Launching Rocket Research
The Rocket Laboratory was quickly built at what is today the Glenn Research Center in the summer of 1945 to augment the laboratory’s existing aircraft propulsion test capabilities. This nondescript cluster of cinderblock test cells at the far end of the campus provided researchers with a safe, versatile environment to study rocket combustion and propellants.
Although initially constructed to evaluate jet-assisted takeoff (JATO) rocket engines for aircraft, the facility’s small contingent of researchers soon began a systematic evaluation of non-traditional, high-energy propellants. Both the scope of the Rocket Lab’s research and its physical footprint expanded in the late 1940s. By 1949, the rocket team acquired enough data to share their early findings with outside organizations.
Birth of the Rocket Lab
In the early 1940s, the National Advisory Committee for Aeronautics (NACA) created the Aircraft Engine Research Laboratory (AERL) in Cleveland, Ohio to improve the piston engines that powered contemporary U.S. military aircraft. The laboratory quickly constructed additional test facilities, such as the Rocket Lab and the Jet Propulsion Static Laboratory, to address the new jet engine and rocket-powered missile that emerged during World War II.
Despite the demonstrated success of Germany’s V–2 missile, NACA management considered missiles to be weapons, which were outside of the organization’s aeronautical mandate. The NACA was, however, open to the use of smaller rocket engines to boost heavily-loaded aircraft taking off from short military runways or to provide quick bursts in combat. According to John Sloop, the Army Air Corps prodded NACA leaders into authorizing the rapid construction of four small test cells at the AERL dedicated to testing JATO engines.
By June 1945, the Rocket Lab’s four initial test cells (Cells 11–14) and the Service Building were in place at the undeveloped western edge of the campus, separated from the AERL’s other buildings built at the front of the property. Earthen mounds were built between the Rocket Lab structures to provide protection to the individual cells.
A former researcher recalled, “the test labs were located in typical backyard garage buildings located behind an earthen embankment just behind the so-called office building.” To disguise the nature of the testing to outsiders, the new facility was officially named the High-Pressure Combustion Laboratory (HPCL) until 1950, although it was referred to as the Rocket Lab from the start.
A paved access road and other infrastructure were added to the Rocket Lab complex, but it soon became apparent that larger test cells were required. In 1947, the laboratory used general operating funds and in-house labor to expand the Rocket Lab’s Operations Building and construct two small control buildings, fuel storage buildings, and an explosives storage unit. The following year four new, larger test cells (Cells 21–24) were added.
Establishing Its Role
The AERL underwent a major reorganization in October 1945 that included the creation of a small Rocket Section in Walter Olson’s Combustion Branch. This rocket team initially utilized the new Rocket Lab cells to study combustion and cooling of JATO-related rockets using established liquid fuels such as aniline, hydrogen peroxide, and alcohol.
Olson became intrigued by rocketry during a visit to Cal Tech University’s Jet Propulsion Laboratory (JPL) in the fall of 1945. JPL had been studying JATO and small rocket engines for several years and had successfully conducted test flights during the war. Rather than duplicate the work the Germans had done with conventional liquid fuels or the JATO efforts at JPL, the NACA rocketeers decided to concentrate on the relatively unexplored field of high-energy liquid propellants.
These untested, “exotic” fuels had the potential to provide significantly higher performance than traditional fuels but were difficult to handle and highly explosive. The goal was to develop rocket engine technology for JATO applications, high-altitude supersonic flight, and guided missiles. The obscurity of the field, coupled with the team’s small size and the Rocket Lab’s isolation, afforded the rocket group a great deal of autonomy during this period.
- High Pressure Combustion Laboratory description (1946)
- Rocket Lab Test Schedules (1945-1950)
- Rocket Research Talk at the NACA’s 1947 Inspection
- Rocket Lab Renaming (1949-1950)
Exploring Exotic Fuels
The NACA researchers began identifying various non-traditional propellant combinations that yielded the highest specific impulse without damaging the engine. They compared these chemicals to standard liquid fuels such as liquid oxygen and alcohol and created thermodynamic charts for future analysis. The engineers calculated the theoretical performance of various combinations and weighed it with tradeoffs such as weight, volume, and toxicity.
The most promising combinations were then tested in small in-house-designed engines in the Rocket Lab test cells. Many of the obscure propellants were difficult to acquire, and during the initial years, the engineers sometimes had to personally transport the dangerous chemicals. The engines, which ranged from 50 to 5,000-pounds thrust, were mounted horizontally on small stands so that the rocket exhaust flowed out the test cell doors and into the atmosphere.
With each fuel combination, the researchers would try different nozzles, injectors, combustion chambers, and cooling systems. They developed different techniques, such as transparent combustion chambers and high-speed photography, to improve their studies.
In the post-War period, the rocket group tested hydrogen peroxide, chlorine, fluorine, and ammonia but became particularly interested in the high specific impulses of hydrazine and diborane.
- Rocket Research Talk at the NACA’s 1947 Inspection
- Rocket Research Talk at the NACA’s 1949 Inspection
- Review of Rocket Research at Lewis (1952)
Supporting Project Zip
After World War II, the military began exploring high-energy fuels such as liquid hydrogen and pentaborane for future development. The Navy initiated Project Zip in an effort to identify a propellant that yielded 30-percent more power than jet fuel. The agency asked NACA Lewis to assess various boron-based fuels and develop combustors to handle them.
The NACA investigations included testing of diborane with different oxidizers in a 100-pound- thrust engine at Cell 14 of the Rocket Lab. The Cell 14 test program, which consisted of a single run with hydrogen peroxide and 11 runs with oxygen in 1948, did not achieve the expected performance levels due to thick exhaust deposits that formed on the nozzle. The deposits were not present during ensuing tests of diborane with liquid fluorine in 1951, but the fluorine posed significant cooling issues. Subsequent testing of diborane in larger engines in the 1950s showed that the deposits were an even more significant problem than initially believed.
- Investigation of the Diborane – Hydrogen Peroxide Combination (1948)
- Investigation of Liquid Diborane – Liquid Oxygen Combination (1949)
- Investigation of Liquid Fluorine – Liquid Diborane Combination (1951)
First Sanctioned Rocket Test
The laboratory held a special conference on May 26, 1948 to explain its rationale for studying high-energy propellants and present the initial findings to military and industry representatives. This included a paper on the diborane testing in Cell 14. Afterwards, the U.S. Navy asked the laboratory to test a 220-pound-thrust Reaction Motors, Inc. engine in the altitude simulation chamber that had recently been added to Cell 24 of the Rocket Lab. It was the NACA’s first sponsored rocket research project.
The Navy wanted to employ the rocket engine on a high-altitude fighter aircraft that would use airbreathing engines to cruise for several hours at high altitudes before igniting the rockets. There was concern that engine’s mono-ethylaniline and mixed acid propellant combination might not ignite at altitude.
In June 1949, the NACA engineers mounted the engine and its components in low-temperature fluid at the Cell 24B tank to simulate the cold temperatures of altitude. A pump expelled the rocket exhaust from the tank to maintain the low pressure of altitude. The team of NACA researchers tested the engine with its original propellants, as well as with several other fuel combinations. They found that the low pressure did not hinder the engine’s performance, but that the effect of the cold temperatures on the hydraulic fluid and fuel created ignition problems.
Although small in scope, the Navy project added legitimacy to Lewis’s new rocket program. The researchers continued to study altitude ignition of hypergolic propellants in Cell 24B for several years. It was determined the ignition delay was affected more by the propellant reaction rate than the ignition system.
- NACA Conference on Fuels (1948)
- Starting of Rocket Engine at Conditions of Simulated Altitude (1950)
- Altitude Ignition of Liquid Propellant Rocket Engines (1949)