The LR91 was an American
liquid-propellant rocket engine
A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...
, 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 (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...
s and
launch vehicles
A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistag ...
. While the original version - the LR91-3 - ran on
RP-1
RP-1 (Rocket Propellant-1 or Refined Petroleum-1) and similar fuels like RG-1 and T-1 are highly refined kerosene formulations used as rocket fuel. Liquid-fueled rockets that use RP-1 as fuel are known as kerolox rockets. In their engines, RP- ...
/
LOX (as did the companion
LR87-3) on the
Titan I, the models that propelled the
Titan II
The Titan II was an intercontinental ballistic missile (ICBM) developed by the Glenn L. Martin Company from the earlier Titan I missile. Titan II was originally designed and used as an ICBM, but was later adapted as a medium-lift space ...
and later were switched to
Aerozine 50
__NOTOC__
Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines ...
/
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 com ...
, with separate
ablative
In grammar, the ablative case (pronounced ; abbreviated ) is a grammatical case for nouns, pronouns, and adjectives in the grammars of various languages. It is used to indicate motion away from something, make comparisons, and serve various o ...
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 International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...
, 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 Titan II was an intercontinental ballistic missile (ICBM) developed by the Glenn L. Martin Company from the earlier Titan I missile. Titan II was originally designed and used as an ICBM, but was later adapted as a medium-lift space ...
, the engine was converted to use Aerozine-50 and nitrogen tetroxide, which are
hypergolic
A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other.
The two propellant components usually consist of a fuel and an oxidizer. The ...
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 uses a rocket engine burning liquid rocket propellant, liquid propellants. (Alternate approaches use gaseous or Solid-propellant rocket , solid propellants.) Liquids are desirable propellants because th ...
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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