Directory of U.S. Military Rockets and Missiles
Appendix 1: Early Missiles and Drones
Copyright © 2003-2004 Andreas Parsch

Boeing SAM-A-1 GAPA

In June 1946, the U.S. Army Air Force began project MX-606, and awarded Boeing a contract to study the general problems involved in the development of a surface-to-air guided missile (briefly designated as JB-8). The project was labeled GAPA (Ground-to-Air Pilotless Aircraft), and in late 1945, MX-606 was extended to cover the development of a tactical supersonic surface-to-air missile. In 1947, the designation SAM-A-1 was assigned to GAPA, and between 1946 and August 1950, more than 100 XSAM-A-1 GAPA test missiles were launched.

Photo: Boeing
XSAM-A-1 (Boeing Model 602)

The XSAM-A-1 vehicles were of several significantly different configurations to test various aspects of the projected operational missile. The first missiles, Boeing Model 600 series, were two-stage solid-propellant rockets of various configurations, and were used for basic aerodynamic research. The first Model 600 launch occurred in January 1946, but the first stable flight did not succeed before July that year. The Model 601 series, first launched in March 1948, had a solid-fueled booster, a liquid-propellant rocket sustainer, and was used to test the GAPA's guidance system. The latter consisted of radar beam-riding mid-course guidance and, in some variants, a target seeker for terminal homing. The Model 602 series was boosted by a solid-fueled rocket and tested ramjets as cruise propulsion system. It was first launched in November 1947. Under the Model 603 designator, many different configurations for the tactical missile were studied, but none were actually built. In general, the operational SAM-A-1 would have used a ramjet sustainer, beam-riding guidance, and some sort of terminal homing system.

Photo: via Gatland
XSAM-A-1 (Boeing Model 601)

The GAPA tactical missile program was terminated in 1949, when the USAF's surface-to-air missile development had turned toward the much larger and more advanced IM-99/CIM-10 Bomarc.


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

Data for XSAM-A-1:

 Model 601Model 601(A)Model 603(3)
Length (w/o booster)5.9 m (19 ft 4 in)6.4 m (21 ft)
Finspan1.22 m (4 ft)1.32 m (4 ft 4 in)2.7 m (9 ft)
Diameter25 cm (10 in)
Weight (w/o booster)290 kg (640 lb)
Booster: 735 kg (1625 lb)
450 kg (1000 lb)
Booster: 890 kg (1960 lb)
900 kg (2000 lb)
Booster: 1800 kg (4000 lb)
SpeedMach 1.8Mach 2.5Mach 2.5
Ceiling?18000 m (60000 ft)
Range (med. altitude)10 km (6.2 miles)27 km (16.5 miles)56 km (35 miles)
PropulsionSustainer: Aerojet 30AL-1000 liquid-fueled rocket
Booster: Solid-fueled rocket
Sustainer: Ramjet
Booster: Solid-fueled rocket

Main Sources

[1] Frederick I. Ordway III, Ronald C. Wakeford: "International Missile and Spacecraft Guide", McGraw-Hill, 1960
[2] "GAPA, Holloman's First Missile Program 1947-1950", Historical Branch, Office of Information Services, AF Missile Development Center
[3] Kenneth W. Gatland: "Development of the Guided Missile", Philosophical Library, 1954
[4] Boeing: A Common Heritage (Boeing history website)

Back to Directory of U.S. Military Rockets and Missiles, Appendix 1

Last Updated: 1 December 2004