CIM-10 Bomarc - Design and Development

Design and Development

In 1946, Boeing started to study surface-to-air guided missiles under the United States Army Air Forces project MX-606. By 1950, Boeing had launched more than 100 test rockets in various configurations, all under the designator XSAM-A-1 GAPA (Ground-to-Air Pilotless Aircraft). Because these tests were very promising, Boeing received a USAF contract in 1949 to develop a pilotless interceptor (a term then used by the USAF for air-defense guided missiles) 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.

Test flights of 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. In October 1957, the first YIM-99A production-representative prototype flew with full guidance, and succeeded to pass the target within destructive range. In late 1957, Boeing received the production contract for the IM-99A Bomarc A interceptor missile, and in September 1959, the first IM-99A squadron became operational.

The IM-99A had an operational radius of 200 miles (~320 km) and was designed to fly at Mach 2.5–2.8 at a cruising altitude of 60,000 feet (18.3 km). It was 46.6 ft (14.2 m) long and weighed 15,500 lb (7,020 kg). Its armament was either a 1,000 pound (455 kg) conventional warhead or a W40 nuclear warhead (7–10 kiloton yield). A liquid fuelled 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.

The operational IM-99A missiles were based horizontally in semi-hardened shelters ("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 and altitude of Mach 2.8 at 20,000 m (65,000 ft).

When the Bomarc was within 16 km (9.9 mi) 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 400 km (250 mi), and it was fitted with either a conventional high-explosive or a 10 kt 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 United States and two in Canada.

The liquid-fuel booster of the Bomarc A was no optimal solution. It took two minutes to fuel before launch, which can be a long time in high-speed intercepts, and its hypergolic fuels (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 KD2U-1/MQM-15A Regulus II drone was intercepted. Because the new booster took up less space in the missile, more ramjet fuel could be carried, increasing the range to 710 km (440 mi). 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.

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, immediately 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.