Faster than Superman: Lockheed multisonic UAVs

The Lockheed Skunk Works has earned its place in 20th-century US aerospace history for building America's most reliable reconnaissance aircraft, most notably the U-2 Dragon Lady (which was shot down over the USSR in May 1960 and also set the stage for the 1962 missile crisis by photographing Soviet SS-4 "Sandal" missiles in Cuba) and the SR-71 Blackbird, the fastest-ever US military aircraft. However, one aspect of Lockheed's aerospace history that some aerospace historians tend to overlook is the fact that generations before NASA and the US Air Force undertook development and flight testing of hypersonic air-breathing technology, the Lockheed Skunk Works undertook development, testing, and deployment of unmanned air vehicles able to travel at high supersonic speeds (Mach 3 to 4), most notably the D-21 Tagboard. Recently, in late 2018, I finally got to see the D-21 in person at the March Field Air Museum. Therefore, I thought it would be appropriate to give an overview of multi-sonic UAVs developed by the Lockheed Skunk Works.

Top: Lockheed X-7 ramjet-powered test vehicle

Bottom: Lockheed Q-5/AQM-60 high-speed target drone

Lockheed's foray into aerospace vehicles able to travel faster than Superman (at speeds exceeding Mach 2.5) started in December 1946 when the US Army Air Force (US Air Force after September 18, 1947) issued a requirement for an unmanned experimental vehicle to investigate air-breathing flight at speeds of the Mach 3. Lockheed immediately responded with a proposal for an unmanned Mach 3 technology demonstrator, the L-171, which was 15 feet long and was to be powered by a Marquardt RJ37 ramjet, which would sustain itself at speeds of Mach 2.3-3.0 for 3 minutes. The performance estimates for the X-7 were rather remarkable, because the L-171 itself was designed several months before Chuck Yeager broke the sound barrier in the Bell X-1 on October 14, 1947. The Air Material Command favorably responded to Lockheed L-171 proposal and assigned it the MX-883 designator in January 1947. The original L-171 design was judged too small to achieve its desired performance targets, so Lockheed refined its MX-883 design to produce a larger test vehicle with better performance. The MX-883 was initially designated PTV-A-1 by the USAF (the prefix "PTV" stood for "Propulsion Test Vehicle"), but later redesignated X-7 in 1951. The first flight of the X-7 took place on April 26, 1951, and a total of 130 test flights were conducted until July 20, 1960. All X-7 test vehicles were launched from B-29 and B-50 motherships, relying on solid-fuel rockets for the boost to Mach 4, and a ramjet for sustained Mach 4 cruise; one X-7 test flight reached an altitude of 106,000 feet, while another reached Mach 4.31 (2,881 miles per hour; 4,636 km/h). The X-7 later evolved into a dedicated high-speed target drone, the Q-5 Kingfisher (redesignated AQM-60 in 1963), which had one Marquardt RJ43 ramjet and two Thiokol XM45 solid-fuel rockets. The Kingfisher was intended to simulate America's anti-aircraft missiles, including the Nike Ajax, Nike Hercules, and Bomarc, and it . Despite being the first air-breathing supersonic drone built in the US, the Kingfisher proved faster than the missiles it simulated, embarrassing the Air Force establishment and some sectors of the US aerospace industry, and by the mid-1960s, the Kingfisher program was axed.

Upper left: D-21 on display at the March Field Air Museum in Riverside, California
Upper right: D-21B being boosted to high supersonic speed by a solid-fueled rocket booster, late 1960s.
Bottom: Lockheed M-21 (s/n 60-6940) carrying a D-21 drone.

The Lockheed D-21, however, stands out as the best-known high-speed UAV ever developed by the Lockheed Skunk Works. In October 1962, the Lockheed Skunk Works proposed a Mach 3+ reconnaissance UAV under the company designation Q-12 for long-range reconnaissance missions or spy missions over enemy territory that were deemed too dangerous for the A-12 or SR-71. Like the Blackbird, the D-21 was made from titanium and radar-absorbent composites. For spy missions, the Q-12 was to be launched from the back of a modified A-12. The Q-12 was later designated D-21 in late 1963 to avoid confusion with the A-12 designator, and two A-12s on contract were modified as launch platforms for the D-21 and designated M-21 (M=Mother). The D-21, codenamed Tagboard by the CIA, utilized a Marquardt RJ43 ramjet for sustained high-supersonic flight, and the drone's fuselage is reminiscent of a stovepipe. The D-21 would be launched from the M-21 at high altitude, coast to Mach 3.8 with the ramjet and scour an enemy target with a Hycon high-resolution camera, eventually releasing a hatch with the onboard camera over a predetermined overwater area to be retrieved by a mid-air recovery system.

Captive carry flights of the D-21 began in December 1964 and continued into 1965; the first free flight of the D-21 occurred on March 5, 1966, and two additional launches followed. On the fourth launch, on July 30, 1966, a D-21 hit the tail of the M-21 mothership shortly after separation, causing both aircraft to crash and the death of one of the M-21 crewmembers. Due to the risks associated with the D-21/M-21 launch procedure, Lockheed opted for launching D-21 drones from the underwing pylon of a B-52H. Given the slower release speed from a B-52H, all D-21s under construction were equipped with a large solid-propellant rocket booster for acceleration to Mach 3+ speeds and designated D-21B. Two B-52Hs were modified as D-21 motherships, each carrying two D-21s. Twelve D-21B test launches were conducted from September 1967 to July 1969, and when the last two of those launches were deemed successes, the Air Force cleared the D-21 for operational missions over the Lop Nur nuclear weapons test site in Xinjiang, China, under codename SENIOR BOWL. Four D-21 overflights of the nuclear weapons test site were conducted from November 1969 to March 1971, but none were successful; the first mission ended in mishap when the D-21 veered off course and crashed in Siberia, the second and third missions completed their flights, but the hatches with the cameras weren't recovered, while the final D-21 mission ended crashed in Yunnan province. Because of the poor success of Operation Senior Bowl and Richard Nixon's finalization of his diplomatic opening to the People's Republic of China, the Tagboard program was cancelled in July 1971. Several D-21 drones that were built but not used in the Tagboard and Senior Bowl programs are now on display at museums in the US, including the one I saw at the March Field Air Museum. (In an interesting footnote, the D-21 that crashed in Siberia after veering off course during its first operational mission was used by the Tupolev Design Bureau as a basis of a planned reverse-engineered drone, the Voron [Raven], which never left the drawing board. More info on the Voron drone can be found in Gordon and Rigmant [2005, pp. 325-327].)

References:

Gordon, Y., & Rigmant, V., 2005. OKB Tupolev: A History of the Design Bureau and its Aircraft.  Hinckley, UK: Midland Publishing.  

Miller, J., 2001. The X-Planes: X-1 to X-45. Hinckley, UK: Midland Publishing.

Peebles, C., 1999. Dark Eagles: A History of Top Secret U.S. Aircraft Programs (Revised ed.). Novato, CA: Presidio Press.

Takeaways from visit to Western Museum of Flight, January 2020, part 2: Northrop and Teledyne Ryan drones

Northrop Grumman has emerged as a key player in the non-combat and combat unmanned air vehicle market since the late 1990s with the RQ-4 Global Hawk and "RQ-180" high-altitude reconnaissance UAVs and X-47B Pegasus UCAV technology demonstrator. However, Northrop actually entered the unmanned aircraft business in 1952 when it acquired the Van Nuys-based Radioplane Company which had produced large quantities of OQ-2/3/7/13/14/TDD target drones in World War II, continuing the manufacturing activities of Radioplane in Van Nuys before moving its UAV business to Newbury Park in Ventura County in 1962, after which Radioplane Division was renamed Northrop-Ventura. Another major player in American subsonic drone development during the Cold War was the Ryan Aeronautical division of Teledyne, which built the Firebee, Lightning Bug, and Firefly drones, and it undertook the design of the RQ-4 high-altitude unmanned reconnaissance drone and RQ-8 Fire Scout rotorcraft in the first decade after the Cold War's end. Since the Radioplane/Northrop Ventura and Teledyne Ryan were key players in US military subsonic UAV development during the Cold War, and the Ryan Aeronautical Division of Teledyne would later become part of Northrop Grumman (which mean that the RQ-4 and RQ-8 became Northrop Grumman products, I've decided to discuss in this post a number of Northrop- and Teledyne Ryan-built drones that I saw at the Western Museum of Flight when it visited the museum last month.

An RP-71/MQM-57 Falconer (aka SD-1) on display at the Western Museum of Flight, photographed by me in January 2020.

The first drone on display at the Western Museum of Flight that deserves discussion is the Northrop (Radioplane) RP-71 Falconer propeller-driven drone (redesignated MQM-57 after 1963). Developed in 1955 from Radioplane's prolific Quail drone (called OQ-19 by USAAF/US Air Force and KD2R-1/2/3/4 by US Navy; later redesignated MQM-33), it was designed for battlefield reconnaissance in support of ground troops and had a slightly bigger fuselage than the Shelduck. The MQM-57 was also called the SD-1 because the US Army allocated the designation AN/USD-1 to the surveillance UAV system that included the drone itself. The Falconer carried a KS-54 or KS-61 camera system (including a KA-39A or KA-30 still picture camera, respectively), flare ejectors, and an AN/DPN-32 (later AN/DPN-62(V)) radar beacon, and it was tracked on the ground using the AN/MPQ-29 radar system. The MQM-57 was launched from a ground-based zero-length launcher and boosted to altitude by a RATO booster, and it could release flares to illuminate the night sky on night reconnaissance missions. After a reconnaissance flight, a Falconer would be recovered by parachute. About 1,500 Falconers were built, and they served the US Army and other armies of main US allies until the 1970s.

Left: Northrop KD2R-5/MQM-36 Shelduck at Western Museum of Flight.

Right: A pair of MQM-36 Shelducks aboard the USS Kearsarge, 1966.

Another early Northrop/Radioplane drone displayed at the museum worthy of discussion, related to the above-discussed Falconer drone, is the KD2R-5 Shelduck (later redesignated MQM-36). It was similar to the naval version of the Quail drone (KD2R-1/2/3/4) in having a McCulloch O-100 piston engine and being launched from a mobile platform, but had an improved autopilot and altitude-hold unit. The Shelduck entered service with the US Navy in the mid-1950s, and it became a training target for anti-aircraft missiles including the Hawk, Sidewinder, Nike, Tigercat, Redeye, Blowpipe, and Sparrow. The last MQM-36 drones were retired in the late 1980s.

Top: Teledyne Ryan AQM-34K (Model 147SRE) at Western Museum of Flight

Bottom: AQM-34L (Model 147SC) on a reconnaissance flight over North Vietnam, 1969.

The Teledyne Ryan Model 147 Lightning Bug drone I saw at the museum was a photo-reconnaissance adaptation of the Ryan Firebee, one of the most successful jet-powered American drones of the Cold War era. Impressed by the success of the Firebee, the US Air Force in 1961 instructed Teledyne Ryan to develop a reconnaissance version of Firebee, the Model 147 Lightning Bug, under Project Firefly. Four BQM-34A Firebees were converted into the first Lightning Bugs and internally called Model 147A, and the first of these flew in this iteration in April 1962. The Model 147B which flew in 1964 was the first high-altitude version of the Lightning Bug, having a longer fuselage and a far greater wingspan than the Model 147A. The Lightning Bug began flying operational missions in a wartime capacity after the US began military involvement in Vietnam in August 1964, and they were launched from DC-130 drone carrier versions of the Hercules tactical airlifter on spy flights over North Vietnam during the Vietnam War, performing tasks such as photo-reconnaissance, signals intelligence, and electronic warfare. While a comprehensive overview of different variants of the Lightning Bug is outside the scope of this post, I should mention that the AQM-34 designation was assigned to some versions of the Model 147. The Lightning Bug on display at the Western Museum of Flight is of the AQM-34K (Model 147SRE) night reconnaissance version of the Model 147S low-altitude day reconnaissance variant of the Model 147. Although the AQM-34K had the short wings of the BQM-34A Firebee, it had the longer fuselage of the Model 147G and 147J, which were powered by a slightly more powerful version of the Continental J69 turbojet, and because the AQM-34K was designed for night operations, it used an infrared strobe barely noticeable from ground view and infrared film, while relying on an improved guidance system with Doppler navigation radar. Other low-altitude versions of the Lightning Bug versions with the AQM-34 designation were the AQM-34J (Model 147NC(M1)) derivative of the AQM-34G/H (Models 147NA and 147NC), the AQM-34L (Model 147SC), and AQM-34M (Model 147SD) with a real-time datalink. Twenty AQM-34Ks along with more than 400 AQM-34Ls and 87 AQM-34Ms were manufactured, and the AQM-34K flew operational missions over North Vietnam from November 1968 to October 1969, while the AQM-34L variant served in Vietnam from 1969 to 1973 and achieved a survivability rate of 87.2% with respect to overflights of North Vietnam. When the Vietnam War ended, all AQM-34K/L/M drones were retired and put in storage. The preserved AQM-34K was acquired by the Western Museum of Flight in 2001, after spending 15 years at the California Science Center.

Top: Northrop NV-144 prototype multirole drone

Bottom: Display panel for NV-144, including 3-view drawing

One last drone design I saw at the Western Museum of Flight during my visit there in January 2020 is the NV-144. In early 1980, after the US Navy initiated a requirement for a new high subsonic target drone (designated BQM-126) to replace the Firebee and Chukar drones Northrop initiated design of a subsonic reconnaissance drone derived from the Chukar, designated NV-144. Four NV-144 prototypes were constructed, and captive carry tests were conducted in early 1984, with the NV-144's first free flight occurring on February 24, a Grumman A-6 Intruder serving as a launch platform for the drone. However, the BQM-126 production contract was awarded to the Beechcraft Model 997, a derivative of the Beechcraft MQM-107 Streaker first flown in March 1984. Unfortunately, production plans for the BQM-126 (the Navy hoped to procure 700 drones) were axed, perhaps due to a lack of funds. Northrop later adapted the NV-144 design to a 1986 requirement by the Air Force, Navy, and Marine Corps for a medium range reconnaissance drone by conceiving a battlefield surveillance version of the NV-144, the NV-144R, which carried cameras, an infrared linescanner, and other reconnaissance equipment inside the nose. The NV-144R and a rival design by Beechcraft and Martin Marietta for a BQM-126 derivative were down-selected for prototyping in 1987, with a fly-off and contract award planned for late 1988, but the medium-range reconnaissance RPV program was shelved before the NV-144R could be built. Northrop also conceived the NV-151 derivative of the NV-144 with a slightly longer fuselage and wings as well as a 1,000 lb (4.45 kN) thrust turbojet for the US Air Force, sometime in 1982/1983 and little else is known about the NV-151's development, although it can be surmised that it does not seem to have advanced beyond the prototype stage. 

References:

Taylor, J.W.R., 1984. Jane's All the World's Aircraft 1984-1985. Coulsdon, UK: Jane's Information Group.

Taylor, J.W.R., 1986. Jane's All the World's Aircraft 1986-1987. Coulsdon, UK: Jane's Information Group.