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Not in citation given. "-C" ( sdsds - talk) 23:41, 10 December 2016 (UTC) reply

• To be clear Bergin's article is a very good source to cite. It just doesn't support the (presumed correct) assertion that the RL10 variant that will be used on EUS is the new RL10-C. Maybe https://www.nasa.gov/exploration/systems/sls/proven-engine-packs-big-in-space-punch-for-nasa-s-sls-rocket.html ? ( sdsds - talk) 23:45, 10 December 2016 (UTC) reply

That says "The EUS will use four RL10C-3 engines, ... NASA recently contracted with Aerojet Rocketdyne of West Palm Beach, Florida for the production of 10 RL10C-3 engines for the rockets second and third flights with Orion, as well as two spare engines." (Oct 2016)

Bergin (April 2016) [1] says "Per the EUS POD, the definitions called for the stage to utilize four RL-1OC-3 engines" - I'll change the cite to the later Oct ref. - Rod57 ( talk) 10:27, 10 January 2018 (UTC) reply

What tests are planned before the flight hardware is built or flown ? - Rod57 ( talk) 13:34, 12 February 2018 (UTC) reply

Need to mention Blue Origins proposed alternative, and NASA's rejection of it. - I'll look for some sources ... - Rod57 ( talk) 14:10, 9 November 2019 (UTC) reply

Made a brief mention, with source. [2] - Rod57 ( talk) 13:42, 17 October 2020 (UTC) reply

EUS development delays are not mentioned. It was to have been used on the first manned SLS/Orion (EM-2?) but funding delays in 2019, 2020, and maybe earlier, seem to have pushed the first planned use of EUS out to Artemis-4 ! (find RS - maybe Upper Stage RL10s arrive at Stennis for upcoming SLS launches Feb 2020 or Amid competing priorities, Boeing redesigns NASA SLS Exploration Upper Stage Dec 2019) - Rod57 ( talk) 15:42, 15 February 2020 (UTC) reply

I went with the first ref; 2nd ref also confirms. 2nd ref also says that NASA asked Boeing for more performance from EUS, and Boeing had responded with about 10 options for NASA to decide between. Development progress seems to be costing about $150 M per annum. - Rod57 ( talk) 18:12, 16 April 2020 (UTC) reply

Looking at the image of EUS, it might need an interstage to fit on the top of the SLS core stage unless the core stage cylinder is lengthened to extend above the main tanks. (SLS block 1 has a substantial conical interstage to support the ICPS.) Is either part of the EUS contracts ? - Rod57 ( talk) 01:02, 14 December 2020 (UTC) reply

NASA completes Exploration Upper Stage CDR, focuses new office on SLS Block 1B development Feb 2021 has dates for structural test article and first flight article, build and test. - Rod57 ( talk) 16:07, 23 February 2021 (UTC) reply