Historic Posts, Camps, Stations and Airfields
San Francisco Defense Area SF-31 (Lake Chabot/Castro Valley)
by Dan Sebby
Military Historian, California Military Department
San Francisco Defense Site SF-31. The Administrative Area (SF-31A) is in the foreground while the Launcher Area (SF-31L) is on the arise above the Administrative Area. The Integrated Fire Control Area (SF-31C) is on the ridgeline above the Launcher Area.
Former SF-31 was established in 1955 when the U.S Army acquired the acreage through a lease with the County of Alameda (7.38 acres) and an undetermined instrument with the EBMUD (110.25 acres). Records at the US Army Corps of Engineers, Sacramento District do not indicate a formal leasehold relationship between the U.S. Army and EBMUD until 26 August 1960.

The U.S. Army's Cold War air defense missile sites were divided up into three distinct areas, each serving a different function. Specific to former SF-31 were the Launcher Area, Administrative Area (also known as the Cantonment Area), and Control Area.

The Launcher Area (SF-31L) was located approximately 270 yards east of the southern end of Lake Chabot. The Launcher Area consisted of eight launchers and two magazines (underground storage "bunkers") that held a total of 20 MIM-3 Nike-Ajax multi-stage, surface-to-air missiles. The Nike-Ajax missile required facilities for the fuelling of the Ajax (second-stage) portion of that missile system. The liquid fuel used for the Ajax was a combination of hydrazine and red fuming nitric acid. The Nike portion (booster or first-stage) used a solid fuel. The magazines were modified from May 1958 until June 1959 to hold 12 of the larger MIM-14 Nike-Hercules missiles (Redstone Arsenal). The Nike-Hercules missile used a solid fuel for both stages. Additional facilities were constructed on SF-31L including missile and warhead assembly, crew readiness, and security buildings. The Nike-Hercules missile was also capable of being armed with a nuclear warhead (Morgan and Berhow 2002).

The Administrative Area (SF-31A) was located adjacent to SF-31L and contained the Site's administrative and support functions. This included troop housing, mess hall, recreational facilities, battery administration, supply buildings, and vehicle maintenance facilities. These buildings were of a standard concrete block construction and were heated by fuel oil (Morgan and Berhow 2002).

The Control Area (SF-31C) was the location of the Site's radar and fire control systems. It was located across Lake Chabot, approximately 1.1 miles to the west of the Launcher and Administrative Areas. This location allowed for 360-degree "line-of-site" radar coverage by the Site's tracking and search radar systems. The missile tracking radar would "lock-on" to the missiles as they sat on the launcher and follow them from launch to impact with the target. The Control Area was located away from the Launcher Area because the high speed of the Nike missiles would have destroyed the mechanisms of the missile tracking radar (Morgan and Berhow 2002).
The Site was initially garrisoned by Battery A, 441st Antiaircraft Artillery Missile Battalion. In September 1958, the U.S. Army reorganized its field and anti-aircraft artillery branches under the Combat Arms Regimental System. As a result of this reorganization the 441st Anti-Aircraft Artillery Missile Battalion was reorganized as the 4th Missile Battalion (Nike-Hercules), 67th Artillery Regiment (Morgan and Berhow 2002).

During the U.S. Army's occupancy of the Site, the 110.25 acres of leased land on which the Site was built on was sold to the Lutheran Church-Missouri Synod (24.75 acres on 16 November 1961) and the South County Joint Junior College District (85.50 acres on 27 May 1966). On 6 February 1963, the U.S. Army acquired an additional 17.552 acres of land from the San Leandro Rock Company in order to allow for the expansion of SF-31C caused by the installation of the High Power Acquisition Radar (HIPAR) system.

In June 1963, the operational control of the Site was transferred to a California Army National Guard unit, Battery B, 1st Missile Battalion (Nike-Hercules), 250th Artillery Regiment (1st California). Although garrisoned by a National Guard unit, the Site remained an active U.S. Army installation as a sub-installation of the Presidio of San Francisco. On 1 April 1972, as a result of another reorganization of the U.S. Army's artillery forces, the garrison was renamed Battery B, 1st Battalion (Nike-Hercules), 250th Air Defense Artillery Regiment (1st California) (Morgan and Berhow 2002).

In March 1974, the Site was deactivated and the garrisoning unit inactivated. On 31 August 1974, the U.S. Army terminated all of the leases and returned control of the Site to the property owners. The USACE real estate records indicate that for the most part, the property owners were provided compensation in lieu of restoration of the property. Research has indicated that restoration actions were limited to removal of some security fencing.
Aerial Images
Administrative (SF-31A) and Launcher (SF-31L) Areas, circa 1965
Integrated Fire Control Area (SF-31C), circa 1965.
The Nike-Ajax and Nike-Hercules Missiles
The Western Electric SAM-A-7/M1/MIM-3 Nike Ajax

The Nike Ajax was the world's first operational surface-to-air guided missile system. Its origins lay in the immediate post-war time, when the U.S. Army realized that guided missiles were the only way to provide air-defense against future fast high-flying bombers. Western Electric became the prime contractor for the XSAM-G-7 Nike missile system and Douglas as the primary subcontractor was responsible for the missile airframe.

The first unguided Nike missiles were fired in 1946, but problems with the original multi-rocket booster (eight solid-fuel rockets wrapped around the missile tail) soon led to delays in the program. In 1948, it was decided to replace this booster pack with a single rocket booster, attached to the back of the missile. The main propulsion of the missile was a Bell liquid-fueled rocket motor, and the flight path was controlled by the four small fins around the nose. In November 1951, the first successful interception of a QB-17 target drone succeeded. The first production Nike (which had been redesignated SAM-A-7 in 1951) flew in 1952, and the first operational Nike site was activated in 1954. By this time, the missile had been designated by the Army as Guided Missile, Anti-Aircraft M1. The name had changed to Nike I, to distinguish it from the Nike-B (later MIM-14 Nike Hercules) and Nike II (later LIM-49 Nike Zeus). On 15 November 1956, the name was finally changed to Nike Ajax.

The Nike Ajax missile used a command guidance system. An acquisition radar called LOPAR (Low-Power Acquisition Radar) picked up potential targets at long range, and the information on hostile targets was then transferred to the Target Tracking Radar (TTR). An adjacent Missile Tracking Radar (MTR) tracked the flight path of the Nike Ajax missile. Using tracking data of the TTR and MTR, a computer calculated the interception trajectory, and sent appropriate course correction commands to the missile. The three high-explosive fragmentation warheads of the missile (in nose, center, and aft section) were detonated by ground command, when the paths of target and missile met.

One of the major disadvantages of the Nike Ajax system was that the guidance system could handle only one target at a time. Additionally, there was originally no data link between different Nike Ajax sites, which could lead to several sites engaging the same target. The latter problem was eventually solved by the introduction of the Martin AN/FSG-1 Missile Master command-and-control system, with automatic data communication and processing. Other problematic features of the Nike Ajax system were the liquid-fuel rocket motor with its highly toxic propellants, and the large size of a complete site with all components, which made Nike Ajax to all intents and purposes a fixed-site air defense system.

By 1958, nearly 200 Nike Ajax sites had been activated in the United States. However, the far more advanced MIM-14 Nike Hercules soon replaced the Nike Ajax, and by late 1963, the last Nike Ajax on U.S. soil had been retired. In 1963, the Nike Ajax had received the new designation MIM-3A. Despite the use of an MIM (Mobile Intercept Missile) designator, the mobility of the Nike Ajax system was more theoretical than actually feasible in a combat situation.

The MIM-3A continued to serve with U.S. overseas and friendly forces for many more years. In total, more than 16,000 missiles were built.


Nike Ajax and Nike Hercules Missiles (NARA)

Western Electric SAM-A-25/M6/MIM-14 Nike Hercules

The Nike Hercules was the only nuclear-armed surface-to-air weapon, which was operational with the U.S. Army. Development of an improved Nike missile began in 1952, with the primary goal to develop a missile with a significantly higher performance than MIM-3 Nike Ajax (then known simply as Nike), which could still be used with the existing Nike ground equipment. After it had been shown that the Nike Ajax could not be equipped with then existing nuclear warheads, nuclear armament became another goal for the new missile. The SAM-A-25 Nike B program was formally established in June 1953. As with Nike Ajax, Western Electric was prime contractor, and Douglas was responsible for the missile airframe.

The Nike B (renamed Nike Hercules on 15 December 1956) used many components of the Nike I (Nike Ajax). The booster consisted of four Nike Ajax boosters, and the original design used 4 of Ajax' liqued-fuel rockets as sustainer propulsion. However, the first flight tests with the liquid-fuel sustainer in 1955 proved very troublesome, and a solid-fueled sustainer rocket was eventually used. The first successful interception of a drone target occurred in 1956, and in 1957 the new solid-fuel sustainer flew for the first time. Nike Hercules used the same command guidance as the MIM-3 Nike Ajax, with essentially the same ground components.

The first production Nike Hercules missiles were delivered in 1958, and quickly replaced the Ajax on many Nike sites. By then, the Nike Hercules had been designated as Guided Missile, Air Defense M6. The M6 could be equipped with either an M17 (a.k.a. T45) blast-fragmentation warhead, or a W-31 nuclear fission warhead with yield selectable as 2 kT or 40 kT. The missile performance was such that even very high-flying bombers could not escpe the Nike Hercules. Capability against low-level targets remained rather limited, however.

As the Nike Hercules began replacing the older Nike Ajax, work was underway to improve the acquisition and tracking radar capabilities to fully exploit the missile's greater performance. The major improvement in what was called the Improved Hercules system was the new L-band acquisition radar, called HIPAR (High-Power Acquisition Radar). The TTR (Target Tracking Radar) and TRR (Target Ranging Radar) were also improved, having better ECM resistance. The missiles of the improved Improved Hercules system were designated as M6A1. In June 1960, an Improved Hercules achieved the world's first successful interception of a ballistic guided missile, when a MGM-5 Corporal SRBM was shot down. The new radars were also far more compact than the original ones, which made moving a Nike site a least somewhat practical for the first time. Lastly, Improved Hercules introduced a viable surface-to-surface capability to the Nike system. The first Improved Hercules systems were installed at Nike sites in June 1961.

In 1963, the M6 and M6A1 missiles were redesignated as MIM-14A and MIM-14B, respectively. The MIM-14C (introduced in 1972) was a modified MIM-14B with an improved missile guidance section for higher manoeuverability and better ECM resistance.

All in all, the U.S. Army established 145 Nike Hercules sites over the years. Production of the nuclear-armed missiles ended in 1964, and gradual phase-out of the MIM-14 began in the late 1960's. The Army originally planned to replace the Nike with the new MIM-104 Patriot missile, but this plan was not implemented in the USA. Therefore, after the last active Nike Hercules sites in the continental U.S. had been deactivated in 1974, there are no long-range air-defense missiles fielded in the U.S.. In Europe, the U.S. Army retired its last MIM-14 units in 1984, when the MIM-104 Patriot was introduced.

In total, more than 25000 Nike Hercules missiles of all wersions were produced, most being of the MIM-14B variant.

Source: Directory of U.S. Missiles and Rockets, http://www.designation-systems.net/

Site Maps
Site Plan
Administrative Area (SF-31A)
Integrated Fire Control Area (SF-31C)
Launcher Area (SF-31L)


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Updated 24 July 2016