Directory of U.S. Military Rockets and Missiles
Appendix 1: Early Missiles and Drones
Copyright © 2003 Andreas Parsch

Naval Ordnance Lab SAM-N-8 Zeus

In June 1947, the Naval Ordnance Laboratory began to develop a gun-launched guided anti-aircraft projectile. Originally known as project "Arrow Shell", it was classed as a guided missile in 1948 and designated SAM-N-8 Zeus. Firings of XSAM-N-8 test rounds began in the same year.

The XSAM-N-8 was a finned 10.2 cm (4 in) shell, which could be fired from a smoothbore 8 in/55 gun, reaching a muzzle velocity of 960 m/s (3150 ft/s) with then-typical gun charges. To change the course of flight (to correct aiming errors and/or follow a manoeuvering target), the Zeus was equipped with a small rocket motor which fired at right angles to the axis of the shell. I have no details about the planned guidance system, but given the late 1940s state-of-the-art, it was most probably some form of radar beam-riding or radio-command guidance. The single-shot kill probability (SSPK) of a conventional 5 in/70 AA gun of the time at a range of 4600 m (5000 yds) was calculated as 0.025, and it was expected that Zeus could achieve an SSPK of 0.3 at that range. Alternatively, Zeus could achieve the same 0.025 SSPK at a much greater range of about 13700 m (15000 yds).

In early 1950, responsibility for the Zeus was transferred from the missile program to the gun fire-control program. The SAM-N-8 missile nomenclature was also dropped at that time, and the designation was much later reused for the SAM-N-8/RIM-50 Typhon LR. More than 100 XSAM-N-8 Zeus shells had been fired, including deflection shots to test the stability under course corrections. A rocket-propelled (in addition to the guidance motor) derivative was planned as Zeus II, but the whole Zeus program was cancelled around 1950/51 when the Navy's guided missile program was tightened.


Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for XSAM-N-8:

Diameter10.2 cm (4 in)
Weight33 kg (72 lb)
Speed960 m/s (3150 ft/s)
Range> 13700 m (15000 yds)
Propulsionnone (small rocket for course corrections)

Main Sources

[1] Norman Friedman: "US Naval Weapons", Conway Maritime Press, 1983

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Last Updated: 22 January 2003