The National Aeronautics and Space Administration (NASA), Marshall Space Flight Center (MSFC), has a continuing requirement for Exploration Upper Stage Engines (EUSE).

• NASA/MSFC has a requirement for twenty (20) human rated SLS Exploration Upper Stage Engines (EUSE), vehicle and program integration, flight support of the Space Launch System (SLS) Artemis missions V thru X
• The first four engines, which will serve as back up engines for Artemis V, may need to be delivered in the mid-FY27 timeframe
• The SLS Program has already invested substantial resources in the acquisition and implementation of RL10 engines (10 previously purchased)
• The EUS has been designed to accommodate RL10 specifications and another engine would need to fit and perform without requiring redesign to the EUS or other elements of the SLS
• NASA seeks a low-cost, mature, and readily available engine to minimize program cost and schedule impacts to the EUS and launch vehicle
• The replacement EUSE shall minimize development time for an engine and reduce manufacturing/production costs while still meeting NASA programmatic, technical, design, construction, and workmanship approaches and standards for human rating
• The current concept for the EUSE is that it is a high-performance liquid oxygen / liquid hydrogen rocket engine consistent with the EUS stage-to-engine interface
• The EUSE would be designed, developed, built, and certified for flight consistent with NASA design, construction, workmanship, and qualification standards and other technical and programmatic requirements associated with human rating considerations including configuration management, reliability analysis, and safety assessment processes
• It would be the broader objective for any proposed engine development effort to minimize the development cost impacts to NASA and to achieve cost-efficient production and operations in the long term
• Current technical requirements for the EUSE are provided below and in Appendix A
• The EUSE program will consist of adapting the engine system for service on the SLS Block 1B vehicle and provide flight units for operations
• The EUSE shall be integrated into the SLS Exploration Upper Stage (EUS)
• The EUSE shall meet the technical requirements under the SLS and certification for the flight program
• The EUSE system shall minimize design impacts to existing EUS vehicle integration, requirements verification, and operational planning associated with existing EUS to EUSE physical and functional interfaces as defined in existing SLS interface control documents (ICD)
• EUSE shall be capable of human-rating certification
• The EUSE shall be capable of meeting the following SLS advanced engine performance goals:
  • EUSE shall maintain EUS physical interfaces and meet the following performance goals:
    • Thrust – 24,750 lbf
    • Isp – 465.5 seconds
    • Mass – 490 to 530 lbm
    • Total Length – 163.5”
    • Diameter – 84.6”