The Little Missile That Could (Intercept, that is)

Seventy years ago this week, at the Naval Ordinanc testing range at China Lake, California, history was made with the successful test of the first heat-seeking Sidewinder missile.

The unofficial but quintessential Department of Government Efficiency (DoGE) has targeted wasteful federal spending. Decades of inertia with outdated practices exacerbates the military procurement process. But every now and then, something extraordinary emerges while nobody is looking. On occasion, a few people who are often buried in narrow technical assignments are able to think outside the box and imagine capabilities beyond the scope of midwit pencil pushers, who are often eager to shut down such efforts. In a prime example occurring in 1959, Canada’s aerospace industry suffered a mortal blow by the abrupt cancellation of the supersonic Arrow interceptor, causing Avro to lay off thousands of employees, many of whom moved to the United States.

Seventy years ago this week, a legendary air-to-air missile demonstrated its dominance against its sophisticated competition, having made its quiet debut two years earlier. Developed initially beyond the prying eyes of Pentagon bureaucracy, this revolutionary device that is responsible for altering aerial combat came to fruition in the Mojavé Desert by a team of dedicated and innovative scientists, engineers, technicians and pilots.

Crucial Innovations in the Age of Jet Engines

In the aftermath of Second World War with the introduction of the British Gloster Meteor and the German Messerschmitt Me-262, jet powered pursuit aircraft replaced reciprocation-driven propellers with thrust producing turbojets. Following the Korean peninsula conflict, increased speeds necessitated augmenting traditional canons with missiles.

The United States Air Force tasked Hughes to develop an intercept missile for defending bombers, and later as a short-range missile for fighters. This missile dubbed “Falcon” initially employed semi-active radar homing, although subsequent variants operated by using infrared seekers. (The difference between active and semi-active radar tracking involves the transmitter source, with the missile containing the receiver. In the former, the missile emits the radar signal, whereas the launch aircraft illuminates the target by radar in the latter.)

In the era of vacuum tubes long before integrated semi-conductor processors or even solid-state transistors, such feasibility presented daunting challenges. Falcon entered service in 1956 as an air intercept missile (AIM) and became designated the AIM-4, which despite its unpopularity with pilots, operated for thirty years.

Out in Central California at China Lake, the US Navy operates a test range larger than Rhode Island, equipped with several laboratories and an airfield. Established in November 1943, the Naval Ordnance Test Station designed and fabricated ordinance that was intended for launch from aircraft or ships, including anti-radar Shrike (AGM-45) and cruise missile Tomahawk (BGM-109). Under Navy reorganization, China Lake is currently Naval Air Weapons Station within the Naval Air Systems Command (NAVAIR).

Sidewinding and Heat Seeking

In June 1963, President Kennedy visited China Lake to witness an air-show and tour the Michelson laboratory, named for America’s first Nobel laureate. The Boeing 707 that was designated Air Force One is displayed at Armitage Field, is named for a fallen test pilot.

Far from the Pentagon, yet only 140 miles away from Cal Tech in Pasadena, China Lake became home to many scientists and engineers who could create new weapons in a dedicated laboratory with drawing boards, machine shops and test fields residing in close proximity. The period of fertile inspiration also occurred in the relative lull of the Eisenhower administration between America’s involvement in the Korean and Viet Nam theaters. Bill McLean led this group of mavericks, initially called Local Fuze Project 602.

A mild-manner physicist with a quiet demeanor, Dr McLean and his team integrated an available five-inch diameter Zuni rocket motor with sophisticated controls to complete the first practical short-range air-to-air intercept missile, designated AIM-9 Sidewinder. As an aside, the USNS William McLean (T-AKE 12) cargo ship is named in his honor.

In 1951, this short-range interceptor derived its name from the thermal-sensing rattlesnakes that resides in the high desert. With advancements in imagery and processing technology over the decades, improved variants remains in use with military services today. Ron Westrum documents related events in his 1999 book Sidewinder.

Although then-prevalent opinion favored radar guidance, McLean incorporated an infrared passive detector from lead-sulfide (PbS) (while modern versions employ alternative materials, such as indium-antimonide (InSb)). Further historical information is available on the physics and materials for infrared detection. The electromagnetic spectrum ranges in wavelength from multi-meter for radio to picometer in gamma rays. Our eyes are tuned to detect light in the visible portion of the spectrum (380 nanometers for violet to 750 nanometers for red). Infrared radiation has longer wavelengths than human vision can detects, and select materials respond electrically to an object that is hotter than the background. An infrared seeker for an aerial combat is then able to home in on the jet exhaust of an adversarial aircraft. Passive infrared homing offers fire-and-forget engagement to the launcher as an additional safety benefit, facilitating escape.

To become a practical and deployable weapon, several technical hurdles had to be recognized and addressed. Many of these are explained in patents issued in Sidewinder’s development. A pair of mirrors reflected the field-of-view through apertures to reach the PbS photocell. To follow a target moving within its field-of-view, the infrared detector had to be mounted on gimbals for multi-axis rotation. U.S. Patent 3,756,538 features an example design illustration.

Maneuverability necessitated turnable canards, with torque applied by a gas generator. To guide the missile towards an intercept point with the target, the seeker incorporated independent gyroscopes for visual detection and for course direction, as shown in the previously referenced patent.

To counteract torque and thereby augment stability irrespective of altitude, the aft fins integrated aerodynamically spun “rollerons” on their aft tips. To increase the likelihood of disabling the target with only a small warhead, Sidewinder employed a proximity fuse and releases shrapnel to cause damage, rather than rely on a blast. These and other innovations kept the missile team busy. As with the design philosophy at Elon Musk’s SpaceX, the McLean placed emphasis on rapid iteration of design, prototype fabrication and test. Before becoming a Mercury astronaut, Wally Schirra carried and launched the Sidewinder as a Navy test pilot. (Schirra holds the historical significance of being the only person to fly aboard Mercury, Gemini and Apollo spacecraft into orbit.)

Between Tuesday and Thursday in mid-June 1955, the Air Force and Navy held an aerial contest between the Falcon and the Sidewinder at Holloman in New Mexico. The complicated Falcon encountered several difficulties. By contrast, Sidewinder’s performance, coupled with minimal support equipment and personnel, demonstrated that simplicity and ingenuity could succeed in such an ambitious goal of intercepting a target after aircraft launch. Early the following year, the Navy fielded Sidewinder to the fleet in the prototype version AIM-9A, which was used for training purposes.

Combat Successes and its Legacy

In September 1958, the AIM-9B variant downed its first aircraft in combat in an encounter over the Taiwan Strait. In a repeat encounter that month, a Sidewinder became lodged in the tail of a Chinese MiG-17, which unfortunately allowed the Soviets to reverse-engineered it as their Vympel K-13 (NATO “Atoll”), which entered service for the Warsaw Pact in 1961.

Over the past seven decades, the Sidewinder has been adopted by many combat air wings, and various surface-launch derivatives have been deployed. The liquid-nitrogen-cooled AIM-9D saw service in Viet Nam, later succeeded by the off-axis lock-on-and-launch AIM-9G. The AIM-9L, with a more powerful booster and optical fuse, further improved the Sidewinder’s lethality, along with the ability to distinguish countermeasures in the AIM-9M. The photograph below shows one of these variants launched by an Air Force F-16.

The Defense department today deploys the AIM-9X variant, and contracts ensure that Sidewinder will continue to operate until 2055. Most weapons reach obsolescence after only a few decades. The Sidewinder, with its story of creativity and adaptability is a historical exception, and a technological inspiration for the modern world.

Photo Credits- Simple Flying, China Lake Museum Foundation, China Lake Alumni, U.S. Patent Images, Library of Congress, Defence Industry Daily, historynet.com, ar.inspiredpencil.com and PeakPx.