File:Nike-Ajax liquid propellant rocket engine 21AL-2600.png

English: Aerojet General Corporation, 1950s, stainless steel and aluminum, 18 5/8 inches tall. There is an similar engine on display in the Smithsonian.

The MIM-3 Nike Ajax was the United States' first operational surface-to-air missile (SAM). It used a solid propellant booster and a liquid propellant second stage to achieve subsonic speeds. The present example is the liquid sustainer engine which produced 2,600 pounds of thrust for about 20 seconds. It used red fuming nitric acid and JP-4, a type of jet fuel, as its propellant.

It was a very simple system with no moving parts for ease of operation and high reliability. The propellants were forced into the combustion chamber by compressed air. Development of the engine was begun in late 1945 by Aerojet-General, who were working with the project's originator Bell. First unguided launches began in 1946. The first successful intercept of a B-17 target drone took place in November 1951. The missile became operational in 1953 and remained in service until 1963, by which time the Nike Hercules had taken over.

It is fascinating how they guided the missile in the era before integrated circuits and lightweight computing. The complex system used an acquisition radar to detect potential targets at long range. Once a single target was designated, it was handed off to a target tracking radar. The Nike was then fired and a separate missile tracking radar tracked it flight. A ground-based computer used data from both radars to calculate the intercept trajectory, which was translated into appropriate steering commands for the four nose fins and radioed to the missile in flight. In order to maximize range, the missile was normally flown almost vertically to a higher altitude than the target, where the thinner air lowered drag and allowed the missile to descend on its target. The three warheads in the missile were detonated on ground command once the computer determined the missile and target tracks had converged.

As jets increased the speed and altitude of military aircraft, it made anti-aircraft guns less effective and motivated the development of anti-aircraft guided missiles (SAMs).

"As the Nike Ajax became operational, the Soviet Union were hot on their heels and also about to field its own SAM systems. Paranoid that the US and Britain wanted to bomb the Soviet Union, like Nazi Germany in WWII, Stalin ordered the quick manufacture of the systems. Soon after, the Soviets developed the S-75 Dvina (Nato codename SA-2) in 1957, which featured significantly improved missile technology and raised the altitude limit to 82,000ft. The effectiveness of this system was shown in 1960, when a U-2 surveillance plane piloted by Francis Gary Powers was shot down by a S-75 SAM battery in the Urals. U-2 flights were all but ended over the Soviet Union after the embarrassing incident." — Airforce Technology

The best preserved Nike installation is site SF88L located in the Marin Headlands just west of the Golden Gate Bridge in San Francisco, California. — Wikipedia