Military Wiki
Place of origin USA
Service history
In service 1947
Used by USA
Production history
Manufacturer Boeing

Rail Launcher

The Boeing SAM-A-1 Ground-to-Air Pilotless Aircraft (GAPA) was a short-range missile for USAF anti-aircraft research by the Boeing Aircraft Company with Aerojet rocket boost that was launched over 100 launched times by 1950[1] from the GAPA Launch Site (cf. Green River Launch Complex).[2] The predecessor of the long range CIM-10 Bomarc, GAPA was based on a preliminary 1945 study for a supersonic vehicle with "a range of 35 miles".[3] At the 100 ft × 100 ft (30 m × 30 m) [4] missile launch complex on the WWII Wendover Bombing and Gunnery Range[5] beginning June 13, 1946, "38 GAPA launchings in a 2-week span…ended with a July 1 shot";[6] and by October 1957, the GAPA range was identified as only 30 miles in a report to the President's Air Policy Commission (by the end of 1947 a "50-mile", Mach 0.9 version was identified as needed for the "interim" air defense system.)[3]:50 In early 1948 the USAF was "ready to buy complete GAPA missiles for test and training purposes, [but] guidance components were not available", and of the planned $5.5 million for GAPA, only $3 million was identified in July 1948. Boeing produced the Boeing Electro-Mechanical Analogue Computer (BEMAC) and the Boeing Electronic Analogue Computer (BEAC) for developing GAPA[7] and at the end of 1948, Air Material Command "was instructed to buy 70 test vehicles". Over 74 launches were at the Alamogordo Guided Missile Test Base[8] beginning on July 23, 1947 (the 39th launch) with 3 JATO for initial liftoff,[9] and the program was cancelled in 1949 when the Joint Chiefs of Staff designated the Army be responsible for short-range air defense. The last GAPA, "number 114, was launched 15 August 1950."[10]

In early 1950 Boeing collaborated on a >100 mile anti-aircraft missile study with the University of Michigan, which was developing a long range defense against ballistic missiles. The study's conclusion announced in June 1950 identified a proposed range of 250 miles against supersonic aircraft, and the resulting program was for the CIM-10 Bomarc.[11]

Alamogorda launch site map (p. 18) & "GAPA Model 601" on launcher (p. 20)


  1. "Bomarc". Encyclopedia Astronautica. Retrieved 2013-08-07. "Boeing began development of surface-to-air missiles under USAAF project MX-606 in 1946. By 1950 over 100 test rockets had been launched as GAPAs (Ground-to-Air Pilotless Aircraft). Promising results led to Boeing receiving a USAF contract in 1949 to develop the exotic MX-1599 ramjet-powered, nuclear-armed long-range surface-to-air missile for defense of the continental United States from high-altitude bombers." 
  2. "Utah's Military Reservations and Energy Withdrawls". Pulbic Lands Information Center. Retrieved 2013-08-10. 
  3. 3.0 3.1 McMullen, R. F. (15 Feb 80). History of Air Defense Weapons 1946–1962 (Report). ADC Historical Study No. 14. Historical Division, Office of information, HQ ADC. p. 176. "Boeing was asked to study the possibilities of building a ram-jet vehicle which would be able to reach 60,000 feet at a range of 35 miles and attain supersonic speed . . Preliminary studies cunsumed most of 1945, but upon their conclusion Boeing was satisfied that the project (GAPA) was feasible and d~sign studies and field tests were begun in February 1946." 
  5. Culbertson, Jeanne (1972). "The Effect of Holloman Air Force Base on Alamogordo" ("unpublished Master's thesis"). Special Collections, New Mexico State University, Las Cruces.  WorldCAT OCLC 024179500 (cited by HAFB Report #1996-006 which has "1,200 personnel, were moved from Wendover Army Air Field in Utah to HAFB (Culbertson 1972:25-26)."
  6. "BOMARC Development History". Retrieved 2013-08-04. "In January 1946, the Boeing Aircraft Company won Army Air Force approval to construct and test a ground-to-air pilotless aircraft (GAPA). Initial design work on the interceptor missile concept had been ongoing during the last 2 years of the war. This effort paid off with the first launch of a GAPA on June 13, 1946, from an area now located just outside Hill AFB, Utah. Nicknamed "Gapa Village," the Boeing launch site witnessed 38 GAPA launchings in a 2-week span that ended with a July 1 shot." 
  7. Small, James S.. The Analogue Alternative.... Retrieved 2013-08-09. "In 1945 the US Army Air Force placed a contract with the Boeing Aircraft Company for the development of a surface-to-air missile system known as GAPA (Ground-to-Air Pilotless Aircraft.47 Between 1945 and 1950 two general-purpose anlogue computers were developed by staff at Boeing in connection with the GAPA programme. The first was a large electro-mechanical system used primarily as a simulator for missile and aeronautical research. This computer, known as BEMAC (Boeing Electro-Mechanical Analogue Computer), was developed entirely for in-house use and was never commercialised.48 The second of the two systems was called the BEAC (Boeing Electronic Analogue Computer). The BEAC was developed by Boeing's Physical Research Unit located in Seattle… The BEAC became available commercially in 1950.50" 
  8. Bushnell (released 08-25-1986) ( image). GAPA: Holloman's First Missile Program (Report). Air Force Missile Development Center: Historical Branch. Retrieved 2013-08-11. "[1st ramjet GAPA] "was launched 14 November 1947 and the initisl liquid-fuel variety 12 March 1948.8 ... The last of the GAPAs, number 114, was launched 15 August 1950, and the project officially terminated at Holloman the following month.11"  (date identified at])
  9. Mattson, Wayne O.; Tagg, Martyn D. (June 1995). ...Early Missile, Rocket,...Development at Holloman Air Force Base (Report). Air Combat Command. 
  10. Alamogordo Guided Missile Test Base (AGMTB): Progress Summary Report (Report). 1 November 1947. p. 85.  (cited by Bushnell)
  11. AMC Historical Study No. 238 (cited by McMullen p. 91)

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