Martin X-23 PRIME

Lore & Background

Each X-23A was constructed from titanium, beryllium, stainless steel, and aluminum. The craft consisted of two sections—the aft main structure and a removable forward 'glove section'. The structure was completely covered with a Martin-developed ablative heat shield 0.75 to 2.75 inches thick, and the nose cap was constructed of carbon phenolic material. Aerodynamic control was provided by a pair of 12 x 12 inch lower flaps, and fixed upper flaps and rudders. A nitrogen-gas reaction control system was used outside the atmosphere. At Mach 2 a drogue ballute deployed and slowed the vehicle's descent. As it deployed, its cable sliced the upper structure of the main equipment bay, allowing a 47-foot recovery chute to deploy. It would then be recovered in midair by a specially-equipped JC-130B Hercules aircraft.

The first PRIME vehicle was launched from Vandenberg AFB on 21 December 1966 atop an Atlas SLV-3 launch vehicle. This mission simulated a low Earth orbit reentry with a zero cross-range. The ballute deployed at 99,850 feet, though the recovery parachute failed to completely deploy, and the vehicle crashed into the Pacific Ocean. The second vehicle was launched on 5 March 1967, simulating a 654-mile (1,053-kilometer) cross-range reentry and banking at hypersonic speeds. The recovery parachute deployed properly and was located by two of the deployed recovery aircraft. During an inspection fly-by of the descending parachute system it was seen that reefing cutters had failed to actuate. These cutters are on the harness suspending the vehicle from the parachute to ensure stability of the vehicle behind the JC-130B recovery aircraft during reel-in, and permit safely boarding the vehicle. As a result, the parachute and vehicle were allowed to descend to the sea. Subsequently, the vehicle separated from its flotation 'balloon' in the rough seas and, with the parachute, sank before a nearby ship could arrive to retrieve it from the ocean.

The final PRIME mission was flown on 19 April 1967, and simulated re-entry from low Earth orbit with a 617 nautical mile cross-range. This time, all systems performed perfectly, and the X-23A was successfully recovered. An inspection by a USAF-Martin team reported the craft 'ready to fly again', although no later missions were carried out. The third X-23A is now on display at the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Ohio.

Reader's Guide

The X-23A PRIME program demonstrated that a lifting-body vehicle could perform controlled, maneuvering re-entries from orbital velocities, achieving cross-range offsets of up to 617 nautical miles from the ballistic track. This capability was critical for future spaceplane concepts, as it allowed a re-entering vehicle to adjust its landing point over a wide area. The program's three flights, conducted between December 1966 and April 1967, tested increasingly demanding cross-range maneuvers, with the final flight achieving a perfect recovery. The successful recovery of the third vehicle, which was found 'ready to fly again' by the inspection team, validated the structural and thermal protection design. Although no further missions were flown, the X-23A provided data on hypersonic aerodynamics, ablative heat shield performance, and high-speed control systems that informed later lifting-body and re-entry vehicle programs. The surviving vehicle remains on public display, serving as a physical record of the program's achievements.

Did You Know?

• The X-23A PRIME was designed to study maneuvering during re-entry, including cross-range maneuvers up to 617 nautical miles from the ballistic track.
• The first X-23A launched on 21 December 1966 crashed into the Pacific Ocean after its recovery parachute failed to fully deploy.
• The third and final X-23A was successfully recovered on 19 April 1967 and was reported 'ready to fly again' by the inspection team.