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Apollo RCS quad.jpg
An RCS quad containing four R-4D thrusters, as used on the Apollo Service Module
Country of origin United States
Manufacturer Kaiser Marquardt
Aerojet Rocketdyne
Application Reaction control system
Liquid-fuel engine
Propellant NTO / MMH
Cycle Pressure-fed
Thrust (vac.)490 N (110 lbf)
Thrust-to-weight ratio 13.74
Chamber pressure6.93 bars (100.5 psi)
Isp (vac.)312 s
Used in
Orion (spacecraft)
H-II Transfer Vehicle
Space Shuttle
Apollo (spacecraft)
Cassini (spacecraft)

The R-4D is a small hypergolic rocket engine, originally designed by Marquardt Corporation for use as a reaction control thruster on vehicles of the Apollo moon program. Today, Aerojet Rocketdyne manufactures and markets modern versions of the R-4D. [1]

Rocket engine jet engine using stored propellant to produce jet propulsion

A rocket engine uses stored rocket propellant mass for forming its high-speed propulsive jet. Rocket engines are reaction engines, obtaining thrust in accordance with Newton's third law. Most rocket engines use combustion, although non-combusting forms also exist. Vehicles propelled by rocket engines are commonly called rockets. Since they need no external material to form their jet, rocket engines can perform in a vacuum and thus can be used to propel spacecraft and ballistic missiles.

Marquardt Corporation

Marquardt Corporation was one of the few aeronautical engineering firms that was dedicated almost solely to the development of the ramjet engine. Marquardt designs were developed through the 1940s into the 1960s, but the ramjet never became a major design and the company turned to other fields in the 1970s. They suffered a particularly bad financial crisis with the ending of the Cold War, and went bankrupt in the 1990s.

Reaction control system spacecraft system that uses thrusters to provide attitude control

A reaction control system (RCS) is a spacecraft system that uses thrusters to provide attitude control, and sometimes translation. Use of diverted engine thrust to provide stable attitude control of a short-or-vertical takeoff and landing aircraft below conventional winged flight speeds, such as with the Harrier "jump jet", may also be referred to as a reaction control system.



Developed as an attitude control thruster for the Apollo Command/Service Module and Lunar Module in the 1960s, each unit for the modules employed four quadruple clusters (pods). It was first flown on AS-201 in February 1966. Approximately 800 were produced during the Apollo program.

Apollo Lunar Module

The Apollo Lunar Module, or simply lunar module, originally designated the lunar excursion module (LEM), was the spacecraft which was flown to and landed on the Moon. The lander spacecraft were built for the US Apollo program by Grumman Aircraft. The lunar module, consisting of a descent stage and an ascent stage, was ferried from the Earth to the Moon attached to the Apollo spacecraft command and service module (CSM), approximately twice its mass. The ascent stage carried a crew of two who flew the spacecraft from lunar orbit to the surface and later back to the command module. Designed for lunar orbit rendezvous, the Apollo Lunar Module was discarded after completing its mission. It was capable of operation only in outer space; structurally and aerodynamically it was incapable of flight through the Earth's atmosphere. The lunar module was the first manned spacecraft to operate exclusively in the airless vacuum of space. It was the first, and to date only, crewed vehicle to land anywhere beyond Earth.


AS-201, flown February 26, 1966, was the first unmanned test flight of an entire production Block I Apollo command and service module and the Saturn IB launch vehicle. The spacecraft consisted of the second Block I command module and the first Block I service module. The suborbital flight was a partially successful demonstration of the service propulsion system and the reaction control systems of both modules, and successfully demonstrated the capability of the command module's heat shield to survive re-entry from low Earth orbit.

Sixteen R-4Ds were mounted on the exterior of each lunar module in four quadruple clusters and sixteen on each service module. Because both the lunar module and service module were jettisoned during the Apollo missions, no flown examples exist. [2]

Post-Apollo, modernized versions of the R-4D have been used in a variety of spacecraft, including the U.S. Navy's Leasat, Insat 1, Intelsat 6, Italsat, and BulgariaSat-1. [3] It has also been used on Japan's H-II Transfer Vehicle and the European Automated Transfer Vehicle, both of which deliver cargo to the International Space Station. [4]

United States Navy Naval warfare branch of the United States Armed Forces

The United States Navy (USN) is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. It is the largest and most capable navy in the world and it has been estimated that in terms of tonnage of its active battle fleet alone, it is larger than the next 13 navies combined, which includes 11 U.S. allies or partner nations. with the highest combined battle fleet tonnage and the world's largest aircraft carrier fleet, with eleven in service, and two new carriers under construction. With 319,421 personnel on active duty and 99,616 in the Ready Reserve, the Navy is the third largest of the service branches. It has 282 deployable combat vessels and more than 3,700 operational aircraft as of March 2018, making it the second-largest air force in the world, after the United States Air Force.

Syncom started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by Hughes Space and Communications. Syncom 2, launched in 1963, was the world's first geosynchronous communications satellite. Syncom 3, launched in 1964, was the world's first geostationary satellite.

Indian National Satellite System series of multipurpose geo-stationary satellites launched by ISRO

The Indian National Satellite System , or INSAT, is a series of multipurpose geo-stationary satellites launched by ISRO to satisfy the telecommunications, broadcasting, meteorology, and search and rescue operations. Commissioned in 1983, INSAT is the largest domestic communication system in the Asia Pacific Region. It is a joint venture of the Department of Space, Department of Telecommunications, India Meteorological Department, All India Radio and Doordarshan. The overall coordination and management of INSAT system rests with the Secretary-level INSAT Coordination Committee.


The R-4D is a fuel-film cooled engine. Some of the fuel is injected longitudinally down the combustion chamber, where it forms a cooling film. [5] The thruster's design has changed several times since its introduction. The original R-4D's combustion chamber was formed from an alloy of molybdenum, coated in a layer of disilicide. [2] Later versions switched to a niobium alloy, for its greater ductility. Beginning with the R-4D-14, the design was changed again to use an iridium-lined rhenium combustion chamber, which provided greater resistance to high-temperature oxidization and promoted mixing of partially reacted gasses. [5]

Alloy mixture or metallic solid solution composed of two or more elements

An alloy is a combination of metals and of a metal or another element. Alloys are defined by a metallic bonding character. An alloy may be a solid solution of metal elements or a mixture of metallic phases. Intermetallic compounds are alloys with a defined stoichiometry and crystal structure. Zintl phases are also sometimes considered alloys depending on bond types.

Molybdenum Chemical element with atomic number 42

Molybdenum is a chemical element with symbol Mo and atomic number 42. The name is from Neo-Latin molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but the element was discovered in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm.

Molybdenum disilicide chemical compound

Molybdenum disilicide (MoSi2, or molybdenum silicide), an intermetallic compound, a silicide of molybdenum, is a refractory ceramic with primary use in heating elements. It has moderate density, melting point 2030 °C, and is electrically conductive. At high temperatures it forms a passivation layer of silicon dioxide, protecting it from further oxidation. The thermal stability of MoSi2 alongside its high emissivity make this material, alongside WSi2 attractive for applications as a high emissivity coatings in heat shields for atmospheric entry. MoSi2 is a gray metallic-looking material with tetragonal crystal structure (alpha-modification); its beta-modification is hexagonal and unstable. It is insoluble in most acids but soluble in nitric acid and hydrofluoric acid.

The R-4D requires no igniter as it uses hypergolic fuel.

It is rated for up to one hour of continuous thrust, 40,000 seconds total, and 20,000 individual firings. [5] [6]

Related Research Articles

An arcjet rocket or arcjet thruster is a form of electrically powered spacecraft propulsion, in which an electrical discharge (arc) is created in a flow of propellant. This imparts additional energy to the propellant, so that one can extract more work out of each kilogram of propellant, at the expense of increased power consumption and (usually) higher cost. Also, the thrust levels available from typically used arcjet engines are very low compared with chemical engines.

Hypergolic propellant

A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other.

Apollo (spacecraft) American spacecraft

The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft consisted of a combined command and service module (CSM) and a lunar module (LM). Two additional components complemented the spacecraft stack for space vehicle assembly: a spacecraft–LM adapter (SLA) designed to shield the LM from the aerodynamic stress of launch and to connect the CSM to the Saturn launch vehicle; and a launch escape system (LES) to carry the crew in the command module safely away from the launch vehicle in the event of a launch emergency.

Space Shuttle main engine liquid-fuel cryogenic rocket engine used on NASAs Space Shuttle and the future SLS

The Aerojet Rocketdyne RS-25, otherwise known as the Space Shuttle main engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle. NASA is planning to continue using the RS-25 on the Space Shuttle's successor, the Space Launch System (SLS).


The RL10 is a liquid-fuel cryogenic rocket engine used on the Centaur, S-IV, and Delta Cryogenic Second Stage upper stages. Built in the United States by Aerojet Rocketdyne, the RL10 burns cryogenic liquid hydrogen and liquid oxygen propellants, with each engine producing 64.7 to 110 kN (14,545–24,729 lbf) of thrust in vacuum depending on the version in use. The RL10 was the first liquid hydrogen rocket engine to be built in the United States, and development of the engine by Marshall Space Flight Center and Pratt & Whitney began in the 1950s, with the first flight occurring in 1961. Several versions of the engine have been flown, with three, the RL10A-4-2, the RL10B-2, and the RL10C-1 still being produced and flown on the Atlas V and Delta IV.

Staged combustion cycle

The staged combustion cycle is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is thus combusted in stages. The main advantage relative to other rocket engine power cycles is high fuel efficiency, measured through specific impulse, while its main disadvantage is engineering complexity.

Pressure-fed engine class of rocket engine designs

The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure.

Aerojet was an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California, with divisions in Redmond, Washington, Orange and Gainesville in Virginia, and Camden, Arkansas. Aerojet was owned by GenCorp. In 2013, Aerojet was merged by GenCorp with the former Pratt & Whitney Rocketdyne to form Aerojet Rocketdyne.

Altair (spacecraft) Planned lander spacecraft component of NASAs cancelled Project Constellation

The Altair spacecraft, previously known as the Lunar Surface Access Module or LSAM, was the planned lander spacecraft component of NASA's cancelled Constellation program. Astronauts would have used the spacecraft for landings on the Moon, which was intended to begin around 2019. The Altair spacecraft was planned to be used both for lunar sortie and lunar outpost missions. On February 1, 2010, U.S. President Barack Obama announced a proposal to cancel the Constellation program, to be replaced with a re-scoped program, effective with the U.S. 2011 fiscal year budget.

Orion abort modes

NASA's Orion multi-purpose crew vehicle (MPCV) was planned as the first American spacecraft since Project Apollo to use an escape system in the event of a launch abort, something its predecessor, the Space Shuttle, had for only its first four orbital test flights in 1981–1982. Like the Apollo command and service module (CSM), the Orion CEV would use the launch escape system (LES), a solid-fueled tractor rocket that would be able to pull the Orion crew module away from a malfunctioning Space Launch System (SLS) rocket during the initial launch phase. Based on the launch escape system found on the Soviet/Russian Soyuz spacecraft, the LAS, designed and manufactured by ATK for the Orion CEV, would be larger than the Soyuz version and will have more thrust than the Atlas 109-D booster that carried astronaut John Glenn into orbit in 1962.

AJ10 hypergolic rocket engine manufactured by Aerojet

The AJ10 is a hypergolic rocket engine manufactured by Aerojet Rocketdyne. It has been used to propel the upper stages of several launch vehicles, including the Delta II and Titan III. It is intended for use as the main engine of NASA's Orion service module.

The descent propulsion system or lunar module descent engine (LMDE) is a variable-throttle hypergolic rocket engine developed by Space Technology Laboratories (TRW) for use in the Apollo lunar module descent stage. It used Aerozine 50 fuel and dinitrogen tetroxide oxidizer. This engine used a pintle injector, a design also used later in the SpaceX Merlin engine.

The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta rocket, referred to as Delta-P, from 1972 to 1988. The rocket engine uses Aerozine 50 as fuel, and N
as oxidizer. It was developed in early 1970s by TRW as a derivative of the lunar module descent engine (LMDE). This engine used a pintle injector first developed by TRW in late 1950s and received US Patent in 1972. This injector technology and design is also used on SpaceX Merlin engines.

Ascent propulsion system

The ascent propulsion system (APS) or lunar module ascent engine (LMAE) is a fixed-thrust hypergolic rocket engine developed by Bell Aerosystems for use in the Apollo lunar module ascent stage. It used Aerozine 50 fuel, and N
oxidizer. Rocketdyne provided the injector system, at the request of NASA, when Bell could not solve combustion instability problems.

Aerojet Rocketdyne is an American rocket and missile propulsion manufacturer. Headquartered in Sacramento, California, the company is owned by Aerojet Rocketdyne Holdings. Aerojet Rocketdyne was formed in 2013 when Aerojet and Pratt & Whitney Rocketdyne were merged, following the latter's acquisition by GenCorp from Pratt & Whitney. On April 27, 2015, the name of the holding company, GenCorp, was changed from GenCorp, Inc. to Aerojet Rocketdyne Holdings, Inc.

Liquid apogee engine

A liquid apogee engine (LAE), or apogee engine, refers to a type of chemical rocket engine typically used as the main engine in a spacecraft.


  1. "Bipropellant Rocket Engines". Aerojet Rocketdyne. Retrieved 7 May 2014.
  2. 1 2 David Meerman Scott (November 2013). "Marquardt R-4D Apollo spacecraft attitude control engine". Apollo Artifacts. Retrieved 5 February 2016.
  3. "BulgariaSat-1". spaceflight101. Retrieved 23 June 2017.
  4. Stechman, Carl; Harper, Steve (July 2010). "Performance Improvements in Small Earth Storable Rocket Engines". 46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference. AIAA. "Derivates of this engine are still used today on satellites and spacecraft including the European autonomous transfer vehicle (ATV) and the Japanese H-2 transfer vehicle (HTV) propulsion systems and the future Orion service module.
  5. 1 2 3 Stechman, Carl; Harper, Steve (2010). "Performance Improvements in Small Earth Storable Rocket Engines- An Era of Approaching the Theoretical". The American Institute of Aeronautics and Astronautics. doi:10.2514/6.2010-6884.
  6. "R-4D". Astronautix. Retrieved 5 February 2016.