When Israeli Aircraft Industries created the Kfir fighter-bomber by replacing the SNECMA Atar turbojet with a more powerful GE J79 engine, the additional modifications required to accommodate the American engine (which was shorter but heavier) along with the avionics needed for the strike role and the heavier undercarriage to increased takeoff weights with heavy bombloads degraded the performance and maneuverability of the the first generation Kfirs. Rather than try increasing the thrust of the J79 engine, IAI engineers decided the solution would have to be an aerodynamic one.

The addition of canards was favored early on and Dassault cautioned IAI about adding canards to the aircraft based on the French experience with the Mirage Milan canard test aircraft. Despite the warnings, no other solution was seen as being viable, so flight testing of the canard proceeded on the Technolog, a two-seat Mirage III that first tested the installation of the J79 engine.

Nose strakes near the tip of the nose were also found (even before the canard solution was reached) to improve high AoA performance but this came at the cost of buffeting at high AoAs, something that would have been unacceptable in air combat. The buffeting was cured on the suggestion of one of the IAI test pilots to add a wing leading edge saw-tooth which helped smooth the local airflow.

These modifications improved the Kfir's performance with the addition of wing area in the form of the canards that shifted the aircraft center of gravity forward, reduced the stability margin enough that the aircraft would be more responsive. The vortices that came off the canard smoothed the airflow over the delta wings which enhanced their lift and performance particularly at high angles of attack. The saw-tooth leading edges also slightly increased wing area and the vortices created by the saw tooth augmented the canard-produced vortices.

The combination of these modifications only added 187 lbs of weight to the new Kfir version designated C2. The side benefit of the structural strengthening of the fuselage for the canards (fuselage Section 10) is that that area was able to also accommodate an additional pair of weapons pylons under the intakes, giving the Kfir a total of five underfuselage pylon stations.

The Kfir C2 entered service with the IDF in 1977. The earlier Kfir C1s only got the nose strakes and a much reduced canard as the structural strengthening and modification to full C2 standards was deemed not worth the effort. Many of those earlier-variant Kfir C1s flew with US Navy and US Marine Corps adversary units in the 1980s as the F-21A Lion.

Source: International Air Power Review, Volume 15. AIRtime Publishing, 2005, "Warplane Classic: IAI Kfir- Israel's Lion Cub" by Shlomo Aloni, p137-139.

The Most Ambitious UAV Ever: Quartz/AARS

One of the most ambitious if not the most expensive UAV design effort came in the 1980s as the Cold War was coming to its climax. Over $1 billion was spent on a black project called the AARS- Advanced Airborne Reconnaissance System or known by its code name, Quartz. The Quartz UAV was designed to be a very stealthy, long-endurance UAV that would penetrate Soviet air space in a time of war and identify what were called "strategic relocatable targets"- the rail- and road-mobile ICBMs of the Soviet's Strategic Rocket Forces. Quartz was sponsored by the US Air Force and the NRO, National Reconnaissance Office.

The requirement for a 24-hour endurance and low-observability tested the limits of aerospace technology of the day. In 1983 Lockheed and Boeing were selected to develop concepts for the Quartz program. Lockheed's initial design was a giant aircraft with a 267-foot wingspan propelled by two turboshaft engines driving massive 47-foot propellers. The engines were actually dual-cycle turboshaft/turbojet engines, with the engines operating as jets and the two-bladed props locked in horizontal for takeoff and landing. Once at cruise altitude, the engines shifted into turboshaft mode to drive the large props.

Little is known of Boeing's design for Quartz other than it may have been a flying wing design along the same lines as the Lockheed proposals. The need for low-observability and autonomous operation in denied airspace resulted in an expensive design that was compounded by the fact that only a few Quartz UAVs would be needed- the technology used was so sensitive that only the strategic imperative made it worth the risk of losing the aircraft in the event of malfunction or shootdown.

As the costs of the program soared, it became a victim of an inter-agency squabble between the CIA and the NRO who wanted Quartz and the USAF, who was losing interest due to the rising costs. In 1990 Lockheed and Boeing were directed to combine their efforts which resulted in a jet-powered flying wing not too dissimilar from the Northrop B-2 Spirit stealth bomber. As the costs still continued to climb, the USAF continued to back away from the program and even a redesign for a slightly smaller version failed to bring the USAF back aboard. Quartz was cancelled in 1992 when the NRO finally withdrew from the program as well.

In the 1990s, there were three "tiers" of UAV development based on operational capability. "Tier I" was for a low-altitude system that became the Gnat-750 UAV. "Tier II" was for a more capable medium altitude system based on the Tier I craft and that became the current Predator UAV family. The specification for "Tier III" would have been filled by the Quartz project, but with its cancellation, Tier III was split into two- Tier II+ was for the Quartz's performance without stealth and this became the RQ-4 Global Hawk UAV. Tier III- ("Tier III Minus") was stealthy but without the performance and payload of Tier II+. This design became the RQ-3 DarkStar. DarkStar, a joint effort between Boeing and Lockheed, had little in common with Quartz and itself would be canceled in 1999 in favor of further development of the Global Hawk.

However, it's believed that the current Lockheed/Boeing proposals for a next-generation bomber (the picture included in this blog post) are nearly identical save the cockpit to the resultant Quartz design.

Source: International Air Power Review, Volume 15. AIRtime Publishing, 2005, "Focus Aircraft: HALE/MALE Unmanned Air Vehicles Part 1: History of the Endurance UAV" by Bill Sweetman, p63-69.

In 1967 Operation Combat Dragon commenced in Vietnam which would be the baptism of fire for the Cessna A-37 Dragonfly. An attack version of the T-37 trainer, the intent of the Dragonfly was to provide a low-cost yet capable close air support aircraft, a role that the faster jet fighter in the theater weren't exactly tailored to perform.

Conceived by Lt. Colonel Lou Weber, a veteran of the World War Two Flying Tigers, Operation Combat Dragon would introduce the Dragonfly into combat in a unique manner- whereas most combat aircraft had their weapons certification, weapons loading and maintenance procedures hammered out in operational testing in the United States before deploying to operational units, the Dragonfly would gain its combat certification by testing in actual combat.

Thirty pilots were selected for Operation Combat Dragon, all of whom had no more than 25 hours in the T-37. All came from all types of aircraft, from fighters to transports- Weber wanted to make sure that a pilot with any experience from any level could fly the A-37 in combat. Most deploying units to Vietnam had nine month training programs stateside before heading overseas- but with the A-37, the training was going to be done "on the job". Combat missions were to be flown in the III and IV Corps area of South Vietnam and forward air controllers favored the A-37- its slower speed allowed for pinpoint accuracy in delivering weapons on target.

The unit had the provisional designation 604th Air Commando Squadron and was based at Bien Hoa AB. In its first 3,000 sorties, not a single A-37 Dragonfly was lost in combat. Operation Combat Dragon ran from August 1967 to December 1967 and in that time frame, Lt. Col. Weber's strategy was soundly vindicated with 19,000 weapons drops and the combat experience led Cessna to develop an improved version, the A-37B. After nine months in combat, the unit had flown an astounding 10,000 sorties and reflected that it only took two men to maintain and turnaround the Dragonfly where as most jet fighters required 10 or more men per plane. On many missions a Dragonfly could be turned around for the next sortie in as little as 90 minutes. The unit would average twice the number of sorties as the more advanced and faster jets in Vietnam.

Source: Air & Space Smithsonian, January 2010. "Super Tweet- The A-37 Dragonfly carried 6,000 pounds of weapons. Bonus: They hit the target" by Stephen Joiner, p42-49.

The Igloo White air-dropped acoustic sensors used in the Ho Chi Minh Trail during the Vietnam War to detect truck traffic weren't the last word in remote sensing technology for airborne interdiction. During Operation Iraqi Freedom, Steel Eagle was developed at the weapons research laboratories at Eglin AFB, Florida. Once a classified program, Steel Eagle came to light during the conflict as a possible asset in detecting and destroying mobile Scud missile launchers used by the Iraqis. Like Igloo White from the Vietnam War, Steel Eagle was a slim aircraft-dropped pod that contained acoustic and seismic sensors that activated once the pod was embedded in the ground near possible travel routes.

According to aviation author Steve Davies in his book on F-15E Strike Eagle units in combat (see source below), only about 35 of the Steel Eagle pods were made and were flight tested from an F-15E at the Nellis AFB ranges during OIF. The problem with the project is that there was no ballistics information on the pod provided for the weapons delivery system of the F-15E which made it difficult to accurately place. However, testing is said to have validated the basics of the system but no Steel Eagle pods were dropped during Operation Iraqi Freedom.

Technology that was validated in Steel Eagle is now part of the military's ARGUS project- Advanced Remote Ground Unattended System.

Source: F-15E Strike Eagle Units in Combat 1990-2005 (Osprey Combat Aircraft No. 59) by Steve Davies. Osprey Publishing, 2005, p86-87.

Following the end of the First World War, Britain and France were determined to put the German aeronautical industry out of business for good with harsh terms being imposed by the Treaty of Versailles. One of the terms involved getting Germany's prized advanced Zeppelin fleet divided between Britain and France. The United States, having operated several LTA (lighter-than-air) patrol stations in France during the war where blimps were used to protect the Atlantic convoys, wasn't a party to the deal but rather than taking on Zeppelins (which the Germans ended up scuttling, infuriating the British and French), Navy personnel were sent throughout Europe to act as "observers" to the Armistice Commission that was essentially dissolving the German aviation industry. One of those Navy personnel, Commander Jerome Hunsaker, who after World War II would become chairman of NACA, NASA's predecessor, made several trips to Europe to study German Zeppelin technology between 1918 and 1920.

By 1919 Commander Hunsaker's influence on what he was learning in Europe convinced the then-Acting Secretary of the Navy, Franklin Delano Roosevelt, to approve preliminary construction of dirigibles to gain experience in LTA operations. The first designs were, like their British and German counterparts, designed for the use of hydrogen gas. But by the end of 1919 FDR on behalf of the Navy established the naval air station at Lakehurst, New Jersey by purchasing 1,700 acres from land that the Army thought was of little use.

During the testing of helium extraction, production and transport methods, the first helium gas arrived at Hampton Roads, Virginia, for testing in a Navy C-class blimp, the C-7. Ten C-class blimps were built in 1918 with production split between Goodyear and B.F. Goodrich and the control cars built by Curtiss Aircraft. It took several months to accumulate enough helium from Fort Worth and on 2 December 1921, the C-7 lifted off with 180,000 cubic feet of helium, making the world's first flight of a helium-filled airship. Fifteen sorties were made to determine the flight characteristics as well as handling methods for a helium-filled airship.

In 1921 the US Navy took the lead in aeronautical development by establishing the Bureau of Aeronautics (BuAer) with the airship-minded Captain William A. Moffett (later Rear Admiral) as its firs chief. One of Moffett's first acts as the head of BuAer was to rationalize airship development, placing Commander Hunsaker in charge. By the following year, the first American dirigible was ready for its first flight. The USS Shenandoah, designated ZR-1 and based on the LZ-49 Zeppelin design would be lifted by helium and the success of the Shenandoah led to the Navy pushing for control of the US helium supply as a strategic asset.

Early flight operations with the USS Shenandoah validated Hunsaker's belief that helium, something that was plentiful in the United States, would be a more suitable lifting gas as it was inert. Helium is often found in some natural gas deposits. Two of Hunsaker's assistants spent most of 1921 working with Linde Air Products Laboratory (then a division of Union Carbide) learning techniques and methods for the extraction, isolation and purification of helium. In 1925 the Bureau of Mines was assigned control of helium extraction and production, taking control of the only helium production plant in the United States at the time in Fort Worth, Texas. Funding would come from both the Army and the Navy defense budgets as helium was already considered a strategic asset.

In the late 1960s the backbone of the Soviet Union's Strategic Rocket Forces (which in the USSR was an independent branch of the military) was the UR-100 ICBM designed by noted Russian rocket designer Vladimir Chelomei. The UR-100 had the NATO designation SS-11 and the code name "Sego" and was a two-stage, liquid propellant missile with a single warhead and was of relatively low accuracy but broadly comparable to the first generation of American Minuteman ICBMs. The Sego was an attempt to reach numerical parity with the United States with a missile that was relatively easy to produce and deploy, reaching IOC with the Strategic Rocket Forces in 1966 after three years of development and flight testing.

With the deployment of the American Minuteman III ICBM which now had three MIRV (multiple independently-targetable re-entry vehicle) warheads instead of a single warhead on the Minuteman I, the Soviets needed to match this technology and in the 1970s to the amazement of US intelligence analysts, deployed three ICBM types to replace the older SS-11 Sego.

The first to reach IOC in 1974 was an upgrade of the SS-11/UR-100 Sego- the UR-100U or SS-11 Mod 3 was based on the original SS-11 design but now had three warheads but the real centerpiece of the upgrade was a newly-hardened missile silo that could better withstand a US nuclear counterstrike.

Next to reach IOC in mid-1975 was the UR-100N which had the NATO designation SS-19 and the code name "Stilleto", which was also designed by Vladimir Chelomei to replace the UR-100/SS-11 Sego missile. The Stilleto was a two-stage liquid fueled missile with six MIRV warheads.

Right behind the Stilleto in reaching IOC with the Strategic Rocket Forces was the competing design to that missile, the UR-100MR which had the NATO designation SS-17 and the code name "Spanker". The Spanker was the first Russian ICBM to be designed with MIRV warheads, having four of them and in a first for the Russians, it used a cold-launch system where compressed gases were used to eject the missile out of the silo before engine ignition. The Spanker was designed by Vladimir Chelomei's rival, Mikhail Yangel .

But the real reason three ICBM systems were fielded by the Soviet Union was that there was disagreement over nuclear strategy. Yangel's SS-17 design would need new hardened silos but offered four warheads over the SS-11's single warhead, making it an effective counterforce to insure retaliation if the USSR were attacked by the United States. However, it was the most expensive of the systems. Chelomei originally offered the upgraded SS-11 Mod 3, which would have fit in existing silos but weren't as hardened as the SS-17 design's silos. Thus, this missile offered more warheads for less money, making it a threatening first strike weapon since it would have been vulnerable to a US counterstrike.

Soviet Premier Leonid Brezhnev called a meeting at his vacation home in Yalta to resolve the dispute with the president of the Russian Academy of Sciences, Mstislav Keldysh, appointed as head of the commission to resolve the dispute and set out a clear Soviet nuclear strategy. Halfway through the meetings Chelomei offered the SS-19 with its six warheads in competition to Yangel's four-warhead SS-17 design. Keldysh lamented in his memoirs that there was a rush to build missiles but there hadn't even been a decision on a strategic nuclear doctrine.

In the end, it was decided the best path forward was to accommodate everyone's interests and that is how in the 1970s the Soviet Union's Strategic Rocket Forces ended up fielding three new ICBM systems at tremendous cost, something that would further hasten the deterioration of the Soviet economy that led the the collapse of the USSR twenty years later.

Source: The Dead Hand: The Untold Story of the Cold War Arms Race and its Dangerous Legacy by David E. Hoffman. Doubleday Books, 2009, p18-19.

Less than six months separated the first flight of the Boeing 377 Stratocruiser and the first flight of the Boeing B-47 Stratojet in December of 1947. While the Stratocruiser represented in many ways the ultimate development of the B-29 Superfortress, there was a design evolution that connects the B-29 and the B-47 as well.

The genesis of the B-47 came in the midst of the Second World War when the US Army Air Forces (the USAF wasn't an independent branch until 1947) looked to the future and knew that jets were the way to go and decided a jet-powered bomber based on their top of the line aircraft, the B-29 Superfortress was what was needed next. Boeing's design team began with what was essentially a jet-powered development of the B-29 but ran into difficulties meeting the range and performance levels that the USAF desired. When the war ended in August 1945, Boeing's chief aerodynamicist, George Schairer, was already in Germany with a USAAF technical team that was evaluating captured German aeronautical research.

At the Luftwaffe research center at Volkenrode, the technical team was reviewing wind-tunnel research into swept wings. In a dry well Schairer and the team found hastily-dumped papers that showed the performance leap possible by combining jet engines and swept wings.

Schairer wrote a seven page later to the engineering team at Boeing working on what would become the B-47 Stratojet. The design process at the time had a design that had fuselage mounted engines and a straight tapered wing and Schairer detailed in his letter what he had found at Volkenrode and his thoughts at how it might benefit the jet bomber design. As a result, the design was reworked to feature a 35-degress swept wing- at the time designated the Boeing Model 448, it was the first of two major technological breakthroughs in the design of the B-47. At this point the design still had its engines mounted in the fuselage and team found that the thin, swept wing could bend excessively in some flight regimes.

The second technological breakthrough was to relocate the jet engines in pods in the wings. The weight of the engines offset bending in the wings and resulted in a more aerodynamic fuselage. It would set the pattern for all large jet aircraft from then onward.

When the XB-47 made its first flight in December 1947, it was only 44 years to the day of the Wright Brothers' first flight at Kitty Hawk. But there was one other aircraft that beat the XB-47 into the air as the first with swept wings, and that was the XP-86 Sabre from North American Aviation (later redesignated F-86). North American also had representatives on the same technical team in Germany with George Schairer.

Source: 747: Creating the World's First Jumbo Jet and Other Adventures from a Life in Aviation by Joe Sutter with Jay Spenser. Smithsonian Books, 2006, p53-57.

In electronic warfare, often the most effective countermeasure to the enemy's attempts at jamming and deception is a well-trained radio or radar operator. Throughout the 1950s as electronic warfare took on added importance during the Cold War, it was difficult at best to get training time on operational ECM systems. Most operational systems were strictly allocated to front-line units and often were scarce as new systems were constantly being developed and entered into service to meet new Soviet threats. As most operational systems were designed specifically to counter Soviet systems, those operational units couldn't be tested or trained since there were no Soviet examples available for training purposes- obviously!

Some units elected to train against US systems (often the service branches might train against each other), but an operational EW system had to be modified to work against US systems for the duration of the exercise and it was often said the surest way to make an electronic warfare system unserviceable was to take it out of the aircraft and put it back in again.

Peacetime exercises often were of limited value due to interservice rivalries. During one exercise in the 1950s in which SAC's B-47 Stratojets were to attempt to penetrate the US air defenses of New England (made up of Army missile units and USAF Air Defense Command interceptor aircraft), the Stratojet crews were instructed to "go easy" on the ADC fighters and "plaster" the Army missile units. The proper training of operators to deal with enemy electronic warfare and countermeasures requires that the students undergo a series of increasingly difficult scenarios rather than overwhelm them outright.

The US Navy was the first to recognize this need and in 1957 created a unit dedicated to creating a realistic ECM environment for training the fleet. Four Grumman TF-1 (redesignated C-1A after 1962) Traders that were usually used for carrier on-board delivery missions were modified into airborne jamming simulators. With a crew of five that included two pilots and three ECM operators, the TF-1s were crammed full of electronic warfare equipment as well as equipment for analyzing and grading the responses of the units being trained.

The weight of all the equipment was so great that the TF-1Q, as it was designated, was too heavy to operate safely from carriers and its range suffered as well. But this was of little issue to the Navy as the TF-1Qs were to be shore based and train fleet personnel in US waters. The first unit was VAW-35 based in NAS North Island in San Diego before the aircraft were split up with two TF-1Qs based at NAS Alameda with VAW-13 to work with the Pacific Fleet and two TF-1Qs were based at NAS Quonset Point, Rhode Island with VAW-33 to work with the Atlantic Fleet. In the years that followed, the TF-1Qs (redesignated EC-1A after 1962) were worked hard acting as enemy "Red" forces for carrier battle groups preparing to deploy overseas.

The value provided by a dedicated electronic aggressor force was such that the Navy in 1969 established the Fleet Electronic Warfare Support Group made up of the squadrons VAQ-34 "Flashbacks" and VAQ-33 "Firebirds" by which time the FEWSG operated a variety of aircraft as well as civilian contractor aircraft to provide the most realistic training environment for the Navy, a mission that continues to this day.

Source: The History of U.S. Electronic Warfare, Volume II- The Renaissance Years, 1946-1964 by Alfred Price. The Association of Old Crows/Port City Press, 1989, p203-205.

During the late 1940s and early 1950s many aircraft manufacturers were conducting studies on the feasibility of converting existing piston-powered transports to turboprop power. The use of turboprops was seen as a low-risk advance that combined proven airframes with higher performance engines without sacrificing fuel economy, one of the weaknesses of jet engines of the day. With the Boeing C-97/KC-97 Stratofreighter in service with the USAF at the time, Boeing had pitched to the USAF several times a turboprop-powered Stratofreighter. All were under the same Model 367 number and at one point in 1953 Boeing went as far to built a partial mockup of the proposed Model 367-41.

The USAF, however, showed little interest in Boeing's proposals but in 1955, decided to investigate further the concept of a turboprop-powered C-97/KC-97 by commissioning Boeing to convert two aircraft (52-2693 and 52-2672, both KC-97Gs) to turboprop power. Pratt & Whitney YT34 turoprop engines (which would later be used on the Douglas C-133 Cargomaster) delivering 5,700 horsepower were substituted for the four R-4360 radial engines. For a brief time the USAF considered redesignating these two Stratofreighters as C-137, but ended up assigning them the designation YC-97J (ironically the C-137 got used for the Boeing 707s used by the military, itself a development of the Model 367-80 prototype).

The conversion to turboprop power shaved nearly 5,0000 lbs off the aircraft's weight as the YT34s were much lighter but more powerful. The first flight was made on 19 April 1955 and the YC-97J demonstrated significant improvements in overall performance. The top speed was 417 mph compared to 375 mph for a regular Stratofreighter and the YC-97J took only 14 minutes to reach 20,000 feet whereas the regular Stratofreighter took 50 minutes!

Both aircraft were flown in regular transport duties as well as trials work by the USAF until 1964, but by the time both aircraft had flown, Boeing and the USAF were shifting their efforts to developing the KC-135 Stratotanker and its even greater potential than the YC-97Js.

The first YC-97J, 52-2693, upon retirement in 1964 was used to provide parts and sections for the prototype Aero Spacelines B-377SG Super Guppy.

Source: International Air Power Review, Volume 20. AIRtime Publishing, 2006. "Warplane Classic: Boeing C/KC-97 Stratofreighter" by Bill Yenne, p128-129.

In the 1950s the United States introduced three different systems to try and solve the problem of conducting electronic intelligence (ELINT) on targets deep in the Soviet Union which couldn't be picked up by the USAF and Navy ferret flights operating on the periphery. The first system was to mount ELINT antennas on giant weather balloons that would be launched in Western Europe and drift over the Soviet Union on prevailing winds before being recovered out in the North Pacific. Approximately 200 "Grand Union" balloons were built for the USAF and only about 20 were actually launched with little to no useful intelligence being recovered. The second system was to use ELINT antennas mounted on Lockheed U-2 spyplanes during overflights of the Soviet Union. Between 1956 and 1959, approximately 30 ELINT overflights were made, but only a handful of those missions were deep penetration missions.

The most productive of the systems and ironically the lowest risk due to its low manpower requirement as well as it could be located in the United States was introduced in 1958 as the PAMOR (Passive Moon Relay) system. Originating from experiments dating back to 1948's Project Diana which determined that communications signals could be bounced off the Moon to receivers beyond the horizon, PAMOR (sometimes referred to Moonbounce) was the natural extension. A CIA engineer, Jim Trexler, postulated that a sensitive receiver pointed at the Moon could pick up radar emissions from sites deep in the Soviet Union.

The first PAMOR dishes were built at the Naval Research Laboratory's Chesapeake Bay Annex on the bay's western shore as well as in California in Palo Alto. The definitive equipment was installed soon after in a valley near Sugar Grove, West Virginia (not far from the radio astronomy observatory at Green Bank). Using 150-foot dishes and sensitive listening and tracking equipment, the system readily produced results as the new early warning radar system code named "Tall King" was discovered. Designated P-14 by the Russians, the Tall King radar was a powerful system used for the detection and tracking at long ranges of airborne aircraft. Using known Moonrise and Moonset times, it was possible to draw a line on a map through the Soviet Union- somewhere along that line would be the transmitting radar. Over several weeks, it was possible to narrow down the precise location as this would be where the Moonrise/Moonset lines intersected.

In the latter half of the 1960s (starting in 1964 when it was first intercepted by a PAMOR dish), the system discovered a new high power advanced radar system that was found to be used by the Soviet ABM system to scan and track incoming ballistic missile warheads. Code named "Hen House" due to the configuration of the antenna, detailed analysis not only revealed the Hen House locations, but also radar characteristics such as frequency, power, dwell time, etc. From this analysis it was determined that the Hen House radar was very sophisticated as it could both track and scan and its dwell times were very short, which suggested a high level of computerization.

As the Soviets upgraded and fine-tuned the Hen House system for its ABM defenses, operators would practice and test the system by tracking the Moon, inadvertently making the job of the PAMOR teams much easier!

The discovery by the PAMOR program of the Hen House ABM system was significant as the characteristics of the system drove the design and planned employment of the US SLBM/ICBM nuclear deterrent. At its height in the late 1960s and early 1970s, the program never employed more than 100 personnel, making it one of the most successful ELINT efforts ever deployed.

Source: The History of U.S. Electronic Warfare, Volume II- The Renaissance Years, 1946-1964 by Alfred Price. The Association of Old Crows/Port City Press, 1989, p157-161.