During the spring of 1958, there were proposals for air-launched ballistic missiles (ALBMs) that could be carried under the B-58. The Lockheed Missiles and Space Systems division was to be given the responsibility of developing the missile, and Convair was to design a special centerline underfuselage missile transport pylon that could carry and launch the missile. B-58 55-660 was allocated to the project.
Four missiles were initially ordered from Lockheed. In order to save money and to speed up the project, Lockheed used proven components from the XQ-5, the X-17, the Polaris, and the Sergeant missile programs. The Lockheed-designed ALBM was 30 feet ling and had a diameter of 31 inches. The missile was guided by an inertial system. The engine was a Thiokol XM-20 solid-fuel motor offering a thrust of 50,000 pounds for 39 seconds. There were four guidance fins installed around the exhaust nozzle skirt.
The first launch took place from 55-660 on September 5, 1958 over the Cape Canaveral range. Unfortunately, several seconds after the ignition of the rocket engine the missile control system failed and sent the missile into violent oscillations, forcing an immediate termination of the flight. The failed missile fell into the Atlantic 30 seconds later.
The second missile tested on December 19. This time the results were much better, with a launch taking place at Mach 1.6. A maximum speed of Mach 6 was reached, and a total range of 185 miles was achieved.
A third launch, which took place on June 4, 1959, and was the first one where the inertial guidance system was used. This launch was also successful, and a maximum altitude of 32 miles was achieved.
The fourth and last launch had somewhat different objectives. Lockheed modified the last ALBM to be significantly lighter than the three predecessors, and equipped it with a longer nose which contained 13 cameras which would be used to photograph an orbiting satellite. The object of the test was to see if it were possible to intercept and destroy an orbiting earth satellite.
The target of the last launch was to be the Explorer IV satellite. However, shortly before the launch it was found that Explorer IVs orbital parameters were inaccurate, and the target was changed to the newly- launched Explorer V. The launch took place on September 22, 1959, with the launching B-58 flying at an altitude of 37,500 feet and a speed of Mach 2. The launch went smoothly enough, but 30 seconds later all contact with the missile was lost.
Even though the Lockheed/Convair ALBM program was modestly successful, very little long-term interest in the project was generated by the Department of Defense, and no further work was carried out.