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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| RS-25 | 8/9 | https://en.wikipedia.org/wiki/RS-25 | reference | science, encyclopedia | 2026-05-05T13:21:33.138292+00:00 | kb-cron |
On 14 September 2011, following the retirement of the Space Shuttle, NASA announced that it would be developing a new launch vehicle, known as the Space Launch System (SLS), to replace the shuttle fleet. The design for the SLS features the RS-25 as part of its core stage, with different versions of the rocket being equipped with between three and five engines. The initial flights of the new launch vehicle are making use of previously flown Block II RS-25D engines, with NASA keeping such engines in a "purged safe" environment at Stennis Space Center, "along with all of the ground systems required to maintain them." For Artemis I, the RS-25D units with serial numbers E2045, E2056, E2058, and E2060 from all three orbiters were used. They were installed on the core stage by November 6, 2019. For Artemis II, the units with serial numbers E2047, E2059, E2062, and E2063 were slated to be used. They were installed on the core stage by September 25, 2023. In spring 2025, engine E2063 was replaced with E2061 after a leak was discovered in its oxygen valve hydraulics. In addition to the RS-25Ds, the SLS program makes use of the Main Propulsion Systems (MPS, the "plumbing" feeding the engines) from the three remaining shuttle orbiters for testing purposes (having been removed as part of the orbiters' decommissioning), with the first two launches (Artemis I and Artemis II) originally predicted to make use of the MPS hardware from Space Shuttles Atlantis and Endeavour in their core stages. The SLS's propellants are supplied to the engines from the rocket's core stage, which consists of a modified Space Shuttle external tank with the MPS plumbing and engines at its aft, and an interstage structure at the top.
For the first two Artemis missions, the engines were installed on the SLS core stage in Building 103 of the Michoud Assembly Facility; they will be installed in the Space Station Processing Facility at Kennedy beginning with Artemis III. Once the remaining RS-25Ds are exhausted, they are to be replaced with a cheaper, expendable version designated the RS-25E. In 2023, Aerojet Rocketdyne reported reductions in manufacturing time and labor requirements during manufacturing of new-production RS-25 engines, such as a 15% reduction in fabrication time for the powerhead and a 22-month reduction in the time needed to produce a main combustion chamber. On 1 May 2020, NASA awarded a contract extension to manufacture 18 additional RS-25 engines, with associated services, for $1.79 billion, bringing the total SLS contract value to almost $3.5 billion. On 29 August 2022, Artemis I was delayed by a problem with engineering sensors on RS-25D #3 (serial number E2058) erroneously reporting that it hadn't chilled down to its ideal operating temperature. On 16 November 2022, Artemis I launched from Kennedy Space Center Launch Complex 39B, the first time the RS-25 engine had flown since the Space Shuttle's final flight, STS-135, on 21 July 2011.