MIT Radiation Laboratory

The Radiation Laboratory, often called the Rad Lab, was a special research group at the Massachusetts Institute of Technology during World War II. It started in October 1940 after the United States learned about a new invention called the cavity magnetron.

The Rad Lab used this technology to create small and powerful radar machines for the military. These radars helped guide airplanes, aim weapons, and protect cities.

From just thirty people, the Rad Lab grew to almost 4,000 members, including scientists from many universities. They designed many of the radar systems used by the United States during the war. Some of these radars helped stop attacks and allowed planes to fly through thick clouds.

The Rad Lab was led by Lee DuBridge and Isidor Rabi. It received a lot of money from the government and worked closely with the United States and British military. After the war ended in 1945, the Rad Lab closed, but its work continued through other MIT labs and helped start new technology companies in the area known as Route 128. Many of the scientists who worked there later won the Nobel Prize.

Origins

Further information: Radar in World War II

In the 1930s, several countries secretly worked on radio detection systems for war. Germany made quick progress, and Britain built the first system to detect airplanes.

American radar work was split into two groups. The Naval Research Laboratory studied longer wavelengths, while the Army Signal Corps worked on shorter microwave wavelengths. Both groups struggled to create enough power for useful radar.

When war broke out in Europe in 1939, American scientists met to discuss using science for defense. After Germany’s advances, President Roosevelt approved the National Defense Research Committee to organize civilian research for military use.

A big advance happened in 1940 when British scientists created the resonant cavity magnetron. This device produced much more power than before. British experts brought this technology to the United States, which led to the creation of the Radiation Laboratory at MIT. The lab aimed to build small radar systems using this new device, gathering top scientists from across the country.

Main article: National Defense Research Committee

Main article: Tizard Mission

Organization

Governance

The Radiation Laboratory, often called the Rad Lab, was a research group at the Massachusetts Institute of Technology (MIT) that worked on radar technology during World War II. It started with just thirty people but grew to nearly 4,000 by the end of the war. The lab was led by Lee DuBridge, with F. Wheeler Loomis as associate director and Isidor Rabi heading research. They worked together with a steering committee to choose projects and decide what to focus on.

The lab worked as a civilian group but had military supervision. It worked closely with the Army and Navy. Officers from these groups visited to talk about what they needed and to help with testing. Scientists from the lab also went to military bases to help set up and improve radar equipment.

Personnel

The Rad Lab began with about twenty scientists in 1940 and grew to almost 4,000 employees by 1945. People came from many different areas, not just physics. Women were hired for many jobs and made up about 36 percent of the workforce by the end of the war.

Government contracts

MIT received a lot of money from the government for this research—over $106 million. This was a big part of the university's work during the war. Most of this money went to the Rad Lab for developing radar technology.

Industrial collaboration

The Rad Lab worked closely with companies like Bell Labs, General Electric, and RCA. These companies provided parts, helped develop systems, and sometimes shared scientists with the lab. The Rad Lab also helped these companies learn new techniques so they could make the equipment needed for the war.

Facilities

The Rad Lab started in a small space at MIT but grew quickly. By the end of the war, it used over 400,000 square feet of lab and office space. They built new buildings and used existing ones to fit all the scientists and equipment.

Field operations

The Rad Lab sent scientists to different parts of the world to help set up and fix radar equipment. In 1943, they set up a branch in England to support British forces. They also planned to set up a branch in the Pacific, but Japan surrendered before this could fully happen.

Early development

Early radar tests

The lab started with three main goals after the Battle of Britain. The first was to build radar to help airplanes find and stop enemy bombers at night. The second goal was to make a system to guide bombers over long distances. The third was to create radar to help direct anti-aircraft guns.

At first, the team tested if microwave radar could work. They worked hard from November to December 1940 to finish a radar system by January. On January 4, 1941, they tested the first system on the roof of MIT’s Building 6. It showed images of Boston across the river.

This first test showed microwave radar was possible, but it wasn’t practical for airplanes. They needed a single antenna that could both send and receive signals. By January 10, they made this work and tested it again on the roof.

Next, they tested the radar in airplanes. On March 10, it flew in a B-18 bomber for the first time. It got better each week. By March 27, it could find airplanes and ships, even submarines from three miles away.

Gunlaying

Main article: SCR-584

They also worked on helping anti-aircraft guns aim. In May 1941, military officers saw the work and liked it. They built a truck with a radar dish that could follow targets automatically.

In November 1941, they tested the truck at Fort Hancock, New Jersey. After Pearl Harbor, they tested it again in Virginia. It worked very well, guiding guns to hit targets without anyone seeing them.

Anti-submarine radar

When German U-boats started sinking ships, the lab shifted to making radar to find submarines. In July 1941, a scientist from Britain arrived to help. They began working on radar for finding submarines from the air.

By fall 1941, they had five different projects for different airplane types. Tests on a ship showed it could guide through fog. The Navy ordered many of these radars.

After Pearl Harbor, the need grew bigger. In early 1942, German U-boats attacked ships along the coast. The lab made microwave radar for airplanes and built ground sets for the military. Some of these were used in North Africa in November 1942.

Entry into war

Pearl Harbor changed everything for the lab. Before December 1941, they thought the work might end in 1942. After, they knew it would last the whole war.

They needed to change how they worked to make equipment that could be used in battles. They started a company to build experimental equipment quickly while factories got ready to make large amounts.

The lab also needed to grow. By the end of 1942, the staff grew from thirty to over a thousand people.

Radar navigation and control systems

The laboratory made important tools to help guide military operations during World War II. These tools helped with traveling long distances, landing planes in bad weather, and watching for enemy planes far away.

Long-range navigation (LORAN)

Main article: LORAN

Long-range navigation was one of the first projects at the Radiation Laboratory. Scientists made a way for ships and planes to find their position using radio signals from stations on the ground. This system, called Loran, helped guide many journeys across the ocean during the war. By the end of the war, Loran covered much of the Earth’s surface and was used for many years after.

Blind landing (GCA)

Main article: Ground-controlled approach

Before the war, landing planes in bad weather was very hard. Scientists at the lab created a new system called Ground Controlled Approach (GCA) that let ground controllers talk pilots through safe landings using radar. This system saved many planes and crews, especially after hard missions. GCA was also useful after the war, especially in bad weather.

Microwave early warning (MEW)

Main article: AN/CPS-1

After Pearl Harbor, people worried about Japanese attacks on the West Coast of the United States. Scientists built a powerful radar system called Microwave Early Warning (MEW) that could see planes from far away. This radar helped guide fighters during important battles and saved many planes and pilots.

Airborne early warning (Project Cadillac)

Main article: AN/APS-20

During the war, some Japanese planes could come close to American ships by flying very low. To stop this, scientists made a radar system that could be carried in planes, called Project Cadillac. This system could see enemy planes from much farther away, helping ships and planes work together better to stay safe.

Major combat systems

Anti-submarine warfare

In the winter of 1942–1943, German submarines, called U-boats, came close to stopping Britain's supplies across the Atlantic Ocean. These submarines attacked ships at night. The radar at that time could find submarines when they were on the surface, but it also warned them, giving them time to dive before planes arrived. In early March 1943, these submarines sank many Allied ships.

New radar technology changed this. The Radiation Laboratory created a small radar system that could find submarines before they could be warned. This let planes attack them effectively. By the end of March 1943, planes with this new radar started flying between Britain, Iceland, and Newfoundland, closing a gap in the Atlantic where submarines had been active. By the end of the war, these radar systems were widely used.

In May 1943, the Allies destroyed many more submarines than before, leading the German submarine commander to stop attacks in the North Atlantic. Experts later said this new radar was key to winning the battle against the submarines.

Blind bombing

Clouds often covered Germany, making it hard for bombers to see their targets. The British created a radar system called H₂S that helped bombers fly through clouds. The Radiation Laboratory improved this with H₂X, a smaller and better radar. In November 1943, bombers using H₂X successfully attacked targets in Germany that had been missed before.

This radar allowed more bombing missions even when the weather was bad. By the end of 1943, most American bombing missions used H₂X. It was especially important when bombing oil targets in Germany, helping to cut down their oil supplies.

Anti-aircraft fire control

Before 1941, anti-aircraft guns relied on searchlights and human operators, which was slow and not very accurate. The Radiation Laboratory developed a new system that could automatically track airplanes and guide guns. This system, called SCR-584, worked with a device that calculated where shells should explode to hit targets.

This new system was very successful, especially against unmanned bombs Germany sent to London in 1944. With SCR-584 and special shells that exploded near targets, anti-aircraft guns destroyed many of these bombs. The system was also used to guide planes to hidden targets, helping them find and attack enemy positions even in bad weather.

Wartime scale

By 1945, the Radiation Laboratory had made about 150 radar systems for use on land, at sea, and in the air. This included the Loran navigation network. Experts thought that for every dollar spent on this research, more than ten dollars' worth of military equipment was created. In 1944, tools from the lab made up over half of all American radar tools.

The lab was not the only place working on radar for the Allies. Its leader reminded everyone that many places worked on radar. Britain helped create important parts and systems. Bell Labs also shared important ideas. The Rad Lab stood out because of how big its work was, how fast it made new tools, and how well it shared its discoveries.

Postwar legacy

The Radiation Laboratory closed on December 31, 1945. Before it closed, its knowledge was collected in the MIT Radiation Laboratory Series. This series helped share important technology with engineers and scientists around the world.

MIT used what it learned to start new research groups. One of these became the Research Laboratory of Electronics, which studied tiny waves and new ways to use electricity. Later, MIT also created Lincoln Laboratory to work on systems for protecting the air, using skills from radar and computer technology.

The work done at the Radiation Laboratory showed how important it is for different kinds of scientists to work together. It also helped change how universities got money for research. Many scientists who worked there went on to lead important labs and universities, and their work helped create new companies and technologies, especially in the Boston area. The lab’s ideas and tools were used in many areas, from navigation to communication systems.

The Radiation Laboratory’s work led to many awards for the scientists involved, including several Nobel Prizes. It remains a key part of history in science and technology.