R-4D
{{Short description|Marquardt-built small hypergolic rocket engine}}
{{for|the aircraft with this designation in US Navy service|Douglas C-47 Skytrain}}
{{infobox rocket engine
|image=Apollo RCS quad.jpg
|image_size=
|caption=RCS quad containing four R-4D thrusters, as used on the Apollo Service Module
|name=R-4D
|country_of_origin=United States
|manufacturer=Kaiser Marquardt
Aerojet Rocketdyne
|purpose=Reaction control system
|type=liquid
|fuel=MMH
|oxidiser=NTO
|capacity=
|thrust(SL)=
|thrust(Vac)= {{convert|110|lbf|N}}
|specific_impulse_vacuum= 312 s
|specific_impulse_sea_level=
|chamber_pressure= {{convert|100.5|psi|bar}}
|thrust_to_weight= 13.74
|cycle=Pressure-fed
|dimensions =
|length = {{convert|12.00|in|cm}}
|diameter = {{convert|6.00|in|cm}}
|dry_weight = {{convert|8.00|lb|kg}}
|used_in=Orion (spacecraft)
H-II Transfer Vehicle (1, 2, 4)
Space Shuttle
Apollo (spacecraft)
Cassini (spacecraft)
ESA Automated Transfer Vehicle
}}
The R-4D is a small hypergolic rocket engine, originally designed by Marquardt Corporation for use as a reaction control system thruster on vehicles of the Apollo crewed Moon landing program. Aerojet Rocketdyne manufactures and markets modern versions of the R-4D.{{cite web |url=https://www.rocket.com/propulsion-systems/bipropellant-rockets |title=Bipropellant Rocket Engines |publisher=Aerojet Rocketdyne |access-date=7 May 2014 |archive-date=12 May 2014 |archive-url=https://web.archive.org/web/20140512214307/https://www.rocket.com/propulsion-systems/bipropellant-rockets |url-status=dead }}
History
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.{{cite web|url=http://www.apolloartifacts.com/2013/11/marquardt-r-4d-apollo-spacecraft-attitude-control-engine.html|title=Marquardt R-4D Apollo spacecraft attitude control engine|publisher=Apollo Artifacts|author=David Meerman Scott|date=November 2013|access-date=5 February 2016}}
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.{{cite web|url=http://spaceflight101.com/falcon-9-bulgariasat-1/bulgariasat/|title=BulgariaSat-1|publisher=spaceflight101|access-date=23 June 2017}} It has also been used on Japan's H-II Transfer Vehicle and the European Automated Transfer Vehicle, both of which delivered cargo to the International Space Station.{{Cite conference |last=Stechman |first=Carl |last2=Harper |first2=Steve |date=July 2010 |title=Performance Improvements in Small Earth Storable Rocket Engines |conference=46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference |publisher=AIAA |doi=10.2514/6.2010-6884 |quote=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.}} It is also used on the Orion spacecraft.{{Cite web|title=Artemis 1|url=https://directory.eoportal.org/web/eoportal/satellite-missions/a/artemis-i}}
Design
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.{{Cite conference |last=Stechman |first=Carl |last2=Harper |first2=Steve |date=2010 |title=Performance Improvements in Small Earth Storable Rocket Engines- An Era of Approaching the Theoretical |conference=46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference |publisher=The American Institute of Aeronautics and Astronautics |doi=10.2514/6.2010-6884 |isbn=978-1-60086-958-7 |s2cid=111626089}}
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. Later versions{{clarify|date=April 2021}}{{when|date=April 2021}} switched to a niobium alloy, for its greater ductility. Beginning with the R-4D-14,{{when|date=April 2021}} 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.
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.{{cite web|url=http://www.astronautix.com/engines/r4d.htm|archive-url=https://web.archive.org/web/20020826021630/http://astronautix.com/engines/r4d.htm|url-status=dead|archive-date=August 26, 2002|title=R-4D|publisher=Astronautix|access-date=5 February 2016}}
Additional literature
- [https://ntrs.nasa.gov/api/citations/20100027315/downloads/20100027315.pdf Remembering the Giants: Apollo Rocket Propulsion Development - Chapter Three & Appendix E]
References
{{Reflist}}
{{Marquardt Corporation aeroengines}}
{{Orbital spacecraft rocket engines}}