West Bath Radar Site

West Bath

A huge cold war experimental radar site that had a unique second life

The radar tower in December 2020 with the giant water tank inside that was used for later sonar research

If you drive from Bath to Cook’s Corner in Brunswick along the State Road, you just might notice a huge metal tower rising over the trees behind some auto repair shops at the top of Witch Spring Hill. It is the remains of a cold war long-range radar installation and lessons learned there led to refinements and advancements in radar technology.

A Secret on the Hill

In December of 1954, “Mr. Sandman” by the Chordettes was at top of the charts and construction began on a secret “experimental electronics station” in West Bath. A press release from the Massachusetts Institute of Technology said that the project was part of the Continental Air Defense research being carried out under a government contract by Lincoln Laboratories, an MIT research facility.

As soon as the massive orange and white striped antenna was put on top of the 100 foot tower, everyone knew that it was actually a radar installation. But what was it for and why was West Bath chosen? The “why” was easy: the hill was one of the tallest points in Midcoast Maine.

The Nitty Gritty

What was installed was the first and only AN/FPS-31 radar. It was a prototype long range search radar system that was part of the Experimental SAGE Subsector. SAGE (Semi-Automatic Ground Environment) was a system consisting of massive computers that collected data from a network of radar sites, processed the data in real time to identify Soviet air attacks, and then directed the military response.

The West Bath site when it was operational. One of the FPS-6 height finder radars is visible on the left.

At the time, radar data had to be manually collected and analyzed which was too slow to be effective. They needed to leverage nascent computer technolgy to handle the data quickly and efficiently.

Initially, the FPS-31 was connected to a computer at MIT’s Lincoln Labs at Hanscom Air Force Base in Massachusetts. Data from the FPS-31, along with data from similar sites in Truro, Mass and Montauk Point, Long Island was sent over phone lines to the IBM FSQ-7 computer (largest computer ever built) for processing.

What was Installed:

  • 100 foot tall steel tower
  • Antenna was 120 feet wide and 16 feet high with bright orange and white stripes
  • Antenna weighed 4.75 tons
  • Rotated 6 times per minute
  • Built to withstand winds of 130 miles per hour and to support up to three inches of ice
  • Also on-site were 2 standard FPS-6 height-finder radars
  • A support building that housed an FST-1 that transmitted the radar data to the FSQ-7 computer (see below)

The designation AN/FPS-31 was based on the naming convention for radar:

  • AN=Army/Navy
  • F=Fixed
  • P=Radar (pulsed)
  • S=Detecting, Range & Bearing, Search
  • 31=generation

Initial Problems

Initial tests showed various problems with the installation. The radar was jamming mysteriously and it was determined that traffic noises from near-by Route 1 were part of the problem.

View from below during operation

They also found that the radar was so strong and sensitive that it was being disturbed by echoes from the Aurora Borealis far to the north.

The design called for the gigantic 4.75 ton antenna to rotate on a set of wheels connected with three spider legs. The wheels would ride on a track at the top of the tower. But the sheer weight of the antenna caused the wheels to wear out prematurely so they swapped out the wheel assembly for one giant central ball bearing (this design was carried over to later units). Although this was an improvement, the bearing would wear out as well and required 3 months of downtime to replace it.

Although the FPS-31 was never mass produced, it was a success. Tests showed that the network could successfully identify and track targets.

The experience that Lincoln Laboratory gained in solving all these problems was shared with others in the defense industry, and led to subsequent successful designs in other early warning ballistic missile tracking systems around the country.

The installation was decommissioned in November 1962.

A Second Life for the Tower: Sonar in a Tank

Five years after it shut down, the tower was taken over by VAST, Inc. out of Newcastle. It retrofit the tower to use as a corporate and military research facility for underwater testing.

The first contract was to evaluate helicopter-suspended Navy sonar equipment under simulated conditions for both hovering and flight.

In order to create such a water simulation, a giant tank was built inside the fret work of the existing tower. This tank (still visible today) could hold up to 450,000 gallons of water and was open at the top. A 328-square foot “control penthouse” was built 30 feet above the top of the tower, and a one-ton electric hoist was also mounted on the top. The hoist was used for lifting test equipment to the penthouse and then lowering it into the research tank. 

For direct viewing into the tank, there were 12 portholes built into the sides at four different levels, and a circular stairway built to surround it on the outside. Eight fixed 500-watt quartz-iodide underwater lamps and one portable 250-watt lamp were used for underwater illumination. A filtering system with a 650- gallon-a-minute capacity enabled researchers to make a complete change of water in only 16 hours. There was a heating element inside as well, which prevented freezing during the winter. The water to fill the tank was pumped from a small pond across the Bath Road (still there). Local fire department tank trucks could siphon water from the tower through special fittings placed there for fire emergencies.

This water research didn’t last long. Only 2 years later in 1974, the Navy decided to discontinue the research and moved their equipment to Maryland. The NAVY took the parts they wanted and VAST was left to dismantle the rest.  The last step was to use a blowtorch to create a hole at the bottom to drain the water (still visible).

VAST eventually became Tracor Marine, now General Offshore Corp, a military contractor based in South Florida.

Since then, emergency communications towers have been added on top of the tower and a cell tower was built off to the side.

Deeper Dive: WW II and the need for SAGE

Radar was used by both the Axis and Allied sides during World War II.  In fact, a small radar installation on the north coast of Oahu spotted the first wave of Japanese planes on their way to attack Pearl Harbor.  The operator called it in but it was famously dismissed as a group of B-17s flying in from San Francisco.  

In 1949, Russia tested their first nuclear bomb and then the U.S. entered the Korean War.  The “Cold War” was in full force and the country was terrified.  President Harry S. Truman felt that postwar prosperity had softened the U.S. and that the country wasn’t vigilant and that the military was vastly underprepared.  Visions of Russian bombers caused fear to ripple through the country and people built bomb shelters and were encouraged to report each other for suspicious activity.

A map of possible Soviet bombing routes showing why radar was installed in the North

It was clear that the military needed to greatly improve defenses so that any attack from Russia by air could be identified as soon as possible.  A series of radar installations were setup across the northern U.S. and in southern Canada.  The installations were placed in the North because it was assumed that the Russian bombers would fly in from the North as it was the most direct route (with the earth being round and all).

These early installations, while state of the art, required time-intensive manual plotting by operators.   There were other issues: this type of radar had trouble identifying low-flying aircraft due to “ground clutter,” there were gaps in the radar coverage, and the Russian jets flew much faster than the prop planes of World War II so any identification delays would be fatal.  

To help fill in the cracks, the Ground Observation Corp (GOC) was begun. The GOC consisted of 750,000 civilian volunteers aged 7 to 86 years old working in shifts at over 16,000 posts and 73 filter centers. They stood on roofs and hills all over the country scanning the skies looking for low-flying Russian planes that had somehow evaded radar. But that GOC story is covered elsewhere on this site.

It quickly became obvious that the radar technology needed to improve, the number of installations needed to increase, and that the entire process needed to be automated as much as possible.

That’s where SAGE comes in. Semi-Automatic Ground Environment.

In late 1950, the Air Force enlisted a number of private companies to help improve America’s air defense network. The SAGE network was built to:

  • create a net of radars and other data sources
  • deploy digital computers that
    • receive the radar and other information to detect and track aircraft,
    • process the track data to form a complete air situation, and
    • guide weapons to destroy enemy aircraft.

A 1956 promo film:

And here’s a 1960 IBM promo:

Deeper Dive: IBM FSQ-7 Computer and Austin Powers

The various radar installations fed their data to one of 23 Direction Centers (DCs) which each contained an FSQ-7 computer (the successor to the Whirlwind 1 built by MIT labs). The FSQ-7 computer was the largest computer ever built.  It occupied an entire floor (22,000 square feet), weighed over 250 tons, contained 60,000 vacuum tubes, used 3 megawatts and performed 75,000 instructions per second.  For comparison, an iPhone 6 can perform approximately 3.36 billion instructions per second.  24 FSQ-7s were built and installed.

Each SAGE Direction Center (DC) actually housed two FSQ-7s for redundancy. They had an “A’ side and a “B” side, which were switched regularly.

Appearances on the Big Screen

Because each FSQ-7 was huge and contained tons of blinking lights, switches and vacuum tubes, parts of them were shown in literally hundreds of movies and TV shows for decades after they were decommissioned. 20th Century Fox acquired an FSQ-7 in the 1960s and it began its historic big-screen run. Picture a big computer with blinking lights and it was probably part of an FSQ-7.

The Batcave with 4 FSQ-7 control panels

In fact, there is an entire website devoted to documenting the appearance of FSQ-7 components.

A partial list includes:

  • Batman
  • Get Smart
  • Soylent Green
  • Planet of the Apes
  • Six Million Dollar Man
  • Close Encounters of the Third Kind
  • WarGames
  • Austin Powers
  • Agents of S.H.I.E.L.D. in 2020!
Battlestar Galactica

Wired wrote an article called The Most The Most Wonderfully Ridiculous Movie Computers of All Time featuring the FSQ-7 along with some other massive old computers.

Deeper Dive: Light Guns and Cigarettes at DC-05 in Topsham
DC-05 in Topsham showing the 4 story concrete blockhouse that housed the 2 FSQ-7 computers

A SAGE direction center (DC-05) was built at the Topsham Air Force Station in 1958 near the spot of the current Mt. Ararat High School. Once constructed, the West Bath radar was switched to send its data to Topsham instead of Hanscom AFB.

Each SAGE direction center was constructed identically. They were 4 story blockhouses, occupying 3.5 acres of floorspace. They were built to withstand the pressure from nearby thermonuclear warheads detonating and were hardened from the effects of electromagnetic pulses (EMPs) so they could actually continue operating during the end of the world.

They were scary looking monstrosities. They were high security, windowless cubes of concrete. The 1st floor contained generators and systems to run the building. The 2nd floor housed the dual FSQ-7 computers. The 3rd floor contained the Sector Command Post which featured a control room with a pit-like theatre that showed the “big board” on a large central screen. Sound like some movies you’ve seen?

SAGE control room with large central screen

The 4th floor contained the operations room which had a large number of operators hunched over their consoles. They used light pens connected to CRT monitors. The light pens could designate/select targets to allow them to be classified and tracked by the folks downstairs in the control room.

Each FSQ-7 had 100 consoles and the ones with light guns also featured a built-in cigarette lighter and ash tray.  Priorities.

A gorgeously sci-fi DC operations room

Paraphrased from Wikipedia: “Information was fed to the DCs from the network of radar stations as well as readiness information from various defense sites. The computers, based on the raw radar data, developed “tracks” for the reported targets, and automatically calculated which defenses were within range. Operators used light guns to select targets on-screen for further information, select one of the available defenses, and issue commands to attack. These commands would then be automatically sent to the defense site via teleprinter.”

Operators with light pens at a console. The built-in lighter and ashtray is next to the guy on the right’s left hand

Topsham DC-05 received data from 4 sites in Maine (along with 2 in VT and 1 in NS). The Maine locations were:

  • Brunswick AFS – 1958-1965 – was eventually absorbed into the Brunswick NAS
  • Caswell AFS near Limestone – 1950, joined SAGE 1959, closed 1980
  • Charleston AFS – 1952-1980
  • Bucks Harbor – 1955, became part of SAGE 1960. This location is now the home of an ARSR-4 FAA radar system

DC-05 in Topsham AFS was closed in September 1969. The SAGE blockhouse was was demolished in August 1985.

Related To:


From Bath, take the State Road towards Cook’s Corner.  At the top of the hill, take a Left before Dr. Coffin’s Garage.  The site is visible from State Road.

25 Tower Lane
West Bath, ME 04530

fas.org, fortwiki.com, timeline.com, airforcemag.com, thedailybeast.com, westbath.org, youtube.com, mainememory.net, thedrive.com, radomes.org, veteransremember.com, National Archives, library.umaine.edu