The Grebe rocket-boosted torpedo was part of a family of 1940s Project Kingfisher anti-ship and anti-submarine guided missiles. It was an ASW weapon that targeted deep-diving enemy submarines. The Navy’s modern anti-submarine missile system, the ASROC (anti-submarine rocket), was influenced by technological developments from the Grebe program.
The Kingfisher programs were established by the Bureau of Ordnance, developed by the Goodyear Aircraft Corporation, and directed by the National Bureau of Standards. The Grebe project was designated Kingfisher E or XSUM-N-2, but commonly called Grebe after the water bird. The idea for this weapon dated to 1946 when a family of weapons systems was designed which essentially took aircraft components and strapped them to a torpedo in an effort to extend the weapon’s range. This concept envisioned using a variety of aircraft components (rockets, jet engines, wings, and control and sensor systems) mounted over a weapon.
Unlike the other Kingfisher missiles, which deployed from aircraft, the Grebe was launched from surface vessels. The Grebe’s design was described as a boost and glide missile because a rocket motor would shoot the missile off the launching rails from the ship’s deck, allowing the missile to glide along a semi-ballistic trajectory to the water entry point. The glide portion of the trajectory substantially increased the weapon’s range or stand-off distance. The acoustic homing, aircraft-launched Mark 41 torpedoes served as the Grebe’s payload, and the Grebe’s missile components extended its range to 20 miles.
The U.S. Naval Undersea Museum’s Grebe is a type IV vehicle, a type first tested in November 1949. It features folded wings, necessary to allow launching operations from a destroyer’s cramped deck. When the rocket booster ignited to thrust the vehicle into the air, the wings automatically unfolded and locked into their flight position. The type IV was also intended to shed its aircraft components once it arrived at the water entry point, so as to allow the ASW torpedo to cleanly enter the water and proceed to search for, and home onto, the target submarine. However, this feature was not incorporated into the type IV’s final design.
To conceal the Grebe’s true purpose, markings painted on its tail labeled it an “AA TARGET MK 52 MOD 2.” These deception markings were meant to trick U.S. enemies into thinking the Grebe was a target instead of a weapon. The Grebe tail also included an identification code that described each specific Grebe. The museum’s Grebe, marked “E-426,” is a Kingfisher E weapon in a type 4 configuration that was the 26th one to be built.
Limitations in sonar technology terminated the Grebe program in 1953. The Grebe’s minimum range proved much greater than the maximum search range of sonar on launching destroyers. Although the project ended, the Grebe influenced development of the ASROC, the surface-launched, anti-submarine missile system the Navy implemented in the early 1960s.