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The Piper Cub Offense

Ubiquity, Volume 2001 Issue January, January 1 - January 31, 2001 | BY Jef Raskin 


Full citation in the ACM Digital Library

Why the Reagan/Clinton/Bush Star Wars defense is useless

August, 1998. On South Uist island in the Outer Hebrides, off the west coast of Scotland, a group of men huddled around a van, jacketed against the 25 knot wind. There was no way that they could hear the sound of the aircraft's engine over the persistent whistling of the gale; they would see it -- if they saw it at all -- before they would hear it. And it was an hour overdue on a potentially historic flight.

The small, single-engined craft was attempting the first solo flight across the Atlantic, but this was more of a solo than the one Lindbergh made some 70 years earlier. Where there had been one pilot on that flight, which was for Lindbergh the irreducible minimum crew, there was none on Laima. The plane was trying to fly itself solo from one side of the ocean to a particular spot on the other side. Instead of a compass and stars to steer by, it had a microprocessor and a global positioning system (GPS) receiver. The men who had built the craft were interested in meteorological research, but if they succeeded, they would also unwittingly show that Reagan's Star Wars (now updated as the Clinton/Bush anti-missile defense against "rogue" nations) was useless. Just as the Germans easily found a way around what the French thought was an impenetrable thicket of defensive bunkers on the ground prior to World War II, the Maginot line, this small plane would barely be noticed, much less brought down, by anything the defense department has in its armamentarium.

It is not unprecedented for small planes to penetrate where bombers cannot go. In 1987, Mathias Rust landed his Cessna on the Kremlin's Red Square by flying low enough to not trigger Russian defense warnings (the Cessna is made of metal, with a solid radar signature). The "Piper Cub Offense" is simpler still. The idea is named after one of aviation's most famous planes: The Piper Cub. This aircraft is a small two-seater, first produced in the 1930s and still popular with pilots. Inexpensive, two-person kit aircraft of even smaller size are available today, built with fabric-covered wooden frames and tiny one- or two-cylinder engines. These engines are the only significant masses of metal in the amateur-built planes, each about as noticeable on an air traffic controller's radar screen as a stealth bomber would be. Compared to a jet, their infrared emissions are negligible, they would not be seen by heat-seeking detectors. And these tiny airplanes look anything but threatening -- scramble some jets after an intruder; will they be looking for a rag-covered homebuilt?

Put a suitcase-size atomic bomb in one of the seats and you could wipe out a city with a home-built, low-tech aircraft. Alternatively, you could carry a few pounds of Sarin or Anthrax spores. But we now can eliminate the "you" in the picture.

The plane that was struggling across the Atlantic was the brainchild of the Insitu Group, led by Dr. Tad McGreer. The tiny aircraft was named "Laima" after the Latvian goddess of good fortune. It was small and, by defense department standards, cheap. Light enough at 26 pounds to be held up by one human arm, it used a wing manufactured for a model glider. In fact, many model airplanes are over twice as heavy and much larger. The engine was a medium-sized model aircraft engine, but you could loft an A-bomb with a readily available model motor that is only a bit larger, about the size of a gas engine from a lawn mower. Lawn mower engines themselves will do; many radio-controlled planes are flown with propellers attached where once a grass-slicing blade had been. There is not much difference between spinning a cutting blade over a lawn and swishing a propeller through the air, except for that wonderful just-mown aroma you get from the lawn.

The Laima should have taken about 25 hours to make the flight. During that time it would have had no need to transmit or otherwise give away its presence. According to the plan, it would use up 1.5 gallons of gasoline during its trip of slightly over 2000 miles. If you care about fuel efficiency, that would be 1,300 miles per gallon. An autonomous bomb-carrier would need less than 10 gallons to go across an ocean. While the Laima was packed with current technology, the aircraft is not super-high-tech. It was certainly cheap compared to piloted aircraft, or even compared to the remote-piloted vehicles the military uses. To put it in financial perspective, a modern jet costs hundreds of millions of dollars, and an intercontinental missile a comparable amount. By comparison, the Laima itself had been built for under $10,000. The infrastructure required for aircraft and missiles is considerable; airfields and missile launching sites also cost hundreds of millions to build, and are easily targeted. A hundred-foot-long stretch of road or farm field -- or even a small boat with a catapult a thousand miles off our coast -- would serve to launch the Laima.

Except for the bomb itself, there is nothing esoteric or hard to buy; and, as the world learned in a Japanese subway, it is easy to make nerve gas. Anybody, even a visitor from another country, can walk into a store in the USA and purchase a GPS unit with a computer interface. Small portable computers are available anywhere, and for this application, not much brain power is required. Off-the-shelf servos powerful enough to operate the controls are racked up in rows on hobby store shelves. All of this can be ordered via the Internet. A hot high-school programmer could write the code, and since an A-bomb or nerve gas doesn't have to be delivered with 1-meter precision, the GPS and a few gyros can handle all the piloting and navigational needs. Modern, non-mechanical gyros that can keep a plane flying straight and level through turbulent skies now sell for under $100. They, too, are a standard hobby-store item. A generator, driven by the motor, can supply the electricity that the computer and other electronics require.

For a million dollars, peanuts in terms of military spending, you could build a hundred bomb carriers. And you could do this in a building the size of a two-car garage, using the simple tools that any model plane enthusiast owns. That's not the kind of site that spy satellites look for. Let's say that an intelligence photo showed a garage with a large model plane outside, who'd care? Planes of the size we're talking about can easily (with their wings dismounted) fit inside an ordinary van. There's nothing to tip off an enemy that something is afoot.

If 100 deadly Laima's were launched nearly simultaneously, it would be impossible to find them all even if you knew that they were coming. If you didn't expect them, you'd probably never notice them until the mushroom cloud or the people keeling over told the story. The Insitu Group launched four planes, of which only one made it. With experience, I'd expect the success rate to grow higher, but even if only 25 of the 100 aircraft succeeded in flying to their targets in the US, the effect would be devastating.

It is hard to conceive of an effective defense against such attacks. Flying above 2000 feet or so, they are invisible to the naked eye on the ground, and completely inaudible. Slightly more sophisticated versions could be solar powered with electric motors, giving them essentially unlimited range and hover time (they can climb high enough during the day to be able to glide through the night). They could be programmed to fly in circles over a city after arrival, waiting a predetermined length of time until all, or nearly all, of them could be expected to have arrived at their targets. They would all explode at once, giving no warning.

The Star Wars missile defense depends on satellites detecting the launch plumes of the enemy missiles. While the Reagan-era system planned on laser-equipped satellites, the current version depends on Raytheon's "Exoatmospheric Kill Vehicle" (EKV). Not much larger than Laima, the EKV is about 40 inches long, 7 or 8 inches in diameter, and weighs a bit over 120 pounds. It is, essentially, a heavy slug of guided metal intended to destroy enemy missiles by colliding with them; it carries no explosives. Using it is like throwing high-tech rocks; only a direct hit will do. The EKV is launched by a massive, costly, three-stage rocket. At the high speeds space vehicles move, even a glancing blow can totally destroy a missile, but EKVs may be easy to decoy away from their real targets and, because they are designed to work only in the airless void of outer space, are useless against atmospheric cruise missiles... or model planes.

While cruise missiles are a potential threat, they have some problems that may make them less of a threat than overgrown model planes They have a large infrared signature that our fighters can detect. They also have a limited range. To get close enough to the US to launch a cruise missile, any enemy (this category, I hope, excludes Mexico and Canada) would have to use a ship, which is relatively detectable. And cruise missiles are hard on the pocketbook of a third-world economy. But what kind of early warning system would notice that dozens of lawn mower engines, scattered over hundreds or thousands of square miles, were being started? Once in the air, these miniature missiles are so small and fly so slowly (the Laima droned along at 75 mph) that a modern jet interceptor would find it hard to see them. The jets fly too fast and go by a tiny target too quickly, and the military might find it hard to convince its top gun pilots to patrol in light planes -- not that that would do much good. Years ago, I flew a kite with a radar reflector to a height of a thousand feet or so. The tiny, aluminum-covered reflector was designed to return a signal the strength that a jumbo jet would show on the radar screen. My flying site was near a naval air station, and within a half hour of launching the kite (which had gone completely out of sight upward by the time I had let all the string out) three jets were circling the area downwind of my location. The next day, the navy called our model airplane club, which was located a few miles away, and asked if we had had any planes flying near the base. The time they mentioned was precisely when I had been flying the kite. They had not been able to spot the kite.

Small things are hard to find when you are zipping by them at 300 mph or more. Especially if you don't know what you are looking for.

The sponsors of the Insitu Group's effort were international; Environmental Systems and Services (from Australia), the Australian Bureau of Meteorology, the University of Washington, Boeing, L-3 Communications and, a bit more ominously, the US Office of Naval Research. The military implications of small, inexpensive, self-piloting vehicles has not been ignored by the military. The hot items these days are really tiny airplanes and choppers that are a few inches across and can carry cameras and other sensors into a battle zone and maneuver their electronic eyes around and even into buildings. But for now, the Laima and its kin are intended to collect and store standard weather information such as temperature, wind speed and direction, rainfall, barometric pressure, precipitation, and relative humidity. Even on this test flight, Laima had been monitoring a few of these parameters, as well as constantly checking its own air speed, cylinder head temperature, and other flight-related information.

On South Uist island, the group had been waiting since the early morning, hours before the scheduled landfall of the miniature drone. Tailwinds could bring it in early. Headwinds could bring it in late. Anxiety was exacerbated by the fact that three previous attempts had failed. With luck, somewhere out over the Atlantic, the 1.2 cubic inch displacement motor was still whirring, the gyros still keeping the wings level, the fuel not lost to an over-rich engine setting or a vibration-induced leak.

At about 1 p.m. the landing team heard one of the ground computers signal that it had received a transmission from the aircraft. That the weak signal could be heard meant that the aircraft was close, not close enough to be seen, but close. Telemetry told them that all was well with Laima and when the GPS indicated that the plane was overhead, human eyes got the first glimpse of it since it had vanished into the air over the North American continent. Switching over to manual control, the plane was landed undamaged; having no wheels, it smoothly and softly slid its belly on the grass. Laima was in one piece, and it was also damp, having passed through between 8 and 10 hours of rain.

When the plane was lifted from the ground, it had accumulated, along with a few grass stains and minor scratches, some world records. It was the smallest plane to have ever crossed the Atlantic. It was the first unmanned plane of any size to have done so. It was a harbinger of the future of over-ocean meteorological research. This year, they plan to fly the Pacific, spanning a distance approximately that from North Korea to, say, Seattle.

Years ago, the far-seeing Vannevar Bush pointed out that our seaports were vulnerable to a sneak attack by means of small boats, indistinguishable from pleasure craft, carrying atomic weapons. Now, every point in the world is vulnerable. Laima demonstrates the foolishness of trying build a Maginot line in the sky.

Author/inventor Jef Raskin is best-known as the inventor of the Macintosh computer project at Apple. His latest book The Humane Interface details how to make computers more usable and their interfaces more efficient.


Even easier and cheaper would be simultaneously launching shoulder-launched rockets at big passenger planes taking off from fifty airports across the country. If a truckload of illegal immigrants can make it into Texas, why not a truckload of rockets? The list of potential terrorists in this country numbers in the thousands, and they don't even need to blow themselves up. The result would be chaos for days and insecurity for years.

— Ralph Swank, Fri, 06 Feb 2015 23:24:53 UTC

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