The LR91 was an American
liquid-propellant rocket engine
A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
, which was used on the second stages of
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
intercontinental ballistic missile
An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapons c ...
s and
launch vehicles
A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and syste ...
. While the original version - the LR91-3 - ran on
RP-1
RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (LH2), but is cheaper, is st ...
/
LOX
Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
(as did the companion
LR87-3) on the
Titan I, the models that propelled the
Titan II and later were switched to
Aerozine 50/
N2O4.
This engine was vacuum optimized and ran the
gas-generator cycle. The thrust chamber used fuel for
regenerative cooling
Regenerative cooling is a method of cooling gases in which compressed gas is cooled by allowing it to expand and thereby take heat from the surroundings. The cooled expanded gas then passes through a heat exchanger where it cools the incoming comp ...
, with separate
ablative skirt.
The
LR87, which was used for the Titan first stage, was used as a template for the LR91.
Early LR91 engines used on the
Titan I burned RP-1 and liquid oxygen. Because liquid oxygen is
cryogenic
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
, it could not be stored in the missile for long periods of time, and had to be loaded before the missile could be launched. For the
Titan II, the engine was converted to use Aerozine-50 and nitrogen tetroxide, which are
hypergolic and storable at room temperature. This allowed Titan II missiles to be kept fully fueled and ready to launch on short notice.
Versions
* LR91-3: Titan I version. Run on RP-1/LOX.
* LR91-5: Titan II version. Propellant was switched to Aerozine50, N
2O
4.
* LR91-7: Similar to LR91-5, it was used on Stage 2 of
Gemini Titan II. This version was human rated.
* LR91-9: Used in earlier versions of Titan III upper stage.
* LR91-11: Version used on the Titan III and Titan IV.
See also
*
AJ-10
*
LR87
*
Titan (rocket)
*
Liquid-propellant rocket
A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid rocket propellant, liquid propellants. Liquids are desirable because they have a reasonably high density and high Specific impulse, specific impulse (''I''sp). T ...
References
External links
Encyclopedia AstronauticaNational Museum of the USAF, Ohio
Rocket engines using kerosene propellant
Rocket engines using hypergolic propellant
Rocket engines using the gas-generator cycle
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