The Honest John was a free flight, solid propellant rocket, 762mm (approximately 30 inches) in diameter. The highly mobile Honest John system was designed to fire like conventional artillery in battlefield areas, but could deliver a conventional explosive, chemical, biological (M79 or M190 warhead) or nuclear warhead. The M31 Honest John system was first deployed in 1954 and was replaced by the M50 Improved Honest John in 1961. The M50 reduced the system's weight, shortened its length, and increased its range.
The Honest John could deliver a 1,500-pound warhead against land targets ranging from 5.3 miles to 15.7 miles distant. The nuclear warhead (W7 or W31) had a yield from 10 to 60 kilotons. The Honest John Missile Launcher Truck was the M289 or M386 (M39-series), 5 Ton, 6x6 or it could be launched from a special M329 trailer launcher.
In 1970, the Honest John rocket battalions were eliminated as divisional units. In July 1982, all Honest John rockets, launchers and equipment items were type classified obsolete.
Test launch of an M50 Honest John.
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Honest John Field Artillery Missile Components
The Honest John rocket consists of four major components; the warhead, pedestal, rocket motor, and fin assembly. Each component has a specific function in the overall operation of the rocket.
Honest John missile on display, Texas Military Forces Museum, Camp Mabry, TX, 30 January 2006. Photo: Courtesy of Bob Pettit.
The pedestal section of the rocket houses eight spin rockets. These small rockets are mounted in pairs in the four quadrants of the pedestal. They are positioned so their thrust is delivered perpendicular to the Honest John's longitudinal axis. The spin rockets are fired immediately after the Honest John clears its launching rail, giving the weapon a two revolution per second spin. Spinning the rocket in this manner distributes errors caused by uneven propellant burning.
The solid propellant filler of the rocket motor weighs over 1 ton. It burns for 4.5 seconds and delivers a 90,000 pound thrust. At burnout, the rocket has a velocity of 2,500 feet per second--about 1800 miles an hour. The propellant is a multiperforated double-base composition which can be stored and fired at temperatures from 0° F to 120° F. An electrical heating blanket covers the entire rocket prior to firing. Thermo-statically controlled heating elements within the blanket attempt to keep the propellant at the optimum temperature of 77° F when the ambient temperature falls below this. At higher ambient temperature the blanket acts as an insulator. When the assembled rocket is being transported on its M329 trailer, power for the blanket is supplied by a 3,500-watt gasoline driven generator mounted over the left wheels. When mounted on the launching rail, power is supplied by another generator mounted on the launcher.
The last major component of an Honest John rocket is the fin assembly, which consists of four fins. These fins stabilize the rocket in flight. By being offset 0.5 degrees to the right, the fins also maintain the spin imparted by the spin rockets. This constant spin alleviates aerodynamic errors which may exist after motor burnout. The fin span is 104 inches.