new version of the Sea Sparrow was produced to address this concern, producing the larger and more capable RIM-162 ESSM. Development Sparrow I The 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. After a protracted development cycle the initial AAM-N-2 Sparrow entered limited operational service in 1954 with specially modified Douglas F3D Skyknight all-weather carrier night fighters. In 1956, they were joined by the McDonnell F3H-2M Demon and Vought F7U Cutlass fighter aircraft. Compared to the modern versions, the Sparrow I was more streamlined and featured a bullet-shaped airframe with a long pointed nose. Sparrow I was a limited and rather primitive weapon. The limitations of beam-riding guidance (which was slaved to an optical sight on single-seater fighters and radar with night fighters) restricted the missile to attacks against targets flying a straight course and made it essentially useless against a maneuvering target. Only about 2,000 rounds were produced to this standard. Sparrow II As early as 1950 Douglas examined equipping the Sparrow with an active radar seeker, initially known as XAAM-N-2a Sparrow II, the original retroactively becoming Sparrow I. In 1952 it was given the new code AAM-N-3. The active radar made the Sparrow II a "fire and forget" weapon, allowing several to be fired at separate targets at the same time. By 1955 Douglas proposed going ahead with development, intending it to be the primary weapon for the F5D Skylancer interceptor. It was later selected, with some controversy, to be the primary weapon for the Canadian Avro Arrow supersonic interceptor, along with the new Astra fire-control system. For Canadian use and as a second source for US missiles, Canadair was selected to build the missiles in Quebec. The small size of the missile forebody and the K-band AN/APQ-64-radar limited performance, and it was never able to work in testing. After considerable development and test firings in