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

It is common knowledge that American drones specifically designed for combat became widespread only in the late 1990s, even though unmanned air vehicles as a whole have been in widespread use by the US military since the 1940s. Thus, most Americans who take a vested interest in US weaponry may not realize that drone technology has existed in the United States for about as long as heavier-than-air powered flight. Although the Northrop Grumman's RQ-4 Global Hawk and RQ-180 reconnaissance UAVs and X-47B Pegasus UCAV technology demonstrator have made some headlines in the US aerospace defense news arena, Northrop actually entered the UAV business design in 1952 when it acquired the Radioplane Company (responsible for developing the OQ-2/3/7/13/14/TDD target drones in World War II) that year, 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. Since the Radioplane Division of Northrop and Teledyne Ryan were key players in US military subsonic drone development during the Cold War, and the Ryan Aeronautical Division of Teledyne would later become part of Northrop Grumman, 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.

Left: Northrop RP-71/MQM-57 Falconer drone at Western Museum of Flight

Right: MQM-57 Falconer being readied for launch

The first drone on display at the Western Museum of Flight that deserves discussion is the Northrop (Radioplane) RP-71 Falconer propeller-driven drone (designated SD-1 by the US Army and designated MQM-57 by the Pentagon after 1963). Developed in 1955 as a derivative of Radioplane's earlier Quail drone (originally called OQ-19 by USAAF and KD2R-1/2/3/4 by US Navy; later redesignated MQM-33), it was designed for battlefield reconnaissance and had a slightly bigger fuselage than the Shelduck. The MQM-57 was launched from a ground platform by RATO booster, and could release flares to illuminate the night sky on night reconnaissance missions. 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) over North Vietnam, late 1968

The Teledyne Ryan Model 147 Lightning Bug drone I saw at the museum is a Cold War-era American drone that most Americans don't think about too much. The Ryan (later Teledyne Ryan) Firebee drone was one of the most successful American drones of the Cold War era, designed to be launched from either a DC-130 Hercules or from a ground platform via rocket boosters. Impressed by the success of the Firebee drone, the USAF in February 1962 instructed Ryan to develop a reconnaissance version of Firebee as the Model 147 Lightning Bug (military designation: AQM-34), recognizing the need for a spy drone able to fly above 55,000 feet, well above detection by enemy radar. The first Model 147s entered operational service in late 1962, but the drone itself had to wait until after the start of US involvement in Vietnam in August 1964 to start flying operational reconnaissance missions. AQM-34s were launched from DC-130 drone carrier versions of the Hercules tactical airlifter on spy flights over North Vietnam during the Vietnam War, performing a variety of tasks like photographic and electronic aerial reconnaissance, surveillance, signals intelligence, and electronic warfare. The Lightning Bug drone on display at the Western Museum of Flight is of the Model 147SRE variant (military designation: AQM-34K). Although similar to the baseline BQM-34A Firebee in appearance, its fuselage was 8 feet longer and power was provided by a Continental J69 turbojet, and the AQM-34K itself was optimized for low-altitude reconnaissance and used an improved guidance system with Doppler navigation radar. Twenty AQM-34Ks were built, with operational missions occurring from November 1968 to October 1969. 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 reconnaissance drone

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

As I had mentioned earlier before, Northrop had been building drones decades before the appearance of the RQ-4 Global Hawk and X-47 Pegasus, having acquired the drone manufacturer Radioplane and building the MQM/BQM-74 Chukar at a facility in Ventura County. However, what is lost in talk regarding Northrop drone design in the last years of the Cold War is the fact that in the mid-1980s Northrop initiated development of a subsonic reconnaissance drone derived from the existing Chukar drone in response to the joint Air Force/Navy requirement for a new-generation high subsonic target drone (designated BQM-126) to replace the Firebee and Chukar drones. The Northrop entry, designated NV-144, first flew in February 1984, with a Grumman A-6 Intruder serving as a launch platform for the drone, but the BQM-126 production contract was awarded to the Beech/Martin Model 997 (first flight March 1984), a derivative of the Beech MQM-107 Streaker. Unfortunately, production plans for the BQM-126 (the Navy hoped to procure 700 drones) were axed, perhaps due to a lack of funds.