{
  "id": "ula-rl10",
  "title": "RL10 engine",
  "maker": "Aerojet Rocketdyne (originally Pratt & Whitney); flown on ULA Centaur",
  "maker_type": "Commercial",
  "kind": "mission",
  "category": "engines",
  "page": "https://spacemushroom.com/space-products/ula-rl10/",
  "website": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
  "summary": "Hydrogen-oxygen expander-cycle upper-stage engine first run in 1959; its thrust chamber is a bundle of thin Type 347 stainless steel tubes brazed together, with aluminum pumps.",
  "application": "RL10 is the upper-stage engine on ULA’s Centaur stage, used on Atlas V and Vulcan. It burns liquid hydrogen and liquid oxygen and is built for restartable in-space burns, so its materials must handle both cryogenic propellant and hot exhaust.",
  "story": {
    "headline": "The RL10 is a hydrogen and oxygen upper-stage rocket engine that first ran in 1959 and is still flying.",
    "intro": [
      "The RL10 is a rocket engine for upper stages, burning liquid hydrogen with liquid oxygen. It first ran in 1959 and began at 15,000 pounds-force of thrust. Current versions are rated at nearly 25,000. Pratt & Whitney designed it, as the company's first rocket engine, and Aerojet Rocketdyne makes it today in West Palm Beach, Florida.",
      "The original design's thrust chamber is a bundle of thin stainless steel tubes brazed together, and its pumps are aluminium. Hydrogen runs through the tubes, picks up heat from the chamber walls, and then drives the turbine that pumps the propellants. This is the expander cycle."
    ],
    "built": [
      {
        "title": "Thrust chamber",
        "text": "The tapered tubes are Type 347 stainless steel, with walls only 0.012 inch thick, rolled by the LeFiell Company. They are silver-brazed together in a gas furnace for 20 hours, with manifolds at each end, to make one light chamber. Hydrogen flowing inside protects the tubes from combustion at nearly 6,000 degrees Fahrenheit.",
        "parts": [
          "Thrust chamber tubes (RL10 as described in P&W-era history)",
          "Tube braze joints",
          "Thrust chamber tube bundle (180 up tubes and 180 down tubes)",
          "Chamber inlet and discharge manifolds with stiffening bands",
          "RL10C-1 thrust chamber tubes"
        ]
      },
      {
        "title": "Injector",
        "text": "The injector face is Rigimesh, stacks of Type 347 stainless steel mesh hot-rolled into a porous sintered plate. It carries 216 injector elements in concentric circles, each a central stream of liquid oxygen wrapped in a ring of gaseous hydrogen. A spark igniter set into the face starts combustion.",
        "parts": [
          "Injector face plate (Rigimesh)",
          "Injector elements (x216)",
          "Spark igniter"
        ]
      },
      {
        "title": "Pumps and turbine",
        "text": "The fuel pump's impellers and body are aluminium, and its shaft and bearings are stainless steel. Both turbine stages, both disks and the hub are machined from one aluminium alloy forging. A gear train of 6260 alloy gears drives the oxygen pump, which has a stainless steel impeller in an aluminium housing.",
        "parts": [
          "Fuel pump inducer, impellers and body",
          "Fuel pump drive shaft and bearings",
          "Turbine blades, disks and hub",
          "Drive gears",
          "Oxidizer pump impeller and inducer"
        ]
      },
      {
        "title": "Nozzle extensions",
        "text": "Some versions add a nozzle extension to improve performance. The RL10A-4 had an extendible, radiation-cooled nozzle of columbium, a name for niobium alloy, and the RL10A-4-2 has a fixed 51-centimetre columbium extension. The RL10B-2 uses carbon-carbon from Safran Ceramics, and no other American liquid engine has flown with one.",
        "parts": [
          "RL10A-4 extendible nozzle",
          "RL10A-4-2 fixed columbium nozzle extension (51 cm)",
          "RL10B-2 carbon-carbon nozzle extension"
        ]
      },
      {
        "title": "A printed copper chamber",
        "text": "Aerojet Rocketdyne has tested an RL10 thrust chamber of copper alloy made by 3D printing. It has only two main copper parts in place of the brazed tube bundle, a part count more than 90 percent lower. A full-scale 3D-printed injector was hot-fired with it.",
        "parts": [
          "Additively manufactured copper-alloy thrust chamber (test article)",
          "Additively manufactured injector (test article)"
        ]
      }
    ],
    "materials": [
      {
        "name": "Type 347 stainless steel",
        "mid": "stainless-347",
        "where": "The thin chamber tubes and the injector face. Pump shafts, bearings and the oxygen impeller are stainless too, grade unstated."
      },
      {
        "name": "Silver braze",
        "mid": "silver-braze",
        "where": "Joins the chamber tubes in a 20-hour furnace cycle. The alloy is unnamed."
      },
      {
        "name": "Aluminium",
        "mid": "aluminium",
        "where": "The fuel pump, turbine blades and disks, and the oxygen pump housings, in unnamed alloys."
      },
      {
        "name": "Columbium (niobium) alloy",
        "mid": "niobium-alloy",
        "where": "The radiation-cooled nozzle extensions of the RL10A-4 and RL10A-4-2."
      },
      {
        "name": "Carbon-carbon",
        "mid": "carbon-carbon-novoltex",
        "where": "The nozzle extension of the RL10B-2, made by Safran Ceramics from a needled preform."
      },
      {
        "name": "Copper alloy",
        "mid": "copper-alloy",
        "where": "The 3D-printed test chamber. It is a development part, not a flight engine."
      }
    ],
    "connections": "The RL10 was created for Convair's Centaur stage. Today one or two power the Centaur on Atlas V, two power Vulcan's Centaur V, and one powers the upper stage of NASA's Space Launch System. Earlier users include the Delta III and IV second stages, Titan Centaurs and, in a cluster of six, the Saturn I's S-IV stage. At least three of its technologies passed into the J-2.",
    "unknown": "The detailed accounts of its materials describe the original Pratt & Whitney engine, so current versions may differ. The alloys of today's valves, bearings, igniters and injectors are not published, and the RL10C-1's chamber tubes are called only stainless steel.",
    "facts": [
      {
        "label": "First run",
        "value": "1959"
      },
      {
        "label": "Propellants",
        "value": "Liquid hydrogen and liquid oxygen"
      },
      {
        "label": "Cycle",
        "value": "Expander cycle"
      },
      {
        "label": "Thrust today",
        "value": "Nearly 25,000 lbf, Isp nearing 467 s"
      },
      {
        "label": "Original thrust",
        "value": "15,000 lbf, Isp about 444 s (RL10A-1 era)"
      },
      {
        "label": "Longest single run",
        "value": "one engine ran at full thrust for 1,680 s (28 minutes)"
      }
    ]
  },
  "specifications": [
    {
      "label": "First run",
      "value": "1959",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "The RL10 first ran in 1959"
    },
    {
      "label": "Propellants",
      "value": "Liquid hydrogen and liquid oxygen",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "using liquid hydrogen (LH2) and liquid oxygen (LOX) propellants"
    },
    {
      "label": "Cycle",
      "value": "Expander cycle",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "This is called the expander cycle"
    },
    {
      "label": "Thrust and Isp (current)",
      "value": "Nearly 25,000 lbf, Isp nearing 467 s",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "today it is rated at nearly 25,000 lbT and an Isp nearing 467 sec"
    },
    {
      "label": "RL10A-4 vacuum thrust",
      "value": "20,800 lbf (upgraded from 16,500 lbf)",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
      "quote": "Vacuum thrust was upgraded from 16,500 to 20,800 Ib"
    },
    {
      "label": "RL10A-4 expansion ratio",
      "value": "84:1 with extendible nozzle",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
      "quote": "bringing the expansion ratio to 84:1"
    },
    {
      "label": "Turbine power",
      "value": "About 644 hp",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "producing about 644 hp drives the propellant pumps"
    },
    {
      "label": "Original thrust and specific impulse",
      "value": "15,000 lbf, Isp about 444 s (RL10A-1 era)",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "It started as a 15,000 lbT engine with an Isp of about 444 sec"
    },
    {
      "label": "First flight-rated production model",
      "value": "RL10A-1, preliminary flight rating testing completed November 1961",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
      "quote": "The first production model, the RL-10A-1, completed its preliminary flight rating testing in November of 1961"
    },
    {
      "label": "First experimental engine test",
      "value": "July 1959",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
      "quote": "The first experimental engine, shown in Figure 3, was tested in July 1959."
    },
    {
      "label": "RL10A-4-2 thrust and Isp",
      "value": "99.2 kN (22,300 lbf), 450.5 s",
      "source_url": "https://www.ulalaunch.com/docs/default-source/rockets/atlasvusersguide2010.pdf",
      "quote": "The RL10A-4-2 engine develops a thrust of 99.2 kN (22,300 lbf) at a specific impulse of 450.5 seconds."
    },
    {
      "label": "RL10B-2 thrust (ICPS)",
      "value": "24,750 lbf (110 kN)",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf",
      "quote": "producing 24,750 lbs. (110 kN) of thrust"
    },
    {
      "label": "RL10C-1-1A thrust (Vulcan Centaur V)",
      "value": "23,825 lbf (106 kN) each",
      "source_url": "https://ulalaunch.com/missions/next-launch/vulcan-ussf-106",
      "quote": "producing 23,825 pounds (106 kilo-Newtons) of thrust"
    },
    {
      "label": "Exploration Upper Stage thrust",
      "value": "about 97,000 lbf from four RL10C-3 engines",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/",
      "quote": "This 97,000 lbs. of thrust will allow more than 38 t (84,000 lbs.) for Block 1B crew"
    },
    {
      "label": "Dual-engine Centaur missions",
      "value": "Centaur evolution proven over more than 260 missions, over 150 with a dual-engine Centaur",
      "source_url": "https://www.ulalaunch.com/docs/default-source/rockets/2023_vulcan_user_guide.pdf",
      "quote": "including over 150 missions featuring a dual-engine Centaur"
    },
    {
      "label": "Engine temperature and pressure",
      "value": "combustion temperature nearly 6,000 F",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "protecting the tubes from the nearly 6,000°F combustion temperature prior to being expanded through the turbine"
    },
    {
      "label": "Longest single run",
      "value": "one engine ran at full thrust for 1,680 s (28 minutes)",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "one engine operated at full thrust for 1,680 seconds (28 minutes)!"
    },
    {
      "label": "RL10C-1 first flight",
      "value": "December 2014 (Atlas V)",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
      "quote": "The new powerplant RL-10C-1 is making its first flight in December 2014."
    }
  ],
  "features": [
    {
      "text": "Hydrogen heated in the chamber tubes drives the turbine, which pumps the propellants",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "This is called the expander cycle"
    },
    {
      "text": "Only US liquid engine to fly a carbon-carbon nozzle extension (RL10B-2)",
      "source_url": "https://ntrs.nasa.gov/api/citations/20170008949/downloads/20170008949.pdf",
      "quote": "The RL10B-2 is the only U.S. liquid engine that has flown with a C-C composite nozzle extension"
    },
    {
      "text": "Thrust chamber is built from thin tubes joined into one lightweight part",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
      "quote": "This process produces a single light-weight thrust chamber."
    }
  ],
  "parts": [
    {
      "assembly": "Thrust chamber and primary nozzle",
      "parts": [
        {
          "part": "Thrust chamber tubes (RL10 as described in P&W-era history)",
          "material": "Type 347 stainless steel",
          "form": "tapered tubes, 0.012 in wall",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Type 347 stainless steel tubes with a wall thickness of only 0.012\"",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "stainless-347"
        },
        {
          "part": "Tube braze joints",
          "material": "silver braze (alloy not stated)",
          "form": "furnace brazed",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "silver-brazed in a gas furnace for 20 hours",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "silver-braze"
        },
        {
          "part": "RL10C-1 thrust chamber tubes",
          "material": "stainless steel (grade not stated)",
          "form": "hydroformed, drawn tubes, brazed together",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The thrust chamber of the current RL10C-1 model design uses a complex array of brazed-together hydroformed, drawn stainless tubes",
          "source_url": "https://3dprint.com/170213/aerojet-3d-printed-rl10-chamber/",
          "profile": null,
          "mid": "stainless-steel"
        }
      ]
    },
    {
      "assembly": "Injector",
      "parts": [
        {
          "part": "Injector face plate (Rigimesh)",
          "material": "Type 347 stainless steel mesh",
          "form": "porous sintered plate",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "a material formed by hot-rolling stacks of Type 347 stainless steel mesh together to form a porous sintered plate",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "stainless-347"
        }
      ]
    },
    {
      "assembly": "Fuel turbopump",
      "parts": [
        {
          "part": "Fuel pump inducer, impellers and body",
          "material": "aluminum (alloy not stated)",
          "form": "machined",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The inducer, impellers, and pump body are made of aluminum",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": "aluminium",
          "mid": "aluminium"
        },
        {
          "part": "Fuel pump drive shaft and bearings",
          "material": "stainless steel (grade not stated)",
          "form": "shaft and bearings",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "while the pump drive shaft and bearings are of stainless steel",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "stainless-steel"
        },
        {
          "part": "Turbine blades, disks and hub",
          "material": "aluminum alloy (grade not stated)",
          "form": "single machined forging",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Both turbine blade stages, both disks and the hub are machined from a single aluminum alloy forging.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": "aluminium",
          "mid": "aluminium"
        },
        {
          "part": "Turbine shrouds",
          "material": "aluminum alloy (grade not stated)",
          "form": "dip-brazed shrouds",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Aluminum alloy shrouds are attached by dip brazing.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": "aluminium",
          "mid": "aluminium"
        }
      ]
    },
    {
      "assembly": "Oxidizer pump and gear train",
      "parts": [
        {
          "part": "Oxidizer pump impeller and inducer",
          "material": "stainless steel (grade not stated)",
          "form": "impeller, shrouded inducer",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The impeller and inducer are made of stainless steel while the housings are machined aluminum.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "stainless-steel"
        },
        {
          "part": "Oxidizer pump housings",
          "material": "aluminum (alloy not stated)",
          "form": "machined housings",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The impeller and inducer are made of stainless steel while the housings are machined aluminum.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": "aluminium",
          "mid": "aluminium"
        },
        {
          "part": "Drive gears",
          "material": "6260 gear alloy with molysulfide coating",
          "form": "gear train",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The gear train gears were fabricated from 6260 gear alloy with a molysulfide coating on the teeth.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "gear-alloy-6260"
        },
        {
          "part": "Shaft seals",
          "material": "carbon",
          "form": "face and ring seals",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Three vented compartments, separated by carbon ring seals",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "carbon-seal"
        }
      ]
    },
    {
      "assembly": "Nozzle extension",
      "parts": [
        {
          "part": "RL10B-2 carbon-carbon nozzle extension",
          "material": "carbon-carbon (Safran Novoltex, CVI-densified)",
          "form": "pseudo-3D needled preform",
          "finish": null,
          "standard": null,
          "hardware_ref": "Safran Ceramics (France)",
          "quote": "pseudo-3D needled Novoltex preform that is densified through chemical vapor infiltration (CVI)",
          "source_url": "https://ntrs.nasa.gov/api/citations/20170008949/downloads/20170008949.pdf",
          "profile": null,
          "mid": "carbon-carbon-novoltex"
        },
        {
          "part": "RL10A-4 extendible nozzle",
          "material": "columbium (niobium) alloy",
          "form": "radiation-cooled extendible nozzle",
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "an extendible, radiation-cooled columbium nozzle was incorporated, bringing the expansion ratio to 84:1",
          "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
          "profile": null,
          "mid": "niobium-alloy"
        }
      ]
    },
    {
      "assembly": "Thrust chamber and nozzle",
      "parts": [
        {
          "part": "Thrust chamber tube bundle (180 up tubes and 180 down tubes)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Initial engines were assembled with 144/288 tube thrust chambers; this was changed to a 180/360 tube configuration",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Regeneratively cooled chamber and primary nozzle built from thin tapered tubes",
          "specs": [
            {
              "label": "Tube wall",
              "value": "0.012 in, Type 347 stainless steel",
              "quote": "Type 347 stainless steel tubes with a wall thickness of only 0.012\"",
              "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml"
            },
            {
              "label": "Tube count (P&W paper)",
              "value": "360 thin-wall tubes form the primary nozzle",
              "quote": "In the RL-10 configuration, 360 thin-wall tubes are formed and flattened (spanked) to form the primary nozzle.",
              "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
            }
          ]
        },
        {
          "part": "Chamber inlet and discharge manifolds with stiffening bands",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "assembled along with inlet and discharge manifolds and stiffening bands on a mandrel under clean-room conditions",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "LH2 inlet and GH2 outlet manifolds brazed to the tube bundle"
        },
        {
          "part": "Fixed primary nozzle and secondary nozzle extension",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "consists of a fixed primary nozzle and a secondary nozzle extension",
          "source_url": "https://www.ulalaunch.com/docs/default-source/rockets/atlasvusersguide2010.pdf",
          "profile": null,
          "mid": null,
          "function": "Primary nozzle is part of the tube bundle; the extension raises expansion ratio"
        },
        {
          "part": "RL10A-4-2 fixed columbium nozzle extension (51 cm)",
          "material": "columbium (niobium) alloy",
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The 51-cm (20-in.) long columbium fixed extended nozzle provides enhanced engine performance through an increase in nozzle expansion ratio.",
          "source_url": "https://www.ulalaunch.com/docs/default-source/rockets/atlasvusersguide2010.pdf",
          "profile": null,
          "mid": "columbium-niobium",
          "function": "Radiation-cooled extension fixed in place before flight on Atlas V"
        },
        {
          "part": "Silver throat insert (RL10A-3-3A and later chamber shape)",
          "material": "silver",
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "with the addition of a silver insert at the throat",
          "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
          "profile": "silver",
          "mid": "silver",
          "function": "Insert at the throat that later became part of the tube shape"
        }
      ]
    },
    {
      "assembly": "Injector and ignition",
      "parts": [
        {
          "part": "Injector elements (x216)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The injector contains 216 injector elements arranged in equally-spaced concentric circles.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Concentric jets, central LOX stream surrounded by an annular GH2 stream"
        },
        {
          "part": "Spark igniter",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "A spark igniter recessed in the propellant injector face initiates combustion chamber ignition.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Electric spark igniter recessed in the injector face"
        },
        {
          "part": "Igniter oxidizer supply valve",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The igniter oxidizer supply valve assures a combustible mixture at the igniter by admitting gaseous oxygen",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Admits gaseous oxygen to the igniter during start"
        },
        {
          "part": "Dual direct spark ignition (DDSI) system",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The most significant change that is part of the RL-10A-4-2 engine is the incorporation of Dual Direct Spark Ignition (DDSI) system.",
          "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
          "profile": null,
          "mid": null,
          "function": "Fully redundant electronic ignition on the RL10A-4-2"
        }
      ]
    },
    {
      "assembly": "Turbomachinery",
      "parts": [
        {
          "part": "Fuel turbopump (two-stage centrifugal)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The two-stage centrifugal fuel pump features back-shrouded impellers, volute collectors, and tangential diffusers.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Pumps LH2 through the chamber walls to the turbine"
        },
        {
          "part": "Oxidizer pump (single stage, gear driven)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The oxidizer pump is a single-stage fully-shrouded centrifugal pump driven through a reduction gear train from the fuel pump drive shaft.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Pumps LOX, driven through a reduction gear train from the fuel pump shaft"
        },
        {
          "part": "Turbine (two-stage, full admission)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "A full admission, pressure compounded, two-stage turbine producing about 644 hp drives the propellant pumps.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Driven by hydrogen heated in the chamber walls (expander cycle)"
        },
        {
          "part": "Prelaunch cool-down check valve",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Cold helium or hydrogen flowing through a prelaunch cool-down check valve partially cools the turbopump before vehicle launch.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Lets cold helium or hydrogen chill the turbopump before launch"
        },
        {
          "part": "Duct flange seals (Teflon-coated conical washers)",
          "material": "Teflon-coated conical washer (base material not stated)",
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The seal was a Teflon-coated conical washer that was captured in an angular cavity machined into the flanges.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": "teflon-ptfe",
          "function": "Hydrogen-tight joints in the solid propellant ducts"
        }
      ]
    },
    {
      "assembly": "Thrust control and valves",
      "parts": [
        {
          "part": "Pneumatic/mechanical thrust control (bellows section and valve section)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The thrust control employs two separate interacting sections – a thrust control bellows section and a thrust control valve section.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Holds chamber pressure steady by bypassing hot hydrogen around the turbine"
        },
        {
          "part": "Turbine bypass valve",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The quantity of GH2 bypassing the turbine is regulated to control pump output as a function of combustion chamber pressure.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Regulates how much hot GH2 skips the turbine"
        },
        {
          "part": "Sonic venturi",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Hot GH2 exiting the thrust chamber wall tubes is routed through a sonic venturi whose upstream pressure is a function of its mass flow.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Senses chamber-exit hydrogen flow for the thrust control"
        },
        {
          "part": "Oxidizer flow control and propellant utilization valve",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The oxidizer flow control and propellant utilization valve has three orifices that perform three functions.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Three orifices set the mixture ratio during start and flight"
        },
        {
          "part": "Main fuel shutoff valve",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The main fuel shutoff valve is a normally-closed, bullet-type valve with a bellows actuator.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Bullet-type valve with a bellows actuator that starts and stops fuel to the injector"
        },
        {
          "part": "Propellant pump inlet shutoff valves",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "These normally-closed helium-actuated ball valves are mounted on the propellant pumps.",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Helium-actuated ball valves on the pumps"
        },
        {
          "part": "Fuel pump cool-down and bleed valves",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "The fuel pump cool-down and bleed valves are sleeve-type valves",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Sleeve valves that chill the pump and vent the fuel system overboard"
        },
        {
          "part": "Prestart and start solenoid valves",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "Start and cutoff are controlled by pneumatic valves actuated by vehicle-supplied pressurized helium",
          "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml",
          "profile": null,
          "mid": null,
          "function": "Electrical signals route vehicle helium to the pneumatic valves"
        }
      ]
    },
    {
      "assembly": "Installation on the stage",
      "parts": [
        {
          "part": "Thrust vector control actuation (electromechanical on single-engine Centaur, hydraulic on dual)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": null,
          "quote": "EMAs for thrust vector control were developed for the SEC program and are used on all single-engine Common Centaurs.",
          "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm",
          "profile": null,
          "mid": null,
          "function": "Gimbals the engine in flight"
        }
      ]
    },
    {
      "assembly": "Development hardware",
      "parts": [
        {
          "part": "Additively manufactured copper-alloy thrust chamber (test article)",
          "material": "copper alloy (grade not stated)",
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Aerojet Rocketdyne",
          "quote": "The RL10 thrust chamber assembly was built from a copper alloy, using SLM technology.",
          "source_url": "https://3dprint.com/170213/aerojet-3d-printed-rl10-chamber/",
          "profile": null,
          "mid": "copper-alloy",
          "function": "Two primary copper parts replace the brazed tube bundle",
          "specs": [
            {
              "label": "Part count",
              "value": "reduced by over 90 percent versus the tube-bundle chamber",
              "quote": "has a significantly reduced part count of over 90%",
              "source_url": "https://3dprint.com/170213/aerojet-3d-printed-rl10-chamber/"
            },
            {
              "label": "Construction",
              "value": "just two primary copper parts",
              "quote": "made of just two primary copper parts",
              "source_url": "https://3dprint.com/170213/aerojet-3d-printed-rl10-chamber/"
            }
          ]
        },
        {
          "part": "Additively manufactured injector (test article)",
          "material": null,
          "form": null,
          "finish": null,
          "standard": null,
          "hardware_ref": "Supplier: Aerojet Rocketdyne",
          "quote": "full-scale testing of a 3-D printed injector and copper thrust chamber",
          "source_url": "https://3dprint.com/170213/aerojet-3d-printed-rl10-chamber/",
          "profile": null,
          "mid": null,
          "function": "Full-scale 3D printed injector hot-fired with the copper chamber"
        }
      ]
    }
  ],
  "materials": [
    {
      "id": "stainless-347",
      "name": "Type 347 stainless steel mesh",
      "material_page": null
    },
    {
      "id": "silver-braze",
      "name": "silver braze (alloy not stated)",
      "material_page": null
    },
    {
      "id": "stainless-steel",
      "name": "stainless steel (grade not stated)",
      "material_page": null
    },
    {
      "id": "aluminium",
      "name": "aluminum (alloy not stated)",
      "material_page": "https://spacemushroom.com/profiles/aluminium/"
    },
    {
      "id": "gear-alloy-6260",
      "name": "6260 gear alloy with molysulfide coating",
      "material_page": null
    },
    {
      "id": "carbon-seal",
      "name": "carbon",
      "material_page": null
    },
    {
      "id": "carbon-carbon-novoltex",
      "name": "carbon-carbon (Safran Novoltex, CVI-densified)",
      "material_page": null
    },
    {
      "id": "niobium-alloy",
      "name": "columbium (niobium) alloy",
      "material_page": null
    },
    {
      "id": "columbium-niobium",
      "name": "columbium (niobium) alloy",
      "material_page": null
    },
    {
      "id": "silver",
      "name": "silver",
      "material_page": "https://spacemushroom.com/profiles/silver/"
    },
    {
      "id": "teflon-ptfe",
      "name": "Teflon-coated conical washer (base material not stated)",
      "material_page": null
    },
    {
      "id": "copper-alloy",
      "name": "copper alloy (grade not stated)",
      "material_page": null
    }
  ],
  "standards": [],
  "relations": [
    {
      "type": "part_of",
      "target": "Atlas V (Common Centaur)",
      "target_slug": "ula-atlas-v",
      "note": "One engine (single-engine Centaur) or two (dual-engine); RL10A-4-2, now RL10C-1",
      "quote": "Primary propulsion is provided by Pratt & Whitney RL10A-4-2 engine(s) with a fixed, radiatively cooled nozzle extension.",
      "source_url": "https://www.ulalaunch.com/docs/default-source/rockets/atlasvusersguide2010.pdf"
    },
    {
      "type": "part_of",
      "target": "Atlas V (Common Centaur)",
      "target_slug": "ula-atlas-v",
      "note": "Current Atlas V Centaur carries the RL10C-1",
      "quote": "the lightweight L3Harris RL10C-1 engine provides industry best thrust-to-weight ratio",
      "source_url": "https://www.ulalaunch.com/rockets/atlas-v"
    },
    {
      "type": "part_of",
      "target": "Vulcan Centaur (Centaur V)",
      "target_slug": "ula-vulcan-centaur",
      "note": "Two RL10C-1-1A engines, 23,825 lbf each",
      "quote": "powered by two RL10C-1-1A engines producing 23,825 pounds (106 kilo-Newtons) of thrust",
      "source_url": "https://ulalaunch.com/missions/next-launch/vulcan-ussf-106"
    },
    {
      "type": "part_of",
      "target": "Space Launch System (ICPS)",
      "target_slug": "nasa-sls",
      "note": "Interim Cryogenic Propulsion Stage: one RL10B-2 engine (24,750 lbf)",
      "quote": "feeding a single Aerojet Rocketdyne RL10B-2 engine producing 24,750 lbs. (110 kN) of thrust",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf"
    },
    {
      "type": "part_of",
      "target": "Space Launch System (Exploration Upper Stage, Block 1B)",
      "target_slug": "nasa-sls",
      "note": "Planned stage with four RL10C-3 engines (about 97,000 lbf total)",
      "quote": "It is powered by four RL10C-3 engines that produce almost four times more thrust than the one RL10B-2 engine that powers the ICPS.",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/"
    },
    {
      "type": "part_of",
      "target": "Saturn I (S-IV second stage)",
      "target_slug": null,
      "note": "Cluster of six RL10 engines (RL10A-3S)",
      "quote": "This model was used, with minor variations, on the Centaur and in a six-engine cluster on the Saturn S-IV.",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Saturn I (S-IV second stage)",
      "target_slug": null,
      "note": "S-IV was 18.3 ft in diameter with six engines",
      "quote": "use six Pratt & Whitney RL10 engines and serve as a Saturn I second stage",
      "source_url": "https://enginehistory.org/Rockets/RPE08.30/RPE08.30.shtml"
    },
    {
      "type": "part_of",
      "target": "Delta IV (Delta Cryogenic Second Stage)",
      "target_slug": null,
      "note": "One RL10B-2-1 engine per stage",
      "quote": "RL-10B-2-1 1 Delta IV DCSS",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Delta IV (Delta Cryogenic Second Stage)",
      "target_slug": null,
      "note": "RL10B-2 upper stage engines with carbon-carbon nozzle extensions",
      "quote": "C-C nozzle extensions used on the Delta IV’s RL10B-2 upper stage engines",
      "source_url": "https://ntrs.nasa.gov/api/citations/20170008949/downloads/20170008949.pdf"
    },
    {
      "type": "part_of",
      "target": "Delta III (Delta Cryogenic Second Stage)",
      "target_slug": null,
      "note": "One RL10B-2 engine per stage",
      "quote": "RL-10B-2 1 Delta III DCSS",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Delta III (Delta Cryogenic Second Stage)",
      "target_slug": null,
      "note": "Delta III chose a carbon-carbon nozzle extension for the RL10B-2",
      "quote": "the Delta III Program decided to use C-C composite extensions on the Centaur Upper Stage’s RL10B-2 engine",
      "source_url": "https://ntrs.nasa.gov/api/citations/20170008949/downloads/20170008949.pdf"
    },
    {
      "type": "part_of",
      "target": "Titan IIIE Centaur (Centaur D-1T)",
      "target_slug": null,
      "note": "Two RL10A-3-3T engines",
      "quote": "RL-10A-3-3T 2 Titan-3E Centaur D-1T",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Titan IV Centaur",
      "target_slug": null,
      "note": "Two RL10A-3-3AT engines on the Titan IVA Centaur",
      "quote": "RL-10A-3-3AT 2 Titan-IVA Centaur T",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Titan IV Centaur",
      "target_slug": null,
      "note": "Two RL10A-4-1T engines on the Titan IVB Centaur",
      "quote": "RL-10A-4-1T 2 Titan-IVB Centaur T",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Atlas II Centaur (D-2)",
      "target_slug": null,
      "note": "Two engines per Centaur",
      "quote": "RL-10A-3-3A 2 Atlas II Centaur D-2",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Atlas III Centaur (D-3A, D-3B)",
      "target_slug": null,
      "note": "One engine on the Atlas IIIA single-engine Centaur",
      "quote": "RL-10A-4-1N 1 Atlas-IIIA Centaur D-3A SEC",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Atlas III Centaur (D-3A, D-3B)",
      "target_slug": null,
      "note": "Two engines on the Atlas IIIB dual-engine Centaur",
      "quote": "RL-10A-4-1N 2 Atlas-IIIB Centaur D-3B DEC",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Atlas-Centaur AC-1 (first Atlas/Centaur vehicle)",
      "target_slug": null,
      "note": "Two RL10A-1 engines on the Atlas SLV-3C Centaur A",
      "quote": "RL-10A-1 2 Atlas SLV3C Centaur A",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "part_of",
      "target": "Delta Clipper DC-X",
      "target_slug": null,
      "note": "Four RL10A-5 engines",
      "quote": "RL-10A-5 4 Delta Clipper DC-X",
      "source_url": "https://b14643.eu/Spacerockets/Specials/P&W_RL10_engine/index.htm"
    },
    {
      "type": "heritage_of",
      "target": "J-2 engine",
      "target_slug": "rocketdyne-j-2",
      "note": "Three RL10 technologies were adopted in the J-2",
      "quote": "At least three technologies pioneered by the RL10 found their ways into the J-2",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml"
    },
    {
      "type": "supplied_by",
      "target": "Aerojet Rocketdyne",
      "target_slug": null,
      "note": "Current maker, West Palm Beach, Florida",
      "quote": "Its RL10 engine is manufactured by Aerojet Rocketdyne in its West Palm Beach, Florida facility.",
      "source_url": "https://www.nasa.gov/wp-content/uploads/2022/03/sls-reference-guide-2022-v2-508-0.pdf"
    },
    {
      "type": "supplied_by",
      "target": "L3Harris Technologies",
      "target_slug": null,
      "note": "Named as maker of the ICPS RL10 engine",
      "quote": "The ICPS uses one RL10 engine made by L3Harris.",
      "source_url": "https://www.nasa.gov/reference/space-launch-system/"
    },
    {
      "type": "supplied_by",
      "target": "Pratt & Whitney",
      "target_slug": null,
      "note": "Original designer; the RL10 was P&W's first rocket engine",
      "quote": "Although Pratt & Whitney (P&W) had extensive turbojet experience, this was its first rocket engine.",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml"
    },
    {
      "type": "supplied_by",
      "target": "LeFiell Company",
      "target_slug": null,
      "note": "Rolled the tapered chamber tubes",
      "quote": "The tapered stainless steel tubes are fabricated by the LeFiell Company using a patented rolling process.",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml"
    },
    {
      "type": "supplied_by",
      "target": "Safran Ceramics",
      "target_slug": null,
      "note": "Carbon-carbon nozzle extension of the RL10B-2",
      "quote": "it uses a French material made by Safran Ceramics (formerly Snecma Propulsion Solide or Herakles)",
      "source_url": "https://ntrs.nasa.gov/api/citations/20170008949/downloads/20170008949.pdf"
    },
    {
      "type": "built_on",
      "target": "Centaur upper stage (Convair)",
      "target_slug": null,
      "note": "Engine was created for the Centaur stage; two 15,000 lbf engines",
      "quote": "Two such engines, each rated at 15,000 lbT, were to power the Convair Centaur upper stage",
      "source_url": "https://enginehistory.org/Rockets/RPE08.21/RPE08.21.shtml"
    }
  ],
  "not_published": "Current-production alloy grades for RL10C versions not confirmed. No standards (AMS/ASTM numbers) are given in the sources. Valve, bearing and igniter materials not covered. More detail: Internals of current RL10C-1, RL10C-1-1A and RL10C-3 hardware (valve, bearing, igniter, injector alloys) are not published in the pages read; the EngineHistory description is of the P&W-era RL10A. The B14643 page is a third-party compilation of two primary papers (Santiago, Pratt & Whitney 1996; Rudman and Austad, Lockheed Martin 2002), used for the variant-to-vehicle table, whose rows are flattened text. Engine counts per stage for Delta IV, Atlas III and Titan rows come from that table. Surveyor, Viking and Voyager launches on Centaur are named only in lists, without a source tying each to a specific RL10 variant. The EUS status should be re-checked (see the SLS entry). More detail: Internals of current RL10C-1, RL10C-1-1A and RL10C-3 hardware (valve, bearing, igniter, injector alloys) are not published in the pages read; the EngineHistory description is of the P&W-era RL10A. The B14643 page is a third-party compilation of two primary papers (Santiago, Pratt & Whitney 1996; Rudman and Austad, Lockheed Martin 2002), used for the variant-to-vehicle table, whose rows are flattened text. Engine counts per stage for Delta IV, Atlas III and Titan rows come from that table. Surveyor, Viking and Voyager launches on Centaur are named only in lists, without a source tying each to a specific RL10 variant. The EUS status should be re-checked (see the SLS entry).",
  "depth": "partial",
  "photos": [
    {
      "file": "products/context/ula-rl10-1.jpg",
      "alt": "RL10 engine on a Pratt & Whitney data card with dimensions, thrust and specific impulse printed beside a photo of the engine",
      "long": "RL10 engine on a Pratt & Whitney data card with dimensions, thrust and specific impulse printed beside a photo of the engine",
      "kind": "product",
      "credit": "NASA/Marshall Space Flight Center | https://images.nasa.gov/details/9801769; originally at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-9801769.html",
      "license": "Public domain",
      "page_url": "https://commons.wikimedia.org/wiki/File:RL-10_rocket_engine.jpg"
    },
    {
      "file": "products/context/ula-rl10-2.jpg",
      "alt": "RL10 engine displayed on a stand against a dark background",
      "long": "RL10 engine displayed on a stand against a dark background",
      "kind": "product",
      "credit": "Les Chatfield | https://www.flickr.com/photos/elsie/30432256313/",
      "license": "CC BY 2.0",
      "page_url": "https://commons.wikimedia.org/wiki/File:RL-10_rocket_engine_(30432256313).jpg"
    },
    {
      "file": "products/context/ula-rl10-3.jpg",
      "alt": "RL10 engine mounted at an angle on a blue stand, showing turbopump plumbing and nozzle",
      "long": "RL10 engine mounted at an angle on a blue stand, showing turbopump plumbing and nozzle",
      "kind": "product",
      "credit": "jurvetson | PRATT & WHITNEY RL-10 ROCKET ENGINE",
      "license": "CC BY 2.0",
      "page_url": "https://commons.wikimedia.org/wiki/File:PRATT_%26_WHITNEY_RL-10_ROCKET_ENGINE_(5003286786).jpg"
    }
  ],
  "context": {
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    "mass": [],
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  "licence": "Product data CC BY 4.0, cite Space Mushroom. Photos keep their own licences, given per photo.",
  "mcp": "https://spacemushroom.com/mcp"
}