-centaur-for-new-sls-upper-stage\/"},"modified":"2026-04-14T13:21:31","modified_gmt":"2026-04-14T18:21:31","slug":"nasa-selects-centaur-for-new-sls-upper-stage","status":"publish","type":"post","link":"https:\/\/newsycanuse.com\/index.php\/2026\/04\/14\/nasa-selects-centaur-for-new-sls-upper-stage\/","title":{"rendered":"NASA selects Centaur for new SLS upper stage"},"content":{"rendered":"
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United Launch Alliance hoists a Centaur V upper stage atop the Vulcan first stage booster into the Vertical Integration Facility adjacent to Space Launch Complex-41 at Cape Canaveral Space Force Station, Florida. The rocket will launch the USSF-106 mission for the U.S. Space Force, Vulcan’s first national security flight. Credit: United Launch Alliance<\/span><\/figcaption><\/figure>\n
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WASHINGTON \u2014 NASA has selected the Centaur upper stage currently used on United Launch Alliance\u2019s Vulcan rocket for future flights of the Space Launch System.<\/p>\n

In a procurement filing<\/a> published March 6, NASA determined that the Vulcan Centaur 5 upper stage is the only option to replace the Exploration Upper Stage, or EUS, that was to be used on SLS launches after Artemis 3.<\/p>\n

The filing, formally known as a Justification for Other than Full and Open Competition, allows NASA to proceed with a sole-source contract to ULA for Centaur upper stages that will be used on the Artemis 4 and 5 missions, along with a flight spare. The filing redacted the estimated cost to NASA to procure the stages.<\/p>\n

The agency announced Feb. 27 it would not pursue development of the Block 1B version of the SLS<\/a>, which was to start flying on Artemis 3 and use the EUS in place of the Interim Cryogenic Propulsion Stage, or ICPS, used on the Block 1 version. The ICPS was used on Artemis 1 in 2022 and will be used on Artemis 2 and 3.<\/p>\n

At the time of the announcement, NASA said it would standardize the SLS on a \u201cnear Block 1\u201d version for missions beyond Artemis 3. Because the ICPS, also built by ULA, is based on the second stage of the now-retired Delta 4, the agency cannot simply procure additional ICPS units because the production line has been shut down.<\/p>\n

When NASA announced the decision not to continue work on the Block 1B, the agency did not disclose what stage it planned to use in place of the EUS. Agency officials deflected questions about alternative stages and even the contracting process for selecting the new stage.<\/p>\n

\"Orion
An infographic released by NASA Feb. 27 showed an Orion spacecraft on what appeared to be a Centaur upper stage. NASA stated March 6 it will use the Centaur in place of the EUS on SLS flights starting with Artemis 4. Credit:<\/span> NASA<\/span><\/figcaption><\/figure>\n

It was clear at the time, though, that there were few alternatives for NASA other than Centaur. The stage has some design similarities to the ICPS, including the use of RL10 engines powered by liquid hydrogen and liquid oxygen. Few other upper stages have similar performance and use the same propellants as Centaur.<\/p>\n

\u201cThis approach leverages current support infrastructure and will use, with relatively minor modifications, an existing ULA upper stage,\u201d the NASA filing states. \u201cAll other alternative solutions fail to meet the performance requirements, would require significant modifications to hardware that is still under development, or would require the development of new hardware that does not currently exist.\u201d<\/p>\n

The document reveals that the only other stage NASA considered was the upper stage for Blue Origin\u2019s New Glenn rocket, powered by BE-3U engines that use liquid hydrogen and liquid oxygen.<\/p>\n

That analysis concluded \u201conly the Centaur is capable (with relatively minor modifications) of meeting the requirements of the Government,\u201d the document states. The New Glenn upper stage, by contrast, \u201cwould require significant modifications.\u201d<\/p>\n

NASA concluded that the New Glenn stage, having flown only twice, \u201cis still considered to be in early phases of development,\u201d whereas versions of Centaur have been in use for more than a half-century. Adapting the New Glenn stage to SLS would also require modifications to both the stage and ground infrastructure, including potentially shortening the stage so the full SLS could pass through the main door of the Vehicle Assembly Building.<\/p>\n

\u201cFull-scale testing and requalification would result in unacceptable schedule impacts and additional cost risk to the SLS Program,\u201d the document concluded about using the New Glenn stage.<\/p>\n

The document did not disclose what \u201cminor modifications\u201d would be needed to Centaur to adapt it for use on SLS, but it emphasized ULA\u2019s familiarity with the SLS program and the common hardware between ICPS and Centaur.<\/p>\n

\u201cULA\u2019s established infrastructure, resources, flight history, existing cross-program integration, and human-rating familiarity with the Centaur upper stage represents the only currently viable opportunity for the Government to accomplish Artemis mission objectives and requirements while also maintaining the agency\u2019s programmatic goals,\u201d NASA concluded in the filing.<\/p>\n

Under current law, NASA is still required to develop the Block 1B version of SLS with the EUS. However, a NASA authorization bill approved by the Senate Commerce Committee March 4<\/a> would allow NASA to replace the EUS with an alternative upper stage if NASA determines the EUS is \u201cunlikely to achieve the mission goals of the Artemis campaign.\u201d<\/p>\n<\/p><\/div>\n

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\n\t\t\t\t\t\t\tJeff Foust writes about space policy, commercial space, and related topics for SpaceNews.<\/p>\n

He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor\u2019s degree with honors in geophysics and planetary science…\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\tMore by Jeff Foust\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n<\/p><\/div>\n<\/p><\/div>\n