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Missiles and Turbojets

In the 1950s, PSL tested turbojet and ramjet engines for military aircraft and missile systems, before transitioning in the 1960s to rocket engines for NASA’s early space program.


As the Cold War took hold after World War II, the Soviet Union and the United States raced to integrate German technology into their military systems, particularly long-range missiles and jet engines. The outbreak of the Korean War in 1950 increased the urgency for aeronautical advances. NACA researchers used PSL during this period to improve airbreathing ramjet and turbojet engines to power missiles and new generations of fighter aircraft. The launch of Sputnik I in October 1957 created a new urgency at the laboratory and across the nation. The lab quickly refocused its efforts towards rocket engines and space as the NACA transitioned into National Aeronautics and Space Agency (NASA). Engineers tested both small Lewis-designed rocket engines and larger engines for the Centaur, Saturn, and Nova rockets in the mid-1960s.


Navaho Program

North American Aviation’s Navaho Missile program, started in 1946, was one of the nation’s most ambitious attempts to expand upon German missile technology. The winged Navaho missile was designed to deliver a nuclear warhead to targets up to 3000 miles away. It was a two-stage vehicle that relied on rocket engines to boost it to altitude and two large ramjets engines for cruising. Lewis researchers immediately began studying the Pratt & Whitney XRJ47-W-5 ramjets that powered the Navaho when the PSL became operational in 1952. They operated the 48-inch diameter engine in PSL No. 2 at Mach 2.75 and in simulated altitudes between 58,000 and 73,000 feet. For three years they studied engine ignition, the exterior shell of the burner, fuel flow control, different flameholder configurations, and overall engine performance.

While these tests in PSL were taking place, an early turbojet-powered version of the missile was successfully launched numerous times. Flight tests for the second phase of the Navaho Program, which used the ramjets, began in late 1956. Only four of the first twelve launch attempts were successful, and those four performed marginally, at best. The military cancelled the program in July 1957, but its legacy has lived on in other programs. Navaho propulsion technology was used on The Redstone, Thor, and Atlas rocket systems used its propulsion technology; the first nuclear submarine, the Nautilus, utilized its guidance system; and the space shuttle ultimately employed the concept of a booster-assisted takeoff for a winged missile.


Bomarc Program

In 1951 Boeing and University of Michigan partnered to develop the Bomarc long-range interceptor missile for the Air Force. Like the Navaho, the missile launched vertically using a rocket engine, but switched to its two 28-inch-diameter Marquardt ramjets for cruising. NACA researchers studied the Marquardt RJ43-MA-3 ramjets in PSL during 1954 and 1955. The studies covered a variety of performance issues, including the system’s dynamics response and pneumatic shock-positioning control unit. Budget constraints and political in-fighting, however, led to a protracted development of the Bomarc. Only ten Bomarc sites were established when the missile was finally deployed in 1962.



The first investigation in PSL No. 1 involved a General Electric J73-GE-1A, the successor to the company’s successful J47. The military primarily used the 12-stage compressor engines to power its F-86H Sabre jet fighters. During 1952 and 1953, Lewis researchers operated the J73 44 times in PSL No. 1. The used the data to create performance curves showing the optimal range for combustion and compressor efficiency. In September 1954, not long after the PSL tests, the J73-powered Sabre set a new world’s speed record at the National Aircraft Show in Dayton. The NACA researchers continued their investigations by running a YJ73-GE-3 version of the engine almost 200 times in PSL. Problems with the aircraft design and General Electric’s production of the engine, however, resulted in the cancellation of the Sabre program in the mid-1950s.

General Electric created the Collier Trophy-winning J79 as an advancement of the J73. The 17-stage engine employed variable stator vanes which prevented stall at high speeds. The Air Force requested that NACA Lewis improve afterburner performance on the engine. In 1957 researchers tested various afterburner configurations for the prototype XJ79-GE-1 in PSL. They were able to make basic modifications to the flameholder and fuel system to increase combustion efficiency and reduced pressure drop. The J79 went on to power most contemporary Mach 2 aircraft and was used extensively in the Vietnam War on the F-4 Phantom, F-104 Starfighter, and B-58 Hustler.

In 1957 PSL also had a chance to test a rare Canadian jet engine, the Iroquois PS.13. The Avro Canada Company began designing its CF-105 Arrow jet fighter in the mid-1950s. Although not originally in the design, engineers decided to power the Arrow with two PS.13 engines developed by another branch of the company. These engines were more powerful than any contemporary U.S. jet engine, lightweight, and fuel efficient. NACA researchers tested PS.13 engine in PSL during the program’s extensive ground testing phase. The Arrow made its debut flight in March 1958 but was cancelled the following year when its perceived mission disappeared.


Pratt & Whitney RL-10

In the late 1950s Pratt & Whitney developed the first commercial liquid hydrogen-liquid oxygen rocket engine. In 1958 the government decided to use two of these 15,000-pound thrust RL-10 engines to power General Dynamics’ new Centaur second-stage rocket. NASA soon decided to employ Centaur to send a series of Surveyor spacecraft to the lunar surface to explore landing sites for the Apollo missions. The RL-10s also powered the upper stages for Saturn I launch vehicle. The performance of the new hydrogen engines was critical to success of the Apollo Program.

Although liquid hydrogen offered more power than traditional rocket fuels, its cryogenic temperature and reactiveness posed many technical issues initially. Pratt & Whitney was having difficulties with combustion instability and low-frequency oscillations in the fuel system. In early 1961 NASA decided to subject the RL-10 to an extensive examination in PSL. Lewis engineers were able to throttle and pivot the engine while firing it simulated altitude conditions. They found that injecting gaseous helium into the cooling liner stabilized the propellant and reduced chugging. This method, which reduced the pre-cooling period during flight, became one of Lewis’ most important modifications to Centaur. A Surveyor spacecraft, launched by the RL-10-powered Centaur, made the first soft landing on the Moon on June 2, 1966. Both Centaur and the RL-10 remain in active use today.


Apollo Contour Nozzle Study

Storable propellants are fuels that can be stored in a tank without any special pressure or temperature control measures. NASA officials intended to use one of these types of propellants, a nitrogen tetroxide and hydrazine blend, for the upper stages of the Saturn V rocket. NASA had been studying the problems of combustion instability and thrust chamber durability for several years, but had yet to perform tests of the overall engine and nozzle efficiency.

In late 1963 and 1964 Lewis researchers used PSL to determine the impulse value of the storable propellant mix, classify the internal engine performance, improve that performance, and compare the results with analytical tools. A special setup that included a device to measure the thrust load and a calibration stand was installed in the chamber. The researchers tested both cylindrical and conical combustion chambers in conjunction with conical large area ratio nozzles. In addition, they tested two contour nozzles, one based on the Apollo Service Propulsion System and the other on the Air Force’s Titan transtage engine. Three types of injectors were investigated, including a Lewis-designed model that produced 98 percent efficiency. The tests demonstrated that combustion instability did not affect the nozzle performance. Although much valuable information was obtained during the tests, attempts to improve the engine performance were not successful.


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