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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