Initial studies During World War II, the
US Army Air Force (USAAF) concluded that existing
anti-aircraft guns, only marginally effective against existing generations of propeller-driven aircraft, would not be effective at all against the emerging jet-powered designs. Like the Germans and British before them, they concluded the only successful defence would be to use guided weapons. As early as 1944 the
United States Army started exploring anti-aircraft missiles, examining a variety of concepts. At the time, two basic concepts appeared possible; one would use a short-range rocket that flew directly at the target from below following a course close to the line-of-sight, and the other would fly up to the target's altitude and then tip over and fly horizontally towards the target like a
fighter aircraft. As both concepts seemed promising, the Army Air Force was given the task of developing the airplane-like design, while the Army Ordnance Department was given the more ballistic collision-course concept. Official requirements were published in 1945. Official requirements were published in 1945;
Bell Laboratories won the Ordnance contract for a short-range line-of-sight weapon under Project Nike, while a team of players led by
Boeing won the contract for a long-range design known as
Ground-to-Air Pilotless Aircraft, or GAPA. GAPA moved to the United States Air Force when that branch was formed in 1947. In 1946, the USAAF also started two early research projects into anti-missile systems in Project Thumper (MX-795) and Project Wizard (MX-794).
Bomarc A Formally organized in 1946 under USAAF project MX-606, by 1950 Boeing had launched more than 100 test rockets in various configurations, all under the designator XSAM-A-1 GAPA. The tests were very promising, and Boeing received a USAF contract in 1949 to develop a production design under project MX-1599. The MX-1599 missile was to be a ramjet-powered, nuclear-armed long-range surface-to-air missile to defend the Continental United States from high-flying bombers. The
Michigan Aerospace Research Center (MARC) was added to the project soon afterward, and this gave the new missile its name Bomarc (for Boeing and MARC). In 1951, the USAF decided to emphasize its point of view that missiles were nothing else than pilotless aircraft by assigning aircraft designators to its missile projects, and anti-aircraft missiles received F-for-Fighter designations. The Bomarc became the
F-99. and continued to denigrate Nike in the press over the next few years, in one case showing a graphic of Washington being destroyed by nuclear bombs that Ajax failed to stop. Tests of the XF-99 test vehicles began in September 1952 and continued through early 1955. The XF-99 tested only the liquid-fueled booster rocket, which would accelerate the missile to ramjet ignition speed. In February 1955, tests of the XF-99A propulsion test vehicles began. These included live ramjets, but still had no guidance system or warhead. The designation YF-99A had been reserved for the operational test vehicles. In August 1955, the USAF discontinued the use of aircraft-like type designators for missiles, and the XF-99A and YF-99A became XIM-99A and YIM-99A, respectively. Originally the USAF had allocated the designation IM-69, but this was changed (possibly at Boeing's request to keep number 99) to
IM-99 in October 1955. By this time, Ajax was widely deployed around the United States and some overseas locations, and the Army was beginning to develop its much more powerful successor,
Nike Hercules. Hercules was an existential threat to BOMARC, as its much greater range and nuclear warhead filled many of the roles that BOMARC was designed for. A new round of fighting in the press broke out, capped by an article in
The New York Times entitled "Air Force Calls Army Nike Unfit To Guard Nation". In October 1957, the first YIM-99A production-representative prototype flew with full guidance, and succeeded in passing the target within the intended warhead's destructive radius. In late 1957, Boeing received the production contract for the IM-99A Bomarc A, and in September 1959, the first IM-99A squadron became operational. The IM-99A had an operational radius of and was designed to fly at
Mach 2.5–2.8 at a cruising altitude of . It was long and weighed . Its armament was either a conventional warhead or a
W40 nuclear warhead (7–10
kiloton yield). A
liquid-fuel rocket engine boosted the Bomarc to Mach 2, when its
Marquardt RJ43-MA-3 ramjet engines, fueled by 80-octane gasoline, would take over for the remainder of the flight. This was the same model of engine used to power the
Lockheed X-7, the
Lockheed AQM-60 Kingfisher drone used to test air defenses, and the
Lockheed D-21 launched from the back of an
M-21, although the Bomarc and Kingfisher engines used different materials due to the longer duration of their flights.
Operational units ) The operational IM-99A missiles were based horizontally in semi-hardened shelters, nicknamed "coffins". After the launch order, the shelter's roof would slide open, and the missile raised to the vertical. After the missile was supplied with fuel for the booster rocket, it would be launched by the Aerojet General LR59-AJ-13 booster. After sufficient speed was reached, the Marquardt RJ43-MA-3 ramjets would ignite and propel the missile to its cruise speed of Mach 2.8 at an altitude of . When the Bomarc was within of the target, its own Westinghouse AN/DPN-34 radar guided the missile to the interception point. The maximum range of the IM-99A was , and it was fitted with either a conventional high-explosive or a 10 kiloton W-40 nuclear fission warhead. The Bomarc relied on the
Semi-Automatic Ground Environment (SAGE), an automated control system used by
NORAD for detecting, tracking and intercepting enemy
bomber aircraft. SAGE allowed for remote launching of the Bomarc missiles, which were housed in a constant combat-ready basis in individual launch shelters in remote areas. At the height of the program, there were 14 Bomarc sites located in the US and two in Canada.
Bomarc B The liquid-fuel booster of the Bomarc A had several drawbacks. It took two minutes to fuel before launch, which could be a long time in high-speed intercepts, and its
hypergolic propellants (hydrazine and nitric acid) were very dangerous to handle, leading to several serious accidents. As soon as high-thrust
solid-fuel rockets became a reality in the mid-1950s, the USAF began to develop a new solid-fueled Bomarc variant, the IM-99B Bomarc B. It used a
Thiokol XM51 booster, and also had improved Marquardt RJ43-MA-7 (and finally the RJ43-MA-11) ramjets. The first IM-99B was launched in May 1959, but problems with the new propulsion system delayed the first fully successful flight until July 1960, when a supersonic
MQM-15A Regulus II drone was intercepted. Because the new booster required less space in the missile, more ramjet fuel could be carried, thus increasing the range to . The terminal homing system was also improved, using the world's first
pulse Doppler search radar, the Westinghouse AN/DPN-53. All Bomarc Bs were equipped with the W-40 nuclear warhead. In June 1961, the first IM-99B squadron became operational, and Bomarc B quickly replaced most Bomarc A missiles. On 23 March 1961, a Bomarc B successfully intercepted a Regulus II cruise missile flying at , thus achieving the highest interception in the world up to that date. Boeing built 570 Bomarc missiles between 1957 and 1964, 269 CIM-10A, 301 CIM-10B. In September 1958 Air Research & Development Command decided to transfer the Bomarc program from its testing at Cape Canaveral Air Force Station to a new facility on
Santa Rosa Island, south of Eglin AFB
Hurlburt Field on the
Gulf of Mexico. To operate the facility and to provide training and operational evaluation in the missile program,
Air Defense Command established the 4751st Air Defense Wing (Missile) (4751st ADW) on 15 January 1958. The first launch from Santa Rosa took place on 15 January 1959. ==Operational history==