The XLR11, company designation RMI 6000C4, was the first

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 ...

engine developed in the United States for use in aircraft. It was designed and built by

Reaction Motors Inc. Reaction Motors, Inc. (RMI) was an early American maker of liquid-fueled rocket engines, located in New Jersey. RMI engines with thrust powered the Bell X-1 rocket aircraft that first broke the sound barrier in 1947, and later aircraft such t ...

, and used ethyl alcohol and

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 applica ...

as propellants to generate a maximum

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 syst ...

of . Each of the four

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...

s produced of thrust. The engine was not

throttle A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ...

able but each chamber could be turned on and off individually.

Development

Development of the engine began in 1943. Reaction Motors called the engine "Black Betsy", though informally it was referred to as "The Belching Black Bastard". Its first official designation was the 6000C4, and it was later given the military designation XLR11.

Operational history

The XLR11-RM-5 engine was first used in the

Bell X-1 The Bell X-1 (Bell Model 44) is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics– U.S. Army Air Forces–U.S. Air Force supersonic research project built by Be ...

. On October 14, 1947, the X-1 became the first aircraft to fly faster than the

speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as w ...

(Mach 1). The XLR11-RM-5 was also used in the X-1A and X-1B, and as a booster engine in the U.S. Navy's D-558-2

Douglas Skyrocket The Douglas D-558-2 Skyrocket (or D-558-II) is a rocket and jet-powered research supersonic aircraft built by the Douglas Aircraft Company for the United States Navy. On 20 November 1953, shortly before the (17 December) 50th anniversary of pow ...

turbojet (where it was designated the XLR8-RM-5). In 1959 and 1960, while development of a more powerful engine was still under way, a pair of XLR11-RM-13's were used as an interim power plant for the initial flights of the X-15 research aircraft. These engines were boosted to of thrust per chamber for a total of . In comparison, the thrust of the X-15's XLR99 engine could be varied from . After 24 powered flights, the XLR11 engines were replaced by the new XLR99 engine in November 1960. The XLR11-RM-13 was also used in the Dryden

lifting bodies A lifting body is a fixed-wing aircraft or spacecraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage ...

, and as a booster engine in the

Republic XF-91 Thunderceptor The Republic XF-91 Thunderceptor (originally designated XP-91) is a mixed-propulsion prototype interceptor aircraft, developed by Republic Aviation. The aircraft would use a jet engine for most flight, and a cluster of four small rocket engines ...

turbojet.

Variants

;RMI 6000C4:Company designation of the LR11 family. ;XLR8-RM-5: ;XLR8-RM-6: (RMI A6000C4-2) ;XLR11-RM-5: ;XLR11-RM-13:

Specifications (XLR11-RM-5)

Data from:Aircraft engines of the World 1959/60

References

External links

Reaction Motors XLR11 Rocket
– National Museum of the United States Air Force
Dryden Flight Research Center

X-Planes at Edwards AFB
{{DEFAULTSORT:XLR11 Aircraft rocket engines