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The WAC Corporal was the first operational sounding rocket developed in the United States. It was an offshoot of the Corporal program, that was started by a partnership between the United States Army Ordnance Corps and the California Institute of Technology (named "ORDCIT") in June 1944 with the ultimate goal of developing a military ballistic missile.
During the first years of World War II, GALCIT had pursued the development of both solid and liquid-fueled Jet Assisted Take Off (JATO) boosters to aid aircraft take off performance. As the group had experimented with rockets for several years before the war they were selected by the Army to pursue ballistic rocket development.
The first rocket designed by the group for the Army was designated as XFS10S100-A, also known as the Private, that being the first Army enlisted rank. The second ORDCIT project, which became the Corporal, named for the next Army enlisted rank, was a project originally named XF30L 20,000. The Corporal project envisioned a liquid propellant missile of diameter and a power of . The Signal Corps had created the requirement for a sounding rocket to carry of instruments to or higher. This was merged with a requirement of the Rocket R&D Division of the Ordnance Corps for a test vehicle. Frank Malina of the Jet Propulsion Laboratory (JPL) proposed the development of a liquid-fueled sounding rocket to meet this request, thus providing a practical developmental step towards the ultimate Corporal missile.
The theoretical work setting the stage for the WAC Corporal was established in a 1943 paper "A Review and Preliminary Analysis of Long-Range Rocket Projectiles" by Malina and Qian Xuesen.The U.S. Army Air Corps Jet Propulsion Research Project GALCIT Project, n°1, 1939-1946 : A Memoir, Essays on the History of Rocketry and Astronautics, Volume II, Proceedings of the Third Through the Sixth History Symposia of the International Academy of Astronautics, 1969-1972, p 356 Design was started by Frank Malina and Homer Joe Stewart to meet the Signal Corps' request with their study "Considerations of the Feasibility of Developing a 100,000-ft. Altitude Rocket." The final design work was done by a team of persons specializing in particular areas and involved significant efforts to derive performance from theoretical means (a relatively new method for America rocketry). The key persons responsible were M.M. Mills (booster), P.J. Meeks (sounding rocket), W.A. Sandburg and W.B. Barry (launcher and WAC nose), S.J. Goldberg (field tests) and H.J. Stewart (external ballistics) and G, Emmerson (photography).
For propulsion, the 38ALDW-1500 Aerojet liquid-fueled engine was chosen, which had been developed as a JATO system for Navy flying boats. The 38ALDW-1500 was modified for hypergolic propellants, with red fuming nitric acid as the oxidizer and furfuryl alcohol as the fuel. The WAC Corporal was intended to use a booster derived from the Tiny Tim air-to-ground attack rocket to gain sufficient speed along a launch tower for the Corporal's three tail fins to provide passive stability. Despite the emphasis upon a theoretical approach, it was deemed necessary to empirically prove the Corporal's aerodynamics, especially the three fin configuration, so a solid propellant one-fifth scale model called the Baby WAC was tested from a scaled-down launcher in July 1945. Four Baby WACs were flown.
The design of the WAC Corporal was innovative in that main structure containing the oxidizer, fuel, and pressurizing air tanks was of monocoque design, and that it had only three stabilizing fins, rather than the four that the Army preferred. Since the WAC Corporal was conceived as an atmospheric sounding rocket to be used in part near populated locations, it was provided with a parachute recovery system for the rocket itself, along with a separate system for recovering the Signal Corps radiosonde payload.
The production of the WAC Corporal was by Douglas Aircraft Corporation with critical parts supplied by JPL and the engines by Aerojet.
The missions flown during the WAC Corporal first series were:
Radar tracking was difficult, as above the radar return was too small to be detected, and radiosonde signals were not received. No previous American liquid-fueled rocket had exceeded a tiny fraction of the altitudes the WAC Corporal regularly achieved.Rockets, by Robert H. Goddard, American Rocket Society, 29 West 39th Street, New York City, New York, 1946Robert H. Goddard The Roswell Years, National Air And Space Museum, Smithsonian Institution, Washington D.C. 1973 It was decided on November 9, 1945, to alter the WAC Corporal design to improve upon it for another series of flights. This redesigned rocket was first deemed "Sergeant" in keeping with the JPL naming scheme but was soon renamed WAC Corporal B.Army Ordnance Research Work Cited as Rebuttal to AAF Demands, Aviation News, July 8, 1946, page 8 The name "Sergeant" was later used for a solid propellant missile designed for the United States Army at JPL. Design of the WAC Corporal B was initiated in March 1946 with P.J. Meeks as Project Coordinator, and differed significantly in detail while its basic shape remained the same. It was longer, weighed less, and contained less propellant. The designs of the fuel pressurization system and fuel valves were simplified. It had a shorter engine with redesigned injectors weighed , rather than the longer engine of the WAC Corporal A. The drastically redesigned rocket body used separate tanks of dissimilar materials. Larger, lighter fins were supplied, which proved problematic on the first WAC Corporal B flight on December 6, 1946.
The flights during the second series of WAC Corporal flights were:
The WAC Corporal program was an extremely successful test program. The last 6 WAC Corporal Bs to fly were used in the Bumper program as the second stage atop captured V-2 missiles in early air-light and staging experiments. For Bumper, the WAC Corporal was modified to provide stability in excess of Mach 5 by increasing the number of fins to four and increasing their size. The WAC Corporal had to be modified so that the engine ignition would be initiated by the integrating accelerometer of the V-2 stage just before cutoff of the V-2 engine. The WAC Corporal was spin-stabilized by two solid rockets placed between the oxidizer and fuel tanks. The Bumper/WAC had a payload capacity of 50 pounds and carried a Doppler transmitter/receiver which transmitted the nose cone temperature as well as velocity information. There were 6 Bumper flights from White Sands, the first two carrying solid-fueled dummy WACs. Flight number six had a failure on the V-2. Bumper 7 and 8, the last two flights of the Bumper program, were the first launches from the new Joint Long-Range Proving Ground at Cocoa Beach, Florida, which would later be known as Cape Canaveral. The reason for the move was the intention to use a depressed trajectory to achieve velocities in the vicinity of Mach number from . This would entail flights downrange in excess of , which would exceed the boundaries of White Sands.
The WAC/Bumper flights were:
Bumper 7's WAC Corporal, the last one ever to fly, achieved Mach 9, the highest speed ever achieved by a projectile in the atmosphere at the time.
While the WAC Corporal was soon replaced in its intended role of sounding rocket, its legacy was long-lasting. Its 38ALDW-1500 engine was the direct predecessor of the Nike Ajax's A21AL-2600 and Aerobee's 45AL-2600, and was developed into the AJ10 series, which includes the AJ10-37 engine on the second stage of the world's first purpose-built satellite launch vehicle, Vanguard. Other AJ10 series members include the AJ10-101, which powered the Able upper stage on a variety of launch vehicles, the AJ10-137 Service Propulsion System on the Apollo spacecraft, and the AJ10-190 that acted as the Space Shuttle Orbital Maneuvering System. WAC Corporals are on display at the National Air and Space Museum and in the White Sands Missile Range Museum.
The earliest public reports of the WAC designation are a series of Aviation Week articles, which seem to support "Women's Army Corps" being the derivation of the acronym. In its March 18, 1946 issue, Aviation Week noted, "under the amusing security code designation of 'WAC Corporal' the project was initiated in 1944...." In the June 1, 1946 of Aviation Week, an article describes how the WAC Corporal "is launched from a triangular 100 ft. launching tower, and thereafter goes its own merry way," and claims that "these characteristics suggest some of the reasons for the female appellation of the 'WAC,' the 'Corporal' coming from the fact that some Army rockets are designated by familiar ranks."
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