R-4D
Marquardt-built small hypergolic rocket engine From Wikipedia, the free encyclopedia
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.[1]
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 |
| Performance | |
| Thrust, vacuum | 110 pounds-force (490 N) |
| Thrust-to-weight ratio | 13.74 |
| Chamber pressure | 100.5 pounds per square inch (6.93 bar) |
| Specific impulse, vacuum | 312 s |
| Dimensions | |
| Length | 12.00 inches (30.5 cm) |
| Diameter | 6.00 inches (15.2 cm) |
| Dry mass | 8.00 pounds (3.63 kg) |
| Used in | |
| Orion (spacecraft) H-II Transfer Vehicle (1, 2, 4) Space Shuttle Apollo (spacecraft) Cassini (spacecraft) ESA Automated Transfer Vehicle | |
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.[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 delivered cargo to the International Space Station.[4] It is also used on the Orion spacecraft.[5]
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.[6]
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[clarification needed][when?] switched to a niobium alloy, for its greater ductility. Beginning with the R-4D-14,[when?] 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.[6]
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.[6][7]
Additional literature
References
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