A Down-to-Earth Guide to Star Wars

You don't have to be a scientist to understand the real issue in the debate over a space-based defense.


An awful lot has been written by now about the Strategic Defense Initiative (SDI), better known as Star Wars. Most of it's been written by humble lay journalists like myself, and most of them prepared themselves for battle by poring over reams of highly technical reports and journal articles purporting to absolutely, positively prove that SDI can work…or can't work.

I know those reports and articles. I've read them. They're full of numbers. And tables. And graphs. And I know my colleagues, and I know they can't understand the important parts of such articles any better than I can. What they can understand are the conclusions, or the executive summaries, where the scientists skip all those equations and give it to you straight.

And what do the executive summaries say? They say that a successful strategic defense against nuclear attack would require 2,400 orbiting defense satellites costing maybe a billion dollars each. Or they say it would require only 90. They say that the satellites would weigh 40,000 tons and could never get up into space. Or they say that the satellites would weigh 25 tons and could be launched by the space shuttle. They also show beyond a doubt that the Soviets could make the object of all this—their intercontinental ballistic missiles (ICBMs)—immune to attack. Except, of course, everyone who knows anything about ICBMs knows that all the suggested countermeasures to strategic defense are absurdly impractical.

But in truth, the key to the debate over Star Wars is not to be found in technical journals or scientific reports. The key is to understand the difference between "the old days" in this nuclear age, and today's realities.

Of First Importance

The only circumstance under which a deliberate nuclear attack by one superpower against another is conceivable is if the attacker has a "first-strike capability"—the ability to destroy the enemy's nuclear arsenal before the enemy has a chance to fire back. Nothing short of complete success is acceptable in a first strike, because partial failure would bring horrible retribution.

Only accurate, high-payload ICBMs, a recent development, hold out even a chance of making a perfect first strike. All other delivery systems, old-fashioned bombers and new-fashioned cruise missiles alike, are meant for nuclear counterpunching.

In the good old days, only counter-punching weapons—mainly bombers—were available. And in a world restricted to second-strike weapons, nobody could ever afford to throw the first punch. So nuclear terror was a different thing in those days. The dominant nuclear fear in the '50s and '60s was, "What if a madman got his finger on the button?"

Today, people fear not insanity but the possibility that rational calculation might convince one side that shooting first would pay off. There is a point to the complaint that "if we just keep piling up missiles, eventually they are going to be used": a truly massive missile attack might bring instant victory. That makes huge missile stockpiles at least faintly destabilizing. Nuclear war is more likely today than it was 20 years ago.

This much seems obvious. Yet the debate over Star Wars is carried on as if no one could remember a time when deterrence was much more of a sure thing.

The essential error in discussions of strategic defense is assuming that the defense would be worthless unless it were impenetrable, with not a single Soviet bomb getting through. Star Wars critics who ridicule the possibility of a perfect defense shield make the same mistake as Star Wars proponents who claim a near-perfect defense is inevitable. And, arguing ultimately over tiny fractions of perfection, they ensure that the debate will become the exclusive property of technically proficient partisan scientists.

The truth is that strategic defense would be a complete success if it accomplished only one goal: pulling us back 20 years in time and eliminating the possibility of a successful first strike. Do that, and we are back to the days when the only punch was a counterpunch. As Bruce Springsteen says, you can't start a fire without a spark. Then we could go back to worrying about a madman getting his finger on the trigger, which, compared to today's worries, would be an amusing pastime.

Whether we can build a defense good enough to make a first strike unacceptably risky is a much simpler question than whether we can build one that is impenetrable. We laymen can address it without having to make a leap of faith in someone else's equations.

How Much Is Enough?

The foremost strategic argument against Star Wars is that the only good defense is a perfect defense. The New Republic's Charles Krauthammer, one of the most responsible and intelligent critics of Star Wars, makes this argument as well as anyone else: "An American defense that is 99 percent effective would still allow a hundred nuclear weapons to land on American soil. That is failure. A Soviet offense that is five percent successful could, if targeted at cities, kill half the U.S. population instantly. That is success."

Krauthammer misses the point of strategic defense, because he misses the point of a first strike. The purpose of a first strike is not to cause misery (hitting cities) but to destroy the enemy's ability to retaliate (hitting nuclear weapons bases). And a first strike that is not perfect is by definition a failure.

What is enough defense to discourage a first strike? Most suggested defense plans come in three stages: (1) Boostphase defense—an attempt to shoot down enemy ICBMs "on the rise," before they have released their MIRVs, or multiple warheads. This must be done from space. (2) Midcourse defense—an attempt to shoot down either the ICBM "buses" that carry the MIRVs or the MIRVs themselves while still in space but after the booster has burned away. This might be done from space, by antiballistic missiles (ABMs) launched from the ground, or from atmospheric aircraft. (3) Point defense—an attempt to destroy individual warheads within a few miles of their targets. This is done from the ground.

Some Star Wars proponents envision 80 percent effectiveness at each stage. Altogether, this would take out 99.2 percent of incoming warheads. This is a tall order, however, and is unlikely to be filled within this century.

Fortunately, a first strike can be deterred with a much less effective shield. A first-strike force must deliver at least two warheads against every enemy nuclear weapons installation—two, because some missiles will fail, some reentry vehicles will go awry, and some warheads will fail to destroy their "hardened" targets (ones that are specially strengthened and reinforced against nearby nuclear blasts).

The consequences of missing any enemy target are huge: a counterattack of a few MX missiles, with their 10 warheads each, could destroy most Russian cities, cities being more likely targets on a second than on a first strike. So a defense that promised any substantial diminution of the attacking force would deter the first-strike attacker.

Gen. Daniel O. Graham, a major figure in the Star Wars debate, argues that even a reduction of 30 percent in the boost phase (before the ICBMs had released their MIRVs) would confront the Russian strategic planner with "a problem full of uncertainties." The planner would "not know how many warheads will arrive over the target area and—even more crucial—which ones will arrive over which targets. This changes the simple arithmetic problem into a calculus full of uncertainties." And the clincher: "Such uncertainties are the essence of deterrence."

A strategic defense that was only 30 percent effective in each of the first two stages and 50 percent effective at the point defense stage (the easiest stage at which to mount a defense) would screen out all but 25 percent of incoming warheads. Moreover, some of those warheads would be doubled up—aimed at the same target—so much of the US nuclear force would be sure to survive. The destruction resulting from such a hypothetical attack would be unspeakable. But it would remain hypothetical, because a 75 percent reduction in the attacking force would make a first-strike attempt unthinkable.

If strategic goals are thus realistically assessed, the technological goals become fairly modest. The boost-phase defense, the only stage that must be placed in space, is the only stage to which fundamental technological objections have been raised (point and midcourse defenses are already known to be possible). But a boost-phase defense that is 30 percent effective doesn't seem so challenging.

What Would They Do Then?

Another criticism leveled by Krauthammer, as well as by such SDI advocates as Dr. Edward Teller, is that any system permanently deployed in space cannot work. They fear that defense satellites in permanent, predictable orbits would be too vulnerable to handle the vital mission of nuclear deterrence. Shooting down permanently orbiting satellites is well within the capabilities of both superpowers, which is enough to make Krauthammer despair and Dr. Teller propose far-fetched "pop-up" satellites to be launched only after the Soviets launch their ICBMs. But these critics forget our first rule: the purpose of defense is not to make attack impossible but to make it impossibly costly.

As General Graham pointed out in some of his early writings about strategic defense, the reason that wise 19th-century generals screened their infantry columns with advance cavalry units was not that they believed lightly armed cavalry could long defend the infantry from an enemy onslaught. Rather, the cavalry screen was intended to force the enemy to reveal his strength and position before the main battle was joined and to protect the infantry from being attacked by surprise.

Should an enemy, preparing to launch a first strike, first move to wipe out the space-borne stage of our strategic defense, he would run into a cavalry screen that would make a successful first strike impossible. The United States, anticipating an immediate attack, might launch its own ICBMs immediately. More likely, US planners would go into a "launch under attack" or "launch on warning" mode under which the first sighting of a Russian ICBM would provoke US retaliation.

Again, a horrible scenario. But the important point is that it would never happen—Russian generals know all about cavalry screens.

Another common strategic objection is that a realistic—that is, "leaky"—US defense would be destabilizing, because it could put the Russians into a "use it or lose it" situation. Suppose the United States builds a leaky defense, goes this objection. Although an all-out Soviet first strike couldn't completely destroy the US arsenal, they might figure that it could destroy the United States as a functioning society and thus produce surrender. On the other hand, the United States, having put up a defense shield, could launch a first strike against the Soviets, very likely destroying enough of the Soviet arsenal that the Soviets would not be able to penetrate even a leaky defense. They would be left no option but surrender. Surveying these possibilities, the Russians might be driven to a preemptive attack.

This scenario is not compelling, however. The Russians have some small chance of launching a successful first strike today. A realistic US defense can only reduce that chance. Though a US defense might make it slightly more risky for the Russians not to shoot first, it would, on the other hand, make it suicidal for them to shoot first.

Neither is the scenario realistic. Despite our technological edge, the Russians may well be ahead in the practical pursuit of strategic defense. By the time we have a reasonably effective defense, we can be pretty certain that they will have a reasonably effective defense, too. Neither side will be able to launch an effective first strike. Back to counter-punching.

The final common strategic objection is that even if we could put up a perfect defense, we couldn't put it up all at once. Seeing us begin the work, the Russians might attack immediately rather than face "nuclear blackmail" once our defense was completed.

This scenario is unrealistic for the same reason: the Russians are heading for strategic defense full throttle. There is never going to come a time when we have a solid defense and they have none. Should we begin to outpace them, it will be much easier to produce a verifiable agreement to phase in SDI gradually than it is to agree on unverifiable arms-limitation treaties. Moreover, since any such agreement would be concluded while we were in the lead, we would have little to fear from Russian treachery.

Strategic Bomb Banning

Understanding the strategic purpose of missile defense helps in sorting out the technological disputes.

The Holy Grail of the most enthusiastic Star Wars advocates is a space-based defense so impregnable to ballistic missiles as to consign them to the junkpile of history. Space-borne battle stations armed with directed-energy weapons (lasers or particle beams) are the weapons of choice for this mission, because such beams travel at or near the speed of light and, in the vacuum of space, with undeviating precision. The beams would reach their targets almost instantaneously. A battle station could fire on the target, learn the results, and fire again at a new target within a few seconds.

In theory, the several-thousand-fold disparity between the speeds of the energy weapons and the speed of a ballistic missile would make the missile obsolete. Sophisticated energy weapons would do to the ballistic missile what the machine gun did to the cavalry charge. Maintaining a missile force would be as pointless as retaining regiments of horse soldiers.

Moreover, a thoroughly reliable space-based defense would make space, not the land on which people live and work, the decisive battlefield. As long as both antagonists had strong space-based defenses, there would be no point in either side attempting a nuclear attack. A thorough space defense consisting of hundreds of space installations would provide virtually perfect reconnaissance of enemy movements on earth. Sophisticated energy weapons might even be able to destroy earth-based targets.

Control of space—that is, defending one's own space installations and destroying the enemy's—would virtually assure victory on earth. Warfare might be confined to a battle for the control of space, which, once won, would produce quick surrender and few civilian casualties. Most important, war would be relegated to space not by treaty or wishful banning of the bomb but by strategic necessity.

The vision is certainly glorious enough to justify the enthusiasm of Star Wars advocates. Unfortunately, its realization requires a leak-proof defense. That, in turn, requires fully mature energy weapons—powerful, cheap, and efficient enough to make ICBMs into antiques.

The potential of energy weapons is so great that it seems inevitable that they will one day dominate strategy. But whether and when these weapons will arrive are questions at which scientists can make only informed guesses. Few laymen have the skill to evaluate such speculations. A more fruitful question for lay inquiry is whether such weapons are a realistic possibility, or are there objections so insuperable that the attempt should be abandoned?

But Could It Work?

In the first phase of the "war against Star Wars," to use Robert Jastrow's phrase, opponents concentrated on (a) suggesting that SDI absolutely requires energy weapons and (b) demonstrating that the problems with such weapons are too overwhelming to make their pursuit realistic. It was in this vein that the Union of Concerned Scientists put out a widely quoted report claiming that 2,400 laser battle stations would be needed, and each would weigh 40,000 tons. The UCS, however, has since quietly retracted its claims. The scientific consensus is that only about 100 satellites would be needed and that they would weigh in the tens of tons, not thousands of tons.

Reviews of other widely circulated charges—such as that adequate laser weaponry might consume 60 percent of US electrical power capacity—have made it clear that these charges were politicized exaggerations. The attempt to characterize energy weapons as impossible fantasies has failed.

Nevertheless, directed-energy weapons do entail enormous technological complications. For laser weapons, three criteria must be satisfied.

The laser must be of sufficient power to destroy a laser-protected ICBM within a fraction of a second. For the sort of lasers most commonly suggested as weapons, that means developing 15 or more megawatts of power. We are progressing very rapidly but are still in the 5+ megawatt range. Higher-efficiency lasers would need less power but are a newer phenomenon.

The laser must be aimed with a pointing and tracking system capable of locking onto a target moving at thousands of miles an hour as much as a thousand miles away. It must be able to hold the beam on track for a few moments despite the tremendous vibrations created by a high-energy laser. The Air Force Talon Gold project had as its goal the construction of a system accurate within two-tenths of a millionth of a degree, but the project was recently abandoned.

Finally, conventional lasers must be focused by sets of mirrors, which must be optically perfect to keep the beam on course and must be perfect reflectors to keep the mirrors from being burned up by the lasers. The more powerful the beam, the larger the mirror. Conventional lasers would probably need 15-meter mirrors, but we have not yet built one half that size. More experimental lasers might use smaller mirrors or even no mirrors at all but are still unproved.

Beam weapons are even less far along than lasers. We do not have near at hand an adequate weapon for a leakproof defense. And even were the weapon at hand, there would be numerous other difficulties with getting 100 or so of them up into space, fueling them, supplying them, controlling and coordinating their actions, and protecting them from attack.

This does not mean that laser or beam technologies should be abandoned. They are far too promising for that. But concentration on advanced technologies is aggravating the worst tendency of US military R&D: the determination to pursue ever-better technology on the drawing board while postponing the construction of the best weapon available today. Indeed, congressional opponents of strategic defense have made it clear that they are willing to give the president some Star Wars funding, but only for the most speculative research projects. They oppose any program that has a chance of being useful within this century.

Whether undertaken in good faith or not, as far as space weapons are concerned this approach amounts to an attempt to skip first-generation, pre-laser weapons. And yet it is far more certain that we can build a pre-laser system today than that we will be able to build a laser or beam system 20 years from now.

What Is Possible Today

The "High Frontier" project, directed by General Graham, kicked off the Star Wars debate almost four years ago with its own suggested first-generation defense system, one to put up while more sophisticated approaches are developed. That system has been placed on the back burner by both Star Wars advocates and opponents, partly because Graham was so forthright in admitting that it was an imperfect, "quick and dirty" suggestion put forth more as an illustration of strategy than as an engineering blueprint.

Yet the High Frontier system is fundamentally sound. Precisely because Graham paid more attention to strategic problems than technological ones, the technology he chose turns out to be very promising for first-generation defense. The High Frontier project never lost sight of the primary goal: not to make attack impossible but to make it impossibly costly.

The High Frontier system is a first-phase, or boost-phase, defense system, meant to be combined with whatever midcourse and terminal defenses seem appropriate. It consists of several hundred orbiting satellites linked to a central control system, each individually capable of detecting enemy missiles in the boost phase. Each satellite carries several dozen simple, self-propelling, rocket-powered projectiles capable of homing in on and colliding with the enemy boosters after being launched in their direction by the satellites. Every task involved is a familiar one: detecting enemy rocket launches, firing an "air-to-air" missile at a high-speed target, making target adjustments from a distance, and building a missile smart enough to handle the terminal approach on its own.

The speeds and distances are greater than those with which the Air Force customarily deals within the atmosphere. But several recent experiences show that the difference is only one of degree. We now know it is possible to shoot down a satellite—the Russians have done it many times, and we are close to having an operational antisatellite weapon ourselves.

Satellites travel at speeds comparable to those of an ICBM, the only difference being that an ICBM is an accelerating target and therefore somewhat more challenging than constant-velocity satellites. In addition, the Soviets have orbited an antisatellite weapon very similar to the antimissile weapon proposed by High Frontier: Cosmos 1267, a 30,000-pound pod-shaped battle station carrying a large number of small, self-guiding projectiles. The Russian weapon is not meant for missile defense. Still, it shows that our adversaries consider a design similar to High Frontier's usable for space missions analagous to knocking out missiles.

Finally, and most important of all, the US military has already successfully tested a weapon that does, under more difficult conditions, what the High Frontier system would have to do. On June 10, 1984, the US Army "hit a bullet with a bullet," intercepting and destroying a reentry vehicle above the atmosphere. The interceptor was a nonexplosive projectile (actually a metal umbrella 15 feet in diameter) launched by the first two stages of an ICBM. The interceptor was deliberately launched 20 miles off-course to test its ability to make in-flight corrections. It put itself back on course, closed on the target at 20,000 miles per hour, and scored a direct hit, completely destroying the target vehicle by impact.

This test proved that reasonably effective midcourse defense against reentry vehicles is possible. Boost-phase defense should be even easier in several respects.

In this experiment, the interceptor was launched from the ground and had to climb into space to find its prey. In boost-phase defense, the satellite would already command the "high ground" of space and be positioned to watch the target climb into its path. And boost-phase satellites would be shooting at boosters, somewhat slower-moving targets than reentry vehicles.

Since we know that terminal defense is easier than either midcourse or boost-phase defense, the chances are good that we could, today, start a practical first-generation SDI program that would yield a defense in the 75 percent effectiveness range. And if we can do it, the Russians, who have a history of pursuing low-tech solutions, can probably do it too.

Nevertheless, current indications are that even Star Wars advocates in the Reagan administration and the military have decided to skip all first-generation, pre-directed-energy weapons. This is the wrong approach. Weapons evolve. They do not emerge in all their fully developed technological glory after spending a few extra formative years on the drawing board. If we allow ourselves to imagine that we can envision the history of space warfare in advance and can know ahead of time which will be the optimal weapons and technologies and when and for which missions they will be used, we may find ourselves in total control of the blackboard but without a position on the battlefield.

We know that a High Frontier system would work as much as we can know that of any untested system. There is no more theorizing to do. The only tasks left are final design, building, and testing—not to determine whether it will work but to determine how it can be made to work.

Someday we will send the ICBM the way of the cavalry charge, but only after long, hard, practical experience with the simpler goal of developing first-generation defensive weapons, bringing back the impossible costs of a first strike. Space warfare, with all its technological challenge, should be the deliverance of the technologically superior West. But if we refuse to put strategy before technology, or if we worship our technology rather than using it, it could be our destruction.

Richard Vigilante recently joined National Review as articles editor. This article is a project of the Fund for Objective News Reporting in Washington, D. C.

What the Hell Is an ICBM?

ICBMs—Inter-Continental Ballistic Missiles. These are land-based, nuclear-armed missiles that typically have three or four "stages" (separate rocket boosters that fire, in sequence, then drop away). The principal US ICBMs are the Minuteman and the MX. The Soviets have 70 percent of all their nuclear warheads on ICBMs, compared with 25 percent for the United States.

Other nuclear weapons are submarine-launched ballistic missiles (SLBMs); manned bombers carrying nuclear bombs; and cruise missiles (small missiles powered by jet engines), which can be launched from aircraft, ships, submarines, or trucks.

Silos—Both US and Soviet ICBMs are housed in these underground concrete structures. Today's silos are generally "hardened" by adding massive concrete and steel reinforcing to protect the silo from being destroyed by a nearby (off-target) nuclear blast.

MIRVs—Multiple Independently targetable Reentry Vehicles. These are the warheads carried by a ballistic missile's top, or last, stage (which is called the MIRV bus). Each reentry vehicle can be aimed at a separate target. Compared to a single-warhead missile, a MIRVed ICBM is an attractive target, because destroying one missile eliminates as many as 10 to 12 nuclear warheads.

ABM—Anti Ballistic Missiles. These are ground-based missiles designed to intercept ICBMs or SLBMs in their mid-course, or reentry, phases of flight. The 1972 ABM Treaty (part of SALT I) prohibits all but a handful of ABMs from being deployed by either the United States or the Soviet Union. Most proposed "Star Wars" capabilities are not permitted by the ABM Treaty, as written.

Directed-energy weapons—In contrast to weapons that operate via explosives (either nuclear or nonnuclear) or by sheer impact, a new type of weapon would be based on energy beams. One variety would use a very high energy laser; the other, a beam of elementary particles (protons, electrons, or neutrons). Either type of beam achieves its destructive result by focusing a tremendous amount of energy on the relatively fragile missile at which it is aimed.

Boost phase—the first phase of an ICBM's flight, during which all the booster stages except the MIRV bus (or single warhead) fire, propelling the bus into space on its ballistic trajectory, and then fall away.

Midcourse phase—the portion of an ICBM's flight during which the bus (or single warhead) coasts through space. If the missile is MIRVed, the independent reentry vehicles are released from the bus during this phase, to begin following separate paths to their targets.

Reentry phase—the final stage of ICBM flight, during which the warhead or MIRVs reenter the atmosphere and proceed to their targets.

—Bill Kauffman