Hughes JB-3 Tiamat

The JB-3 Tiamat was subsonic air-to-air missile program that began in January 1944 for the U.S. Army Air Force under project MX-570. Prime contractor was Hughes Aircraft Company Electronics Division which developed the Tiamat with the assistance of the NACA. Testing continued into 1946, but the project was cancelled due to ongoing problems in a period of limited development funding as well as the appearance of more promising missile designs.

Development
The JB designation was introduced by the U.S. Army Air Force in 1943, and covered guided missiles with rocket and/or air-breathing jet (turbojet, pulsejet, ramjet) propulsion. The JB-3, which contractor Hughes called the Tiamat, was a subsonic air-to-air design intended for used against bombers. "It was intended to arm the Northrop-built JB-1 Bat bomber." Development began in January 1944, and the cylindrical vehicle was propelled by a dual-thrust (boost/sustain) solid-fueled rocket motor and had three comparatively large wings with control surfaces for stability and control. The Tiamat used a semi-active radar seeker and the warhead was triggered by a proximity fuze. A large weapon for the time, it weighed 625 pounds with a 100-pound warhead, with a range of about nine miles at about 600 mph up to 50,000 feet.

The JB-3 "conducted its first test launch on 6 August 1945, the same day that Col. Paul Tibbets flew the B-29 Enola Gay to Hiroshima." In initial tests, the JB-3 was ground-launched with a booster, but in later tests it was dropped from the wings of a JB-26 Invader.

A report for Headquarters Air Material Command at Wright Field, Ohio, dated 1 October 1945, states:

"Wind tunnel tests have been run in the five-foot tunnel at Wright Field and in the Free Flight Tunnel at NACA, Langley Field. Free-flight rocket-propelled model tests are now in progress at NACA, Langley Field. Tests of the first group of four Hughes JB-3's [sic] have been tested at Wendover Field, Utah. The first JB-3 test failed because of premature operation of the camera rescue parachute. The second JB-3 flew approximately a straight line controlled flight into the ground. The third JB-3 tumbled before the motor fired. The fourth had one or two seconds of controlled flight after the accelerating rocket failed to operate. The fifth JB-3 oscillated violently on its mount before release, rolled immediately after release and the rocket motor exploded after 15 seconds of flight. The sixth JB-3 flew in a steady 12° dive for its entire flight exhibiting fairly good stability. The seventh JB-3 developed a pre-launching oscillation and tumbled upon release. Its rocket motor exploded after 4 seconds. Both the oscillation experienced before launching and the rocket motor failures are expected to be eliminated in the near future. Flight data indicates that control rates in roll and pitch should be decreased. Sufficient tests have not been made to obtain performance data."

The report says of future testing, "Tests on the aerodynamic configuration and control characteristics and [sic] to continue at Langley and Wendover. Variations of three and four winged missiles and swept-back wing missiles will be made at Langley. Difficulties in development of the radar seeker are being experienced and at this time a date cannot be set for the test of the JB-3 under seeker control. Tests of ten JB-3's [sic] with Flight Test Assemblies which simulate seeker control will begin approximately 15 January 1946." Of NACA testing, the report states that "The dummy and No. 1 instrumented model have been launched. Trouble was experienced in the phase of flight where the launching booster leaves the model due to instability of the booster unit. A new booster unit incorporating a single boosting rocket is now being designed around the Monsanto ACL-1 rocket."

The report concludes that "The first seven JB-3's [sic] have been tested at Wendover Field, Utah. Three JB-3's [sic] are scheduled for delivery on 8 October 1945. These missiles are auto-pilot controlled and are set to fly a straight line trajectory. Of the thirty-five (35) full scaled models planned, the NACA has six (6) under construction."

On 31 March 1946, the Air Proving Ground Command, Eglin Field, Florida, completed the tactical suitability test of the JB-3 Tiamat, Project MX-570.

Cancellation
Testing and development of the JB-3 continued after World War II, but it was found unsatisfactory and in September 1946 the program was terminated. Funding was also a consideration. "During Christmas week, known at Wright Field as the black Christmas of 1946, the president ordered a drastic cutback in fiscal year 1947 research and development spending, effective immediately. After hasty study, the Air Staff deleted more than 55 percent of the guided missile budget, reducing it from $29 miilion to $13 million." Additional tests by Hughes and the Air Force with existing examples continued into 1947. By this time, more promising air-to-air missile projects had been started, notably the AAM-A-1 Firebird and AAM-A-2/F-98/GAR-1 Falcon. The MX-798, a development of the MX-570 with a five-mile range, under test in 1947, marked the end of the project, as it gave way for the Falcon.