The missile that has rattled enemy pilots since 1958.
- By Preston Lerner
- Air & Space magazine, November 2010
USAF/TSGT Fernando Serna
(Page 2 of 5)
Even after all these years, the latest Sidewinder variant still retains the five-inch diameter and rough dimensions of the cigar-shaped original. It’s gotten longer (from just over 109 to 119 inches) and leaner, from 155 pounds to 118 pounds. But like George Washington’s hatchet (“Only the handle and the blade have been replaced”), the Sidewinder has been modified so thoroughly over the past half-century that just about all that remains of the original is the name. Well, that and the fundamental concept, which dates back to 1947, when an engineering genius named Bill McLean made a rough sketch of what he called a “target-seeking gyro.” A few years later, he filed a patent application for a “heat homing rocket.” By the time McLean and his merry band of missileers at China Lake were finished, the Sidewinder had earned a spot on the short list of weapons that have changed the way battles are fought.
After World War II, the Naval Ordnance Test Station at China Lake (now the Naval Air Warfare Center Weapons Division) was the Promised Land for weapons development and testing. Situated in the Mojave Desert three hours northeast of Los Angeles, it featured 1,200 square miles of largely unpopulated terrain that was perfect for blowing things up. Its remote location also fostered a self-reliant spirit and contrarian mentality that attracted unconventional thinkers. McLean, a graduate of the California Institute of Technology whose genial and unassuming demeanor hid a mighty intellect (later Sidewinder program manager Frank Cartwright describes him as “a 108 on a scale of 100”), arrived in 1945 to work on air-to-air rockets.
Rockets serve a lot of useful functions, but shooting down airplanes isn’t one of them, a truth demonstrated all too clearly in 1956, when a pair of F-89 Scorpions fired 208 rockets against a wayward drone that was threatening southern California, and failed to score a single hit. After World War II, various military contractors developed nearly a dozen guided missiles. The most promising guidance system seemed to be radar, which was, after all, a proven technology. But because the equipment was too bulky to fit inside a rocket, the airplane firing the missile had to “paint” the target with radar, and the pilots had to stay locked on until the warhead detonated.
McLean had a better idea: Why not create a weapon that carried its own control system, so the missile was guided by the target? This led him to investigate the use of an infrared seeker to detect the target’s heat. McLean wanted to give a conventional rocket—a dumb weapon—eyes and a brain. The missile would “see” via a transparent seeker head, through which infrared radiation from the exhaust of a jet engine would reflect off a gimballed, rotating mirror onto a lead-sulfide photocell. As the gyroscopically stabilized mirror moved to track the heat source, a servo motor manipulated the canards that controlled the missile’s flight, maintaining a constant bearing with respect to the target. Proportional navigation, as the technique is called, enabled the missile to anticipate where the target was going to be rather than aiming at where it was, like a quarterback leading a receiver.
Compared with radar-guided missiles, McLean’s alternative was cheap, simple, and robust. Also, unlike radar guidance, it was a passive weapon that gave the targeted pilot no warning until he saw the missile flying toward him. Small, lethal, and able to strike quickly and outmaneuver its quarry, it shared several qualities with another heat-seeking predator native to the Mojave Desert: the sidewinder rattlesnake. So in 1950, another proposed name—Low I.Q. Homing Head—was rejected, and Sidewinder was adopted.
There was no official backing for the project, and on several occasions it was nearly canceled. But the tiny team working on the Sidewinder was persistent as well as ingenious, and the engineers, faced with seemingly intractable problems, developed a host of elegant solutions. A good example was the so-called rollerons: spur-like discs that unlocked from the tail fins in flight. The gyroscopic effect of the spinning discs prevented the missile from rotating on its axis. And then there was the famous Sidewinder tone, a menacing growl—once heard, it is never forgotten. During early flights, test pilots had to check a small voltmeter in the cockpit to determine whether the seeker was sensing a heat source, an unwanted distraction in the middle of a dogfight. By running an additional wire to the missile, the Sidewinder team was able to create a sound that could be piped into pilots’ headsets to alert them that the seeker had acquired a target.
Tom Amlie worked on the Sidewinder project as a young Navy lieutenant, and he later became technical director at China Lake. He says the secret of the missile’s success is simplicity: “In flight, it had seven vacuum tubes and five moving parts. The competition [Falcon] was complicated almost beyond description.” For professor Ron Westrum, the author of Sidewinder: Creative Missile Development at China Lake, the project demonstrated the triumph of lean R&D and imaginative management. “They had less than 25 people in the beginning, and they did it as a bootleg project,” he says. “The Sidewinder demonstrated that what we now call a skunk works actually works.”
Well, not at first.