he struck him down through the right buttock; straight through
into the bladder under the bone the spear-point passed;
he dropped to his knees screaming, and death embraced him.
as well as by rock:
But the son of Tydeus took in his hand
a boulder, a great feat, which two men could not lift,
. . . with this he struck Aeneas on the hip joint . . .
And the jagged stone crushed his hip socket, snapped the tendons on both sides,
and forced the skin away.12
With the emergence of fortifications and ship-to-ship or ship-to-shore engagement, there arose a need for new kinds of weapons that would be effective at greater distances. Artillery superseded the arrow and the spear. The challenges of distance reputedly also gave rise to practices such as catapulting beehives or diseased corpses over a city wall, or even leaving obvious caches of not-obviously-poisonous honey to be consumed by an enemy’s advancing troops—early versions of bio-warfare. Such innovations in weaponry sometimes proved as important as a commander’s clever strategizing.
By the late fifteenth century, Leonardo da Vinci would conclude that the best way to recommend himself to a potential patron, Ludovico Sforza, the Duke of Milan, was to foreground his manifold skills in designing the machinery of battle, from portable bridges to “big guns, mortars, and light ordnance of fine and useful forms . . . and other machines of marvellous efficacy and not in common use,” adding only as an afterthought, “I can carry out sculpture in marble, bronze, or clay, and also I can do in painting whatever may be done, as well as any other, be he whom he may.”13 Helping to equip armies promised to be a surer way for Leonardo to support himself than painting portraits and religious murals—a pattern that has held across the ages.
Commentators often invoke Clausewitz’s famous dictum concerning the nature of war—that it is “a mere continuation of policy by other means”14—but war and weapons can also be considered as problems in physics. Virtually all weapons ever devised are means of moving energy from here to there. “Here” is the device on one side of the conflict; “there,” some distance away, is the enemy or the enemy’s property. The device can be a boomerang, a bullet, a catapult, a cannonball, a harpoon, a trident, a grenade, a ballistic missile, a bomb, a laser. The energy can be in the form of kinetic mass, fissionable material, explosives, incendiary chemicals, light. The physical agenda—omitting all considerations of politics, law, religion, commerce, history, hatreds, honor, and the like—is to deliver that energy to a preselected location, where it can kill people and break things.
Nonbiological, nonexplosive modern weapons are of two main types: those that propel a certain amount of mass at high speed against a target (kinetic-energy weapons), and those that send destructive energy—chemical, nuclear, or electromagnetic—against a target (directed-energy weapons). A barrage of bullets fired at a line of soldiers a hundred yards away is a kinetic-energy weapon, while a downward-pointing laser aimed by an orbiting satellite at the main generator of a city’s water-purification plant would be a directed-energy weapon. Or how about examples from science fiction? Both Star Trek’s photon torpedo and Star Wars’ proton torpedo are kinetic-energy weapons that carry explosive warheads, while Star Trek’s ship-mounted and handheld phasers are directed-energy weapons. Star Wars’ classic personal weapon, the light saber, cleverly combines the directed-energy weapon’s futuristic capacity to annihilate at a distance with the ancient practice of hand-to-hand combat.
Through most of history, weapons tended to rely on kinetic energy, whether of a twenty-pound rock, a thirty-two-pound cast-iron sphere, or a twenty-gram lead bullet. Tomorrow’s hypervelocity tungsten rods—tall, slim, massive, fairly radar-proof—are a fearsome, though largely fictional, space-age kinetic weapon that would be discharged from a satellite. The destructive potential of these “Rods from God” would be supplied by their gravity-accelerated descent from Earth orbit to Earth’s surface.
Sometimes a weapon combines kinetic energy with another kind of energy. The kinetic energy of a white-phosphorus-filled exploding grenade hurled into a crowd will bruise anyone it hits, but the highly incendiary chemical energy contained within it is what will do the real damage. The kinetic energy of a long-range or intercontinental ballistic missile (ICBM) that falls on a distant city will destroy a building simply by virtue of its mass and speed, but if the ICBM carries a nuclear warhead or two, as most have done since the 1960s, it can destroy entire cities.
Until the space age, weapons largely depended on mass and speed to do damage to their targets. Only when space became a potential domain of warfare, and lasers became the ultimate concentration of light, did nearly massless energy—cheap to launch and inherently able to move at the fastest speed in the universe—become the dream weapon for the highest-altitude battle zones.
Lasers rank high on the wish list for a space arsenal. The laser is the quintessential directed-energy weapon: a needle-thin but intensely strong beam of light that can be precisely aimed at a narrow target. While civilian versions are sufficiently mild to be used as lecture pointers, more powerful versions are used for eye surgery, cosmetic hair removal, and printing. Military versions are meant to range from highly damaging to lethal. There are also peaceable, scientific lasers. One such is perched on NASA’s Curiosity rover, which has been trundling across the surface of Mars since 2012. Whenever Curiosity encounters an interesting rock formation, its ChemCam laser instrument aims a series of brief million-watt pulses at it. While the laser vaporizes the target area, a camera picks up the flash and determines the chemical composition of the target, the ultimate goal being to assess the Red Planet’s habitability.
The word “laser” is an acronym, derived from the phrase “light amplification by stimulated emission of radiation.” And the laser has a sibling, the maser, with an “m” standing in for “microwave.”15 Neither occurs naturally here on Earth. Both result from the interaction of photons with specific atoms whose electrons both absorb and emit exactly the same kinds of photons. The task at hand is to generate as many of these identical photons as possible and send them out through a hole. In a laser, the photons of a single frequency accumulate in a customized cavity and are emitted in resonance with one another, with all the crests and troughs of the light waves aligned. Physicists call that state “coherence,” and it is singularly responsible for the focused intensity of a laser beam.
Literature—specifically, H. G. Wells’s 1898 novel War of the Worlds, the inspiration for multiple movies and other spin-offs—was the birthplace of the laser, in the form of a death-dealing beam called the Heat-Ray, which a Martian invasionary force that lands near London “pitilessly flourishes” against anything and anyone in its path. The armor-clad globlike invaders—hundred-foot-tall “boilers on stilts . . . striding along like men”—wield an “invisible sword of heat” emitted by a “camera-like generator.” One soldier who has witnessed the effects of the Heat-Ray at close range says of Britain’s twelve-pound guns that have been set up to repel the invaders, “It’s bows and arrows against the lightning, anyhow.”16
During the decades that followed publication of War of the Worlds, especially those following the uneasy conclusion of World War I, the Heat-Ray morphed into the more general “death ray” and became a recurring warrior fantasy/nightmare. In 1924, during his antiwar days on the backbench, Winston Churchill warned in a widely reprinted magazine article that among the weapons in a coming war would be “electrical rays which could paralyze the engines of motor cars, could claw down aeroplanes from the sky and conceivably be made destructive of human life or vision.”17 Britain’s upper-echelon defense planners were not immune to the seductive potential of the fantasy, and Churchill, after becoming a vocal advocate of defensive technologies, urged its implementation. A. P. Rowe, assistant to the director of the Air Ministry’s Directorate of Scientific Research and himself soon to be director of the Telecommunications Research Establis
hment, described the British military’s response:
For many years the “death ray” had been a hardy annual among optimistic inventors. The usual claim was that by means of a ray emanating from a secret device (known to us in the Air Ministry as a Black Box) the inventor had killed rabbits at short distances and if only he were given time and money, particularly money, he would produce a bigger and better ray which would destroy any object, such as an aircraft, on to which the ray was directed. Inventors . . . invariably wanted some of the taxpayers’ money before there could be any discussion of their ideas. The Ministry solved the problem by offering £1,000 to any owner of a Black Box who could demonstrate the killing of a sheep at 100 yards, the secret to remain with its owner.
The mortality rate of sheep was not affected by this offer.18
Interest in a death ray persisted nonetheless. With radio-wave transmissions and the electrification of the world’s cities proceeding apace, Henry Wimperis, Rowe’s superior at the Directorate of Scientific Research, wrote that he was “confident that one of the coming things will be the transmission by radiation of large amounts of electric energy along clearly directed channels. If this is correct the use of such transmissions for the purpose of war is inevitable.” The assumption was that radio waves would provide the energy, and so Wimperis asked radio researcher Robert Watson-Watt in mid-January 1935 to come up with an answer to what Rowe describes as “the problem [of] whether it was possible to concentrate in an electromagnetic beam sufficient energy to melt the metal structure of an aircraft or incapacitate the crew.” Avoiding any reference to planes or people, Watson-Watt handed the problem to an underling, Arnold Wilkins, asking him in a scribbled note to “calculate the amount of radio-frequency power which should be radiated to raise the temperature of eight pints of water from 98°F to 105°F at a distance of 5 km and at a height of 1 km.” As eight pints is the amount of blood in an average adult human male, Wilkins wasn’t fooled by the obfuscation:
It seemed clear to me that the note concerned the production of fever heat in an airman’s blood by a death-ray and I supposed that Watson-Watt’s opinion had been sought about the possibility of producing such a ray.
My calculation showed, as expected, that a huge power would have to be generated at any radio frequency to produce a fever in the pilot of an aircraft. . . . it was clear that no radio death ray was possible.
But Wilkins suggested another idea to Watson-Watt: exploiting an earlier discovery by a couple of radio engineers that metal airplanes invariably interfered with radio communication. That interference, he said, amounted to an announcement of their presence, even when they couldn’t be seen. Watson-Watt rushed off a memo to Wimperis, omitting the fact that Wilkins had supplied the information.19 Thus was born the concept of radar.
Was the death ray dead? No, only the radio death ray. As Rowe opined in 1948, “The idea of a death ray however was not absurd and something of the kind may come within a hundred years.”20
And so it has.
While astrophysical lasers are a rarity, astrophysical masers are semi-common. You can find one variety deep within colossal gas clouds scattered across spiral galaxies. In dense, bright, star-forming regions within those clouds, countless electrons that belong to molecules of hydroxyl (OH) or water (H2O) or ammonia (NH3) are primed to emit resonant photons.
Picture a large cavity within a blob of gas. Now picture the light from nearby stars bathing the region. The photons get absorbed by selected molecules. What happens next is part of the weird world of quantum mechanics. The same bath of photons that the molecules absorbed stimulates those same molecules to emit photons of the same wavelength—the same energy—mostly in the microwave part of the spectrum. Excite a gas with microwaves; the molecules of gas emit microwaves; the microwaves cause the molecules to emit more microwaves. Next, the microwave energy punches through the cloud, creating a powerful, concentrated beam that funnels out in one direction. Behold an astrophysical maser, aimed wherever the opening in the cloud happens to face.
Unlike their astrophysical relatives, human-made lasers must be pointed with exactitude. Bad aim brings disaster. A common ground-based, military-grade thirty-kilowatt laser (with its six million times the power of an ordinary laser pointer) can punch a hole in a truck engine or in the fuel tank of a booster rocket sitting on a launch pad.21 Space-based lasers, once perfected, would be dominant and lethal. Deployment presents challenges, however. While in motion around Earth, the laser must generate and direct colossal power to a specific target, which is also in motion. What’s more, the laser beam must be delivered swiftly, unattenuated by clouds and unmolested by atmospherics.
Coming up with the initial power is the first step, and there are many possible sources. A common chemical laser, for instance, depends on the conversion of stored chemical energy into intense infrared energy—harnessing the energy of molecules that are zealously engaged in a chemical reaction and then channeling that energy into a beam of light. A less benign option would be a small nuclear bomb or nuclear reactor investigated in the 1970s and 1980s for use in weapons such as the space-based X-ray lasers of the failed US missile-defense program Project Excalibur. Once the energy has been produced, you need a cavity of some kind that will hold and, ideally, further stimulate the already hyped-up molecules. A recent development is the fiber laser, in which extremely long, hair-thin, light-transmitting glass or plastic fibers, saturated with rare-earth elements, are the operative technology. Notable attributes of this kind of laser include its potential to offer huge amounts of power and to be bent into a compact shape. Furthermore, it’s stable at high temperatures, and the inherent light-wave-guiding properties of a fiber produce an extremely precise, intense beam.
Once you’ve got the power, the medium, and the beam, you face the challenge of aiming. For that, you’ll need an optical apparatus capable of high resolution, so that the target area can be clearly seen. Does that sound like a telescope? It should, because it is. Today, the largest optics (mirrors rather than lenses) are the ones developed for telescopes.
Early in the twenty-first century, a comprehensive report from the RAND Corporation, a think tank devoted mainly to US military policy, proposed that the optics required for a space-based laser weapon designed to destroy terrestrial targets could become available and affordable once the optics required for the “next-generation space telescope” had been mastered. Today’s real-life next-generation space telescope, the seven-ton James Webb Space Telescope, has a 6.5-meter gold-coated mirror made up of eighteen separate hexagonal segments constructed from pure beryllium, a metal that’s both strong and light. But all that high design doesn’t come close to the report’s estimate of what would be needed for a space-to-Earth laser: a mirror measuring more than ten meters across, millions of watts of available power, and the capacity to withstand overwhelming heat.
After all is said and done, according to RAND’s researchers, much more progress would have to happen before a space-based laser becomes “feasible,” let alone “reasonable.”22 Many other analysts arrived at the same position, including, a few years later, the authors of a report from the American Academy of Arts and Sciences, who concluded that the technology for a “usable” laser of this sort “does not currently exist and will not for the foreseeable future.”23 Even the people who themselves develop directed-energy technologies or oversee the acquisition of these technologies for the Department of Defense now cite time frames such as the 2020s for the first flight test of an aircraft-mounted 60–150-kilowatt laser.24 In other words, space-based, long-distance, million-watt laser weapons remain the stuff of fantasy.
Aware of this mismatch between needs and expectations, RAND offered an interim solution: laser weapons aimed at space could be located on high, dry mountaintops down here on Earth. Yes, but . . . Those mountaintops happen to be the very places where we astrophysicists like to put our telescopes. Shouldn’t be a problem, said the researchers—just put the weapon and the science in the same
location, since both groups use laser beams to monitor and correct for atmospheric turbulence in their observations. The scientists “might even welcome the laser if its large optics could also be used to increase observing time when not needed for weapon operations, maintenance, or training,” said RAND.25 Given that astro-folk tend to be a peaceable crew, “accept” might be a more suitable word than “welcome.”
Since its founding in 1948, by the way, the RAND Corporation has supported a fair bit of “thinking about the unthinkable.”26 To this and other ends, it has consistently hired impressive individuals, ranging from Daniel Ellsberg, who made public the Pentagon Papers, to Donald Rumsfeld, who served as a RAND trustee for a quarter century before becoming George W. Bush’s secretary of defense. RAND’s very first report, commissioned by Major General Curtis LeMay and published in 1946, bears the exciting sci-fi title Preliminary Design of an Experimental World-Circling Spaceship—i.e., a satellite—and its very first client was the Air Force.27 In 1958 a RAND author, Robert W. Buchheim, produced a classified space tutorial, The Space Handbook, for the enlightenment of the House Select Committee on Astronautics and Space Exploration. The following year, Buchheim and the RAND staff updated and declassified the handbook for publication by Random House.28 And by the beginning of the twenty-first century, RAND had generated hundreds of policy papers on space science, space exploration, and space warfare.
Speaking on national radio and television in late March 1983, halfway through his first term of office, President Ronald Reagan drew an alarming picture of the defunding and decay of US military forces and military technology during the 1970s in contrast to the USSR’s concurrent military buildup. According to Reagan, the imbalance was overwhelming and terrifying:
Accessory to War Page 27
