The LR87 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 accorda ...

used on the first 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 weapo ...

s and launch vehicles. Composed of twin motors with separate combustion chambers and

turbopump A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpo ...

machinery, it is considered a single unit. The LR87 first flew in 1959. The LR87 was developed in the late 1950s by

Aerojet Aerojet was an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California, with divisions in Redmond, Washington, Orange and Gainesville in Virginia, and Camden, Arkansas. Aerojet was owned by GenCorp. I ...

. It was the first production rocket engine capable (in its various models) of burning the three most common liquid rocket propellant combinations:

liquid oxygen 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 app ...

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 s ...

, nitrogen tetroxide (NTO)/ Aerozine 50 (a 50:50 mixture by mass of

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

and UDMH), and liquid oxygen/

liquid hydrogen Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully l ...

. The engine operated on an open gas-generator cycle and utilized a regeneratively cooled combustion chamber. For each thrust chamber assembly, a single high-speed turbine drove the lower-speed centrifugal fuel and oxidizer pumps through gearing, a configuration designed for high turbopump efficiency. This lowered fuel use in the gas generator and improved specific impulse. The LR87 served as a template for the LR-91, which was used in the second stage of the Titan missile. The LR87 was a fixed-thrust engine, which could not be throttled or restarted in flight. The LR87 delivered approximately 1,900 kilonewtons (430,000 pounds) of thrust in its

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. T ...

configuration. Early LR87 engines used on the

Titan I The Martin Marietta SM-68A/HGM-25A Titan I was the United States' first multistage intercontinental ballistic missile (ICBM), in use from 1959 until 1962. Though the SM-68A was operational for only three years, it spawned numerous follow-on mode ...

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 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 l ...

, the engine was converted to use Aerozine 50 and nitrogen tetroxide, which are

and storable at room temperature. This allowed Titan II missiles to be kept fully fueled and ready to launch on short notice. For the Titan III and IV, which were larger, more capable space launch vehicles, the LR87 was modified further. Thrust and nozzle area ratio were progressively increased, requiring heavier turbopumps, pipes, and other parts.

Variants

LR87-3

Used on the

, the LR87-3 burned liquid oxygen and RP-1. Following the retirement of the Titan missile program, these engines saw no further use. The LR87-3 was also operated with NTO/Aerozine 50 and ground tested with LOX/H2 (with a new fuel pump), making it one of very few engines to have been run on three different propellant combinations.

LR87-5

Instead of liquid oxygen and RP-1, the

used nitrogen tetroxide and Aerozine 50. This change was done for storability at the request of the US Air Force. The engine was generally lighter and simpler than its predecessor, partly due to the use of

propellants, which do not need an independent ignition system. The engines also had simpler controls, solid-propellant cartridges to start the turbopumps, simplified injectors, and autogenous pressurization, replacing the heavy tanks of cold helium gas. Instead, the fuel tank was pressurized with fuel-rich gas-generator exhaust, and the oxidizer tank with NTO evaporated in a heat exchanger using turbine exhaust. Beginning in 1984,

missiles were decommissioned and became available as launch vehicles. Their engines were modified for this use.

LR87-7

The LR87-5 was adapted to the needs of the

Gemini program Project Gemini () was NASA's second human spaceflight program. Conducted between projects Mercury and Apollo, Gemini started in 1961 and concluded in 1966. The Gemini spacecraft carried a two-astronaut crew. Ten Gemini crews and 16 individual ...

. The LR87-7 had added redundancies and safety features for

human-rating certification Human-rating certification, also known as man-rating or crew-rating, is the certification of a spacecraft or launch vehicle as capable of safely transporting humans. There is no one particular standard for human-rating a spacecraft or launch veh ...

. The performance was similar to the previous version, only reducing the chamber pressure and nozzle thrust to meet human-rating requirements. This version was only used on the

Titan II GLV The Titan II GLV (Gemini Launch Vehicle) or Gemini-Titan II was an American expendable launch system derived from the Titan II missile, which was used to launch twelve Gemini missions for NASA between 1964 and 1966. Two uncrewed launches foll ...

LR87-9

Used on the Titan IIIA, IIIB, and IIIC.

LR87-11/LR-87-11A

Used on Titan 24B, 34B, IIIBS, IIID, 34D, 34D7, IIIE. The LR-87-11A was used on the Titan IV A/B.

LR87 LH2

Modified to burn liquid oxygen and liquid hydrogen. The development coincided with other variants of the late 1950s. Compared to the -3, it had a number of changes associated with the use of lighter and colder liquid hydrogen. The fuel injectors were greatly modified, and the RP-1 pump was replaced with a purpose-designed single-stage hydrogen pump. Developed 1958–1961, a total of 52 static tests were performed without serious issue.

took part in the selection process for a new engine for the second stage of the

Saturn IB The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, 43 ...

and

Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...

. Though LR87 LH2 was the best in 10 out of 11 criteria,

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

selected Rocketdyne's J-2. Lessons learned were used during development of the Aerojet M-1. It was only built with 1 chamber.

LR87 / Alumazine

The LR87 was also tested with a gelled Dnitrogen Tetroxide / Alumizine fuel. Though the earlier tests with the LR87 were terminated due to combustion instabilities and funding restraints development of gelled fuel and oxidizers continued to produce fuels for engines currently used in space.

Engine comparison

References

External links

Encyclopedia Astronautica

National Museum of the USAF, Ohio

{{Rocket engines Rocket engines using kerosene propellant Rocket engines using hypergolic propellant Rocket engines using hydrogen propellant Rocket engines using the gas-generator cycle Rocket engines of the United States