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Engine Room

PISTON ENGINE - A reciprocating engine burns fuel in an enclosed cylinder which forces a piston to move up and down the cylinder. The pistons are connected to a shaft which turns the propeller. There can be many different arrangements of the cylinders, but aircraft engine manufacturers found the best arrangement for larger aircraft engines is a radial engine with the cylinders arranged around in a circle around the propeller shaft.


Liberty L-12

The Liberty L-12 was a water-cooled V-12 440 hp aircraft engine.  In 1917, a federal task force asked top engine designers to design an aircraft engine as quickly as possible. They specified it must have a high power-to-weight ratio and be adaptable to mass production. In five days they came up with a design for the engine and in July an eight cylinder prototype was sent to Washington for testing. In August a 12 cylinder version was tested and approved so that the War Department placed an order for 22,500 engines, splitting the contract between engine and automobile manufacturers Buick, Ford, Cadillac, Lincoln, Marmon and Packard.



Cadillac was asked to produce Liberty engines, but William Durant was a pacifist who did not want General Motors facilities to be used for producing war materials.  This led to Henry Leland leaving Cadillac and forming the Lincoln company to make Liberty engines. Lincoln constructed a new plant in record time, devoted entirely to Liberty engine production and assembled 2,000 engines in 12 months. Durant later changed his mind and both Cadillac and Buick produced the engines.

The Liberty engine proved so adaptable, it would be installed in a variety of tanks as well as aircraft. By the time of the Armistice, the various companies had produced 13,574 Liberty engines, attaining a production rate of 150 engines per day. Production continued after the war, for a total of 20,478 built between 1917 and 1919.


Wright  R-1820 Cyclone


The Wright Cyclone R-1820 was a 9 cylinder, single-row, air-cooled radial engine. Horsepower ranged from 700 hp to 1,500 hp depending on the model and configuration. Wright Cyclone R-1820 engines were produced from 1931 until well into the 1950s by several companies under license that included Studebaker, Lycoming and Pratt & Whitney. It was also built in the Soviet Union as the M-25 and in Spain as the Hispano-Suiza 9V. The R-1820 Cyclone radial represented the continuing development of the Wright P-2 engine dating back to 1925One of the features of the new R-1820 was greater displacement resulting in an increase in horsepower. It proved  successful and powered a range of aircraft that included the Boeing B-17 Flying Fortress, Grumman J2F Duck, Curtiss P-36, Boeing 307 Stratoliner and Douglas SBD Dauntless. A gas-burning version was developed to power the American M6 heavy tank, and a diesel version powered the M4A6 Sherman tank.


Wright  R-2600 Twin Cyclone

In 1935, Curtiss-Wright began work on a more powerful version of their successful R-1820 Cyclone. The result of their efforts was the R-2600 Twin Cyclone with 14 cylinders  arranged in two rows. The 1,600 hp R-2600-3 was originally intended for the C-46 Commando, but due to changing requirements, the Pratt & Whitney R-2800 would be used instead.


The R-2600 Twin Cyclone went on to power several key World War II production aircraft , including the Douglas A-20 Havoc, North American B-25 Mitchell used by Jimmy Doolittle for the first bombing raid on Tokyo, Grumman TBF Avenger, Curtiss SB2C Helldiver, and the PBM mariner flying boat.

Over 50,000 R-2600s were built at plants in Caldwell, NJ and Cincinnati, OH.


Pratt & Whitney R-2800 Double Wasp (Cut-a-way)


The P&W Double Wasp was the first 18 cylinder radial aircraft engine developed in America. After its first run in 1937, it became one of the world's smallest and most compact engines in its class. Due to its nominal size, problems dissipating heat from the cylinder heads had to be resolved before entering service. 

By 1939, the R-2800 was introduced into service, producing 2,000 horsepower, an astonishing number for an air cooled engine of the day.  Liquid cooled engines of the period could barely match its performance. In October 1940, a Navy F4U Corsair with a R-2800 set a world speed record of 403 mph in level flight.


The R-2800 would go on to power some of the most famous fighters and medium sized bombers of World War II. Airplanes such as the Republic P-47 Thunderbolt, Northrop P-61 Black Widow, XP-56 Black Bullet, Douglas A-26 Invader, Vought F4U Corsair and the Grumman  Hellcat all carried the R-2800. By the end of the war, various versions of the Double Wasp were achieving 2,800 hp with little effort. Even after the war, the Double Wasp would serve the civilian aviation community in the Convair 440, Douglas DC-6, Martin 404 and even the first Lockheed Constellation.

A total of 125,334 R-2800s were produced from 1939 to 1960 and, after more than seventy years of service, the venerable R-2800 still powers restored vintage aircraft around the world.

Lycoming O480

Lycoming G-50-O480-B1B6


The O-480 was a high performance, air-cooled, six-cylinder, horizontally-opposed engine. It powered numerous general aviation aircraft, including the Aero Commander, Beech Twin Bonanza and Queen Air, and Helio Courier. This geared and supercharged model powered the L-23B/D Beech Seminole, Beech Twin Bonanza F-50, Dornier DO-27-H2, and Aeritalia AM-3C.


In 1907, Lycoming's parent company was restructured as the Lycoming Foundry and Machine Company, which produced automobile engines, and later was a subsidiary of the Auburn Auto Company. Although its early aircraft engines were radials, Lycoming entered the light-aircraft engine field early in 1938 with the introduction of the air-cooled, four-cylinder, horizontally opposed O-145 engine.


Wright R-3350 Duplex Cyclone

The Wright R-3350 duplex Cyclone was a twin-row, supercharged, air-cooled, radial engine with 18 cylinders. Power ranged from 2,200 to over 3,700 hp, depending on the model. Along with the Pratt & Whitney R-4360 Wasp major, it was one of the most powerful radial aircraft engine produced in the United States. 

Although the prototype of the R-3350 was run in May of 1937, it took a while for the engine to mature for several reasons. First it was a very complicated engine, and second Wright was focusing its main attention on the R-2600. With war clouds looming, the U.S. Army Air Corp released a contract for a long range bomber that would be able to carry a 2,00 lb bomb load from America to Germany in case Britain should fall to the Nazi Blitzkrieg. 

Three of the four designs for the new long-range bomber were centered around the R-3350 engine, causing the development of the R-3350 to be stepped up considerably so that it could go into production. By 1941, the R-3350 started its flight testing when it replaced the Allison V-3420 on the Douglas XB-19 prototype.

The Boeing B-29 Superfortress was eventually selected as the new long-range bomber. When the R-3350 was mated to the B-29, design short comings in the flow of air around the rear row of cylinders led to overheating and engine fires that would plague the B-29 all through World War II.

After the war, the 350 would be redesigned, eliminating many of the problems that haunted it during the war years. Ultimately, the R-3350 would become a favorite for large post war aircraft, notably the Lockheed Super Constellation and the Douglas DC-7.




Cut-a-way of R-3350


Pratt & Whitney R-4360 Major Wasp


The Pratt & Whitney R-4360 was a 28-cylinder four-row air-cooled radial engine and was the pinnacle of radial engine development. Each row of seven air-cooled cylinders possessed a slight angular offset from the previous, forming a semi-helical arrangement to facilitate effective airflow cooling of the cylinder rows behind them, inspiring the engine's "corncob" nickname. It was the most technically advanced and complex reciprocating engine produced in the United States. Depending on the version, it produced 3,000-4,300 HP.

The primary mission for the R-4360 was heavy transports and bombers. Among the aircraft outfitted with this engine were the Boeing C-97 Stratofreighter,

C-124 Globemaster II, Boeing Superfortress, Convair B-36 Peacemaker and the Northrop B-35 Flying Wing. The Major wasp also found its way on to the Goodyear FG2 Corsair and Republic XP-72 fighters.

From 1944-1955, Pratt and Whitney produced seven different models of the Major wasp and a total of 18,697 units were eventually produced. 

turbo prop.png

TURBOPROP - a turboprop is an engine that uses a turbine jet engine to drive the aircraft propeller. Air is drawn into the intake, compressed and sent to the combustion chamber. The hot gases drive the propeller and the compressor, with the exhaust adding a relatively small amount to thrust.


Pratt & Whitney T34 Turbo Wasp

A turboprop uses a jet turbine to spin the propellers. In 1945 The US Navy contracted Pratt & Whitney to develop a turboprop engine. Even though the Navy funded the research and development of the turboprop engine and tested it on two Navy Lockheed R7V-2 Constellation (C-121) variants, it was the U.S. Air Force that would adopt the T-34 and use -t on production aircraft, not the Navy.

In September 1950, a modified Boeing B-17 Flying Fortress would serve as a test bed for a T34 turboprop mounted in the nose of the bomber. The first application for the T34 was the Boeing YC-97J Stratofreighter, which later became the Aero Spacelines Super Guppy.


A major difference between a piston engine and the T34 turboprop engine is the rpm operating range. Efficient operation of the turbine engine is restricted to a relatively narrow range of high rpm, whereas a piston engine can operate over a broad rpm  range. Thus the power output of a piston engine is spread over a wider range in contrast to the narrow range of the T34. This results in a significant difference in propeller operation. The turbine type engine requires less change in rpm for a corresponding power increase so that response is more rapid and requires that the pitch change mechanism for the propeller operate at a much faster rate than is necessary with a piston engine.


TURBOJET - a turbojet is  a simple turbine engine that produces all of its thrust from the exhaust from the turbine section. Air is drawn in, compressed and the fuel/air mixture ignited to produce thrust. The air must all pass through the whole engine.


General Electric J31 Turbojet


In 1940, inventor Harry Tizard, along with a British delegation met with U.S. representatives to discuss the exchange of technological secrets for American production support in the war against Germany. One secret shared with the U.S. was the Whittle W.1 jet engine. A Prototype of jet engine technology, the Whittle W.1 gave birth to General Electric's (GE) I-A, America's first jet engine, and the I-16 (U.S. Army Air Force renamed J31). The J31 was the first jet engine to be mass produced in the U.S.

In 1941, thanks to General Henry "Hap" Arnold's request, the J31 found its place powering America's first jet engine airplane, the Bell P-59 Airacomet. GE, along with Bell Corporation, produced 66 P-39s. Although

none of the aircraft saw combat, the J31 would power the aircraft to a noteworthy altitude of 46,700 feet.

With 1,650 lbs of thrust and weighing in at 850 lbs, the J31 became the Godfather of jet engine technology in America. GE ultimately produced 241 J31 engines and concluded the project in 1945.


General Electric (Allison) J33Turbojet


The J33-A-37 turbojet engine was developed by General Electric in response to an Army request in 1943 for a 3,000-4,000 lb thrust turbojet and was developed  out of its work with Frank Whittle’ W-1 engine  during the Second World War. For wartime needs, production was licensed to the Allison division of General Motors. Our display is the actual very first J-33 assembled by Allison. When the war ended, the Army re-evaluated its engine program, and turned over all production to Allison. The J-33 employed a single-stage, double-entry centrifugal-flow compressor for its fourteen straight through combustion chambers. The single-stage axial-flow turbine behind the combustion chamber assembly drives the compressor. In this design, almost three-fourths of the power generated is consumed by the compressor and only a fourth is translated into thrust. This is the


 great limiting factor of the design, only 3,900 pounds of thrust for its 1,820 pound weight.


The J33 was GE's first turbojet engine of its own design, its last all-centrifugal-flow engine; as well as the last to be used in U.S. military combat aircraft. It powered other first generation jet aircraft including: Martin XB-51; Lockheed XP-81,

F-80A/B/C, RF-80A, QF-80F, XF-14/A, TF-80C, T-33A/B, AT-33A, DT-33A/B/C, RT-33A, QT-33A, WT-33A, T-1A; North American

F-86C; Northrop F-89J; and Bell XP-83.

Westinghouse J34


The Westinghouse J34 (company designation, Westinghouse 24C) was a turbojet engine developed by Westinghouse Aviation Gas Turbine Division in the late 1940s. Essentially an enlarged version of the earlier Westinghouse J30, the J34 produced 3,000 lb of thrust, twice as much as the J30. Later models produced as much as 4,900 lbs with the addition of afterburner. The J34 first flew in 1947.

Built in an era of rapidly advancing gas turbine engines technology, the J34 was largely obsolete before it ever saw service and often served as an interim engine. For instance, the Douglas X-3 Stiletto was equipped with two J34 engines when the intended J46 engine proved to be unsuitable. 

The Stiletto was developed to investigate the design of an aircraft at sustained supersonic speed. However, equipped with the J34 instead of its intended J46 engines, the Stiletto was seriously underpowered and could not exceed Mach 1 in level flight.

Developed during the transition from piston-engined aircraft to jets, the J-34 was sometimes fitted to aircraft as a supplement to other power plants, as with the Lockheed P-2 Neptune and Douglas Skyrocket. It was also used in experimental aircraft, such as the McDonnell XF-85 Goblin parasite fighter and  the Lockheed XF-90 designed to be a long range replacement for the F-104 Starfighter.


General Electric J47-33

The General Electric (GE) J47 turbojet, originally adapted from the GE J35, made its first flight in 1948 Thanks to this successful flight, the demand for the J47 quickly soared. With the success of the J47 engine, GE's Lynn, MA plant could not support the influx of demand, and the company was forced to seek an additional facility to meet the production requirements of the military.

GE would eventually select a location near Cincinnati, OH and formally open the plant on February 28, 1949. The new J47 production line (later known as Evendale) would complement the production at Lynn, and eventually become GE's Aviation world headquarters.


The Korean War's high demand for the J27 would make it the world's most produced gas turbine engine. It would go on to power almost all new front-line military aircraft, including the famed MIG killer F-86 Sabre Jet. The J-47 achieved two major milestones in aviation history: it would be the first turbojet to be certified for civil use by the U.S. Civil Aeronautics Administration , and the first to use an electronically controlled Afterburner to boost its thrust.

By the end of the 1950s, more than 35,000 engines  were delivered making it the most mass-produced turbojet engine in history. They continued in military service until 1978. The J47 powered a wide variety of aircraft including the North American B-45 Tornado bomber, Consolidated-Vultee B-36 bomber (boost power), Boeing B-47 Stratojet bomber, Martin XB-51 attack bomber, North American F-86 Sabre Jet fighter, North American FJ-2 Fury fighter, Republic XF-91 interceptor, Chase XC-123A transport, and Boeing KC-97 Stratotanker (boost power). This J47-GE-17 engine powered the North American F-86D Sabre Jet and the Italian Fiat F-86K.

Turbo fan.png

TURBOFAN - a turbofan has a larger fan at the intake, and some compressed air bypasses the engine. The bypassed air is added to the exhaust from the fuel/air turbine to create thrust. In a high-bypass engine, most of the compressed air bypasses the engine and provides most of the engine thrust.


Pratt & Whitney TF30 Turbofan


The Pratt & Whitney (P&W) TF30 was a military low-bypass turbofan engine originally designed for the subsonic F6D Missileer aircraft. Even though the Missileer project would be cancelled, the TF30 would later be adapted with an afterburner for supersonic application. In this form, it was the world's first production afterburning turbofan engine that would power the F-111 and the F-14A Tomcat, as well as seeing use in early versions of the A-7 Corsair II without an afterburner. First flight of the TF30 was in 1964 and production continued until 1986.

The General Dynamics F-111 suffered inlet compatibility problems with the TF30, many faulted the placement of the intakes behind the disturbed air of the wing causing poor performance of the TF30.


Pratt & Whitney J57

The J57 was the first Pratt & Whitney designed turbojet. It was a twin-spool axial flow configuration, which was a substantial departure from earlier centrifugal-flow designs. The J57 was an instant success with its performance being described in superlatives.  With the axial flow design, Pratt & Whitney had leapfrogged the industry with its first turbojet design. In 1952, the J57 won the prestigious Collier Trophy for greatest achievement in American Aviation.

In 1953, a J57 powering a North American F-100 Super Sabre became the first production aircraft to exceed the speed of sound in level flight, a feat accomplished on its maiden flight.  Other aircraft that utilized the J57 were the Convair F-102 Delta Dart, Chance Vought

F8U-1 that set an official speed record in excess of 1,000 mph, Lockheed's U-2 reconnaissance aircraft , Republic's F-105 Thunderchief prototype and Northrop's Snark intercontinental guided missile.

The commercial version of the J57, the JT3, was so far ahead of the competition that virtually every aircraft manufacturer in the United States designed an airplane around this engine. By 1958, four JT3s powered Pan American World Airways' Boeing 707 on its inaugural jet service from New York to Paris. The 707 obtained a cruising speed of 575 mph, which was 225 mph faster than the fastest propeller driven aircraft of the day.

By the time production ceased in 1965 on the J57 and JT3 turbojet engines, a total of 21,186 had been built for military and commercial applications.

Pratt & Whitney J60-P-6 Turbojet

Pratt & Whitney Canada began design of the Pratt & Whitney J60 (civilian designation JT12) in July 1957, and later turned responsibility over to the U.S. Pratt & Whitney Aircraft in January 1958. Of Pratt & Whitney’s final turbojets, the 3,300-pound-thrust JT12 was the smallest. First run of the engine was on May 16, 1958, and first flight was in January 1960 on a Canadair CL-41 Tutor. Shipment of production engines began in October 1960. Production ended in 1977 with 2,269 JT12/J60 engines and 352 JFTD12 (military designation T73) derivative turboshaft engines built.


The single-spool JT12/J60 was used on the North American Sabreliner (military designation T-39) and Lockheed JetStar (military designation C-140). The J60 also powered the Fairchild SD-5 surveillance drone and the North American T-2B Buckeye, the U.S. Navy's first production jet trainer. The turboshaft version of the engine, the JFTD12/T73 powered the Sikorsky S-64 Skycrane helicopter (military designation CH-54 Tarhe). This J60-P-6 engine powered the North American T-2B jet trainer.


Newer F-111 variants would incorporate improved intake designs and most of these variants featured more powerful versions of the TF30 engine.

The Vought A-7A used a non-afterburning variant of the TF30 since close air support missions for ground troops does not require supersonic speeds. TF30 engines would continue to be used on the A-7B and C models. The first F-14 Tomcats also used the TF30 but the engines were found to be underpowered  for the Tomcat. It was also realized that the TF30 was ill-adapted to the demands of air combat and was prone to compressor stalls at high angle of attack if the throttles were moved aggressively. They were later replaced by the F110-GE-400 engines


General Electric TF39 Turbofan

In 1965, the USAF contracted General Electric (GE) to develop an engine for the next generation of cargo aircraft, the Lockheed C-5A Galaxy. In response, GE showcased the TF39, the world's first high bypass turbofan engine. With substantially increased take off thrust and decreased fuel consumption, the TF39 was the most advanced engine of its class.  Equipped with the latest in cooling technology and a uniquely designed thrust reverser, the TF39 would have an 8-to-1 bypass ratio, 25-to-1 compressor pressure ratio, and an astounding 2,500 F turbine temperature.


From 1968 to 1971, 463 TF39-1 and -1A engines were produced and delivered for powering the new C-5A fleet. More than a decade later, Lockheed Martin, in contract with the Air Force, would develop 50 C-5B aircraft and sub contract GE to deliver 200 TF39-1C engines and thrust reversers. The first T39-1C made its way off the assembly lines in January 1985 and by November 1988 the last of 200 engines was delivered.

Eventually, GE would carry on the TF39 legacy and subsequently develop the CF6 engine series powering the DC-10, Boeing 747 and MD-11. The Tf39 and CF6 series would also give birth to the LM2500 gas turbine engine, which to this day still powers ships in the US and abroad.


Soviet Mikulin AM-5/Tumansky RD-9


The Tumansky RD-9 (initially designated Mikulin AM-5) was an early  Soviet turbojet engine, not based on pre-existing German or British designs. The AM-5 was available in 1952 and completed testing in 1953; it produced 5,700 lb thrust without afterburner. AM-5 engine is notable for making the first Soviet supersonic interceptor possible, the MiG-19 and the first all-weather area interceptor, the Yak-25. When Sergei Tumansky replaced Alexander Mikulin as the OKB-24's chief designer in 1956, the engine was renamed RD-9.


Rocket Engines -

Rocket engines are fundamentally different from the previous engines. Rocket engines are reaction engines. The basic principle driving a rocket engine is the Newtonian principle that "to every action there is an equal and opposite reaction." A rocket engine is throwing mass in one direction and benefiting from the reaction that occurs in the other direction (thrust). In a rocket engine , fuel and a source of oxygen, called an oxidizer, are mixed and exploded in a combustion chamber. The combustion produces hot exhaust which is passed through a nozzle to accelerate the flow and produce thrust.

Aerojet General XLR73

Proposed rocket engine for the X-15


On 5 October 1954, NACA passed Resolution recommending the construction of a hypersonic research aircraft (later named the X-15).A suitable engine for the X-15 was a problem due to lack of an acceptable rocket engine. The Hermes A-1 engine selected by the NACA planners was not capable of being developed into a safe engine for a manned vehicle.

The primary requirement for an X-15 engine  was that it be capable of operating safely under all conditions. The engine need not be as reliable as a production article, but it should approach such reliability as nearly as possible. There could be no altitude limitations for starting or operating the engine, and the power plant would have to be entirely safe during start, operation or shutdown, no matter what the altitude. The engine was also to be capable of safe operation under the highest ”g” conditions to be encountered during the operation of the X-15 and have variable thrust be capable of repeated restarts.

The XLR73 has single thrust chamber that used white fuming nitric acid and jet fuel as propellants. The engine developed 10,000 lb at sea level, but a new nozzle upped it to 11,750 lbf. The engine was re-startable in flight and infinitely variable between 50% and 100% thrust.

The original suggested engine list included the Bell XLR81, the Aerojet General XLR73, North American's NA-5400 and Reaction Motors' XLR10. Eventually the engineers settled on a variation of the XLR10, the XLR30 then the XLR99.


Aerojet LR87-AJ-11

Rocket engine

The LR87 was an American liquid-propellant rocket engine used on the first stages of  the Titan intercontinental ballistic missiles and launch vehicles. It was composed of twin motors with separate combustion chambers and turbopump machinery,[ it is considered a single unit and was never flown as a single combustion chamber engine or designed for this. The LR87 first flew in 1959. Thrust was approximately 550,00lb.  The LR87 was developed in the late 1950s by Aerojet.   It was the first production rocket engine capable (in its various models) of burning the three most common liquid rocket propellant combinations. 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. Early LR87 engines used on the Titan I burned RP-1 and liquid oxygen. Because liquid oxygen is cryogenic, 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 (spontaneously igniting upon mixing) and storable at room temperature. This allowed Titan II missiles to be kept fully fueled and ready to launch on short notice.


Aerojet LR91-AJ-11

Rocket engine

The LR91 is a liquid-propellant rocket engine, which was used on the second stages of Titan intercontinental ballistic missiles and launch vehicles. Thrust was about 105,000Lb.
Early LR91 engines used on the Titan I burned RP-1 and liquid oxygen. Because liquid oxygen is cryogenic, 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 (spontaneously igniting upon mixing) and storable at room temperature. This allowed Titan II missiles to be kept fully fueled and ready to launch on short notice.

This engine was "vacuum optimized” and ran the gas-generator cycle. The thrust chamber used fuel for regenerative cooling, with separate ablative skirt. 

Vacuum optimized: A rocket engine's nozzle is specifically designed so that the exhaust air is expanded to be equal in pressure with the ambient pressure - this is when maximum efficiency is created. At sea level, there is high ambient air pressure, so most sea-level or first-stage rocket engines have less expanded nozzles. In a vacuum, there is very little ambient pressure, so the exhaust air expands much more as compared to its expansion at sea level. This means that, when you use the same nozzle as the one at sea level, the exhaust plume would continue to expand further than the walls of the nozzle - reducing efficiencies. To counter this, vacuum-based nozzles are more expanded (wide) and are generally longer than its first-stage atmospheric counterparts to allow the exhaust air to expand much more:

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Hound Dog


Although the Hound dog's engine is not on display, it is an example of a typical  turbojet type engine. The North American Aviation AGM-28 Hound Dog was a supersonicturbojet-propellednuclear armedair-launched cruise missile developed in 1959 for the United States Air Force. It was primarily designed to be capable of attacking Soviet ground-based air defense sites prior to a potential air attack by B-52 Stratofortress long range bombers during the Cold War. The Hound Dog was first given the designation B-77, then redesignated GAM-77, and finally AGM-28. It was conceived as a temporary standoff missile for the B-52, to be used until the GAM-87 Skybolt air-launched ballistic missile was available. Instead, the Skybolt was cancelled within a few years and the Hound Dog continued to be deployed for a total of 15 years until its replacement by newer missiles, including the AGM-69 SRAM and then the AGM-86 ALCM.

A  Pratt & Whitney J52-P-3 turbojet propelled the Hound Dog. The J52 engine was located in a pod located beneath the rear fuselage. The J52-P-3 used in the Hound Dog, unlike J52s installed in aircraft like the A-4 Skyhawk or the A-6 Intruder, was optimized to run at maximum power during the missile's flight. As a result, the Hound Dog's version of the J52 had a short operating lifetime of only six hours.[6] However, in combat, the Hound Dog was expected to self-destruct in less than six hours.

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