Sparrow emerged from a late-1940s United States Navy program to develop a guided rocket weapon for air-to-air use. In 1947 the Navy contracted Sperry to build a beam riding version of a standard HVAR, the standard unguided aerial rocket, under Project Hotshot. The weapon was initially dubbed KAS-1, then AAM-2, and, from 1948 on, AAM-N-2. The airframe was developed by Douglas Aircraft Company. The diameter of the HVAR proved to be inadequate for the electronics, leading Douglas to expand the missile's airframe to diameter. The prototype weapon began unpowered flight-tests in 1947, and made its first aerial interception in 1952.