The HG-3 was a
liquid-fuel cryogenic rocket engine which was designed for use on the
upper stage
A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...
s of
Saturn rockets in the post-
Apollo
Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...
era.
Designed in the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
by
Rocketdyne
Rocketdyne is an American rocket engine design and production company headquartered in Canoga Park, California, Canoga Park, in the western San Fernando Valley of suburban Los Angeles, California, Los Angeles, in southern California.
Rocketdyne ...
, the HG-3 was to have burned
cryogenic
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...
liquid hydrogen
Liquid hydrogen () is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecule, molecular H2 form.
To exist as a liquid, H2 must be cooled below its critical point (thermodynamics), critical point of 33 Kelvins, ...
and
liquid oxygen
Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing.
Physical ...
propellants, with each engine producing of
thrust
Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...
during flight.
The engine was designed to produce a
specific impulse
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...
(''I''
sp) of in a vacuum, or at sea level.
Developed from Rocketdyne's
J-2 engine used on the
S-II
The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...
and
S-IVB
The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 rocket engine. For lunar missions it was fired twice: first for Earth ...
stages, the engine was intended to replace the J-2 on the upgraded
MS-II-2 and
MS-IVB-2 stages intended for use on the
Saturn MLV,
Saturn IB-B and Saturn V/4-260 rockets, with a sea-level optimised version, the HG-3-SL, intended for use on the
Saturn INT-17.
The engine was cancelled, however, during the post-Apollo drawdown when development of the more advanced Saturn rockets ceased, and never flew, although the engine was later used as the basis for the design of the
RS-25
The RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is used on the Space Launch System.
Designed and manufactured in the United States by Rocketd ...
engine.
See also
*
J-2X engine
References
Rocket engines using hydrogen propellant
Rocketdyne engines
Rocket engines of the United States
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