ROTOR facts for kids

Entrance to the former ROTOR station at Kelvedon Hatch

ROTOR was a big radar system built by the British Government in the early 1950s. Its main job was to protect the UK from possible attacks by Soviet bomber planes. To get it working fast, it first used older systems from World War II. These included the Chain Home radars for spotting planes far away, and the AMES Type 7 for tracking them and guiding fighter jets. Information from these stations was sent to control centers, many of which were built underground. They used a large network of telephones and telex machines.

Later, new and better radars were developed. One experimental system, called Green Garlic, worked so well that it started replacing the older Chain Home radars in 1954. These new radars were very accurate. They could even replace the Type 7 radars. They also had a much longer range. This meant fewer radars were needed to cover the whole United Kingdom. This led to the creation of "Master Radar Stations." These stations could both give early warnings and guide fighter planes to intercept enemy aircraft. The original plan for 66 ROTOR radars was cut down. In the end, only about half that number of stations were needed. Many of the control rooms, which had just been finished, were then sold off.

ROTOR was designed to be updated over time. This included both the radars and the control systems. However, a new type of radar jammer called the carcinotron appeared in the mid-1950s. This was a big problem. Just one enemy plane with a carcinotron could completely block the ROTOR radars, making them useless. At the same time, the invention of the hydrogen bomb and ballistic missiles changed how wars might be fought. The idea of defending the whole country became very difficult. The only way to stop missile attacks was to make sure no one dared to attack. If that failed, interceptor aircraft and missiles would not make much difference.

ROTOR was meant to be replaced by a new network. This new network, called the "1958 Plan," would mostly protect Britain's V-bomber planes. But this idea was later dropped. The new system's main job became finding planes that carried jammers. This was to keep the BMEWS radars clear and prevent a surprise missile attack. Such a system did not need many radars or cover the whole country. To save money, military radars were combined with civilian air traffic control. This led to the Linesman/Mediator system, which had only five main stations. The original ROTOR system was slowly replaced by Linesman starting in 1967.

Why ROTOR Was Built

After World War II, radar operations in the UK were mostly shut down. People thought another war was at least ten years away. So, there seemed little need to improve the existing radar system.

But things changed fast in 1949. The Soviets tested their first atom bomb. It was known that the Soviets had copied the American B-29 Superfortress plane. They called it the Tupolev Tu-4. These planes could reach the UK carrying a nuclear bomb. A report in 1949, called the Cherry Report, looked at this problem. It suggested that the 170 existing Royal Air Force radar stations should be reduced to 66 sites. The electronic parts of these stations would be greatly improved.

Most of the new network would use 28 rebuilt Chain Home systems. The rest would come from other existing radars. These included Chain Home Low, Chain Home Extra Low, and various Ground-controlled interception (GCI) radars. This was a temporary plan. A much better radar, called the Microwave Early Warning, was expected around 1957. Guiding fighter planes would still be done by existing systems.

All the radars were to be improved. They would be placed in better locations. Hardened control bunkers would be added to protect the operators from attacks. On the east coast, where a Soviet attack was most likely, the bunkers were built underground. These were called the 'R' series (like R1, R2, R3). On the western side of the UK, the buildings were usually partly buried ('R6') or above ground ('Secco' huts). The 'R' series bunkers were very strong. They had 10-foot-thick (3.0 m) concrete walls. All the equipment, generators, and air conditioning were kept inside.

ROTOR also changed how the RAF Fighter Command was set up. It created six "Sector Operational Commands" (SOC). Each had its own command bunker. These were three-level 'R4' protected buildings. Only four of these were built. Extra "Anti-Aircraft Operations Rooms" were also built. These helped coordinate the British Army's anti-aircraft guns. The whole network of bunkers, radars, and control centers used a huge amount of materials. This included 350,000 tons of concrete, 20,000 tons of steel, and thousands of miles of telephone and telex wires.

The work was mainly done by the Marconi Wireless and Telegraph Company. It was carried out in several stages. These were called ROTOR 1, ROTOR 2, and ROTOR 3.

After ROTOR Was Built

While work on the Microwave Early Warning system began, scientists at the Royal Radar Establishment were trying out new parts. These included cavity magnetrons and crystal detectors. When put together with a simple antenna, these parts made their existing microwave radars four times more powerful. This new system, called "Green Garlic," wasn't exactly what was planned for the Microwave Early Warning. But it was close enough and would be ready years earlier.

So, it was decided to make the Microwave Early Warning a long-term project. It would have extra features like tracking moving targets. Meanwhile, Green Garlic would be connected to a huge antenna. This would give it a range of over 200 nautical miles (370 km; 230 mi). These new systems, called AMES Type 80, started to be installed in 1954. The first ones were ready for use the next year. As more were installed, it was found that they were so accurate they could also guide the fighter planes. This meant the information didn't need to be sent to the ROTOR control centers anymore. By doing all the tracking at one place, fewer operators were needed.

Because of the Type 80 radar, many ROTOR sites were changed into Master Radar Stations (MRS). The rest were no longer needed. Some closed only two years after opening. Around the same time, the first surface-to-air missiles were introduced. These made anti-aircraft guns old-fashioned. The Army then gave the air defense job entirely to the RAF. All the anti-aircraft operations centers were closed.

A few of the ROTOR stations were used again for other purposes. Some became Regional Seats of Government or local wartime headquarters. Many sites were kept by the government until the end of the Cold War. Later, they were sold to private buyers. Some were turned into museums, like Hack Green. Others were given to the National Air Traffic Control Centre.

ROTOR Sites in the UK

At the Radar Research Establishment in Malvern, Worcestershire, a ROTOR bunker was built above ground. This allowed equipment to be tested in a real-life setting. This building, known as H Building, had a copy of the control center at RAF Bawburgh. The building was taken down in June 2020.

What Happened to the Sites Today

RAF Staxton Wold is the only Chain Home site still used for military radar. But there are no original Chain Home buildings left there. It was rebuilt in 1964 for the Linesman/Mediator system. Today, it is home to an RAF TPS 77 RRH (remote radar head).

RAF Boulmer is still a working RAF building. It is located in an old "ROTOR" R3 bunker. This site is part of the UK Air Surveillance and Control System.

The condition of the old ROTOR sites today varies a lot. Some have been completely taken down. Others are still standing.

For example, West Myne in Somerset was the last ROTOR 3 CHEL site. It was finished in 1957. This was after the Type 80 radar was introduced. Many other ROTOR stations had already closed by then. The site was inside Exmoor National Park. The National Trust strongly opposed its creation. They quickly removed the site after it closed.

Many of the ROTOR buildings have been used for new purposes. For instance, the Bawburgh R4 SOC was changed to SRHQ4.1 and then RGHQ4.1. This was to meet the changing needs of the government. The building is still there, but it has been changed a lot. An extra floor was added, and the original operations area was covered over.

In July 2019, a group called Kent Underground Exploration started talking with TDC. They hope to get permission to find and uncover the Foreness station in Kent. Its grid reference is TR 385710.