The Cold War (66 page)

The Cold War began before the advent of ICBMs and surely would have been waged without them, but in a manner difficult to imagine. The crux of the matter was that an ICBM attack could be delivered in a remarkably brief span of time and, in practical terms, was unstoppable. But the incoming warheads had no place to hide in the empty vastness of space and could be detected by radar as they rose above the curvature of the earth, leaving ample time to deliver a counterblow. Later, geosynchronous reconnaissance satellites armed with infrared detectors tuned to the heat emission spectra of rocket exhaust plumes extended warning time to the moment of liftoff. In round figures, an ICBM could traverse the distance between America and the Soviet Union in about thirty minutes, but from 1961–62, American ICBMs, and presumably Soviet ones, could be out of their silos within a minute of receiving an authenticated launch order.

The essential elements of the equation were in place by the early 1960s and, the Soviet deployment of antimissile missile batteries around Moscow notwithstanding, remained in place through the end of the Cold War. Without the residual threat posed by ICBMs standing ready in their silos in the missile fields of Central Asia and North America, a disabling surprise attack by manned bombers or submarine-launched ballistic missiles would, in principle, have been possible. Ironically, the transparently self-evident nature of ICBM deterrence left both the Soviet Union and the United States free to wage conventional war, both by proxy and in person, by relaxing the fear that tensions rising
from, say, war in Korea, Vietnam, or Afghanistan might unleash an unanswerable thermonuclear attack out of the blue.

Conversely, the balance of terror in Europe was complicated by intermedi-ate-range ballistic missiles (IRBMs), vastly increasing the dangers posed by conventional warfare and—with benefit of hindsight—effectively ruling it out. With much shorter flight times than their intercontinental cousins, IRBMs complicated the warning-and-notification deterrent calculus, all the more so since they were based close to, and ostensibly targeted against, vital industrial and population centers. The problem was particularly acute for the Soviets, inasmuch as the western Soviet Union was within IRBM reach of European NATO. The United States was not, of course, within reach of Soviet IRBMs, and by the mid-1970s the specter of a “limited” nuclear exchange in Europe seemed plausible, at least to some; analysts grimly joked about America's willingness to fight to the last European. The story is an involved one, as much a part of diplomatic as military history, and is too complicated to recount here. Suffice it to say that concern for a surprise attack by European-based IRBMs, including Soviet missiles west of the Urals, was a major driving force in nuclear arms control negotiations almost from the beginning—the quid pro quo for the removal of Soviet missiles from Cuba in 1962 was the removal of U.S. IRBMs from Turkey and Italy—and that here, as with the Soviet and American response to the strategic dilemmas posed first by the possibility and then by the reality of the ICBM, technology ruled. The presence of mobile Soviet SS-20 IRBMs in Europe from 1977, and the threat of a subsequent tit-for-tat Pershing II deployment by the U.S., loomed large in the logic behind the negotiations between President Ronald Reagan and Premier Mikhail Gorbachev that, as we now know, marked the beginning of the end of the Cold War.

The logic of the scenarios posited above is debatable. What is not is that ICBM-based mutual deterrence was central to the Cold War, a reality reflected in the strategic vocabulary. Such expressions as circular error probable (CEP), preemptive first strike, survivable second-strike capability, and launch on warning, while not exclusively related to ICBMs, arose within a context shaped by the intercontinental ballistic missile. IRBMs were important mainly as a theater-level deterrent or, as we shall see, a first-strike threat. Manned bombers, the first nuclear delivery system and the only one with intercontinental reach until the late 1950s, influenced Cold War strategic calculations not so much because of the awesome power of their bombs but because, unlike ICBMs, they could be launched and then recalled to “send a message.” It is worth noting,
too, that while ICBMs had a major impact on strategic bomber operations, driving the U.S. Strategic Air Command to a fifteen-minute runway alert posture and to continuous airborne alert during times of heightened tension, the converse was not true: So long as a launch order could get through, the ICBM in its hardened silo of reinforced concrete or, in its final Soviet incarnations, on a mobile transporter-erector-launcher (TEL), was operationally self-sufficient and thus strategically credible. The ballistic missile submarine assumed strategic importance not because of the power or accuracy of its weapons—submarine-launched ballistic missiles (SLBMs) were generally inferior to gravity bombs and ICBMs on both counts—but because the submarine, hidden in the ocean deeps, was effectively immune to preemptive attack by ICBM.

The ICBM had its origins in the aftermath of World War I, in the spaceflight societies of Weimar Germany. Advocating manned exploration of space, the societies combined utopian futurism with hardheaded technological realism. Their first and most basic contribution was to recognize that black powder, hitherto the only rocket propellant, would never suffice to lift a payload beyond the atmosphere. Although powerful, black powder fell short when it came to imparting acceleration to a rocket. The relevant measure of merit was specific impulse; that is, the number of pounds of thrust produced by each pound of propellant burned per second. Expressed in seconds, specific impulse is in fact a measure of efficiency: The higher the value, the more efficient the propellant. As the formula indicates, the key integer was the molecular weight of the decomposition products, the lighter the better, and the products of a blackpowder explosion were heavy indeed. Oxidizing alcohol, gasoline, or kerosene with liquid oxygen offered substantially better performance, and it was on these combinations that the rocket pioneers based their calculations. To highlight the difference, black powder's specific impulse is about 150 seconds, while that of liquid oxygen and kerosene is on the order of 300. Other combinations that offered better performance—for example, liquid oxygen or liquid fluorine and liquid hydrogen—were clearly impractical: Hydrogen is liquid only at extremely low temperatures (the stuff boils at – 423 degrees), posing formidable containment problems, and fluorine is horribly corrosive. The German space enthusiasts were remarkably good prophets; all first-generation ICBMs used the propellants they identified. Liquid hydrogen, the most efficient fuel of all, was not tamed until the mid-1960s and even today is used only for the most demanding applications, in the upper stages of rockets for deep-space exploration
and in the space shuttle's main engines, where extreme performance requirements justify the immense time, effort, and cost that liquid hydrogen entails and where quick launch response is not important.

The story of the German army's co-option of the rocket societies, of the establishment of the Peenemünde test facility, of the development of the A-4/V-2 bombardment rocket, and of Wernher von Braun's pivotal role in the process is well known. In essence, von Braun and his engineers solved the two most basic problems of high-performance rocketry: propulsion and guidance-and-control, the former with a liquid oxygen/alcohol engine weighing 2,484 pounds and producing 28 tons of thrust; the latter by graphite vanes thrust into the rocket exhaust, assisted by aerodynamic control surfaces on the tail fins and controlled by an electronic analog computer that could be reprogrammed to accommodate changes in range and direction, the first reprogrammable electronic analog computer ever.

The V-2 had a maximum range of only 180 miles, indifferent accuracy—miss distances of a mile in range and two and a half miles laterally were typical—and a warhead containing only 1,650 pounds of high explosive. In terms of its contribution to the Third Reich's war effort, the V-2 was a gross waste of resources, not least of all because, as historian Gerhard Weinberg has noted, it was useless on the Eastern Front by the time it became operational, since the urban complexes it could hit were out of range. It was, however, effective in bombarding the cities of an industrialized nation, as the British learned to their dismay, and von Braun and his group had toyed with the idea of extending its range to intercontinental dimensions by adding wings or a second stage. In the aftermath of Hiroshima and Nagasaki, the possibility that such a vehicle could be used to loft a nuclear warhead was starkly evident, and, at least theoretically, there was no limit to range. Engineers in the Soviet Union and the United States had initiated design studies for such a combination before the Cold War started.

There is a general mistaken notion that the V-2 was the direct ancestor of all American and Soviet ICBMs and high-performance space boosters. Without diminishing the technical achievements of the Peenemünde design group, that is at best a half-truth. The Soviet Union was well advanced in rocketry before World War II and successfully tested a rocket-powered fighter plane in 1941, well ahead of the Germans. But the Soviet lead was compromised by Stalin's paranoia, for the Great Purge decimated not only the ranks of his officer corps but those of his engineers as well. Sergei Korolyov, designer of the first Soviet ICBMs, was condemned to the gulag in 1938 and released only in 1944, when
rocketry's strategic importance became evident. The United States came late to high-performance rockets, as it had to jet engines, but, with its seemingly bottomless reservoir of competent engineers, quickly made up lost ground. North American Aviation had begun design studies on high-performance liquidfueled rocket engines before war's end, and other companies, notably Douglas and Martin, were not far behind.

To be sure, both the Soviets and the Americans milked the V-2 for what they could. The U.S. Army absorbed the von Braun group, giving it responsibility for army ballistic missile development at the Redstone Arsenal near Huntsville, Alabama. The group was later absorbed by NASA to become a major component of America's space program. By contrast, the Soviets exploited German rocket engineers individually before releasing the survivors to go home. The Soviets put the V-2 into production in 1950 and fielded enhanced versions later in the decade, in large part to train the launch crews of what was to become the Strategic Rocket Forces, independent of the Red Army and Air Force. That said, the only direct V-2 descendants of consequence were the huge first-stage booster rockets, designed at Huntsville under von Braun's guidance, that powered Apollo astronauts into earth orbit en route to the moon. While inspired by the V-2 and exploiting German engineering breakthroughs, the American and Soviet ICBMs fielded during the Cold War were distinctive products of their respective national industries. Nor could it have been otherwise, for as World War II drew to a close, the means by which intercontinental range might be achieved with a nuclear-tipped ballistic missile were anything but clear—if, indeed, it could be done at all.

Three basic problems confronted would-be ICBM designers: propulsion, guidance-and-control, and warhead design. Measured against existing systems, propulsion required the greatest advances but, ironically, would be easiest to master. The Germans had solved the basic problems of combustion-chamber design and had developed turbopumps to deliver fuel and oxidizer under pressure. The challenge was to increase scale and efficiency, which, while hardly simple, required no major breakthroughs. In guidance-and-control, too, the Germans had shown the way, using gyroscopically stabilized platforms to provide precise vertical and horizontal orientation, linear accelerometers and integrating circuits that compared acceleration with elapsed time to calculate velocity, and an electronic computer to translate the inputs into discrete commands in thrust, roll, pitch, and yaw. Mechanically deflecting exhaust gases
was a crude stopgap, but the idea of controlling thrust by gimballing—that is, mounting the entire rocket engine on a ball joint and swiveling it to control the direction of thrust—had an intellectual pedigree that went back to the prewar rocket societies. Development of the hydraulic pistons, servomotors, and electronic control boxes capable of aligning a rocket motor firing at full thrust within tenths of a degree in pitch and yaw would be difficult, but the basic technologies were reasonably well understood.

Warhead development was another matter. First, the warheads had to be sufficiently light and compact for the rocket to loft, and the shrinking of warheads entailed forbidding problems of nuclear physics, of precision manufacture, and of controlling the focused implosion of the high-explosive charges that squeezed the bomb's plutonium or uranium core to critical density. Second, intercontinental trajectories involved reentry into the atmosphere at unprecedented velocities, and that, for reasons of basic physics, entailed unprecedented temperatures. The short-ranged V-2's modest reentry velocities produced a fraction of the heat generated by the collision with the atmosphere that intercontinental trajectories entailed, and the engineers started with blank paper. They quickly learned that the V-2's sharply pointed nose was
not
the way to go. The intense concentration of heat caused by the formation of a hypersonic shock wave around a single point created temperatures nearly twice the melting point of steel. The obvious solution was a massive metal shield that would absorb the heat until the warhead reached the lower atmosphere, where convective cooling could take over.

We are unsure about developments in the Soviet Union, but American engineers favored copper heat shields, both because of copper's great heatabsorptive capacity and because it was easy to calculate the thickness needed for a given reentry velocity. But copper is extremely heavy. The Germans came to the rescue, recalling that a plywood-encased instrument package installed in an experimental V-2 had survived reentry intact, though with the plywood charred. In charring, the plywood had clearly been an efficient heat absorber; moreover, plywood was light and provided good thermal insulation. From this insight came the development of heat shields made of materials designed to dissipate reentry heat by ablation, literally by wearing away. American engineers initially balked, for calculating the thickness of an ablative shield was dauntingly complex, depending not only on thermal conductivity but also on heat loss due to burning, melting, sublimation, and physical loss of material. Indeed, the required
thickness could be determined only by repeated testing. But the weight advantages of ablatives were compelling, and their use became standard.