{
  "id": "aerojet-rs-25",
  "title": "RS-25 engine",
  "maker": "Aerojet Rocketdyne (originally Rocketdyne)",
  "maker_type": "Commercial",
  "kind": "mission",
  "category": "engines",
  "page": "https://spacemushroom.com/space-products/aerojet-rs-25/",
  "website": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
  "summary": "Staged-combustion LOX/LH2 engine first built as the Space Shuttle Main Engine; the NASA HAER report names its copper-alloy chamber liner, Inconel 718 jacket and the other alloys.",
  "application": "NASA’s Space Launch System core stage uses RS-25 engines, the same design that powered the Space Shuttle for 30 years. The engine shows how a copper-alloy liner and a nickel superalloy jacket survive hydrogen-oxygen combustion, so it is a common reference for reusable high-pressure engines.",
  "story": {
    "headline": "The RS-25 is the Space Shuttle Main Engine, now used on the core stage of NASA's Space Launch System.",
    "intro": [
      "The RS-25 burns liquid hydrogen with liquid oxygen. It began as the Space Shuttle Main Engine, three to an orbiter, and flew on 135 shuttle missions from 12 April 1981. Four now power the core stage of NASA's Space Launch System, which first flew on 16 November 2022.",
      "In its staged-combustion design, two preburners make hot gas that drives the turbopumps, and that exhaust then burns in the main chamber. Hydrogen flowing through channels and tubes cools the chamber and nozzle. Inconel 718, a nickel superalloy, makes up roughly 51 percent of the engine's weight."
    ],
    "built": [
      {
        "title": "Chamber and liner",
        "text": "The inner wall of the main chamber is NARloy-Z, a copper alloy with silver and zirconium that Rocketdyne developed, cut with 430 coolant channels. An electroformed nickel layer covers the outside, and a jacket of Inconel 718 holds in a pressure of 3,000 psi.",
        "parts": [
          "Chamber liner (inner wall, 430 coolant channels)",
          "Chamber liner exterior",
          "Chamber support jacket",
          "Main injector (600 coaxial elements)"
        ]
      },
      {
        "title": "Nozzle",
        "text": "The nozzle wall is lined with 1,080 stainless steel tubes, each an eighth of an inch across, that carry hydrogen to cool it. Four layers of metallic batting under Nichrome foil insulate the outside. The exhaust leaves the nozzle at 17,000 feet per second.",
        "parts": [
          "Nozzle coolant tubes (1,080 tubes, brazed to jacket)",
          "Nozzle external thermal shield"
        ]
      },
      {
        "title": "Preburners and turbopumps",
        "text": "The two preburners have Inconel 718 bodies and burn most of the hydrogen with part of the oxygen to drive the turbopumps. The high-pressure fuel pump, the engine's most complex part, spins at about 36,000 rpm. New oxygen-pump ball bearings are silicon nitride, a ceramic 30 percent harder and 40 percent lighter than steel.",
        "parts": [
          "Preburner body and inlet manifold",
          "High-pressure fuel turbopump (HPFTP)",
          "High-pressure oxidizer turbopump bearings (Block I)"
        ]
      },
      {
        "title": "Controls and valves",
        "text": "The shuttle-era controller, built by Honeywell with two redundant computers, ran start-up, throttling and shutdown, updating every 20 milliseconds. Five hydraulic valves controlled the propellant flow. Two actuators swivelled each engine, up to 10.5 degrees in pitch and 8.5 in yaw.",
        "parts": [
          "Main engine controller",
          "Five hydraulically actuated propellant valves",
          "Thrust vector control actuators (x2: pitch and yaw)"
        ]
      },
      {
        "title": "Changes for SLS",
        "text": "SLS engines have new controllers and software, and nozzle insulation to protect them from booster exhaust. A 3D-printed pogo accumulator, a beachball-sized shock absorber that regulates the oxygen flow, removed more than 100 welds. New-production engines, from Artemis V, are rated for 111 percent thrust against the shuttle engines' limit of 109.",
        "parts": [
          "New engine controller and nozzle insulation (SLS upgrades)",
          "Pogo accumulator assembly (3D printed)"
        ]
      }
    ],
    "materials": [
      {
        "name": "NARloy-Z",
        "mid": "narloy-z",
        "where": "The inner wall of the main combustion chamber, a copper-silver-zirconium alloy cut with 430 coolant channels."
      },
      {
        "name": "Inconel 718",
        "mid": "inconel-718",
        "where": "The chamber support jacket and preburner bodies. It is in about 1,500 components."
      },
      {
        "name": "Electroformed nickel",
        "mid": "electroformed-nickel",
        "where": "The outer layer of the chamber liner, applied by electroforming."
      },
      {
        "name": "Stainless steel",
        "mid": "stainless-steel",
        "where": "The 1,080 nozzle cooling tubes and the oxygen heat exchanger coil. NASA does not name the grades."
      },
      {
        "name": "Silicon nitride",
        "mid": "silicon-nitride",
        "where": "Ball bearings in the high-pressure oxygen pump of the Block I engine."
      },
      {
        "name": "Nichrome",
        "mid": "nichrome",
        "where": "Foil and screen over the batting on the outside of the nozzle."
      }
    ],
    "connections": "Three RS-25s sat at the back of each Space Shuttle orbiter, and four power the SLS core stage. The first four SLS missions use 14 flight-proven shuttle engines and two assembled from shuttle-era parts. Pratt & Whitney Rocketdyne made the nozzle, chamber and powerhead. Honeywell built the controller and HR Textron the valve actuators. L3Harris has restarted production, aiming for a 30 percent lower cost.",
    "unknown": "NASA's detailed report covers the shuttle-era engine, so the SLS version's changes are described only in outline. The grades of the turbine blade superalloy, nozzle tubes and heat exchanger tube are not named, and neither are the materials of most rotors, injectors, valves and ducts.",
    "facts": [
      {
        "label": "Propellants",
        "value": "Liquid oxygen and liquid hydrogen"
      },
      {
        "label": "Cycle",
        "value": "Staged combustion"
      },
      {
        "label": "Sea-level thrust, shuttle era",
        "value": "About 380,000 lb"
      },
      {
        "label": "Mass",
        "value": "About 7,775 lb"
      },
      {
        "label": "Size",
        "value": "About 14 ft long, 7.5 ft diameter at nozzle exit"
      },
      {
        "label": "Shuttle missions flown",
        "value": "135 space shuttle missions"
      }
    ]
  },
  "specifications": [
    {
      "label": "Propellants",
      "value": "Liquid oxygen and liquid hydrogen",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "burned a mixture of LO2 and LH2 to lift the vehicle into space"
    },
    {
      "label": "Cycle",
      "value": "Staged combustion",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "The staged combustion engine"
    },
    {
      "label": "Sea-level thrust (rated power level)",
      "value": "About 380,000 lb",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "approximately 380,000 pounds at rated power level (RPL)"
    },
    {
      "label": "Throttle range",
      "value": "67 to 109 percent of rated power",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "over a thrust range of 67 to 109 percent RPL"
    },
    {
      "label": "Mass",
      "value": "About 7,775 lb",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "weighed approximately 7,775 pounds"
    },
    {
      "label": "Size",
      "value": "About 14 ft long, 7.5 ft diameter at nozzle exit",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "approximately 14’ in length and 7.5’ in diameter at the exit of the nozzle"
    },
    {
      "label": "Chamber pressure",
      "value": "3,000 psi (main combustion chamber)",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "contain the internal pressure of 3,000 psi"
    },
    {
      "label": "Nozzle area ratio",
      "value": "77.5:1",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "area ratio of 77.5:1"
    },
    {
      "label": "Thrust, sea level, full power level",
      "value": "about 420,000 lbf at 109 percent",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "and 420,000 pounds at full power level (FPL) or 109 percent RPL"
    },
    {
      "label": "Thrust levels, vacuum",
      "value": "about 470,000 / 490,000 / 512,000 lbf at 100 / 104.5 / 109 percent",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "or approximately 470,000 pounds, 490,000 pounds, and 512,000 pounds, respectively, in a vacuum"
    },
    {
      "label": "First SLS flight with four RS-25 engines",
      "value": "16 Nov 2022 (Artemis I) from Launch Complex 39B",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/",
      "quote": "On Nov. 16, 2022, SLS took to the sky from Launch Complex 39B at NASA’s Kennedy Space Center in Florida"
    },
    {
      "label": "First Space Shuttle flight with three RS-25 engines",
      "value": "STS-1, Columbia, 12 April 1981",
      "source_url": "https://www.nasa.gov/history/40-years-ago-columbia-takes-flight/",
      "quote": "lifted off on April 12, 1981, aboard space shuttle Columbia"
    },
    {
      "label": "SLS operating thrust",
      "value": "109 percent, about 512,300 lbf (2,279 kN) in vacuum",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf",
      "quote": "approximately 512,300 lbs. (2,279 kN) maximum thrust in a vacuum"
    },
    {
      "label": "Part count",
      "value": "about 50,000 parts, 7,000 tracked for replacement",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "The SSME contained approximately 50,000 parts, of which 7,000 were tracked periodically for replacement."
    },
    {
      "label": "Flight experience in the shuttle program",
      "value": "over 57 hours of flight time and 246.7 hours of ground tests",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "the SSMEs accumulated more than fifty-seven hours of flight time and another 246.7 hours of ground testing"
    },
    {
      "label": "Design life",
      "value": "55 starts and 27,000 s of run time",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "the main engines were designed for fifty-five starts and 27,000 seconds of run time before needing replacement"
    },
    {
      "label": "Shuttle missions flown",
      "value": "135 space shuttle missions",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf",
      "quote": "It flew successfully on 135 space shuttle missions."
    },
    {
      "label": "Burn",
      "value": "about eight and a half minutes from ignition to main engine cutoff",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "The engines operated for an approximate total eight-and-one-half minutes from ignition to MECO"
    },
    {
      "label": "Propellant burned",
      "value": "over 1.6 million lb (about 528,000 gal) per flight",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "burned over 1.6 million pounds (approximately 528,000 gallons) of propellant"
    },
    {
      "label": "Nozzle size",
      "value": "10.3 in diameter at the throat, 90.7 in at the exit",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "The SSME nozzle measured 10.3” in diameter at the throat, and 90.7” at the nozzle exit."
    },
    {
      "label": "Nozzle propellant flow",
      "value": "1,035 lb/s at 100 percent power",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "At 100 percent power level, propellants flowed through the nozzle at a rate of 1,035 pounds per second."
    },
    {
      "label": "Nozzle exit velocity",
      "value": "17,000 ft/s",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "accelerates the combustion products to 17,000 feet per second at the nozzle exit"
    },
    {
      "label": "Fleet leader",
      "value": "Engine 2019 flew nineteen missions",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "Engine 2019 was the fleet leader during the SSP. It flew nineteen missions"
    },
    {
      "label": "New-production affordability",
      "value": "design changes and advanced manufacturing to eliminate more than 700 welds and 700 parts",
      "source_url": "https://www.nasa.gov/humans-in-space/nasa-tests-3-d-printed-rocket-part-to-reduce-future-sls-engine-costs/",
      "quote": "will eliminate more than 700 welds and more than 700 parts, while reducing engine costs"
    },
    {
      "label": "New-production engines",
      "value": "Artemis V onward, rated for 111 percent thrust",
      "source_url": "https://www.nasa.gov/reference/sls-space-launch-system-block-1b/",
      "quote": "Artemis V will use new production RS-25 engines made to operate at 111% thrust versus the shuttle engines limited to 109%."
    },
    {
      "label": "Engines being built",
      "value": "24 engines",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/",
      "quote": "It is currently building 24 engines."
    }
  ],
  "features": [
    {
      "text": "Dual preburners drive the high-pressure turbopumps; turbine exhaust burns in the main chamber",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "First, the dual preburners burned most of the hydrogen and part of the oxygen from the turbopumps"
    },
    {
      "text": "Chamber and nozzle are cooled by hydrogen flowing through channels and tubes",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "The main combustion chamber was cooled by super-cold hydrogen"
    },
    {
      "text": "Engine alloys were developed for extreme temperature swings",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
      "quote": "exotic alloys were developed, such as NARloy-Z (Rocketdyne) and Inconel Alloy 718"
    }
  ],
  "parts": [
    {
      "assembly": "Hot gas manifold",
      "parts": [
        {
          "part": "Hot gas manifold outer wall liner",
          "material": "alloy 903",
          "form": "sheet metal liner",
          "finish": null,
          "standard": null,
          "hardware_ref": "Two halves joined by electron-beam welding",
          "quote": "The structural outer walls consisted of an alloy 903 sheet metal liner",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "alloy-903"
        }
      ]
    },
    {
      "assembly": "Preburners",
      "parts": [
        {
          "part": "Preburner body and inlet manifold",
          "material": "Inconel alloy 718",
          "form": "forgings and preformed sheet metal",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The structural body and inlet manifold of each preburner were machined from Inconel alloy 718",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "inconel-718"
        }
      ]
    },
    {
      "assembly": "Main combustion chamber",
      "parts": [
        {
          "part": "Chamber liner (inner wall, 430 coolant channels)",
          "material": "NARloy-Z (copper-silver-zirconium)",
          "form": "machined liner",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Rocketdyne developed NARloy-Z, a high conductivity copper-based alloy that contained silver and zirconium.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "narloy-z"
        },
        {
          "part": "Chamber liner exterior",
          "material": "structural nickel",
          "form": "electroformed layer",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The exterior of the liner was made from structural nickel which was applied by an electroforming process.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "electroformed-nickel"
        },
        {
          "part": "Chamber support jacket",
          "material": "Inconel alloy 718",
          "form": "jacket",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The support jacket of the main combustion chamber was made from Inconel alloy 718.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "inconel-718"
        }
      ]
    },
    {
      "assembly": "Nozzle",
      "parts": [
        {
          "part": "Nozzle coolant tubes (1,080 tubes, brazed to jacket)",
          "material": "stainless steel (grade not stated)",
          "form": "1/8 inch tubes, brazed",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The inside wall of the nozzle was lined with 1,080, 1/8” stainless steel cooling tubes that carried hydrogen.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "stainless-steel"
        },
        {
          "part": "Nozzle external thermal shield",
          "material": "Nichrome foil and screen over metallic batting",
          "form": "four layers of batting, foil, screen",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "four layers of metallic batting covered with a metallic foil (Nichrome)",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "nichrome"
        }
      ]
    },
    {
      "assembly": "Heat exchanger",
      "parts": [
        {
          "part": "Oxidizer heat exchanger coil",
          "material": "stainless steel alloy (grade not stated)",
          "form": "single 41 ft tube coil, 0.50 in OD",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "continuous piece of coiled stainless steel alloy tubing",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "stainless-steel"
        }
      ]
    },
    {
      "assembly": "Turbomachinery",
      "parts": [
        {
          "part": "High-pressure fuel turbopump turbine blades (original design)",
          "material": "nickel-based super alloy (grade not stated)",
          "form": "cast blades",
          "finish": null,
          "standard": null,
          "hardware_ref": "Later Block I/II blades used a different material",
          "quote": "The blades were cast from a nickel-based super alloy developed by Martin Metals.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "nickel-base-superalloy"
        },
        {
          "part": "High-pressure oxidizer turbopump bearings (Block I)",
          "material": "silicon nitride",
          "form": "ball bearings",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "new ball bearings made of silicon nitride, a ceramic material 30 percent harder and 40 percent lighter than steel",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "silicon-nitride"
        },
        {
          "part": "Low-pressure fuel turbopump housing insulation",
          "material": "Kevlar jacket over foam",
          "form": "foam insulation with jacket",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Foam insulation encased in a Kevlar jacket covered the pump housing.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "kevlar"
        },
        {
          "part": "Low-pressure oxidizer turbopump (LPOTP)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Pratt & Whitney Rocketdyne (Canoga Park)",
          "quote": "The Low-Pressure Oxidizer Turbopump (Figure No. C-19) contained an axial-flow inducer driven by a six-stage hydraulic turbine.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Boosts LO2 pressure so the high-pressure pump can run fast without cavitating",
          "specs": [
            {
              "label": "Speed",
              "value": "about 5,150 rpm",
              "quote": "The low-pressure oxidizer turbopump operated at approximately 5,150 rpm.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            },
            {
              "label": "Pressure rise",
              "value": "100 psia to 422 psia",
              "quote": "It boosted the LO2 pressure from 100 psia to 422 psia.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        },
        {
          "part": "Low-pressure fuel turbopump (LPFTP)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Pratt & Whitney Rocketdyne (Canoga Park)",
          "quote": "The Low-Pressure Fuel Turbopump (Figure No. C-20) contained an axial-flow inducer driven by a two-stage, axial-flow turbine powered with gaseous hydrogen.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Boosts LH2 pressure; turbine runs on gaseous hydrogen",
          "specs": [
            {
              "label": "Speed",
              "value": "about 16,185 rpm",
              "quote": "The low-pressure fuel turbopump operated at approximately 16,185 rpm.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            },
            {
              "label": "Pressure rise",
              "value": "30 psia to 276 psia",
              "quote": "It boosted LH2 pressure from 30 psia to 276 psia",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        },
        {
          "part": "High-pressure oxidizer turbopump (HPOTP), mainstage pump",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Pratt & Whitney Rocketdyne (West Palm Beach, Block II)",
          "quote": "The mainstage pump was a double entry centrifugal impeller flanked by two inducers.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Double-entry centrifugal impeller between two inducers, three-stage hot-gas turbine",
          "specs": [
            {
              "label": "Speed and pressure",
              "value": "about 28,120 rpm; LO2 from 422 psia to 4,300 psia",
              "quote": "The main pump boosted LO2 pressure from 422 psia to 4,300 psia while operating at approximately 28,120 rpm.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            },
            {
              "label": "Turbine",
              "value": "three-stage hot-gas turbine on a common shaft",
              "quote": "The turbopump had a common shaft and was driven by a three-stage, hot gas turbine.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        },
        {
          "part": "HPOTP preburner pump",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The final path entered the preburner impeller to raise the LO2’s pressure from 4,300 psia to 7,420 psia for use in both preburners.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Single centrifugal impeller that raises LO2 to 7,420 psia for the preburners"
        },
        {
          "part": "High-pressure fuel turbopump (HPFTP)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Pratt & Whitney Rocketdyne (West Palm Beach, Block II)",
          "quote": "The three-stage centrifugal pump was driven by a twostage, hot gas turbine.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Three-stage centrifugal pump on a two-stage hot-gas turbine; the most complex part of the engine",
          "specs": [
            {
              "label": "Speed and pressure",
              "value": "about 36,000 rpm; LH2 from 276 psia to 6,515 psia",
              "quote": "boosted LH2 pressure from 276 psia to 6,515 psia, and operated at a speed of approximately 36,000 rpm",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            },
            {
              "label": "LH2 flow",
              "value": "162 lb/s",
              "quote": "It supplied 162 pounds of LH2 fuel per second",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            },
            {
              "label": "Complexity",
              "value": "most complex component of the SSME",
              "quote": "was the most complex component of the SSME",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        },
        {
          "part": "Low-pressure to high-pressure duct bellows",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "contained flexible bellows that enabled them to flex when loads were applied",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Flexible bellows that take up load between the pumps"
        },
        {
          "part": "LPOTP speed transducer",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "A triple-redundant, magnetic-type, speed transducer was located on the turbine end.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Triple-redundant magnetic speed sensor on the turbine end"
        }
      ]
    },
    {
      "assembly": "Whole engine",
      "parts": [
        {
          "part": "Inconel 718 across about 1,500 components",
          "material": "Inconel alloy 718",
          "form": "various forged, cast and sheet parts",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The latter, a nickel-based superalloy, was used in approximately 1,500 engine components and comprised roughly 51 percent of the SSME, by weight.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": "inconel-718"
        }
      ]
    },
    {
      "assembly": "Powerhead, injectors and ignition",
      "parts": [
        {
          "part": "Main injector (600 coaxial elements)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "It included 600 coaxial elements which injected LO2 through their center posts.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Injects LO2 through hollow posts into the main chamber; sits in the centre of the hot gas manifold",
          "specs": [
            {
              "label": "Diameter",
              "value": "about 17.7 in",
              "quote": "The main injector measured approximately 17.7” in diameter at the end",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        },
        {
          "part": "Main injector flow shields",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Flow shields, bolted to the outer row of elements, helped to protect them from damage and erosion from the high-velocity gas.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Bolted to the outer row of elements against hot gas erosion"
        },
        {
          "part": "Fuel preburner injector (264 coaxial elements)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The injector was made up of 264 coaxial elements, arranged in a concentric row pattern.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "First-stage combustion of hydrogen-rich gas to drive the fuel turbopump"
        },
        {
          "part": "Oxidizer preburner injector (120 coaxial elements)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The injector was comprised of 120 coaxial elements, arranged in a concentric row pattern.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "First-stage combustion to drive the oxidizer turbopump"
        },
        {
          "part": "Preburner combustion baffles (x3 per preburner)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "supported and cooled three baffles that helped to stabilize combustion",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Elements that support and cool baffles to stabilize combustion"
        },
        {
          "part": "Dual-redundant spark igniters (main chamber and both preburners)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The dual-redundant igniter was used during the engine start sequence to initiate combustion.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Light the engine and switch off after about three seconds"
        },
        {
          "part": "Two-duct hot gas manifold (redesign, first flown July 1995)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The redesigned two-duct hot gas manifold, first flown in July 1995, replaced the three small fuel ducts with two enlarged ducts.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Replaced three small fuel ducts with two enlarged ducts"
        }
      ]
    },
    {
      "assembly": "Nozzle structure",
      "parts": [
        {
          "part": "Nozzle hatbands (x9) and structural jacket",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Nine hatbands were welded around the jacket for hoop strength",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Welded around the jacket for hoop strength"
        },
        {
          "part": "Steerhorn hydrogen feed line (1.625 in)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "a hydrogen feed line (“steerhorn”) measuring 1.625” in diameter also was attached to the nozzle exterior",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Carries hydrogen to the nozzle coolant circuit"
        },
        {
          "part": "Nozzle coolant manifolds, fuel transfer ducts and drain lines",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Coolant manifolds were welded to the top and bottom of the nozzle, along with three fuel transfer ducts and six drain lines.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Top and bottom manifolds with three transfer ducts and six drains"
        },
        {
          "part": "Engine heat shield support ring",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "A support ring welded to the throat of the nozzle was the attach point for the engine heat shield.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Attach point at the nozzle throat for the engine heat shield"
        }
      ]
    },
    {
      "assembly": "Valves, controller and actuators",
      "parts": [
        {
          "part": "Five hydraulically actuated propellant valves",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: HR Textron (valve actuators)",
          "quote": "the oxidizer preburner oxidizer valve, the fuel preburner oxidizer valve, the main oxidizer valve, the main fuel valve, and the chamber coolant valve",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Preburner oxidizer valves set thrust and mixture ratio; main valves feed the chamber"
        },
        {
          "part": "Valve actuators",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: HR Textron (Hydraulic Research), Valencia, California",
          "quote": "Major SSME subcontractors were HR Textron (also known as Woodward HR Textron and Hydraulic Research, Inc.) in Valencia, California, for engine valve actuators",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Hydraulic actuators driven by controller signals"
        },
        {
          "part": "Main engine controller",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Honeywell, Clearwater, Florida",
          "quote": "The pressurized, thermally conditioned controller, manufactured by Honeywell",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "On-board digital computer that runs start, throttle, mixture ratio and shutdown",
          "specs": [
            {
              "label": "Processors",
              "value": "two redundant digital computer units, Block II used Motorola 68000 32-bit microprocessors",
              "quote": "Each controller contained two redundant digital computer units, and each Block II computer used Motorola 68000 32-bit microprocessors.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            },
            {
              "label": "Update rate",
              "value": "every 20 milliseconds",
              "quote": "Instructions to the engine control elements were updated 50 times per second, or every twenty milliseconds.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        },
        {
          "part": "Bleed valves (one LH2, one LO2)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Two bleed valves were contained in each SSME, including one LH2 bleed valve and one LO2 bleed valve.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Circulate propellant for thermal conditioning and dump LH2 after cutoff"
        },
        {
          "part": "Helium system",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Helium was used to pneumatically close the five main hydraulically-actuated valves in the propellant lines should a hydraulic failure occur.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Closes the five main valves if hydraulics fail and purges the HPOTP intermediate seals"
        },
        {
          "part": "Pneumatic control assembly",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Each SSME had one pneumatic control assembly.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Solenoid valves for seal purge, pogo postcharge and pneumatic shutdown"
        },
        {
          "part": "Thrust vector control actuators (x2: pitch and yaw)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Two main engine TVC actuators were connected to the powerhead of each SSME.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf",
          "profile": null,
          "mid": null,
          "function": "Gimbal each engine; pitch up to 10.5 degrees, yaw up to 8.5 degrees",
          "specs": [
            {
              "label": "Gimbal range",
              "value": "pitch 10.5 degrees, yaw 8.5 degrees",
              "quote": "The pitch actuator could move the engine 10.5 degrees up or down and the yaw actuator a maximum of 8.5 degrees up or down.",
              "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
            }
          ]
        }
      ]
    },
    {
      "assembly": "New-production hardware",
      "parts": [
        {
          "part": "Pogo accumulator assembly (3D printed)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The 3-D printed part tested, called the pogo accumulator, is a beachball-sized piece of hardware",
          "source_url": "https://www.nasa.gov/humans-in-space/nasa-tests-3-d-printed-rocket-part-to-reduce-future-sls-engine-costs/",
          "profile": null,
          "mid": null,
          "function": "Beachball-sized shock absorber that regulates LOX movement to stop pogo vibration",
          "specs": [
            {
              "label": "Effect of 3D printing",
              "value": "more than 100 welds eliminated, about 35 percent cost and 80 percent production time saved",
              "quote": "more than 100 welds were eliminated, reducing costs by nearly 35 percent and production time by more than 80 percent",
              "source_url": "https://www.nasa.gov/humans-in-space/nasa-tests-3-d-printed-rocket-part-to-reduce-future-sls-engine-costs/"
            }
          ]
        },
        {
          "part": "New engine controller and nozzle insulation (SLS upgrades)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Upgrades to the engines include development of new engine controllers and software and the addition of nozzle insulation",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf",
          "profile": null,
          "mid": null,
          "function": "New controllers and software, nozzle insulation for booster exhaust"
        }
      ]
    }
  ],
  "materials": [
    {
      "id": "alloy-903",
      "name": "alloy 903",
      "material_page": null
    },
    {
      "id": "inconel-718",
      "name": "Inconel alloy 718",
      "material_page": null
    },
    {
      "id": "narloy-z",
      "name": "NARloy-Z (copper-silver-zirconium)",
      "material_page": null
    },
    {
      "id": "electroformed-nickel",
      "name": "structural nickel",
      "material_page": null
    },
    {
      "id": "stainless-steel",
      "name": "stainless steel alloy (grade not stated)",
      "material_page": null
    },
    {
      "id": "nichrome",
      "name": "Nichrome foil and screen over metallic batting",
      "material_page": null
    },
    {
      "id": "nickel-base-superalloy",
      "name": "nickel-based super alloy (grade not stated)",
      "material_page": null
    },
    {
      "id": "silicon-nitride",
      "name": "silicon nitride",
      "material_page": null
    },
    {
      "id": "kevlar",
      "name": "Kevlar jacket over foam",
      "material_page": null
    }
  ],
  "standards": [],
  "relations": [
    {
      "type": "part_of",
      "target": "Space Shuttle orbiter (three engines)",
      "target_slug": null,
      "note": "Three engines per orbiter: centre, left, right",
      "quote": "The three engines, almost interchangeable in the launch position, were referred to as the center (Engine 1), left (Engine 2), and right (Engine 3).",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
    },
    {
      "type": "part_of",
      "target": "Space Shuttle orbiter (three engines)",
      "target_slug": null,
      "note": "Engines are mounted on the aft end of the orbiter",
      "quote": "the three main engines mounted on its aft end",
      "source_url": "https://www.nasa.gov/reference/the-space-shuttle/"
    },
    {
      "type": "part_of",
      "target": "Space Shuttle orbiter (three engines)",
      "target_slug": null,
      "note": "First flown on STS-1, 12 April 1981",
      "quote": "lifted off on April 12, 1981, aboard space shuttle Columbia",
      "source_url": "https://www.nasa.gov/history/40-years-ago-columbia-takes-flight/"
    },
    {
      "type": "part_of",
      "target": "Space Launch System core stage (four engines)",
      "target_slug": "nasa-sls",
      "note": "Core stage: four engines, in every SLS configuration",
      "quote": "Every SLS configuration uses the core stage with four RS-25 engines.",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/"
    },
    {
      "type": "part_of",
      "target": "Space Launch System core stage (four engines)",
      "target_slug": "nasa-sls",
      "note": "Formerly the Space Shuttle Main Engine",
      "quote": "The RS-25 is formerly known as the Space Shuttle Main Engine (SSME).",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf"
    },
    {
      "type": "heritage_of",
      "target": "Space Shuttle Main Engine (SSME)",
      "target_slug": null,
      "note": "RS-25 is the SSME, reused on SLS: 14 flight-proven engines plus two assembled from shuttle parts for the first four missions",
      "quote": "The first four SLS missions will be powered by 14 flight-proven engines and two new engines assembled from shuttle-era engine components.",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf"
    },
    {
      "type": "supplied_by",
      "target": "Pratt & Whitney Rocketdyne (earlier Rocketdyne, now Aerojet Rocketdyne / L3Harris)",
      "target_slug": null,
      "note": "Nozzle, chamber, powerhead, low-pressure pumps, valves and ducts",
      "quote": "The nozzle, main combustion chamber, powerhead, low-pressure turbopumps, valve assemblies, and ducts were manufactured by Pratt & Whitney Rocketdyne",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
    },
    {
      "type": "supplied_by",
      "target": "L3Harris Technologies",
      "target_slug": null,
      "note": "Restarted engine production (30 percent cost-reduction goal)",
      "quote": "L3Harris has also restarted engine production with the goal of a 30% cost reduction compared to the shuttle RS-25.",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/"
    },
    {
      "type": "supplied_by",
      "target": "Honeywell",
      "target_slug": null,
      "note": "Main engine controller, Clearwater, Florida",
      "quote": "Honeywell, Inc. in Clearwater, Florida, for the main engine controller",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
    },
    {
      "type": "supplied_by",
      "target": "HR Textron (Hydraulic Research)",
      "target_slug": null,
      "note": "Engine valve actuators, Valencia, California",
      "quote": "HR Textron (also known as Woodward HR Textron and Hydraulic Research, Inc.) in Valencia, California, for engine valve actuators",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
    },
    {
      "type": "supplied_by",
      "target": "Special Metals Corporation",
      "target_slug": null,
      "note": "Inconel alloy 718 named as a key alloy",
      "quote": "such as NARloy-Z (Rocketdyne) and Inconel Alloy 718 (Special Metals Corporation)",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
    },
    {
      "type": "supplied_by",
      "target": "Martin Metals",
      "target_slug": null,
      "note": "Developed the nickel-based super alloy of the original turbine blades",
      "quote": "The blades were cast from a nickel-based super alloy developed by Martin Metals.",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2015/12/3.pdf"
    }
  ],
  "not_published": "Grades for turbine blade superalloy, nozzle tubes and heat exchanger tube not given. No data on the SLS-era RS-25 changes. Injector, valve and bearing materials (other than Block I silicon nitride) not covered. More detail: Block II shuttle-era hardware (NASA HAER TX-116) is the only component-level source; alloys of the turbopump rotors, injectors, valves, bearings and ducts remain unnamed except those already in the entry. SLS-era differences (new controller, nozzle insulation, additively manufactured pogo accumulator and other new-production parts) are described only at program level on NASA pages. The Space Shuttle is not a catalog product, so the orbiter relations use a plain-name target. Honeywell and HR Textron supplier statements are Shuttle-era; current SLS controller and actuator makers are not named in the NASA pages read. More detail: Block II shuttle-era hardware (NASA HAER TX-116) is the only component-level source; alloys of the turbopump rotors, injectors, valves, bearings and ducts remain unnamed except those already in the entry. SLS-era differences (new controller, nozzle insulation, additively manufactured pogo accumulator and other new-production parts) are described only at program level on NASA pages. The Space Shuttle is not a catalog product, so the orbiter relations use a plain-name target. Honeywell and HR Textron supplier statements are Shuttle-era; current SLS controller and actuator makers are not named in the NASA pages read.",
  "depth": "partial",
  "photos": [
    {
      "file": "products/context/aerojet-rs-25-1.jpg",
      "alt": "RS-25 engine firing on a Stennis test stand, large nozzle with frost and white exhaust",
      "long": "RS-25 engine firing on a Stennis test stand, large nozzle with frost and white exhaust",
      "kind": "product",
      "credit": "NASA & Aerojet Rocketdyne | https://www.nasa.gov/sites/default/files/rs-25_engine_test_2_0.jpg",
      "license": "Public domain",
      "page_url": "https://commons.wikimedia.org/wiki/File:RS-25_Engine_Hot_Fire_Test.jpg"
    },
    {
      "file": "products/context/aerojet-rs-25-2.jpg",
      "alt": "Exhaust cloud rising beside the Stennis A-1 test stand during an RS-25 engine hot fire",
      "long": "Exhaust cloud rising beside the Stennis A-1 test stand during an RS-25 engine hot fire",
      "kind": "product",
      "credit": "NASA | NASA Tests New RS-25 Engine",
      "license": "Public domain",
      "page_url": "https://commons.wikimedia.org/wiki/File:NASA_Tests_New_RS-25_Engine_(new-rs-25-engine).jpg"
    },
    {
      "file": "products/context/aerojet-rs-25-3.jpg",
      "alt": "Four RS-25 engine nozzles on the aft end of an SLS core stage at Michoud (installed in the vehicle)",
      "long": "Four RS-25 engine nozzles on the aft end of an SLS core stage at Michoud (installed in the vehicle)",
      "kind": "context",
      "context": "RS-25s on an SLS core stage",
      "credit": "Jared Lyons | https://images.nasa.gov/details-MAF_20191107_Engine%20Section%20Full_Jnl-3951",
      "license": "Public domain",
      "page_url": "https://commons.wikimedia.org/wiki/File:SLS_Core_Stage_Nov_8_2019.jpg"
    }
  ],
  "context": {
    "size": [],
    "mass": [],
    "orbit": []
  },
  "licence": "Product data CC BY 4.0, cite Space Mushroom. Photos keep their own licences, given per photo.",
  "mcp": "https://spacemushroom.com/mcp"
}