Continental Air Defense

As the Cold War started heating up in the late 1940s and early 1950s, particularly after the USSR detonated its first atom bomb in 1949, the great fear was that fleets of Soviet bombers would attack the US.  The opacity of the USSR meant we had no real idea of the size of the Soviet bomber fleet. At a minimum, we knew they were equipped with a cline of the B-29, known as the Tupolev Tu-4 “Bull.” As we advanced our own bomber designs, it was sensible to presume the Soviets were likewise building more advanced designs.

The challenge of defending the airspace of the US lead to two massive defense programs, one Air Force and the other Army.

The Air Force spent billions forming and equipping the Air Defense Command, and later integrating it with the Royal Canadian Air Force as the North American Air Defense Command. Why Canada? The shortest, most logical route for any Soviet bomber attack against the US would be by flying over the arctic and through Canada’s airspace.

ADC, and later NORAD had a network of radar stations to detect any incoming attack, air defense sector control stations to direct interceptions, and widespread fighter interceptor bases from which to attack the Soviet bombers. Plus, of course, hundreds of interceptors to actually do the attacking.

But US experience in World War II had clearly shown that no matter how determined any fighter attacks were, at least some bombers would penetrate to the target area. Clearly, some form of terminal defense was needed.

The Army first started by emplacing large numbers of anti-aircraft guns in rings around major US cities. But WWII had also clearly shown that even the best anti-aircraft guns had low probabilities of killing a target. In the age where only one bomber had to reach a target, something better was needed. The advent of jet propulsion would also mean bombers would soon be flying far above the range of any conceivable gun.

The Army had actually began to explore the possibility of using guided missiles for air defense as early as 1944. The V-1 buzz bomb attacks were bad enough. But the frustration at having no defense against the V-2 ballistic missiles lead the Army to consider the possibility of using missiles as a defense. Alas, it was beyond the state of the art at that time, but the germ of an idea was planted. The need for improved terminal defense in the US lead the Army to launch Project Nike.

After a development program at speeds that would stun any procurement official today, the first fruits of Project Nike lead to the Nike Ajax missile, which made its first intercept in 1951. By 1953, the missile was ready for deployment.

Nike Ajax

Nike Ajax Missile

The Nike Ajax was a two-stage guided missile fired from a rail launcher. The missile itself was 21 feet long, and the booster stage was 13 feet long. The booster was a solid fuel rocket, while the sustainer motor of the missile was liquid fueled, with kerosene as the fuel, and red-fuming nitric acid as the oxidizer.

Four launchers, and a Battery Control Section consisting of an Integrated Fire Control (IFC) van, and the three associated radars formed a battery.

The missile was guided by a command guidance system that consisted of three separate radars. First, a long rang target acquisition radar (cued by one of the Sector ADC commands) would detect the target. The acquisition radar would then hand off the contact the the Target Tracking Radar. When the target was in range, the battery commander would launch the missile. By way of a transponder in its tail, the Missile Tracking Radar tracked the Ajax missile. By comparing the positions of both the target and the missile, the IFC could develop an intercept solution, and then send steering commands to the missile by injecting them into the MTR signal. The missile would be detonated by command from the IFC.  The Nike Ajax had an unusual, and large, three part warhead, spread along the length of the missile body to help ensure target destruction. The Nike Ajax had a range of about 25 miles, which wasn’t bad for a first generation guided missile.

The Army originally intended the Nike Ajax system to be semi-mobile, but since the targets it would defend weren’t going to move, they redesigned the system to operate from fixed locations. Since major metropolitan areas are spread out, that meant that cities such as New York, Los Angeles and Chicago would need several batteries to form a ring around them. Between 1953 and 1962, the Army built 300 Nike batteries scattered across the country, most near major metropolitan areas or Strategic Air Command bomber bases.


Nike Ajax Batteries in the US- Click to embiggen.

Each battery had three sites- The Control Site, the Launcher Site, and the Administration Site.

The Control Site housed the Integrated Fire Control van, and also housed the three radars of the battery. It was usually located on the highest ground available in the sector that was being covered. The Launcher Site was usually located within a mile or two of the Control Site. Originally, the Launcher Sites had been intended to store their missiles above ground, but the pressure to reduce the real estate footprint of the batteries lead to the Army building underground magazines to store the missiles. Each Launcher Site had four launchers, and an underground magazine holding twelve missiles. Missile assembly, checkout, maintenance and preparation would take place in the magazine, then a powered elevator would lift the missile above ground. It would then be transferred to the launcher rail, and ready to fire.  The Admin Site was home to the offices, motor pool, barracks and messing facilities for the battery. It was usually, but not always, co-located with the Control Site.

Each battery had just over 100 soldiers assigned. Batteries were assigned to a Defense Area responsible for the target area defended. These Defense Areas controlled anywhere from two to twenty-tw0 batteries. All these Defense Areas reported to the Army Air Defense Command or ARADCOM.

Nike Ajax was a remarkable achievement, and would have been fairly effective against Soviet Tu-4 and Tu-95 Bear bombers. But the missile had a short range, and if the Soviets started developing higher flying, supersonic bombers like the US was developing, something better would be needed. In response, Nike Hercules was developed.

Nike Hercules was intended from the start to be used from the same bases as Nike Ajax, with minimum modifications. The main improvement was not to the guidance systems, but to the missile itself. Hercules was a much larger, faster, and higher flying missile. It too was a two stage missile. It’s booster was essentially four Ajax boosters strapped together. Improvements in solid fuels meant the finicky liquid propellants could be disposed with and the sustainer motor of the Hercules was solid fueled. A maximum speed of almost Mach 4 gave the Hercules a range credited from about 85 miles to up to 100 miles. It could engage any existing or projected bomber, and it could even target short and medium range ballistic missiles.

Nike Hercules

Nike Hercules

The Hercules much longer range also meant fewer batteries were needed to cover a given target area. This meant the Army could relinquish expensive land in metro areas, and reduce the total number of soldiers dedicated to the air defense mission.

Most Nike Hercules used in the US were armed with a 20 kiloton nuclear warhead. Now, the idea of popping off a nuke twice the power of the one dropped on Hiroshima over Manhattan might not have been terribly appealing, but Army planners figured it beat the alternative of a 5 megaton nuke detonating right on Wall Street.

The Nike Hercules was also widely deployed overseas, particularly where the US had bomber and missile bases, such as in Germany, Greece, Turkey, Okinawa and Korea. Missiles overseas were armed either with the nuclear warhead or an 1100 pound conventional warhead.

The Nike Hercules system remained operational in the US continental air defense role until 1974 though a handful of sites were still employed along the eastern seaboard. By that time, the primary threat to the continental US was Soviet intercontinental ballistic missile systems. Further, the SALT I agreements categorized the Hercules as an anti-ballistic missile system.  Budget pressures in the post-Vietnam era also reduced the ability to provide what was increasingly a very limited capability.

Even as the Nike Hercules was being designed, the Army recognized that intercontinental ballistic missiles (ICBMs) would become the primary threat to the US. Development began in 1959 on a missile system to counter that threat, the Nike Zeus.  Unlike the Hercules, the Nike Zeus used entirely new radars as well as a radically different missile.

Nike Zeus

Nike Zeus

As early as 1962, Zeus actually intercepted an ICBM target at Kwajalein Island in the Pacific. In spite of this impressive achievement, the program was plagued with technical difficulties and cost overruns. Development was scrapped in 1963, but technologies from the program were used in the development of the Sprint/Spartan Anti-Ballistic Missile program that was (very briefly) deployed in 1975.

As the Army got out of the continental air defense business, hundreds of sites were decommissioned and either turned over to the National Guard (in fact, many batteries had been operated by the Guard), other federal agencies, or to the states or cities.  San Francisco is home to the only preserved launch site, SF-88L, which is open for tours. The remains of other launch sites can be discovered with a little detective work.

Addendum: Since shooting live missiles over cities was generally frowned upon, and the launching equipment was of a fixed site design, crews would travel to White Sands Missile Range in New Mexico for live fire training. All Ajax missiles used a conventional warhead, and Hercules crews would live fire the conventional warhead version of the missile.

Addendum 2: For you sharp eyed observers out there, you probably noticed a similarity between the Nike Ajax and the Soviet SA-2 Guideline missile system. They were in fact contemporary systems, and used similar configurations and guidance techniques. The similarity between them isn’t so much an example of espionage leading to reverse engineering, but of the state of the art leading separate groups of engineers to propose similar concepts to solve a given problem. But where the Ajax system was withdrawn from service fairly quickly, and replaced by the Hercules, the Guideline can still be found in service in modified form in some former Soviet client states. Modest improvements in the missile itself and more radical changes to the radars supporting the system kept the Guideline viable as a mid-range, mid- to high-altitude anti-aircraft system.

4 thoughts on “Continental Air Defense”

  1. I’m not big on video games, but strangely I have the urge to play “Missile Command” now. Not sure why…

    1. Mostly because I got tired of writing. I’ll save the Air Force efforts for another day. After all, I gotta have something to write about in the future!

  2. It was a clear beautiful Tuesday morning, a small group of Vets had agreed to meet for a late breakfast. There were about a dozen of us at a local McDonalds. One of the regulars came in and quietly said to one of our group, “Did you hear a plane hit the the World Trade Center?” One of our group asked, “Do you mean a little one?” The answer was, “No, this was a big one.” I saw a friend who was attached to a local Air National Guard Base and his family. He was joined by another male from the Base. They were also neighbors. I asked him to confirm our thinking. He walked outside and made the call, nodded to me, walked back in and inhaled his breakfast. The two families split, the males went immediately to the base and families went home. At the same time all of this was happening, it was like a similar to the ‘Silent Drill Team’. There was much more that happened that day. The Air National Guard Base was an Air Superiority Base.

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