Searching the Skies During the Cold War Era
The intent of this article is to provide some history about a Cold War-era defense radar project—the AN-FPS 24 Long Range Search Radar System. The acronym AN/FPS stands for Army-Navy, Fixed Position, Search radar.
I was a GE Tech Rep and Crew Chief at the test site in Alabama for three years and participated in the Air Force acceptance testing of systems at Baudette, MN and Port Austin, MI. When this project was completed, I moved on with GE to work 12 years in the Space Program.
But, before I get to the project, since many people may not even remember or know there was a Cold War, I will give a short synopsis on the Cold War.
What Was the Cold War?
The Cold War was the name given to the confrontational relationship that developed primarily between the USA and the USSR after World War II. The Cold War was to dominate international affairs for decades and many major crises occurred—the Cuban Missile Crisis, Vietnam, Hungary and the Berlin Wall being just some. The Berlin Blockade (1948–49) was the first major crisis of the Cold War but was resolved without war. The growth in weapons of mass destruction was the most dangerous issue for both countries. The Cold War also created expenses for homeland defense by the USA, with one project being the Semi Automatic Ground Environment (SAGE) system, which is the main topic of this article.
The two superpowers never engaged directly in full-scale armed combat but they each armed heavily in preparation for an all-out nuclear war. Both the USA and the USSR built up an arsenal of inter-continental nuclear missiles, which could be launched at a moment's notice.
It was referred to as a "Cold War" because there was no military fighting directly between the two sides, although there were major regional wars in Korea, Vietnam and Afghanistan which the two sides supported.
Historians have not fully agreed on the Cold War timeline, but the date 1947–1991 is commonly used.
A clash of very different beliefs and ideologies, capitalism versus communism, formed the basis of an international power struggle with the two major world powers. This was evident in the technological competitions as well, with USSR putting the first man in space and the USA putting the first man on the Moon.
The Cold War between the USA and USSR began to change following President Reagan's remarks at the Brandenburg Gate, Germany on June 12, 1987, in which he said, “Mr. Gorbachev, tear down this wall!” By the fall of 1989, East and West Germans were tearing down the Berlin Wall with pickaxes. The unraveling of the USSR began in Poland in June 1989, and soon other members of the USSR began declaring their independence. The USSR was declared officially dissolved on December 25, 1991.
I have included only a tidbit of the Cold War Era here, but if you have further interest, Wikipedia, the free encyclopedia, has more information.
FPS-24 Radar Overview
The radar project was the AN/FPS-24 radar system, a long-range, multiple frequency, ground search radar system. The radar system would provide early warning data to a system of control centers called the Semi-Automatic Ground Environment (SAGE) system. These long-range radars would be installed around the perimeter of the USA in the late fifties and early sixties to detect intruding enemy aircraft.
The US Air Force was responsible for the development of the radar system through government contracts, and the Air Force would eventually operate the radar sites with a Radar Squadron for each site. The General Electric Company had a contract to build the AN/FPS-24, test the prototype at Eufaula Air Force Station, Eufaula, AL, train Air Force squadron personnel and install the production systems around the perimeter of the USA.
The multiple frequencies of the FPS-24 radar gave us a great advantage over any incoming aircraft. An advantage of having a multiple-frequency radar is when you have an incoming aircraft jamming the radar frequency so that you cannot track the aircraft, the radar frequency can be changed to a different channel to continue tracking it. With the FPS-24 radar system, this was done from an anti-jam operator console which was always manned at operational sites. The anti-jam operator could see the frequency being jammed on a display and switch the radar to a different frequency.
Twelve AN/FPS-24 radar systems were built between 1958 and 1962, installed around the perimeter of the U.S. and most sites were operational into the 1980s. A couple of the operational sites used a fiberglass radome to cover the huge rotating antenna, due to weather conditions. The FPS-24 radars at Mt Hebo AFS, OR and Cottonwood AFS, ID were protected by a radome.
US Map Showing AN/FPS Radar Locations
7 Baudette AFS, MN
8 Port Austin AFS, Mi
9 Bucks Harbor AFS, ME
10 Oakdale AFS, PA
11 Winston Salem AFS, NC
12 Eufaula AFS, AL
1 Almaden AFS, CA
2 Point Arena AFS, CA
3 Mt. Hebo AFS, OR
4 Blaine AFS, WA
5 Cottonwood AFS, ID
6 Malmstrom AFB, MT
Bearing problems often occurred at some sites due to the weight of the huge rotating antenna. Failure of the huge hydrostatic bearings caused the early closure of some sites. Goodyear Aerospace, under contract with RADC, was the developer of the bearings for the AN/FPS-24 antenna system.
Searching the Skies
The AN/FPS-24 Radar System
The AN/FPS-24 antenna was a huge structure with the rotating assembly weighing more than 70 tons and its pedestal, which fastened it to the roof/tower, was approximately another 20 tons. The rotating antenna reflector was 120 feet across and 50 feet high, painted with a red and white checkerboard pattern. The feed horn was about 6 feet wide and 9 feet tall. The feed horn and waveguide were supported by a huge tubular steel boom. When operating, the FPS-24 radar antenna rotated between 5 to 6 revolutions per minute.
The FPS-24 was designed to operate at longer ranges and higher altitudes than other search radars of that time despite interference, jamming and enemy countermeasures.
The heart of the FPS-24 radar system consisted of a large amount of electronic equipment which included high-power transmitters, receivers, antenna control systems, servo systems, video processing systems, 10,000-volt power supply systems, 9-inch diameter (round) waveguide and more.
The power output stage of each FPS-24 transmitter was located in a round steel, pressurized tank about ten feet high and six feet in diameter. Access to the power output stage was through a hatch on top of the tank which opened for maintenance. The power output tube weighed about 100 pounds and needed a hoist for installation or removal. The tube was water cooled, with water lines connected and water leaks had to be frequently repaired. The tube's RF power was sent to the antenna feedhorn through the 9-inch round waveguide.
I have not included details of the radar operational frequencies, RF power output, and other features, intentionally, even though most of it has been declassified and is public information.
I also have not included information regarding the FPS-24 tower floors and equipment layout. This type of information has been compiled by Steve Weatherly, former Air Force Radar Maintenance Officer on the AN/FPS-24 radar system. You can find this tower information here and the radar tower equipment layout by floor here.
Alabama Test Site
The prototype at the Eufaula, AL test site had the huge rotating antenna mounted on the top of a steel lattice structure tower. The radar equipment was housed in a separate building, located close to the antenna.
Operational Radar Sites
The FPS-24 operational systems antennas were mounted on top of a 85' high and about 63' x 63' wide five-story cement tower which housed all of the radar equipment on different floors.
The Baudette, MN AFS, shown above, was one of the operational sites where I spent one month during the project. As a transmitter expert, I went from the test site in Alabama to the Baudette site to help the GE team with the Air Force acceptance testing. I recall that the temperature was 45 degrees below zero some nights when I was at the site.
The small fiberglass radome, on the right of the photo above, is a height finder radar system, which was separate from the FS-24 search radar system. The technology of that time frame required both a search radar and a height finder radar to supply aircraft data to the SAGE Centers. The search radar gave the azimuth location of the aircraft and the height finder gave the height level of the aircraft.
The photo above shows the Mount Hebo, AFS Radar Site with the FPS-24 radar system under a hugh fiberglass radome. Mount Hebo rises abruptly to an elevation of 3,176 ft. in the Northern Oregon Coast Range on the border between Tillamook County and Yamhill County. Mt. Hebo has extreme weather and this was one of two sites which required a radome for the FPS-24. Note the personnel tunnels which were used during extreme weather.
The photo to the right (above on mobile) shows the Port Austin AFS in Michigan with the FPS-24 radar tower and antenna in the top left corner. I worked at this site for 6 months in 1962, preparing the equipment and performing the final Air Force acceptance testing.
This was the last FPS-24 radar site I worked on. I could have stayed on the site as a GE Tech Rep, but I returned to GE in Syracuse, NY for reassignment. I transferred to the GE Space Division and spent 12 years working on the Apollo and SkyLab programs at Marshall Space Flight Center, Huntsville, AL.
As a note of history, the Port Austin AFS was closed in 1988 by the Air Force.
In the early 1980s, the main bearing of the Port Austin AFS AN/FPS-24 search radar failed catastrophically. The AN/FPS-24 search radar was replaced with the AN/FPS-91A in 1983. The Air Force closed the radar site permanently in September 1988. It is my understanding that the site property was turned over to the local government.
Part of the site is now used by a Bible study group.
Note: Port Austin is a village in Huron County, Michigan. The population was 664 at the 2010 census. From my experience at the Port Austin AFS, it can grow to thousands of temporary people, who vacation on the lake, on July 4th weekend and during the summer.
- The AN/FPS-24 Radar was a Long Range Search Radar used by the United States Air Force Air Defense Command during the Cold War era to detect incoming enemy aircraft.
- General Electric built this frequency diverse (FD) long range search radar.
- Eufaula, AFS, AL was the location of the AN/FPS-24 Prototype Test Site.
- Twelve systems were built between 1958 and 1962 and deployed in a perimeter around the U.S.
- Bearing problems often occurred due to the 85.5-ton weight of the antenna. Failure of the 9-foot hydrostatic bearings, developed by Goodyear Aerospace, caused early site closure of some sites due to catastrophic damage to the support tower, sail, and feed horn.
- The Air Force phased out the AN/FPS-24 radar sites in the 1980s as new technologies could be used for the same effect.
- The Cold War era essentially ended when the USSR was declared officially dissolved on December 25, 1991.
On a Personal Note
Writing this article has brought back many fond memories of the AN/FPS--24 radar project. I met a lot of dedicated Air Force personnel, including squadron level which we trained on the radar, plus high-ranking Air Force Officers.
I recall that while at the Eufaula AFS, Alabama test site, we did a lot of countermeasure tests where US Air Force planes would fly from as far away as Maine, attempting to penetrate our range of airspace undetected. They would drop "chaff" as interference and try to jam the FPS-24 radar with their airborne jamming systems. Chaff is a radar countermeasure in which aircraft or other targets spread a cloud of small, thin pieces of aluminum, metallized glass fibre or plastic, which either appears as a cluster of primary targets on radar screens or swamps the screen with multiple returns
The multi-frequency, multi-channel, anti-jamming capability of the FPS-24 radar, when operated properly, made it impossible to jam so that a plane would not be detected on a radar screen.
I am glad I had the opportunity to be part of "searching the skies" on this Cold War radar project.