Exploration Upper Stage

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Wikipedia

Exploration Upper Stage
2020 design of the Exploration Upper Stage
ManufacturerBoeing[1]
Country of originUnited States
Used onSpace Launch System (Block 1B/2)[2]
General characteristics
Height17.3 m (57 ft)[3]
Diameter
  • LH2 tank: 8.4 m (28 ft)
  • LOX tank: 5.5 m (18 ft)[4]
Propellant mass129,000 kg (284,000 lb)
Empty mass14,110 kg (31,110 lb)[5]
Engine details
Powered by4 × RL10C-3[3]
Maximum thrust433.1 kN (97,360 lbf)
Specific impulse460.1 s (4.512 km/s)[6]
Burn time1,275 seconds
PropellantLH2 / LOX

The Exploration Upper Stage (EUS) is a rocket stage under development for future flights of NASA’s Space Launch System (SLS). Designed for use on the SLS Block 1B and Block 2 configurations, it will replace the Interim Cryogenic Propulsion Stage used on the Block 1 variant. The EUS will be powered by four RL10C-3 engines burning liquid oxygen and liquid hydrogen, generating a total thrust of 433.1 kN (97,360 lbf). Its first flight is planned for Artemis IV in 2028.[7] However, the Trump administration has proposed terminating the SLS program after Artemis III, which would eliminate the need for the EUS.

Development

The Block 1 configuration of the SLS, which first flew the Artemis I mission, has a core stage powered by four RS-25 engines, two Space Shuttle-derived five-segment solid rocket boosters, and an Interim Cryogenic Propulsion Stage (ICPS) upper stage.[8][9]

NASA is developing the EUS to increase SLS performance for trans-lunar injection beyond Block 1 specifications. The improved upper stage was originally named the Dual Use Upper Stage (DUUS, pronounced "duce"),[10] but was later renamed the Exploration Upper Stage (EUS) due to concerns that DUUS sounded like a profanity in Japanese.[11]

In 2014, NASA announced it would proceed with development of the Block 1B configuration using the EUS,[12] initially planning to use it on Exploration Mission 2, now referred to as Artemis II.[13] In April 2016, NASA selected a design using four RL10-C3 engines for the EUS,[6] and in October 2016 confirmed an order for 10 of the engines.[14]

In 2018, NASA decided to optimize the EUS for lunar missions by using smaller tanks.[15] By February 2020, delays in the development contract led NASA to plan on using the ICPS for the first three SLS launches.[16]

On 21 December 2020, Boeing announced that the EUS had completed a critical design review (CDR) with NASA, allowing hardware development to proceed.[17]

In March 2022, Boeing explored the use of a carbon composite liquid oxygen tank on the EUS, which could reduce mass by up to 30%.[18]

On 2 May 2025, the Trump administration released its fiscal year 2026 budget proposal, which called for terminating the SLS and Orion spacecraft programs after Artemis III.[19][20] The proposal described the SLS program as "grossly expensive" and exceeding its budget, and allocated funding to transition to "more cost-effective commercial systems".[21]

Funding history

Fiscal year Nominal
(in millions)		 Inflation adjusted
(FY24, in millions)[22]
2016 $77.0 $98.9
2017 $300.0[23] $377.4
2018 $300.0[24] $368.1
2019 $150.0[25] $180.6
2020 $300.0[26] $353.4
2021 $400.0[27][a] $454.0
2022 $636.7[28] $684.4
2023 $648.3[29] $669.0
2024 $600.0[30] $600.0
Total $3,412.0 $3,785.9

See also

Notes

  1. ↑ The spending plan indicates that this is for "Block 1B (non-add) (including EUS)"

References

  1. ↑ "NASA, Boeing Finalize US$2.8 billion SLS Core Stage Contract". SpaceNews. 4 July 2014. Archived from the original on 27 July 2014. Retrieved 25 July 2014.
  2. ↑ "Space Launch System Fact Sheet" (PDF). NASA. Retrieved 16 May 2023.
  3. 1 2 "Space Launch System". Spaceflight Insider. 9 September 2018. Archived from the original on 5 October 2021. Retrieved 4 October 2021.
  4. ↑ "1 year down, a galaxy to go". Boeing. Retrieved 13 April 2024.
  5. ↑ Donahue, Benjamin; Sigmon, Sheldon; Cooper, Darby (9 July 2018). The NASA SLS Exploration Upper Stage Development & Mission Opportunities. 2018 Joint Propulsion Conference. Cincinnati, Ohio: American Institute of Aeronautics and Astronautics. doi:10.2514/6.2018-4639. ISBN 978-1-62410-570-8.
  6. 1 2 "RL10 Engine". Aerojet Rocketdyne. Archived from the original on 7 November 2021. Retrieved 18 November 2021.
  7. ↑ Foust, Jeff (30 October 2022). "Lunar landing restored for Artemis IV mission". SpaceNews. Retrieved 31 October 2022.
  8. ↑ "SLS". Gunter's Space Page. Retrieved 25 July 2014.
  9. ↑ "Space Launch System Data Sheet". SpaceLaunchReport.com. Archived from the original on 11 April 2013. Retrieved 25 July 2014.
  10. ↑ "SLS prepares for PDR – Evolution eyes Dual-Use Upper Stage". NASASpaceflight.com. June 2013. Retrieved 25 July 2014.
  11. ↑ Bergin, Chris (28 March 2014). "SLS positioning for ARRM and Europa missions". NASASpaceflight.com. Retrieved 8 November 2014.
  12. ↑ Bergin, Chris (30 July 2012). "Wind Tunnel testing conducted on SLS configurations, including Block 1B". NASASpaceFlight.com. Retrieved 12 March 2015.
  13. ↑ "NASA confirms EUS for SLS Block IB design and EM-2 flight". NASASpaceflight.com. 6 June 2014. Retrieved 25 July 2014.
  14. ↑ "Proven Engine Packs Big, In-Space Punch for NASA's SLS Rocket". NASA. 21 October 2016. Retrieved 18 November 2021.
  15. ↑ NASA completes Exploration Upper Stage CDR, focuses new office on SLS Block 1B development. Feb 2021.
  16. ↑ Upper Stage RL10s arrive at Stennis for upcoming SLS launches. February 2020.
  17. ↑ "SLS Exploration Upper Stage passes review". SpaceNews. 22 December 2020. Retrieved 22 December 2020.
  18. ↑ "With all-composite cryogenic tank, Boeing eyes mass-reducing space, aviation applications". 28 January 2016. Retrieved 2 June 2024.
  19. ↑ Berger, Eric (2 May 2025). "White House budget seeks to end SLS, Orion, and Lunar Gateway programs". Ars Technica. Retrieved 2 May 2025.
  20. ↑ Dooren, Jennifer M.; Stevens, Bethany (2 May 2025). "President Trump's FY26 Budget Revitalizes Human Space Exploration" (Press release). NASA. 25-035. Retrieved 2 May 2025.
  21. ↑ "Fiscal Year 2026 Discretionary Budget Request" (PDF). United States Office of Management and Budget. 2 May 2025. p. 37. Retrieved 2 May 2025.
  22. ↑ "NASA FY24 Inflation Tables – to be utilized in FY24". NASA. p. Inflation Table. Retrieved 2 June 2024. Public Domain This article incorporates text from this source, which is in the public domain.
  23. ↑ "NASA outlines plan for 2024 lunar landing". SpaceNews. 1 May 2019. Archived from the original on 30 September 2021. Retrieved 15 May 2019.
  24. ↑ Berger, Eric (20 May 2019). "NASA's full Artemis plan revealed: 37 launches and a lunar outpost". Ars Technica. Archived from the original on 23 May 2019. Retrieved 20 May 2019.
  25. ↑ Sloss, Philip (18 December 2019). "Amid competing priorities, Boeing redesigns NASA SLS Exploration Upper Stage". NASASpaceFlight.com. Archived from the original on 7 August 2020. Retrieved 25 July 2020.
  26. ↑ "NATIONAL AERONAUTICS AND SPACE ADMINISTRATION FY 2020 SPENDING PLAN FOR APPROPRIATIONS PROVIDED BY P.L. 116-93 and P.L. 116-136" (PDF). July 2020. Retrieved 2 June 2024.
  27. ↑ "NATIONAL AERONAUTICS AND SPACE ADMINISTRATION FY 2021 SPENDING PLAN FOR APPROPRIATIONS PURSUANT TO P.L. 116-260" (PDF). June 2021. Retrieved 2 June 2024.
  28. ↑ "NATIONAL AERONAUTICS AND SPACE ADMINISTRATION FY 2022 SPENDING PLAN FOR APPROPRIATIONS PROVIDED BY P.L. 117-103" (PDF). July 2022. Retrieved 2 June 2024.
  29. ↑ "NATIONAL AERONAUTICS AND SPACE ADMINISTRATION FY 2023 SPENDING PLAN FOR APPROPRIATIONS PROVIDED BY P.L. 117-328" (PDF). March 2023. Retrieved 2 June 2024.
  30. ↑ "COMMERCE, JUSTICE, SCIENCE, AND RELATED AGENCIES APPROPRIATIONS ACT, 2024" (PDF). March 2024. Retrieved 2 June 2024.