The Cold War (67 page)

Ablative heat shields were only half of the solution. The other half was discovered in 1952 by the National Advisory Committee on Aviation (NACA, later NASA) engineer H. Julian Allen in wind tunnel tests that showed blunt shapes pushed the heat-laden shock wave well out in front, dissipating some 60 percent of the reentry heat in a parabola-shaped wave. In combination with ablative heat shields and warhead miniaturization, their discovery made the ICBM a practical reality. It also put America's Mercury astronauts into orbit: John Glenn and his successors returned to earth aboard Atlas ICBM reentry bodies fitted with a cockpit instead of a warhead. The early Soviet cosmonauts returned to earth aboard larger, and conceptually cruder, spherical spacecraft exploiting the same basic phenomenon.

Meanwhile, beginning with manned bombers, the Soviets and Americans developed other delivery systems as insurance—with great success in the U.S. and indifferently so in the Soviet Union. The relevant comparison is between the Boeing B-52, still a mainstay of America's aerial might half a century after entering service, and the marginally successful Myasishchev M-4, which offered only an incremental performance increase over the turboprop-powered Tupolev Tu-95. (The British fielded a highly capable nuclear bomber force during the mid-1950s but lacked the wherewithal to develop strategic missiles and became increasingly dependent on the American nuclear deterrent as the Cold War progressed.) Next, while pressing the development of ICBMs, both the U.S. and the Soviets turned to intercontinental cruise missiles. The initial American contracts were let in 1945–48, and by the early 1950s two prime contenders had emerged: the subsonic Northrop Snark and the supersonic North American Navaho. Both Snark and Navaho were large, a reality dictated by warhead size and weight, but there the similarities ended. Apart from its lack of horizontal tail surfaces, the Snark was a relatively conventional vehicle. Turbojet-powered, it was boosted from its launcher by two strap-on solid-fuel rockets and was guided by an inertial system that incorporated stellar navigation. Development was anything but smooth, and repeated unsuccessful launches from Patrick AFB, Florida, led to quips about Snark-infested waters. Worse, one Snark failed to self-destruct as programmed and proceeded southward, turning up in the Brazilian rain forest and inspiring the couplet “Hark, hark, the Snark. Where she goes, nobody knows!” For all this, the Snark briefly achieved operational status at Presque Isle, Maine, in 1960–61.

The Navaho was considerably more complex, consisting of a ramjetpowered Mach 3 cruise vehicle of advanced design that was launched vertically and accelerated to flight speed by a liquid-fueled rocket booster. The booster was powered by a North American Rocketdyne liquid oxygen/kerosene rocket with exceptional promise but a short track record, and the staging sequence— the Navaho was the first to use “piggyback” staging, with the cruise vehicle mounted atop the booster—embodied major technical unknowns. The ramjet engines were of novel design and unprove; the flight control and navigation systems were complex and (the fatal flaw), like those of the Snark, used vacuum tubes. As the Navaho demonstrated graphically, vacuum tube reliability, while sufficient for relatively straightforward systems with built-in backups, including first- and second-generation ICBMs, was inadequate for a vehicle in which hundreds of interdependent events had to occur in precise sequence for extended periods. In sum, the Navaho was an extraordinary mix of promise and disappointment. A turbojet-powered version of the cruise vehicle, the X-10, was highly successful as an unmanned research craft, and the booster's rocket engine was the progenitor of a host of high-performance American designs, but the total vehicle was an utter flop, earning the sobriquet “Never go Navaho” with a series of spectacular pad explosions and post-launch failures. Still, its promise was so great, and the hurdles to be surmounted to produce a successful ICBM so forbidding, that for a short time in 1955, Navaho enjoyed the highest funding priority, receiving substantially more money than the Atlas ICBM.

The Soviets got off to a more measured start, developing and fielding V-2 derivatives that culminated in the 725-mile-range R-5, the first Soviet missile to carry a nuclear warhead. It was dubbed SS-3 Shyster by NATO. (The actual model designations were unknown to Western intelligence, and NATO identified Soviet systems by an elaborate alphanumeric system: “SS” stood for ballistic missile; “Shyster” was the code name of the third such system identified, and so on. The names were chosen arbitrarily, and many were whimsical or ironic.) Like the Americans, the Soviets hedged their bets by developing rocket-boosted, ramjet-powered, supersonic cruise missiles, one by the Myasishchev design bureau and the other by Semyon Lavochkin. The more advanced Lavochkin design followed a trajectory strikingly parallel to that of the Navaho, pioneering the use of novel materials, notably titanium, and producing much useful test data but no operational vehicle. As with Navaho and Snark, both programs were canceled when ICBMs made them superfluous.

Following the R-5's success, Korolev, by now in effective charge of Soviet
rocket design, pressed for the development of a genuinely intercontinental missile, the R-7, nicknamed Semyorka (a diminutive of seven) and named SS-6 Sapwood by NATO. The R-7's boosted fission warhead was considerably heavier than the Atlas's thermonuclear weapon, and the thrust requirement correspondingly greater. Moreover, Korolev's team was handicapped by a lack of alloys suitable for the hundred-ton-thrust engine their calculations called for. They responded by clustering rockets in groups of four, using common oxidizer and fuel turbopumps, and surrounding a core cluster with four booster clusters. Each rocket produced only about twenty-three tons of thrust, somewhat less than that of the V-2, but they were lighter and far more efficient, and the total thrust was more than sufficient (by comparison, the Atlas's booster rockets, direct descendants of the Navaho engine, produced sixty tons of thrust each). The first successful R-7 launch was in August 1957, two months later than that of the Atlas.

A comparison of the two missiles is instructive. Both used liquid oxygen and kerosene for propellant. Both had short careers as operational ICBMs, a consequence of the extended launch sequence that liquid oxygen demanded. Both would enjoy spectacular careers as space boosters, but there the similarities end. Paraphrasing Sovietologist Steven Zaloga, if Atlas's engineering was Gothic in lightness, Semyorka's exhibited Romanesque raw strength. Atlas had just three engines; the central rocket elegantly gimballed for control. Semyorka had twenty and was controlled by comparatively primitive vernier rockets: The thruster nozzles were fixed, and adjustments in pitch, roll, and yaw were provided by small auxiliary rockets, a simple but inherently inefficient solution, since the vernier rockets required independent fuel and control systems. The Russian missile's skin would support a man's weight; that of Atlas was so thin that the internal pressure of the propellants was all that kept it from collapsing.

More telling is a common design feature that underlines the incredible urgency with which both missiles were developed, an urgency rendered more terrifying by each power's ignorance of its rival's capabilities and intentions. Both missiles were stage-and-a-half vehicles; that is, they rose from the pad with all engines firing, Semyorka discarding the four outer rocket clusters and their fuel tankage, and Atlas jettisoning two of its three engines after the initial boost phase. This was less than optimal for reasons basic to rocket engineering. Maximum thrust is required at liftoff when weight is greatest; then, as fuel is expended and as atmospheric drag falls off with increasing altitude, the thrust
requirement diminishes. It therefore makes sense to lift off with a separate lower stage that drops off when its fuel is expended, leaving its weight behind. The upper stage or stages then proceed to apogee powered by smaller, more efficient engines. The advantages of staging are enhanced by the fact that optimum rocket-nozzle length varies inversely with air density. Maximum thrust at liftoff calls for a long bell-shaped nozzle to permit the propellant gases to fully expand in the dense air of the lower atmosphere, but such a nozzle becomes increasingly inefficient at higher altitudes. It is for this reason that high-perfor-mance satellite and space boosters, designed to loft the maximum payload by minimizing airframe and fuel weight, use multiple stages, typically three, with each successive stage's engines having progressively shorter nozzles. Solidfueled ICBMs also use multiple stages, but for somewhat different reasons, as we shall see.

Both Semyorka and Atlas were magnificent designs, sufficiently reliable for manned space flight: Yuri Gagarin rode Semyorka into orbit, and Atlas orbited John Glenn (and Ham the chimpanzee before him). But both rockets were first and foremost ICBMs, and their designs were finalized so early that the engineers were not certain liquid oxygen and kerosene would ignite spontaneously in the hard vacuum of space. They therefore accepted substantial penalties of weight and nozzle inefficiency to place hardware on the launch pad capable of lofting a nuclear warhead to intercontinental ranges at the earliest possible date: Atlas in September 1959 and Semyorka that December. Further underlining the haste with which the early ICBMs were developed, the American Titan I—a two-stage missile, still using liquid oxygen and kerosene but stored belowground in a reinforced concrete silo and fueled by high-speed pumps that reduced launch time to fifteen minutes—became operational at about the same time as Semyorka. That all of these competing and highly expensive systems, any one of which could have filled the strategic bill, were rushed to deployment at the same time speaks for itself. Both the Soviet Union and the United States had to be absolutely certain that they had at least one system that actually worked, reliably and on short notice. It is worth noting that the strategic backdrop to this period of frenzied technological development included, to hit the high points, the 1948 Berlin Blockade, the Korean War, and the Hungarian uprising and Suez crisis of 1956. The last of these provided the stage for Nikita Khrushchev's famous and, as we now know, empty “missile rattling” threats.

Atlas and Semyorka, in any case, were recognized as interim solutions long before they achieved operational status. Their extended launch sequences rendered them vulnerable to preemptive attack, and they could be held ready to fire only briefly. Their silo-based successors depended on propellants that did not require refrigeration and could be stored in the missile's tanks for extended periods. The American Titan II, which entered service in 1964, burned a mixture of unsymmetrical dimethyl hydrazine (a volatile and environmentally nasty fuel) and nitrogen tetroxide (an even more volatile oxidizer that was worse); the Soviet R-16 (NATO designation SS-7 Saddler), which entered service the same year, was powered by hydrazine and red fuming nitric acid, both dangerous and difficult to work with. Both fuel-oxidizer combinations are highly volatile and hellishly toxic; their sole virtue was that they could be stored in the missile's tanks without refrigeration. That they were used at all speaks volumes for the strategic imperative.

The ideal, of course, was a missile that could be stored indefinitely in a silo, ready to fire, a requirement that no liquid fuel combination could satisfy. The answer lay in solid propellants, rocket fuels that could be poured into a mold to solidify and remain inert until ignited, requiring no pumps, no corrosive liquids, and no refrigeration. The solution was found in asphalt-stabilized, per-chlorate-based solid propellants, discovered by engineers at the Guggenheim Aeronautical Laboratory of the California Institute of Technology in 1942 and subjected to accelerated development as the Cold War got under way. By the late 1950s, these propellants were sufficiently stable and had sufficiently long shelf lives for operational use. Their main drawback, like that of black powder, was low specific impulse: They produced impressive initial acceleration but yielded significantly less thrust per pound of fuel per second than liquid propellants. The solution was to use multiple stages. The deployment in 1962 of the first operational solid-fueled ICBM, the three-stage Minuteman I, was a major Cold War benchmark, in part because it heralded the creation of an ICBM force that could be kept indefinitely on a high state of alert, and in part because it underlined a qualitative lead for the U.S. in strategic weaponry: The Soviets would not field their first solid-fueled ICBM, the SS-13 Savage, until 1969. It is worth noting that the Minuteman I and the Minuteman III, which replaced it beginning in 1970, had relatively modest throw weights; that is, the warhead, reentry vehicle, and guidance system were relatively light, positively diminutive
when compared with their Soviet equivalents. The compensatory mechanism was the superior accuracy produced by miniaturized guidance systems.

Rapid advances in missile capabilities forced equally swift changes in basing modes and in the way crews lived and worked. The first ICBMs were erected on open pads, then filled with liquid oxygen and kerosene, a process that consumed hours and left the missile and crew horribly vulnerable to a counterstrike. Next came pits in which the missile could be stored horizontally below ground level, with underground fuel storage, launch control centers, and living facilities for the crew. Called coffin shelters, these provided limited protection against a preemptive strike; constructed in haste, they were only partially hardened (that is, made of steel-reinforced concrete thick enough to withstand the force of a nuclear blast). Next came underground reinforced concrete silos in which the missile could be stored and fueled vertically, then raised above ground for launch. The definitive basing mode was a hardened underground silo fitted with vents and cooling systems so that the missile could be launched from underground. The silos were sealed with massive blast doors mounted on tracks and opened and closed by electric motors. The underground launch complex, itself hardened, was typically reached by elevators and isolated from the surface and the silo by multiple blast doors. Equipped with electric generators, air filtering and conditioning systems, and living quarters, the underground complexes were home for missile crews during their periodic alert tours. In them, the crews faced a combination of claustrophobic confinement and boredom on the one hand, and the awful possibility of nuclear war on the other, something that can only be imagined by those who have not experienced it.