{
  "id": "rocketdyne-j-2",
  "title": "J-2 engine",
  "maker": "Rocketdyne (for NASA)",
  "maker_type": "Commercial",
  "kind": "mission",
  "category": "engines",
  "page": "https://spacemushroom.com/space-products/rocketdyne-j-2/",
  "website": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
  "summary": "Rocketdyne's liquid-hydrogen/liquid-oxygen gas-generator engine for the Saturn V second stage (five engines) and third stage (one restartable engine); sources name brazed stainless-steel chamber tubes, a sintered-metal injector face and an earlier copper injector.",
  "application": "Five J-2 engines powered the Saturn V second stage and one J-2 powered the third stage, which restarted in Earth orbit to send Apollo toward the Moon. The engine is a reference for early hydrogen-oxygen engine construction: a brazed stainless-steel tube chamber, a propellant-lubricated turbopump pair and a hydrogen-fed start tank.",
  "story": {
    "headline": "The J-2 is a restartable hydrogen and oxygen engine that powered the upper stages of the Saturn V.",
    "intro": [
      "The J-2 is a liquid hydrogen and liquid oxygen engine that Rocketdyne developed for NASA under a contract dated 1 September 1960. Five J-2 engines powered the second stage of the Saturn V. A single J-2 powered the third stage, which restarted in Earth orbit to send Apollo toward the Moon. Rocketdyne delivered 152 production engines.",
      "The chamber wall is made of stainless-steel tubes brazed together, with liquid hydrogen running down 180 tubes and back up 360 to cool them. The first injector was copper and melted in development. The production injector has a porous sintered-metal face, and part of the fuel flows through it. The propellants also lubricate the pump bearings."
    ],
    "built": [
      {
        "title": "Chamber and nozzle",
        "text": "The chamber body is a set of longitudinal stainless-steel tubes, brazed together and held by external stiffening bands. Hydrogen runs down 180 tubes and back up 360, cooling the wall on the way. Exhaust from the turbines is dumped into the nozzle at the point where the 180 tubes split into 360.",
        "parts": [
          "Chamber tubes",
          "Tube circuit (180 down, 360 up)",
          "External stiffening bands",
          "Turbine exhaust injection into the nozzle"
        ]
      },
      {
        "title": "Injector and igniter",
        "text": "The first injector had a flat copper face. It melted in development, and the vaporised copper turned the exhaust plumes green. The production face is Rigi-Mesh, a porous screen of sintered metal, and part of the fuel flows through it to keep it cool. An igniter with two spark plugs lights the chamber.",
        "parts": [
          "Injector face (production)",
          "Original injector (flat-faced)",
          "Augmented spark igniter chamber",
          "Augmented spark igniter spark plugs (two)",
          "Igniter fuel line"
        ]
      },
      {
        "title": "Turbopumps",
        "text": "The fuel pump is a high-speed axial machine with an inducer and a seven-stage rotor and stator. Its design came from pumps used in nuclear rocket programmes. The oxygen pump is a single-stage centrifugal pump. Gas from the gas generator drives the fuel turbine and then the oxygen turbine, and the propellants lubricate the bearings.",
        "parts": [
          "Fuel turbopump (axial, self-lubricated)",
          "Fuel pump rotor",
          "Oxidizer turbopump (centrifugal)",
          "Series turbine drive",
          "Propellant-lubricated bearings"
        ]
      },
      {
        "title": "Gas generator and start system",
        "text": "A small combustion chamber with two spark plugs, the gas generator, makes the hot gas that spins the turbines. To start the engine, cold hydrogen from a start tank is discharged through both turbines. A heat exchanger in the turbine exhaust duct boils liquid oxygen to pressurise the oxygen tank.",
        "parts": [
          "Gas generator",
          "Hydrogen start tank",
          "Heat exchanger (LOX tank pressurisation)"
        ]
      },
      {
        "title": "Valves, seals and gimbal",
        "text": "The main fuel valve and the main oxygen valve are both butterfly valves, and the oxygen valve is spring loaded closed. Teflon-coated seals keep the hydrogen in at duct flanges and pipe joints. On the third stage, two hydraulic actuators swivel the engine.",
        "parts": [
          "Main fuel valve",
          "Main oxidizer valve",
          "Hydrogen seals at duct flanges and pipe joints",
          "Gimbal actuators (two)"
        ]
      }
    ],
    "materials": [
      {
        "name": "Stainless steel",
        "mid": "stainless-steel",
        "where": "The brazed chamber tubes, and the igniter fuel line with its braid-covered flexible bellows."
      },
      {
        "name": "Rigi-Mesh sintered metal screen",
        "mid": "rigimesh-sintered-metal-screen",
        "where": "The face of the production injector. Part of the fuel flows through it to cool it."
      },
      {
        "name": "Copper",
        "mid": "copper",
        "where": "The original flat-faced injector, which melted during development."
      },
      {
        "name": "Teflon-coated seals",
        "mid": "teflon-ptfe",
        "where": "Seals at duct flanges and pipe joints that keep the hydrogen contained."
      },
      {
        "name": "Liquid hydrogen",
        "mid": "liquid-hydrogen",
        "where": "The fuel. It cools the chamber tubes and, with the liquid oxygen, lubricates the pump bearings."
      }
    ],
    "connections": "Five J-2 engines sat at the back end of the Saturn V second stage, the S-II, and the four outer ones swivelled. One more powered the third stage, the S-IVB. The J-2 first flew on 26 February 1966, on a Saturn IB second stage, as part of AS-201. Rocketdyne built it, and Moog Industries made the third-stage gimbal actuators. Its fuel pump was derived from Rocketdyne's nuclear rocket programme pumps.",
    "unknown": "Published accounts name few of the metals. The grade of the stainless steel, the braze alloy and the alloy of the injector face are missing, as are the metals of the pump rotors and housings, the valve bodies, the gas generator and the hydrogen start tank. Rigi-Mesh is a trade name, not an alloy.",
    "facts": [
      {
        "label": "Vacuum thrust",
        "value": "Up to 230,000 lbf"
      },
      {
        "label": "Specific impulse",
        "value": "425 s"
      },
      {
        "label": "Propellants",
        "value": "Liquid oxygen and liquid hydrogen"
      },
      {
        "label": "Restart",
        "value": "Restartable in space"
      },
      {
        "label": "Production",
        "value": "152 production engines"
      },
      {
        "label": "First flight",
        "value": "26 February 1966, AS-201 (Saturn IB second stage)"
      }
    ]
  },
  "specifications": [
    {
      "label": "Vacuum thrust",
      "value": "Up to 230,000 lbf",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "an open-cycle gas generator engine delivering up to 230,000 pounds of thrust"
    },
    {
      "label": "Cycle",
      "value": "Open-cycle gas generator",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "It was an open-cycle gas generator engine"
    },
    {
      "label": "Specific impulse",
      "value": "425 s",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "The specific impulse of 425 seconds"
    },
    {
      "label": "Chamber pressure",
      "value": "A little over 700 psia",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "Chamber pressure was relatively modest, a little over 700 pounds per square inch absolute (psia)"
    },
    {
      "label": "Mixture ratio",
      "value": "5.5:1 oxidizer to fuel",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "the mixture ratio was 5.5:1 at that chamber pressure"
    },
    {
      "label": "Alternate mixture ratio",
      "value": "4.5:1",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "It also had the capability of operating at a mixture ratio 4.5:1."
    },
    {
      "label": "Nozzle area ratio",
      "value": "27.5:1",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "Nozzle area ratio was 27.5:1."
    },
    {
      "label": "Propellants",
      "value": "Liquid oxygen and liquid hydrogen",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "Propellants were liquid oxygen and liquid hydrogen."
    },
    {
      "label": "Restart",
      "value": "Restartable in space",
      "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
      "quote": "The J-2 was capable of being restarted in space."
    },
    {
      "label": "Engines per vehicle (S-II)",
      "value": "5 on the Saturn V second stage",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "There were five J-2 engines at the back end of the S-II Stage."
    },
    {
      "label": "Engines per vehicle (S-IVB)",
      "value": "1 on the Saturn V third stage",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "In the S-IV-B stage, it was a single engine, but that single engine had to restart."
    },
    {
      "label": "Production",
      "value": "152 production engines",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "We delivered 152 production engines."
    },
    {
      "label": "Development contract",
      "value": "1 September 1960 (Rocketdyne)",
      "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
      "quote": "gave Rocketdyne a development contract on 1 Sep 1960"
    },
    {
      "label": "First flight",
      "value": "26 February 1966, AS-201 (Saturn IB second stage)",
      "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
      "quote": "The J-2 first flew on 26 Feb 1966 as a Saturn 1B second stage, part of AS-201."
    }
  ],
  "features": [
    {
      "text": "Fuel turbopump is an axial machine derived from nuclear rocket programme pumps",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "It was derived from machines that had been used in the nuclear rocket programs."
    },
    {
      "text": "Cold hydrogen from a start tank spins both turbines at engine start",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "it was this start tank that would discharge cold hydrogen through the two turbines to get the engine started"
    },
    {
      "text": "Augmented spark igniter with two spark plugs lights the chamber",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "The thrust chamber was ignited by an augmented spark igniter in the middle with two spark plugs"
    },
    {
      "text": "Turbopump bearings are lubricated by the propellants, with no separate lubrication system",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "The bearing lubrications were liquid oxygen and liquid hydrogen, so there was no separate lubrication system."
    },
    {
      "text": "Turbine exhaust is dumped into the nozzle at the point where the tube circuit splits two up for one down",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "we used the opening at the 2:1 split to dump the hot gas into the nozzle of the thrust chamber"
    },
    {
      "text": "Fuel runs down 180 tubes and back up 360 tubes in the regeneratively cooled chamber",
      "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
      "quote": "LH2 fuel from the fuel manifold circulated downward through 180 tubes, and back upward through 360 tubes"
    },
    {
      "text": "The original copper injector melted in development and was replaced by a porous sintered-metal face",
      "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
      "quote": "Injectors melted and the vaporized copper turned exhaust plumes green"
    },
    {
      "text": "Apollo 6 anomaly was traced to the bellows in the augmented spark igniter fuel line",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "The fuel line to the augmented spark igniter had a single-ply bellows"
    },
    {
      "text": "Coffman credits J-2 development experience for later Shuttle main engine, RS-68 and X-33 engine work",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
      "quote": "enabled us to be satisfactory on the space shuttle main engine"
    }
  ],
  "parts": [
    {
      "assembly": "Thrust chamber",
      "parts": [
        {
          "part": "Chamber tubes",
          "material": "stainless steel (grade not stated)",
          "form": "longitudinal tubes, brazed; regeneratively cooled by LH2",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The thrust chamber body was constructed of longitudinal stainless steel tubes that were brazed together",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": "stainless-steel"
        },
        {
          "part": "Tube circuit (180 down, 360 up)",
          "material": null,
          "form": "fuel circuit through the chamber tubes",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "LH2 fuel from the fuel manifold circulated downward through 180 tubes, and back upward through 360 tubes",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "External stiffening bands",
          "material": null,
          "form": "bands around the tube bundle",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "supported by external stiffening bands around the tubes",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Nozzle (27:1 expansion)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Sources also give 27.5:1 for the engine",
          "quote": "a divergent nozzle with an expansion ratio of 27:1",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Turbine exhaust injection into the nozzle",
          "material": null,
          "form": "turbine exhaust dumped at the nozzle midpoint",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "we used the opening at the 2:1 split to dump the hot gas into the nozzle of the thrust chamber",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": null
        }
      ]
    },
    {
      "assembly": "Injector and igniter",
      "parts": [
        {
          "part": "Injector face (production)",
          "material": "porous sintered metal screen (Rigi-Mesh, alloy not stated)",
          "form": "porous face; part of the fuel flows through to cool it",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The porous sintered metal screen material (Rigi-Mesh®) that formed the injector face",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": "rigimesh-sintered-metal-screen"
        },
        {
          "part": "Original injector (flat-faced)",
          "material": "copper",
          "form": "flat-faced injector",
          "finish": null,
          "standard": null,
          "hardware_ref": "Replaced after injectors melted in development",
          "quote": "The original J-2 injector was a flat-faced copper affair",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": "copper",
          "mid": "copper"
        },
        {
          "part": "Augmented spark igniter chamber",
          "material": null,
          "form": "integral with the injector",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The ASI chamber was an integral part of the injector.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Augmented spark igniter spark plugs (two)",
          "material": null,
          "form": "two spark plugs, burning fuel with hydrogen and oxygen",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The thrust chamber was ignited by an augmented spark igniter in the middle with two spark plugs",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": null
        },
        {
          "part": "Igniter fuel line",
          "material": "stainless steel (grade not stated)",
          "form": "line to the fuel inlet manifold",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The stainless-steel ASI fuel line was attached to the fuel inlet manifold",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": "stainless-steel"
        },
        {
          "part": "Igniter fuel-line bellows",
          "material": "stainless steel (grade not stated)",
          "form": "braid-covered flexible bellows",
          "finish": null,
          "standard": null,
          "hardware_ref": "Single-ply bellows later implicated in the Apollo 6 anomaly and removed (SP-2009-4545)",
          "quote": "Stainless-steel braid-covered flexible bellows in three places",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": "stainless-steel"
        }
      ]
    },
    {
      "assembly": "Turbopumps",
      "parts": [
        {
          "part": "Fuel turbopump (axial, self-lubricated)",
          "material": null,
          "form": "axial flow",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "self-lubricated high-speed axial-flow fuel turbopump",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Fuel pump rotor",
          "material": null,
          "form": "inducer plus seven stages",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "consisted of an inducer and a seven-stage rotor/stator assembly",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Oxidizer turbopump (centrifugal)",
          "material": null,
          "form": "single-stage centrifugal",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The oxidizer turbopump was a self-lubricated, high-speed, single-stage centrifugal pump",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Series turbine drive",
          "material": null,
          "form": "gas generator drives the fuel turbine then the oxidizer turbine",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "in a series turbine arrangement, through the fuel turbopump and then over into the oxidizer turbopump",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": null
        },
        {
          "part": "Propellant-lubricated bearings",
          "material": null,
          "form": "bearings wetted by LOX and LH2",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The bearing lubrications were liquid oxygen and liquid hydrogen, so there was no separate lubrication system.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": null
        }
      ]
    },
    {
      "assembly": "Gas generator, heat exchanger and start system",
      "parts": [
        {
          "part": "Gas generator",
          "material": null,
          "form": "combustion chamber with two spark plugs",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The gas generator consisted of a combustion chamber containing two spark plugs",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Heat exchanger (LOX tank pressurisation)",
          "material": null,
          "form": "in the turbine exhaust duct",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "LOX boiled by the turbine exhaust duct heat exchanger pressurized the LOX tank.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Hydrogen start tank",
          "material": null,
          "form": "cold hydrogen tank with an internal helium tank",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "it was this start tank that would discharge cold hydrogen through the two turbines to get the engine started",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": null
        }
      ]
    },
    {
      "assembly": "Valves and seals",
      "parts": [
        {
          "part": "Main fuel valve",
          "material": null,
          "form": "butterfly valve",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The main fuel valve (MFV) was a butterfly-type valve",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Main oxidizer valve",
          "material": null,
          "form": "butterfly valve, spring loaded closed",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The MOV was a butterfly-type valve, spring loaded in the closed position",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": null
        },
        {
          "part": "Hydrogen seals at duct flanges and pipe joints",
          "material": "Teflon-coated seals",
          "form": "coated seals",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "They also developed special Teflon®-coated seals to keep hydrogen contained",
          "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml",
          "profile": null,
          "mid": "teflon-ptfe"
        }
      ]
    },
    {
      "assembly": "Gimbal (S-IVB installation)",
      "parts": [
        {
          "part": "Gimbal actuators (two)",
          "material": null,
          "form": "linear hydraulic actuators",
          "finish": null,
          "standard": null,
          "hardware_ref": "Douglas (DAC) contracted Moog Industries to build the actuators to MSFC specifications",
          "quote": "Two linear hydraulic actuator assemblies gimbaled the J-2 engine.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.30/RPE08.30.shtml",
          "profile": null,
          "mid": null
        }
      ]
    },
    {
      "assembly": "Propellants",
      "parts": [
        {
          "part": "Oxidizer",
          "material": "liquid oxygen (LOX)",
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Propellants were liquid oxygen and liquid hydrogen.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": "liquid-oxygen"
        },
        {
          "part": "Fuel",
          "material": "liquid hydrogen (LH2)",
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Propellants were liquid oxygen and liquid hydrogen.",
          "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf",
          "profile": null,
          "mid": "liquid-hydrogen"
        }
      ]
    }
  ],
  "materials": [
    {
      "id": "stainless-steel",
      "name": "stainless steel (grade not stated)",
      "material_page": null
    },
    {
      "id": "rigimesh-sintered-metal-screen",
      "name": "porous sintered metal screen (Rigi-Mesh, alloy not stated)",
      "material_page": null
    },
    {
      "id": "copper",
      "name": "copper",
      "material_page": "https://spacemushroom.com/profiles/copper/"
    },
    {
      "id": "teflon-ptfe",
      "name": "Teflon-coated seals",
      "material_page": null
    },
    {
      "id": "liquid-oxygen",
      "name": "liquid oxygen (LOX)",
      "material_page": null
    },
    {
      "id": "liquid-hydrogen",
      "name": "liquid hydrogen (LH2)",
      "material_page": null
    }
  ],
  "standards": [],
  "relations": [
    {
      "type": "part_of",
      "target": "Saturn V (S-II second stage)",
      "target_slug": "nasa-saturn-v",
      "note": "Five J-2 engines on the second stage; the four outer engines gimbal",
      "quote": "There were five J-2 engines at the back end of the S-II Stage.",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf"
    },
    {
      "type": "part_of",
      "target": "Saturn V (S-IVB third stage)",
      "target_slug": "nasa-saturn-v",
      "note": "One restartable J-2 on the third stage",
      "quote": "In the S-IV-B stage, it was a single engine, but that single engine had to restart.",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf"
    },
    {
      "type": "supplied_by",
      "target": "Rocketdyne",
      "target_slug": null,
      "note": "Engine developer; development contract awarded 1 September 1960",
      "quote": "gave Rocketdyne a development contract on 1 Sep 1960",
      "source_url": "https://enginehistory.org/Rockets/RPE08.22/RPE08.22.shtml"
    },
    {
      "type": "supplied_by",
      "target": "Moog Industries",
      "target_slug": null,
      "note": "Built the S-IVB gimbal actuators to MSFC specifications",
      "quote": "DAC contracted with Moog Industries to build actuators to MSFC specifications.",
      "source_url": "https://enginehistory.org/Rockets/RPE08.30/RPE08.30.shtml"
    },
    {
      "type": "heritage_of",
      "target": "Nuclear rocket programme turbopumps (Rocketdyne)",
      "target_slug": null,
      "note": "The axial fuel turbopump was derived from machines used in the nuclear rocket programs",
      "quote": "It was derived from machines that had been used in the nuclear rocket programs.",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2023/04/sp-4545.pdf"
    }
  ],
  "not_published": "No alloy grades, braze alloy or standards stated. Turbomachinery and valve materials not published in the sources read.",
  "depth": "partial",
  "photos": [],
  "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"
}