The use of microwaves for radio and radar was highly desired before the war, but existing microwave devices like the klystron were far too low powered to be useful. Alfred Lee Loomis, a millionaire and physicist who headed his own private laboratory, organized the Microwave Committee to look for improvements for these devices. In early 1940, Winston Churchill organized what became the Tizard Mission to introduce U.S. researchers to several new technologies the UK had been developing.
Loomis arranged for funding under the National Defense Research Committee (NDRC) and reorganized the Microwave Committee at MIT to study the magnetron and radar technology in general. Lee A. DuBridge served as the Rad Lab director. The lab rapidly expanded, and within months was larger than the UK's efforts which had been running for several years by this point. By 1943 the lab began to deliver a stream of ever-improved devices, which could be produced in huge numbers by the U.S. industrial base. At its peak, the Rad Lab employed 4,000 at MIT and several other labs around the world, and designed half of all the radar systems used during the war.
By the end of the war, the U.S. held leadership in a number of microwave-related fields. Among their products were the SCR-584, the finest gun-laying radar of the war, and the SCR-720, an aircraft interception radar that became the standard late-war system for both U.S. and UK night fighters. They also developed the H2X, a version of the British H2S bombing radar that operated at shorter wavelengths in the X band. The Rad Lab also developed Loran-A, the first worldwide radio navigation system, which originally was known as "LRN" for Loomis Radio Navigation.[2]
During the 1930s, several nations developed radio detection systems under tight secrecy. The United States Naval Research Laboratory and Army Signal Corps Laboratories pursued separate radar programs focused on different wavelengths and applications. The Navy developed VHF systems for fleet air warning, installing its first production sets (CXAM) on capital ships in 1940. The Army concentrated on searchlight control and gun laying, fielding mobile sets like the SCR-270 for long-range aircraft detection.[3] Britain established the first operational radar network in December 1935, installing five stations on its east coast that expanded to a comprehensive Chain Home system by 1939.[4]
The potential advantages of shorter-wavelength microwave systems were understood, particularly for airborne applications where compact antennas were essential, but existing microwave generators like the klystron produced insufficient power for practical radar.[5] In February 1940, physicists John Randall and Harry Boot at Birmingham University invented the resonant cavity magnetron, generating kilowatts of microwave power at ten-centimeter wavelengths and representing a thousandfold improvement over competing technologies.[6] By August 1940, British researchers had demonstrated the magnetron tracking aircraft in flight.[6]
Mobilization of civilian science
First NDRC meeeting, June 1940
In June 1940, responding to European military developments, Vannevar Bush and a group of top academic officials proposed mobilizing American scientists for defense research. President Roosevelt approved Bush's plan on June 12, issuing an executive order on June 27 creating the National Defense Research Committee (NDRC).[7] The NDRC organized into five divisions addressing different military-scientific problems, with Division D covering detection, controls, and instruments.[8]
MIT president Karl Compton, head of Division D, established a microwave section in mid-1940. Heading the section, which became known as the Microwave Committee, was Alfred Loomis, a physicist and banker who operated a private laboratory at Tuxedo Park.[9] During summer 1940, committee members investigated American radar efforts and concluded that microwave techniques offered significant potential, though they encountered the same fundamental obstacle British researchers had faced: the lack of a suitable high-power microwave source.[4]
Following the fall of France in June 1940, Prime Minister Winston Churchill and President Roosevelt agreed to pool technical secrets for joint weapons development. In late August 1940, Britain organized the Tizard Mission to share recent technological advances with American researchers.[10] Among the mission's contents was a cavity magnetron, brought to the United States by "Taffy" Bowen, a radar scientist from Britain's Telecommunications Research Establishment.[11]
On September 19, 1940, Bowen demonstrated the magnetron at Alfred Loomis's apartment in New York, producing results that astonished the assembled NDRC Microwave Committee members. The device generated approximately 15 kilowatts at 10-centimeter wavelength.[12] Subsequent meetings at Tuxedo Park in mid-October established priorities for microwave radar development, including airborne interception radar, navigation systems, and gun-laying systems.[13]
The committee concluded that exploiting the magnetron required establishing a dedicated central laboratory staffed by research physicists. Initial plans to locate the facility at Bolling Field in Washington encountered delays, and it became clear that NDRC lacked authority to operate laboratories directly but could contract with existing institutions.[14] Independent surveys by Bush and the Microwave Committee both identified MIT as the institution best positioned to provide the necessary space, scientific staff, and capacity for rapid expansion.[15]
Frank Jewett of Bell Telephone Laboratories proposed locating the laboratory at Bell's facilities, citing his organization's experience managing similar research during World War I. However, Bush, Loomis, and Edward Bowles pressed for an academic location. On October 17, 1940, they secured Compton's agreement to host the laboratory at MIT, though Compton had reservations and recused himself from the formal decision.[16][17]
NDRC approved the contract on October 25, 1940, with initial funding of $455,000. Loomis selected the laboratory's location on the MIT campus and chose the name "Radiation Laboratory" to suggest similarity to Ernest Lawrence's nuclear physics facility at Berkeley rather than reveal its radar mission.[18] Recruitment began immediately, drawing primarily on nuclear physicists familiar with high-frequency techniques from accelerator work. Lawrence declined the directorship, but used his extensive network to recruit top researchers, including Kenneth Bainbridge from Harvard and Lee DuBridge from the University of Rochester, whom NDRC appointed as director.[19]
Late October 1940, approximately 600 scientists gathered in Boston for a conference on applied nuclear physics. Loomis and Bowles organized laboratory visits and special seminars on microwave techniques. At an October 30 luncheon at the Algonquin Club, Loomis and Compton briefed about two dozen recruits who signed secrecy agreements before receiving details on the laboratory's mission.[20] Within weeks, the effort had attracted Isidor Rabi from Columbia, who brought students Jerrold Zacharias and Norman Ramsey, as well as Luis Alvarez and Edwin McMillan from Berkeley. The laboratory officially opened in November 1940 with approximately 20 scientists working in MIT's Building 4.[21]
Operations
Governance
The laboratory operated as a civilian contractor under OSRD's Division 14, which was reorganized from the original Microwave Committee in November 1942.[22] Alfred Loomis chaired Division 14, which supervised the laboratory's work and coordinated radar research across multiple contractors. Lee DuBridge directed the laboratory itself, supported by two associate directors: Isidor Rabi oversaw scientific and technical matters, while F. Wheeler Loomis managed administrative operations beginning in January 1941.[23] One laboratory member characterized the division of labor succinctly: DuBridge said "Yes." Loomis said "No."[24]
DuBridge maintained a collegial management style, operating the laboratory as what he termed a "scientific republic" rather than imposing hierarchical control. A steering committee met weekly to review general tasks and set priorities, leaving implementation to individual research teams.[25] The steering committee drew members from leading universities across the country, reflecting the laboratory's role in aggregating top researchers at MIT.[26] MIT handled facilities, security, and fiscal administration, while technical direction remained with the laboratory's scientific leadership.[26]
The laboratory's status as a civilian contractor managing classified military research represented a novel organizational model. OSRD maintained relationships with both Army and Navy through liaison officers who resided at the laboratory. The laboratory worked directly with military commands to understand operational requirements and deployed personnel to battlefronts and bases to refine systems and train operators.[27] Ed Bowles, the Microwave Committee's first secretary, served as expert consultant to Secretary of War Henry Stimson beginning in April 1942, advising on all radar matters including procurement, training, and operations.[27][28] Tizard Mission members Taffy Bowen and Denis Robinson remained at the laboratory as liaisons from its British counterpart, the Telecommunications Research Establishment.[29]
Personnel
The laboratory grew from approximately 20 scientists in November 1940 to a peak of 3,897 employees in August 1945, comprising 1,189 staff members (scientists and engineers), 1,301 nonstaff men, and 1,407 nonstaff women.[30] Over the course of the war, the laboratory employed a cumulative total of more than 6,200 people.[30]
Recruitment drew primarily on university physics departments, exploiting networks established through prewar accelerator research. Ernest Lawrence proved an effective headhunter, using his connections to attract researchers familiar with high-frequency techniques.[19] By 1945, sixty-nine academic institutions were represented on the staff.[31] Although physicists predominated, recruits came from fields including physiology, political science, architecture, music, optics, mathematics, anthropology, and astronomy.[25] Nevertheless, one observer noted, the laboratory remained "a physicist's world, run for, and as completely as possible by, physicists."[25]
Microwave radar development depended heavily on young male scientists whose training in the new techniques older researchers often lacked.[32] This created recurring tensions with Selective Service. In spring 1944, the Massachusetts State Selective Service Director demanded fifty men from the laboratory, which would have disrupted a substantial portion of its work. MIT President Karl Compton protested directly to Undersecretary of War Robert P. Patterson, writing that "nine tenths of the worries of my most effective colleagues have been spent on this subject" and that morale had reached "an all-time low."[32] Intervention by Vannevar Bush and OSRD secured the retention of the selected staff.[32]
As the draft depleted male technicians, draftsmen, and mechanics, the laboratory recruited and trained women. By war's end, roughly as many women worked in technical positions as in secretarial and clerical roles.[33] Salary administration posed its own challenges: staff members on academic leave received salaries tied to their home institutions, while those recruited from industry commanded higher pay. Discrepancies grew pronounced enough that a 1942 restructuring authorized selective merit increases to prevent what administrators feared would be a collapse in morale.[34]
Contracting and industrial collaboration
MIT received $106.8 million in OSRD research contracts, making it the largest university contractor and accounting for 23.1% of all OSRD research spending; 94% of MIT's funding supported radar research at the Radiation Laboratory.[35] The radar program consumed $156.9 million across 183 contracts, with the Radiation Laboratory representing 64.9% of this total.[36] OSRD contracts operated on a cost-reimbursement basis, covering direct expenses plus overhead calculated proportionally to the contractor's overall operations.[37] The laboratory operated under OSRD's 'short form' patent clause, giving the government title to inventions rather than merely licensing them.[38]
Industrial collaboration proved central to the laboratory's operations. From its inception, the laboratory worked closely with Bell Labs, General Electric, RCA, Westinghouse, and Sperry Gyroscope, who supplied components, collaborated on systems development, and exchanged technical staff.[39] As the laboratory expanded, it contracted research and development work to other institutions when projects required distinct expertise, placing liaison staff with these contractors.[39] The laboratory also organized limited "crash" production of experimental units through the Research Construction Company, enabling rapid fielding of prototypes before full military procurement began.[39][40] Between 1943 and 1945, these "red ticket" procurements delivered over $30 million worth of equipment to the Army and Navy, representing approximately 22% of Division 14's total allocations.[41]
Research organization
The laboratory initially organized work around radar components. Early recruits chose specializations collaboratively, selecting transmitters, receivers, or antennas in what Rabi characterized as choosing sides "just like a baseball team."[42] This component-based structure evolved as specific system development projects grew in scale.
As projects multiplied, the laboratory developed a functional division structure addressing different applications: airborne interception, fire control, navigation, blind bombing, and early warning systems. The steering committee established priorities among conflicting projects after consultation with service representatives.[43] Division 14 supervised 136 contracts with 18 academic or private research institutions and 110 contracts with 39 industrial organizations for fundamental research, component development, systems development, and training equipment.[44]
The laboratory established an overseas presence beginning in September 1943 with the British Branch of the Radiation Laboratory (BBRL) at Malvern, England, directed by L.C. Marshall.[45] BBRL's mission prioritized supporting U.S. forces in the European theater while collaborating with British scientists on radar development and modification. John Trump later expanded and reorganized the British Branch in early 1944 to handle increased demands from the Eighth Air Force.[46]
As the Rad Lab started, a laboratory was set up to develop electronic countermeasures (ECM), technologies to block enemy radars and communications. With Frederick E. Terman as director, this soon moved to the Harvard University campus (just a mile from MIT) and became the Radio Research Laboratory (RRL). Organizationally separate from the Rad Lab, but also under the OSRD, the two operations had much in common throughout their existences.
Facilities
The laboratory began operations in November 1940 in modest quarters: approximately 10,000 square feet in MIT's Building 4 and rooftop space atop Building 6.[47] Within months, the laboratory had spread across MIT's campus and into nearby buildings. Flight testing commenced at the National Guard Hangar at East Boston Airport in July 1941.[47][48]
The laboratory's dispersal accelerated through 1941. By early 1942, operations spanned five separate locations: the original spaces in Buildings 4 and 6, laboratories and shops borrowed from the Mechanical Engineering Department in Building 3, Building 24 (a permanent fireproof structure erected in autumn 1941), and the old Hood Milk Company Building on Massachusetts Avenue two blocks from the main campus.[49][47] This fragmentation across 111,000 square feet of scattered space created coordination challenges as the laboratory's work intensified following Pearl Harbor.[49]
MIT campus with Rad Lab buildings, circa 1945
MIT built aggressively to keep up with personnel growth. Construction began in April 1942 on Building 22, a three-story temporary wooden frame structure that connected to Building 24 by an overpass, while Building 24 itself gained four additional floors and a penthouse.[50] Yet the laboratory continued to outpace available space. President Compton protested the ongoing practice of renting rooms in scattered Cambridge buildings and pushed for a third major structure.[51]Building 20, hastily designed and constructed of mill lumber with transite interior walls, rose in three wings in 1943, ready for occupancy in early 1944. Two additional wings followed as personnel continued to arrive.[51]
Flight operations similarly outgrew their initial quarters. Larger aircraft and the need for longer runways drove relocation from East Boston to Bedford Army Air Base in May 1944, where the laboratory occupied 43,000 square feet of hangar space.[48] The Army and Navy each established dedicated flight units to support testing operations: by war's end, the Navy's Special Project Unit Cast operated 35 aircraft with 138 personnel, while the Army's 1st Electronics Experimental Detachment maintained 60 aircraft with 166 personnel.[52] At its August 1945 peak, the laboratory's 3,897 employees worked across more than 400,000 square feet of laboratory and office space, a forty-fold expansion from its November 1940 origins.[52]
The laboratory's "crash program" production required sending personnel to combat theaters. Devices shipped before systematic testing needed scientists who had built them to handle installation and develop techniques for operational use.[53]
In September 1943, the laboratory established the British Branch of the Radiation Laboratory (BBRL) at Great Malvern, England, alongside the British Telecommunications Research Establishment. John Trump directed BBRL through most of its existence, reorganizing and expanding the operation in early 1944 to meet growing demands from the Eighth Air Force.[54] The branch eventually numbered approximately 100 personnel, with most deployed to air bases across Britain and the continent. Following the liberation of Paris in summer 1944, BBRL established an Advanced Service Base there.[55] The official OSRD historian characterized BBRL as "pools of personnel, equipment, shop, and know-how" for modification, debugging, and field assistance rather than a laboratory in the traditional sense.[56]
Plans for a similar field operation in the Pacific took shape in spring 1945, when OSRD organized a Pacific Branch under Karl Compton's direction. General Douglas MacArthur's headquarters approved the arrangement, but Japan's surrender came before the organization became fully operational.[57]
Early development
Early microwave radar tests
The laboratory's first months tested whether microwave radar could work at all. Staff members spent November and December 1940 in an intensive effort to meet a self-imposed January deadline: build a working radar system around the British cavity magnetron.[58] The device presented formidable challenges. No American had built a microwave radar, and the short wavelengths required entirely new components. The laboratory's initial staff—physicists, not radar engineers—improvised as they went. On January 4, 1941, two days ahead of schedule, the first test system came to life on the roof of MIT's Building 6. An unwieldy transmitting antenna occupied one end of the rooftop, with the receiving aerial on the other, shielded from its counterpart by a loose screen cage. Within minutes of being switched on, the system registered echoes from the Boston skyline across the Charles River.[n 1]
The rooftop success proved microwave radar feasible but left critical engineering challenges unsolved. The test system used separate transmitting and receiving antennas, an arrangement impossible in aircraft, where size and weight were tightly constrained. A practical airborne radar required a single antenna that could both transmit pulses and receive echoes. This demanded a transmit-receive (TR) switch that could shield the delicate crystal detector from the outgoing pulse's energy, then recover within microseconds to let in the faint returning signals. Jim Lawson, one of the few staff members with a strong amateur radio background, attacked the problem. By January 10, his team had fashioned a workable TR box using a klystron tube as a buffer. A second rooftop test that day demonstrated the first single-antenna microwave radar, prompting DuBridge to telegram Washington: "have succeeded with one eye."[59] Luis Alvarez later asserted that "if we had been paid in proportion to our contributions to the success of the first microwave radar program, Jim Lawson would have earned more than half the monthly payroll."[60]
Flight tests followed. On March 27, Edwin McMillan's team flew the first American microwave radar in a B-18 bomber, detecting aircraft and ships—and, unexpectedly, a surfaced submarine three miles away over water near New London.[61] The discovery pointed toward a capability the laboratory had not originally prioritized.
The U-boat peril
The laboratory's founding projects had emphasized aircraft interception and anti-aircraft fire control, reflecting the Battle of Britain's lessons about the threat of night bombing. By mid-1941, however, Britain had defeated the Luftwaffe's daylight offensive, and a different crisis demanded attention. German U-boats operating from French ports were sinking merchant ships faster than Allied shipyards could replace them. Longwave air-to-surface-vessel radar (ASV) existed but performed poorly against submarines: sea clutter cut detection ranges, and the radar's meter-length waves allowed U-boats to detect approaching aircraft in time to submerge before attack.[62]
In July 1941, Denis Robinson arrived from Britain's Telecommunications Research Establishment with instructions to redirect the laboratory toward anti-submarine radar. Robinson, whose family had already evacuated to Massachusetts, brought firsthand knowledge of the submarine war's urgency.[63] DuBridge began phasing out the original aircraft interception project and raising the priority of air-to-surface-vessel work.[64]
That summer, comparison tests between British and American airborne sets revealed that British crystal detectors and TR boxes significantly outperformed their American counterparts.[65] Norman Ramsey returned from England with samples of the superior components, sparking intensive efforts to match and exceed them. By fall 1941, the laboratory carried at least five ASV projects on its books, each tailored to different aircraft types.[64] Trials aboard the destroyer USS Semmes demonstrated shipboard potential: a prototype radar incorporating the Plan Position Indicator guided the vessel and three submarines safely into harbor through heavy fog, detecting buoys that visual lookouts could not see.[66] The Navy placed a production order with Raytheon for what became the SG radar, later called "one of the most widely used and effective of all shipboard radars."[61]
The shift from research to production accelerated after Pearl Harbor. In early 1942, German U-boats began Operation Paukenschlag, attacking virtually undefended American coastal shipping. In January and February, Army Air Forces planes without radar managed attacks against only four U-boats in 8,000 flying hours.[67] DuBridge made ASV his top priority. Ten B-18 bombers arrived at East Boston Airport for crash installation of microwave radar. The laboratory's model shop, the Research Construction Company, built fifty ground-based sets by hand for the Signal Corps; five of these became the first microwave ground equipment to see combat, deployed during the North Africa invasion in November 1942.[61][68]
The crisis also forced organizational changes. In early 1942 the laboratory reorganized into specialized divisions—transmitter components, receiver components, indicators, and so on—to handle the expanding workload.[1] By the end of that year, staff had grown from the original thirty to over a thousand, and the laboratory occupied fifteen buildings across the MIT campus.[69] The pattern established in these months—identify an operational problem, develop a prototype solution, support field deployment while handing production to industry—would define the laboratory's approach throughout the war.
Major combat systems
Anti-submarine warfare
German U-boats nearly severed Britain's Atlantic lifeline in the winter of 1942–43. Wolf packs attacked convoys at night, surfacing to use their high speed for pursuit and escape. Existing longwave radar could detect surfaced submarines, but the meter-length waves also triggered receivers aboard U-boats, giving crews warning to submerge before aircraft arrived.[62] In the first twenty days of March 1943, U-boats sank ninety-five Allied ships—more than half a million tons—while the Allies destroyed only twelve submarines, barely half Germany's monthly production.[70]
SG radar console, including Plan Position Indicator (PPI) display
Microwave radar changed the equation. The laboratory's 10-centimeter ASV (air-to-surface-vessel) sets detected surfaced submarines before U-boat receivers could warn of approaching aircraft; German technology could not yet detect the shorter wavelengths. The SG radar provided similar capability for escort vessels, displaying targets on a Plan Position Indicator that showed bearing and range at a glance.[61] At the end of March 1943, Liberators equipped with extra fuel tanks and microwave radar, navigating by Loran, established a shuttle service between Britain, Iceland, and Newfoundland, closing the mid-Atlantic gap where wolf packs had operated beyond the reach of shore-based aircraft.[71] By war's end, Loran stations covered approximately 30 percent of the Earth's surface and served 75,000 aircraft and surface vessels.[72]
The results were immediate. In May 1943, the Allies destroyed forty-one U-boats while losing forty-five merchant ships—a ratio unthinkable two months earlier.[73] Admiral Karl Dönitz withdrew his submarines from the North Atlantic on May 24.[73] British naval historian Stephen Roskill later judged that centimetric radar "stands out above all other achievements because it enabled us to attack at night and in poor visibility."[74]
Blind bombing
The Eighth Air Force's strategic bombing campaign faced a simple problem: weather. Cloud cover over Germany was persistent and thick; severe storms swept the corridor between London and Berlin every three days on average.[75] During the winter of 1942–43, heavy bombers could operate only one or two days per month.[76]
The British had developed H2S, a 10-centimeter radar that displayed terrain on a scope, allowing bombers to navigate and release weapons through overcast. The Radiation Laboratory built H2X, a 3-centimeter version with sharper resolution and immunity from German detection equipment.[77] On November 3, 1943, nine B-17 Pathfinders equipped with H2X led sixty bombers against the Wilhelmshaven docks—a target that eight previous visual missions had missed entirely.[76][78]
H2X transformed the tempo of operations. In November 1943, no day's weather forecast would have warranted a visual attack on Germany, yet the Eighth attacked German targets nine times.[79] In December, the Eighth dropped more bombs than in any previous month and for the first time exceeded RAF Bomber Command's tonnage.[79] By year's end, the original twelve H2X aircraft were leading 90 percent of American bombing missions; bomb tonnage dropped via H2X in the last two months of 1943 exceeded the total dropped by visual sighting over the entire year.[76] From mid-October 1943 to mid-February 1944, the official Army Air Forces history notes, "the story of daylight strategic bombing from the United Kingdom is essentially the story of an experiment in radar bombing."[75]
H2X accuracy was poor by precision-bombing standards—a circular error probable of roughly two miles.[80] Air planners concluded that "it seemed better to bomb low-priority targets frequently, even with less than precision accuracy, than not to bomb at all."[75] General James Doolittle acknowledged the limitations but remained committed: he "was willing to send 100 planes to do a 10 plane job" rather than wait for better equipment.[80]
The radar proved essential when strategic bombing turned to oil. On June 8, 1944, General Carl Spaatz ordered that denying oil to Germany would be the primary strategic aim—an order that remained in force until the war ended.[81] German defenders responded with smoke screens that made visual bombing of refineries "almost impossible."[82] The Fifteenth Air Force relied on H2X to attack the Ploești refineries through artificial smoke, eventually flying twenty daylight missions that denied the Germans an estimated 1,800,000 tons of crude oil.[83] By September 1944, German oil production had fallen to 23 percent of pre-campaign levels; of ninety-one installations still in German hands, only three were in full production.[84]
Anti-aircraft fire control
Existing anti-aircraft systems in 1941 relied on searchlights to illuminate targets and human operators to track them. The process was slow and inaccurate; guns fired static barrages hoping bombers might fly into the flak.[85] German chaff and jamming rendered longwave fire-control radars nearly useless.[86]
The laboratory's physicists proposed something more ambitious. While parallel British and Canadian programs aimed merely to add microwave radar to existing manual tracking, Louis Ridenour pushed for a fully automatic system. He assembled a team including Ivan Getting and Lee Davenport to develop a radar that would lock onto targets and follow them through evasive maneuvers without human intervention.[85]
The cornerstone was conical scanning, a technique in which a rotating antenna beam traced a cone in space. A target on axis returned a constant signal; any deviation produced amplitude variations that servomotors converted into corrections, automatically realigning the radar.[85] To test the concept, the team conscripted a servo-driven gun turret from General Electric's B-29 program and mounted their prototype in the Building 6 rooftop laboratory. Local air traffic was too sparse to provide reliable test targets, so Harvard geologist Dave Griggs agreed to fly his personal Luscombe aircraft around Cambridge for $10 an hour, simulating an enemy.[87] On May 31, 1941, with Davenport in the back seat radioing observations, the team achieved the first automatic tracking of an aircraft by radar.[88]
When tested at Fort Monroe in February 1942, the prototype located objects within six-hundredths of a degree and twenty yards in range.[89] The Army ordered over 1,200 units, designating the radar SCR-584.[90] Connected to the Bell LabsM-9 predictor, which calculated where targets would be when shells arrived, the system transformed anti-aircraft gunnery. Nearly 1,700 sets were produced.[91]
The SCR-584's most dramatic success came against the V-1 flying bomb. Beginning in June 1944, Germany launched thousands of pilotless weapons against London. The SCR-584, combined with the proximity fuze—a miniature radar in the shell nose that detonated when near a target—eliminated the need for direct hits.[91] Before this combination entered service, anti-aircraft guns destroyed fewer than one V-1 in four; afterward, they destroyed approximately 85 percent of targets engaged.[92][93]
Tactical air control
Coordinating hundreds of aircraft over a battlefield required real-time tracking at long range. The laboratory's Microwave Early Warning (MEW) system used a phased-array antenna 24 feet wide that could track aircraft to 175 miles.[94] The first operational MEW, installed at Start Point in Devon, captured a time-lapse photographic record of the D-Day air operations.[95]
A second application emerged from an informal gathering at Claridge's Hotel on March 23, 1944. DuBridge, Ridenour, and other laboratory representatives discussed using the SCR-584—originally designed for anti-aircraft fire—to control tactical bombers in close support of ground forces.[96] Ridenour presented the concept to General Lewis H. Brereton at Ninth Air Force headquarters, leading to a formal evaluation under General Otto P. Weyland.[96]
A demonstration on June 25, 1944 made the case dramatically. At a site near Malvern, observers watched through a loudspeaker system as a controller directed Typhoon pilots by radio. Just as the countdown reached zero, the squadron leader wheeled into a 120-degree turn and led his flight in a steep dive directly toward the watching party—having located the target solely through radar guidance.[97] The first operationally modified SCR-584 reached Normandy on July 9.[98]
When V-1 attacks began, the MEW relocated to Hastings, where it detected buzz bombs 130 miles away—more than twenty miles beyond any other radar—providing crucial minutes for interceptors to reach position.[95] Night fighters, including P-61 Black Widows equipped with the laboratory's SCR-720 airborne interception radar, operated under MEW control.[99] Mobile MEW units accompanied advancing armies for tactical air support. General Orvil Anderson declared: "Within the range of MEW every one of my fighters is worth two outside its range."[100]
Other projects
A radically different type of antenna for X-band systems was invented by Luis W. Alvarez and used in three new systems: an airborne mapping radar called Eagle, a blind-landing Ground Control Approach (GCA) system, and a ground-based Microwave Early-Warning (MEW) system. The latter two were highly successful and carried over into post-war applications. Eagle eventually was converted to a very effective mapping radar called H2X or Mickey and used by the U.S. Army Air Force and U.S. Navy as well as the British Royal Air Force.[101]
The most ambitious Rad Lab effort with long-term significance was Project Cadillac. Led by Jerome B. Wiesner, the project involved a high-power radar carried in a pod under a TBM Avenger aircraft and a Combat Information Center aboard an aircraft carrier. The objective was an airborne early warning and control system, providing the U.S. Navy with a surveillance capability to detect low-flying enemy aircraft at a range in excess of 100 miles (161km). The project was initiated at a low level in mid-1942, but with the later advent of Japanese Kamikaze threats in the Pacific Theater of Operations, the work was greatly accelerated, eventually involving 20 percent of the Rad Lab staff. A prototype was flown in August 1944, and the system became operational early the next year. Although too late to affect the final war effort, the project laid the foundation for significant developments in the following years.[102]
Demobilization and legacy
Postwar transition
When the Radiation Laboratory closed on December 31, 1945, the armed services moved quickly to preserve its capabilities. The laboratory's Basic Research Division continued under OSRD funding through the spring of 1946, then became part of MIT on July 1 as the Research Laboratory of Electronics (RLE).[103] The Joint Services Electronics Program provided $600,000 annually for basic, unclassified research, with the services seeking "a laboratory from which the military services can draw competent technical help at critical times."[104] RLE opened with seventeen faculty members, twenty-seven staff, and graduate students formerly employed by the Rad Lab, occupying the temporary wooden structure of Building 20.[105] MIT's Laboratory for Nuclear Science was founded simultaneously, and both laboratories remained in Building 20 until 1957.[103]
The pattern established at MIT was replicated elsewhere: the Office of Naval Research, drawing on millions of dollars from canceled procurement contracts, became the dominant patron of academic research before the National Science Foundation existed. By August 1946, ONR had issued 177 contracts worth $24 million to eighty-one universities and laboratories.[106]
In 1951, MIT established Lincoln Laboratory to develop air defense systems, building directly on RLE's expertise in radar and digital computing. Located adjacent to Hanscom Air Force Base near Route 128, Lincoln grew rapidly to a staff of two thousand and an annual budget approaching $20 million.[107] Its first major project, the SAGE air defense network, became the largest military R&D enterprise since the Manhattan Project, eventually costing $8 billion.[108]
The laboratory's technical knowledge was preserved in the MIT Radiation Laboratory Series, a 28-volume compilation edited by Louis Ridenour and published by McGraw-Hill between 1947 and 1953. Rabi had initiated the project in fall 1944, concerned that without systematic documentation "there would only be one group who would know all this technology—the Bell Telephone Laboratories."[109] Some 250 staff members stayed after the war's end to work as authors and editors, and Rabi termed the completed effort "the biggest thing since the Septuagint."[106] The series served as the standard reference for a generation of physicists and engineers. The physicist Louis Brown observed that volumes "would be found on the bookshelves of almost every electronics engineer and experimental physicist for more than a generation."[110]
Organizational influence
The Radiation Laboratory demonstrated what MIT physicist John Slater called the "complementarity of basic and applied research"—the productive integration of physics and electrical engineering that the postwar RLE sought to perpetuate.[111] Slater argued that scientists and engineers working together in an interdisciplinary setting could accomplish far more than either could alone, and that such laboratories should supplement the traditional departmental structure of universities.[112]
The wartime contracting model pioneered by OSRD shaped postwar arrangements. Cost-reimbursement contracts covering direct expenses plus overhead, and the short-form patent clause granting the government title to inventions, became standard features of federal research funding.[113] MIT, as the largest OSRD university contractor at $106.8 million (23.1 percent of all OSRD research spending), was the principal beneficiary of these innovations.[35] By 1946–47, MIT's research budget of $8.3 million dwarfed its academic budget of $4.7 million, a relationship that would persist.[111] Leslie has argued that this "golden triangle" of military agencies, defense industry, and research universities reshaped American science in ways that extended well beyond budgets, channeling research toward military applications at the expense of other priorities.[114]
The laboratory also influenced research style. Buderi characterized the wartime approach as "interdisciplinary, cooperative, hard-driven," and noted that this manner of working shaped postwar academic, industrial, and government laboratories.[106] Rabi and Norman Ramsey drew on their Rad Lab experience when organizing Brookhaven National Laboratory in 1946 as a shared facility for East Coast universities.[106] Two former RLE directors emerged from the Rad Lab, Julius Stratton and Jerome Wiesner, and later became MIT presidents; Wiesner also served as science advisor to President Kennedy.[115]
Technological and regional impact
The Boston area was not an electronics center before the war. The Radiation Laboratory and the smaller Harvard Radio Research Laboratory transformed it into one.[116] Middlesex County experienced what Gross and Sampat describe as a "nearly thirtyfold increase in electronics patenting during the war," with patenting in 1960 remaining ten times prewar levels.[117] The Rad Lab has been widely credited with jump-starting the Route 128 technology corridor by establishing an ecosystem of universities, government laboratories, and firms.[117]
RLE gave rise to fourteen companies in its first two decades, most specializing in microwave electronics and devices.[118] Lincoln Laboratory spawned additional spinoffs. A 1961 Boston bank study suggested replacing the textile spindle with the Hawk missile as the symbol of the local economy.[118]
Commercial applications proliferated. Raytheon, General Electric, and Westinghouse built marine radar and air traffic control systems derived from wartime designs. The SG radar became the basis for postwar navigation systems, and the Microwave Early Warning radar influenced civilian air traffic control.[119] Loran was adopted by commercial shipping and aviation; by war's end the system covered approximately 30 percent of the Earth's surface.[72] Microwave techniques opened roughly two hundred times more radio channels than had previously existed, enabling the postwar expansion of telecommunications.[120]
The laboratory's influence extended through its personnel. Director Lee DuBridge left in 1946 to become president of the California Institute of Technology, a position he held for twenty-three years; he subsequently served as science advisor to Presidents Truman, Eisenhower, and Nixon. Several laboratory members moved between the major wartime research centers: Kenneth Bainbridge and Luis Alvarez, among others, worked at both the Rad Lab and Los Alamos before the war ended.[110] Nine laboratory members later won Nobel Prizes:
At least two Nobel Prizes—for nuclear magnetic resonance and the maser—can be traced directly to wartime radar work.[121] Denis Robinson, who had come from Britain in 1941 to redirect the laboratory toward anti-submarine radar, found after the war that mentioning his Radiation Laboratory experience was "like an 'open sesame' to leading physicists in the United States and Britain."[122]
With the cryptographic work at Bletchley Park and Arlington Hall and the Manhattan Project, the Radiation Laboratory represents what Baxter called one of "the most significant, secret, and outstandingly successful technological efforts" of the Anglo-American wartime alliance.[123] The laboratory was designated an IEEE Milestone in 1990.
Buderi, Robert (1996). The Invention that Changed the World: How a Small Group of Radar Pioneers Won the Second World War and Launched a Technological Revolution. Simon & Schuster.
Zimmerman, David (1996). Top Secret Exchange: the Tizard Mission and the Scientific War. McGill-Queen's Univ. Press.
Fine, Norman (2019). Blind Bombing: How Microwave Radar brought the Allies to D-Day and Victory in World War II. Nebraska: Potomac Books/University of Nebraska Press. ISBN978-1640-12279-6.
Willoughy, Malcom Francis (1980). The Story of LORAN in the U.S. Coast Guard in World War II. Arno Pro.
Studies
Gross, Daniel P.; Sampat, Bhaven N. (2023). "America, Jump-Started: World War II R&D and the Takeoff of the U.S. Innovation System". American Economic Review. 113 (12): 3323–3356. doi:10.1257/aer.20221365.
Participant accounts
Bowen, Edward G. (1987). Radar Days. Inst. of Physics Publishing.
Historical MIT Radiation Laboratory Book Series(archive)
Volume 1 - Radar System Engineering; Louis Ridenour; 1947
Volume 2 - Radar Aids to Navigation; John Hall; 1947
Volume 3 - Radar Beacons; Arthur Roberts; 1947
Volume 4 - LORAN, Long Range Navigation; J.A. Pierce, A.A. McKenzie, R.H. Woodward; 1948
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
