A WAC Corporal sounding rocket on display at the Smithsonian Air and Space Museum in Washington, D.C.

The WAC Corporal was the first sounding rocket ever built by the United States. Sounding rockets were not intended to reach orbit. Rather, they were designed to reach high into the atmosphere (between 30 and 950 miles) to gather data and test instruments. Most WAC Corporals were launched from White Sands Proving Grounds in New Mexico.

The Guggenheim Aeronautical Laboratory had been working on rockets with a powdered fuel source since 1936, but in 1940 (under a grant from the National Academy of Science) it turned to liquid propulsion. The work switched to CalTech's Jet Propulsion Laboratory in 1941 (which was doing all the work for Guggenheim anyway). By December 1944, CalTech had developed the Private -- an unguided surface-to-surface missile. It was experimental, and never deployed.

Work began that same month on the WAC Corporal. The Army wanted a rocket capable of lifting a 25-pound payload about 20 miles. A one-fifth size model, called the "Baby WAC" (WAC stands for "Women's Army Corps"), was tested at the Goldstone Firing Range in July 1945.

The WAC Corporal's rocket-motor was developed by the Aerojet Engineering Corporation. The motor was hypergolic, which meant that two inert chemicals exploded powerfully when they came together. (These fuels were fuming nitric acid, and aniline and furfuryl alcohol.)

A solid fuel Tiny Tim booster rocket got the WAC Corporal in the air, and then the hypergolic rocket took over. The Tiny Tim was an American air-to-ground rocket used near the end of the World War II. (It had been developed by CalTech and the Naval Air Weapons Station at China Lake.)

The first WAC Corporal was launched on September 16, 1945, from White Sands Missile Range. It reached an altitude of 43.5 miles, more than twice what was expected.

Initial firings of the WAC Corporal were so successful that the Army immediately began work on a larger model, the Corporal. The Corporal was the first surface-to-surface nuclear-tipped missile developed by the United States Army, Firestone Tire and Rubber Company, Gilfillan Brothers, Douglas Aircraft Company, and the Jet Propulsion Laboratory at CalTech.

Early U.S. rocket programs were named for enlisted ranks in the U.S. Army: Private, Corporal, and Sergeant. After the Private, the next step was the Corporal. But because the first "Corporal" rocket was smaller than the Private, the Army decided name it after the Women’s Army Corps (WAC).