Jim Baen's Universe

Featured Article

Quarks to Quasars:The Science of Science Fiction

Columns

Buck Rogers Redux

Written by Ben Bova

And now for something completely different.

Lasers.

Well, yes, this column is about the development of high-power lasers and their coming use in missile defense. But it’s also about the way science works, both in the laboratory and in the halls of political decision-making.

The laser was invented in 1960, and the earliest lasers were built from solid materials such as artificial ruby. Their power outputs were minuscule, usually measured in thousandths of a watt (milliwatts).

By 1965, lasers were little more than laboratory curiosities. They produced very brilliant pulses of light, brighter than the Sun for a fraction of a second. But what good did that do? Lasers were widely called “a solution looking for a problem.”

At that time I was working at the Avco Everett Research Laboratory, near Boston, Massachusetts. AERL had been founded by Arthur R. Kantrowitz in 1955 specifically to solve the re-entry problem for ballistic missiles. The lab’s work in re-entry physics led to the heat shields that protected our Apollo astronauts when they returned from the Moon and hit Earth’s atmosphere with the speed of a falling meteor.

The lab’s team of physicists went on to other areas of research, most of them involving the physics of high-temperature gases. We were known internationally as “hot air specialists.”

I am not a scientist. My work at AERL involved helping the scientists to publish their research results and, later, to writing proposals and running the lab’s marketing group. I wrote science fiction in my own time, while at the lab I was helping to make science fiction become reality.

By 1965 several research organizations had produced lasers that used gases as their working medium, rather than artificial ruby or other solid materials. The most powerful of these gas lasers used carbon dioxide to produce the lasing action. They emitted a few kilowatts of infrared energy from glass tubes that were, in some cases, as long as a football field.

Laser output power was going up, but the devices were impractical outside a laboratory setting.

Arthur Kantrowitz had a better idea.

He called a meeting of the lab’s senior scientists. They were specialists in fluid dynamics, gas physics, chemical physics, plasma dynamics and other disciplines. Many of them had been graduate students at Cornell University when Kantrowitz taught there, before founding the Avco Everett Laboratory.

He pointed out to them that the factor limiting the output power from gas lasers was heat. The laser gas heated up as the laser reactions took place in it; when the gas reached a critical temperature, laser action shut down. Kantrowitz characterized the problem as “garbage removal.” Existing gas lasers were made of long glass tubes; the longer the tube, the more gas and the more output power. But the only way to remove heat from a gas sealed in a glass tube was for the heat to trickle to the walls of the tube and escape by radiation. Kantrowitz likened this to a cesspool: the “garbage” can only seep out of the walls of the enclosure.

Far better, he suggested, to build a sewer line, where the “garbage” flows out of the laser chamber and is replaced by fresh incoming gas. Power output could be much, much better because the heated gas (the “garbage”) was exiting the laser chamber while fresh gas—full of energy—was coming in.

The lab’s scientists all dealt, in one way or another, with the behavior of flowing gases. They immediately started to work on a “gas dynamic” laser, where the working gas flowed at supersonic speed through a sort of rocket nozzle. By arranging the gas flow appropriately, the carbon dioxide molecules in the mixture could become excited, then give up their energy of excitation as they flowed through the laser cavity.

The first gas dynamic laser was built in one of Avco Everett’s laboratory spaces. To produce the right mixture of carbon dioxide, nitrogen and water vapor, the device burned lethal cyanogen gas with oxygen. When the hot gas flowed through the nozzle, the carbon dioxide molecules “hung up” in an excited state long enough to dump their energy in the laser cavity section immediately downstream of the nozzle.

The man-tall assembly delivered 10 kilowatts of output power in its infrared beam. In its first ten seconds of operation, it put out more energy than all the lasers that had been built and operated up until that moment.

There was so much energy bouncing around inside the laser cavity that the scientists had a difficult time finding a window material that would not shatter from its intensity. The cavity itself had walls of solid copper, through which water lines had been drilled for cooling. Two of the copper walls were highly polished mirrors that allowed the laser energy to cascade back and forth and build up in intensity.

Only a sheet of solid diamond could stand up to the laser’s energy intensity; anything less shattered. Diamond was impractical, so the Avco scientists invented the “aerodynamic window,” which was nothing more than a series of holes drilled in one of the mirror walls, aligned to focus the individual beamlets outside the laser into a single coherent beam. Nitrogen gas was blown across the “window” to prevent room air from leaking into the laser cavity, which operated at a lower pressure than ambient.

We applied for a patent on the aerodynamic window. The application had to go through a special section of the Patent Office, because the work we were doing was classified Secret by the government. The patent came through much sooner than the Patent Office’s normal procedures would have allowed. When the approval document arrived on my desk, stamped SECRET in bright red, I immediately took it to Kantrowitz’s office and suggested that, since we had won a patent on what was essentially a bunch of holes, we should forget about lasers and take over the doughnut industry. He was not amused.

All right, we had a working high-power laser. More important, we had the understanding to build lasers of much higher power. Megawatts or more.

I helped to arrange a Top Secret briefing in the Pentagon to reveal to the Department of Defense that lasers of weapons-grade power were now feasible. Originally scheduled for January 1966, the meeting was canceled by a snowstorm that blanketed the east coast. I dutifully traveled to Washington DC by Amtrack train. The ride was like a scene out of Dr. Zhivago. Scheduled to reach Washington’s Union Station by noon, we actually pulled into the snow-buried city close to midnight. By then, of course, the meeting scheduled for the next morning had been cancelled. It was rescheduled for a date in February.

DoD gathered together nearly two dozen of the nation’s top experts on optics, gas physics, laser technology and other allied areas of knowledge. We met in a basement conference room in the Pentagon. Right away we ran into a problem. The room’s slide projector refused to work and none of the PhDs assembled around the table was able to fix it. We had to find a tech sergeant to come in and get the thing working. Our material was too highly classified for the sergeant to see it, so we parked him out in the corridor while I ran the repaired projector.

Kantrowitz and several of the lab’s top scientists gave the presentation, which lasted a little more than an hour. At the end, after the last slide had been shown and the ceiling lights turned on again, there was more than a minute of utter silence. The top experts were stunned by what the Avco team has accomplished.

Work went ahead on developing higher-power lasers. The government demanded that we share our knowledge with General Electric’s research people at their Schenectady facility. Washington insisted that a development this momentous should not be left in the hands of a single contractor; DoD wanted competition, presumably to keep everybody honest.

Along with the technology development, we began to study ways in which high-power lasers could be used. Military applications were uppermost in everyone’s mind, although I eventually helped make presentations to the U.S. Bureau of Mines about using lasers to help drill through the hardest of rock, to NASA about interplanetary communications using lasers, and to industry about lasers for welding and cutting metal.

It became obvious that a high power laser beam, striking with the speed of light, could destroy a ballistic missile in flight, especially during its boost phase when its rocket engines were roaring away and the missile was easily detectable and quite vulnerable. A megawatt or more of energy focused on a spot of about one square centimeter could burn through the rocket’s skin and ignite the propellants inside.

If you picture what happened to the space shuttle Endeavor when its solid-rocket booster burned through and exploded, you can imagine what happens to a missile when a megawatt-sized laser beam hits it during its boosting phase of flight.

The idea of developing “ray guns” for military applications had a lot of giggle factor to overcome, but by the time Ronald Reagan became President of the United States, laser weaponry became an integral part of his Strategic Defense Initiative. The news media dubbed it “Star Wars,” but SDI helped to convince Soviet Russia’s military that they had no hope of keeping up with the West technologically.

Over several decades the USSR had spent trillions to build an immense fleet of ballistic missiles armed with hydrogen bombs. Now the possibility arose that those missiles could be made, in Reagan’s words, “obsolete and impotent.” When Gorbachev began to reform the Soviet system, the generals did not object.

SDI helped lead to the collapse of the Soviet Union and the end of the Cold War.

Today, in addition to the nuclear-armed missiles of Russia and China, we are faced with threats from terrorists and nations such as North Korea and Iran—both of which are developing nuclear weapons and long-range missiles.

The U.S. has deployed missile interceptors at Fort Greeley, Alaska, and Vandenburg Air Force Base, California. These are anti-missile missiles, intended to destroy attacking missiles by smashing into their warheads, the “kinetic kill” technique.

The Missile Defense Agency is also flight testing the Airborne Laser, a specially modified Boeing 747 four-engine jet that carries a megawatt-plus chemical oxygen-iodine laser (COIL).

The thought of this lumbering plane reminds me of discussions we had at the Avco Everett lab back in the late 1960s. With laser weapons, we reasoned, the fighter plane of the future won’t be some nimble supersonic jet piloted by a fighter jock like Chuck Yeager; it will be a lumbering big-ass jumbo jet carrying the most powerful laser we can build. While the plane may be slow, the weapon strikes with the speed of light.

That plane is flying now. It is ABL-1, and it is being tested against ballistic missiles. More will follow.

Warfare is about to make its first major change since the advent of the ballistic missile, some seventy years ago. Since Nazi Germany’s V-2 of World War II, ballistic missiles have been called “the ultimate weapon,” because there was no defense against them.

Lasers and other beam weapons are the answer to “the ultimate weapon.” Unlike missiles and nuclear bombs, lasers are not weapons of mass destruction. They are weapons of pinpoint destruction, inherently defensive in nature.

A new era of warfare is dawning, and its light is the coherent beam of the laser.

****

Ben Bova is the author of 120 books of fiction and nonfiction, including THE IMMORTALITY FACTOR, his latest novel. Dr. Bova is President Emeritus of the National Space Society and a past president of Science Fiction Writers of America.