The LR-101 is a fixed thrust, single start

vernier thruster A vernier thruster is a rocket engine used on a spacecraft for fine adjustments to the attitude or velocity of a spacecraft. Depending on the design of a craft's maneuvering and stability systems, it may simply be a smaller thruster complementin ...

developed by

Rocketdyne Rocketdyne was 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. The Rocke ...

in the mid-to-late fifties and used in the

Atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic ...

Thor Thor (; from non, Þórr ) is a prominent god in Germanic paganism. In Norse mythology, he is a hammer-wielding æsir, god associated with lightning, thunder, storms, sacred trees and groves in Germanic paganism and mythology, sacred groves ...

and

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D ( NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also ...

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 ...

until 1990. Each of these rockets used two LR-101 secondary engines to provide yaw, pitch and roll control during their ascent to space. The pair of LR-101

vernier thrusters A vernier thruster is a rocket engine used on a spacecraft for fine adjustments to the attitude or velocity of a spacecraft. Depending on the design of a craft's maneuvering and stability systems, it may simply be a smaller thruster complementi ...

would receive their propellant flow from the

turbopumps 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 ...

of the sustainer engine until it was shut off. After sustainer burnout, this pair of thrusters would switch to feed off the remaining propellant, effectively becoming a

Pressure-fed engine The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed th ...

. The remaining fuel would then be spent for the last

trajectory A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete traj ...

corrections and stabilization of the rocket before separating the payload.

Variants

Due to several modifications the LR-101 underwent over the years, there are many different variants of this engine. One of the first changes was the downrating of the engine to a lower thrust level, both because the engine provided far more thrust than required to steer the rocket and to save fuel for the main engines. Another major change was the replacement of the original pyrotechnical ignition system with an igniter using a hypergolic fuel mixture composed of

Triethylaluminum Triethylaluminium is one of the simplest examples of an organoaluminium compound. Despite its name it has the formula Al2( C2H5)6 (abbreviated as Al2Et6 or TEA), as it exists as a dimer. This colorless liquid is pyrophoric. It is an industrially ...

and

Triethylborane Triethylborane (TEB), also called triethylboron, is an organoborane (a compound with a B–C bond). It is a colorless pyrophoric liquid. Its chemical formula is or , abbreviated . It is soluble in organic solvents tetrahydrofuran and hexane. Pr ...

. Additionally, the Atlas, Thor and Delta Rockets each possessed unique aerodynamically shielded gimbal mounts in the vicinity of their primary engines to provide large arcs for the vernier thrusters. While the pair of LR-101s on the Atlas was mounted radially above the booster engines of the vehicle, on the Thor they were placed at the base of the vehicle.

Role in experimental rocketry

The LR-101 is one of the most common

utilized in US-American rocketry and has become a sought-after object for item collectors and builders of amateur spacecraft. Rocket engineer Robert C. Truax, who had led the initial design studies for the

PGM-17 Thor The PGM-17A Thor was the first operational ballistic missile of the United States Air Force (USAF). Named after the Norse god of thunder, it was deployed in the United Kingdom between 1959 and September 1963 as an intermediate-range ballistic m ...

missile had planned on propelling his 'X-3 Volksrocket' with four Rocketdyne LR-101 Engines, but despite many test firings the rocket never left the ground. On the 'Galactic Aztec', the engine used RP-2 (Kerosene) as a propellant instead of

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 ...

, which was utilized in the

SM-65 Atlas The SM-65 Atlas was the first operational intercontinental ballistic missile (ICBM) developed by the United States and the first member of the Atlas rocket family. It was built for the U.S. Air Force by the Convair Division of General Dyna ...

and

ICBMs 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 ...

as well as the later commercial

Rockets.

References

External links

Rocket engines using kerosene propellant Rocketdyne engines North American Aviation Rocket engines using the pressure-fed cycle Rocket engines of the United States Spacecraft components Spacecraft attitude control {{rocketry-stub

Variants

Role in experimental rocketry

See also

References

External links