This is awfully important if you want to control nuclear proliferation. It's very difficult to convince other countries that they shouldn't pursue nuclear weapons programs if we ourselves are actively developing a component of a strategic defense system.
Some of the Nobel laureates who signed the letter were doubtless concerned about the cost, the very great cost of the missile defense system, [and] what it would take away from other things including other forms of national defense.
There was of course a sense that many of us have -- some more expert than others -- that it was really an impractical effort; that this sort of thing has been worked on for many decades now, and was unlikely to develop into a system that would really defend us against a plausible threat.
Some of the statements that were in the letter led me to the article that you wrote. ... You posed three big questions. ... The first is, would a missile defense system actually protect the U.S. against even the sort of attack that might be launched by rogue states?
If you tell our military planners that the United States is going to be attacked at such-and-such a time and date with an offense consisting of certain missiles which carry certain penetration aids -- decoys or other aids that allow them to defeat our defenses -- that we can probably develop a defense that will work against that particular threat.
But that's of course completely unrealistic. We won't know what the offense will be. We may know the nature of the nuclear warhead. But we will not know what other things are sent along with the warhead in the form of decoys that will exhaust our defenses. I don't see how that problem can ever be solved.
It's a problem that has been worked on for a long time.
We've been trying to develop methods of discriminating decoys in warheads for many years. I worked on that in the mid-1960s. It was hard then, and it's just as hard now. In some ways, [now it's] harder, because the planned defense system of the administration would intercept missiles above the earth's atmosphere where the atmosphere doesn't provide any screening that separates decoys from missiles. ...
An offensive rocket would travel up out of the atmosphere, and then coast toward its target above the earth's atmosphere. In the plan that's at the center of both the Clinton and the Bush missile defense program, we would send up rockets that would strike the warhead while it's still coasting above the earth's atmosphere.
The problem is that when the warhead is deployed by the rocket coming up out of the earth's atmosphere from our adversary's launch site, it can be accompanied by other things. It can be accompanied, for example, just by balloons that reflect radar, that are visible to infrared sensors onboard the anti-missile missile.
As long as they stay above the earth's atmosphere, they travel the same way. Galileo pointed out that the rate at which a body falls doesn't depend on its mass. That isn't really true in the earth's atmosphere, as you can easily see. If you drop a feather and a bullet at the same time, the bullet will strike the ground faster, because the feather is supported by the earth's atmosphere.
But above the atmosphere, it is true. A feather and a bullet will travel at exactly the same speed. It's also true of a warhead and a decoy. So their trajectory gives you no indication of which one is the dangerous one that has a nuclear weapon in it, and which is something that's just meant to spoof you.
There are ways of trying to distinguish them. They might look differently to a telescope or an infrared sensor. But it's not hard at all to make the decoy look just like a warhead. Or you can make the warhead look like a decoy by putting it inside the same kind of balloon that you're using as a decoy.
We won't know in advance. We can't know in advance just what will be the strategy adopted by the attacker. So I don't see how we can defend against it. ...
These aren't realistic operational tests. You know, when the Army wants to test its strategic doctrines, wants to test its equipment, wants to test the abilities of its officers, they have maneuvers. In the maneuvers, the blue team is not told in advance exactly what the red team is going to do. The tests so far have been like a maneuver in which the blue team is told exactly what the red team's plans are. That's not a serious test of a system. ...
Someone ... [said] that both the United States and the former Soviet Union spent billions of dollars developing its own decoys that would go with [their] warheads. ... [He] was skeptical that a rogue state, for example, could develop a sophisticated decoy system.
... I would say it's a lot easier to develop a decoy system than to develop the intercontinental ballistic missile itself. I would think that any country that could develop the missile could develop quite a decoy system. It doesn't have to be terribly sophisticated.
It would have to be terribly sophisticated, I think, if we were trying to intercept these missiles near the end of their flight, when they re-enter the atmosphere. There it's harder to make a decoy, because lightweight decoys like balloons simply don't travel the same way that warheads do once they're in the atmosphere. But above the earth's atmosphere, it's not that hard.
Talk to me about the what's called "bomblets."
There is another way of defeating an anti-missile defense that was suggested, for example, or at least discussed in the Rumsfeld report a few years ago. That is, instead of carrying a single nuclear warhead or perhaps two or three nuclear warheads, the rocket would launch hundreds of little biological warfare bomblets each containing, for example, anthrax spores.
Because there are hundreds of them, they wouldn't need to have decoys. There would be far too many targets for any missile system to defend us against. Also, because there are large numbers of them, these could spread the biological warfare agents over a large urban area.
It's been estimated that that sort of attack striking the city could kill perhaps 100,000 people, where a nuclear weapon would kill 50,000. And the kind of missile defense that's being contemplated in the Clinton/Bush national missile defense program would have no effectiveness against that at all.
... How would we defend against bomblets of anthrax?
I'm afraid that it's not possible to design a defense against every conceivable threat that you can think of. ... Von Clausewitz said, "He who tries to defend himself against everything defends himself against nothing." ...
However, if what you're worried about are threats that are launched by intercontinental ballistic missiles, there is a method of defending that we might have to consider, and that's pre-emption -- ... - or as it's sometimes called a little waggishly, "pre-boost phase interception."...
If we are concerned that a country like Iraq, for example, is about to set up intercontinental ballistic missiles [and is] about to put them on launch pads, [then] just as the Israelis did in destroying the Osiris nuclear reactor some years ago because they thought it would give Iraq a nuclear capacity, we might be forced to be in the position of destroying the potential enemy ICBMs before they're made operational.
Fortunately, these days, that doesn't mean a nuclear attack. Our conventionally armed cruise missiles are quite accurate enough and powerfully armed enough to do the job. That's a form of defense that I think would be very effective, and we might have to adopt [it].
It's much harder to think how to defend ourselves against other threats which are not launched by intercontinental ballistic missiles -- threats like nuclear weapons on freighters coming into our harbors. Threats like rent-a-trucks coming across our borders carrying nuclear weapons. I'm much more worried about those than I am about a nuclear weapon fired by a rogue state on an ICBM. ... Those threats have the great advantage to the attacker that they can be carried out anonymously, whereas an ICBM can never be anonymous. We would always know who the attacking country is, because our satellites will identify the launch site. ...
I would not want to be a leader of a country that had launched ICBMs against the United States. ...
You were talking about the problems of decoys and then of defending against bomblets. There's something we didn't get to, and that is so-called boost-phase [interception]. ...
There is a possible missile defense system that doesn't have most of the disadvantages of the midcourse interception system that's at the heart of the Clinton and Bush missile defense programs. It's called boost-phase intercept. ...
When a rocket rises above the atmosphere but it's still firing its rockets, and before it has a chance to deploy warheads or biological warfare bomblets or decoys or anything, it's still just one rocket boosting up. If you can attack it at that moment, then decoys are irrelevant. ... It doesn't have a chance to deploy hundreds of bomblets which we can't intercept. So it's technologically very attractive to be able to hit a rocket at the end of its boost phase. ...
But it also has a technological disadvantage, because the boost phase only lasts a short period. In order to be able to hit the rocket during that short time, you have to be close to it. You have to be within a few hundred miles if you're going to hit it with another rocket of your own, or within a few hundred miles if you're going to try to zap it with a laser beam from an airplane, for example.
So a boost-phase intercept system will only defend you against attacks from a specific adversary. For example we could defend ourselves against attacks from North Korea by having ship-borne boost-phase intercept systems in the Sea of Japan. It's harder to think of how to [intercept a rocket fired from Iraq in its boost phase].
But the point is that the defense would only work against that country toward which it's aimed. A system based on the Sea of Japan would have no capability against missiles launched from the heart of Russia or China. That technological disadvantage is a political and a strategic advantage, because the boost-phase intercept system does not threaten the deterrent capability of countries like Russia and China, who we are trying to convince our missile defense is not aimed at.
The best way to convince them that our system is not intended to work against them is to make it incapable of working against them. That's what the boost-phase intercept system would do. ...
We don't know whether it can be developed, but that doesn't seem to be the center of interest for the Bush administration's proposal. I'm not sure why it isn't. It seems to me if certain technical problems could be solved, [it's] the one kind of missile defense system that might make sense at some future time. ...
This technology doesn't exist yet. ...
Certainly the laser boost-phase intercept system does not yet exist, even on the drawing boards, as something that we could imagine building. I think research should continue on this. It's premature to imagine testing any such system. ...
There's a current rationale, so to speak; an argument that we need missile defense because other countries may develop ICBMs, and they'll be using those as a deterrent against our actions.
There's one respect in which you might imagine that a so-called rogue state would want to develop ICBMs [for purposes other than simply being] able to threaten us. ... That is not that they would actually plan to launch them, because that would be crazy. ... But that having nuclear-armed ICBMs, they would then be in the position to preserve themselves against an American attack like the sort we launched in Afghanistan.
One can really wonder, would we have moved into Afghanistan the way we have if the Afghans had nuclear-armed ICBMs? That's a strong point. I think there are two answers to it. One is that if you were going to resist that kind of blackmail, we'd better be sure that our system is 100 percent effective.
I don't think we would be. If in fact the Afghans had nuclear-armed ICBMs, and we had the kind of missile defense system that is being planned under the Bush administration, I don't think we would have enough confidence in it to be able to resist the kind of blackmail that we're talking about. In fact, if we had confidence in it but we were wrong, we would be much worse off. ...
It sounds brutal to say it, but I don't think we would allow a country like Afghanistan under the Taliban or Iraq under Saddam Hussein to deploy ICBMs. I think we would prevent that. We can, and I think we would. ...
This is all bringing you to your second big question that you posed, and that is ... is it plausible that the U.S. would be attacked by ICBMs from terrorist rogues, or even by accident?
... An attack by ICBMs, nuclear-armed ICBMs, is just one of many ways we can be attacked. It's the least plausible [way] we would be attacked, because it would not be anonymous. ... The Al Qaeda organization has never taken credit publicly ... for the attack on the skyscrapers and the Pentagon on Sept. 11. Muammar Qaddafi has never taken credit for the explosion of an airliner over Libya. He's never acknowledged that that was planned in his own country.
We do face people who are willing to see themselves killed in order to hurt us. But the leaders of the organizations and the countries that threaten us apparently do not want to see themselves killed. I think that would be a powerful argument against an ICBM attack on them.
Now, a mistake is always possible. ... I think it's something we have to worry about. It could be anything from a purely mechanical malfunction of a single rocket to a madman in Russia launching a whole missile field or a whole nuclear submarine full of rockets at us to the worst danger of it all: some Russian leader under the mistaken impression that his country is under attack launching their whole arsenal at us.
That last possibility is the only one of these threats that could destroy the United States beyond our ability to recover. It would be much worse than anything we can imagine from a terrorist or a rogue state. ... It's conceivable that a missile defense system might save us a great deal of damage from an accidental launch by an unsophisticated attacker who has not deployed much in the way of penetration aids -- decoys or other things -- along with the missiles. ... [But] Russian missiles are probably accompanied with decoys. ...
The missile defense system that's under consideration certainly has no capability against a massive accidental attack, which is the most serious danger. In fact, it's advertised not to be able to protect us against a massive Russian attack, because this is how we tell the Russians that they shouldn't be concerned about it. So it is irrelevant against the greatest danger that faces us.
What we do need to do to deal with that very great danger of a mistaken launch of a large number of rockets at us is not develop a missile defense system, but try to reduce the number of missiles in the hands of the Russians and Chinese, and also our own. Missile defense works against that. It works against any effort to reduce the number of missiles down from the level of thousands -- which is the number now held by the United States and Russia -- down to hundreds, or perhaps at some future date, even dozens.
Furthermore, it's almost certain to increase the number of Chinese missiles that we face, so that our danger from accidental launch, on balance, I think is greater with a missile defense system than it will be without it.
How does moving forward with a missile defense system work against reducing the number of missiles, nuclear missiles?
The Russians have lost much of their military power. But they still have an enormously potent strategic nuclear capability. In a way, it's the last vestige of their status as a superpower. ... They don't have the capability of increasing it. They're not economically capable of building up larger numbers. But they will hold on to what they have. If the United States and Russia can agree to lower the number of missiles on both sides, they will go along with that very gladly.
But if we have a missile defense system that threatens to eliminate their deterrent capability, that will set a floor in the number of missiles they have, below which they won't go. Unfortunately, in looking at our missile defense system -- even though we outside the government may express a lot of skepticism about its capability -- defense planners tend to be prudent about this sort of thing, and will always give the defense in their planning greater capabilities than it actually has.
So our missile defense system will be magnified in their eyes. I'm not just speculating about this, because I've seen this on our side. I've seen the way the United States has reacted to early Russian attempts at missile defense. ... The Russians have a primitive missile defense system around Moscow called the Galosh system. When that was put into place, it really stirred up American defense planners. It was one of the reasons we had a very large increase in the number of our warheads in the 1960s.
After the Galosh system had been deployed and the United States had reacted, Moscow was in greater danger then it had been before the defense system had been deployed. ...
[Editor's note: See the timeline for more about the history of missile defense since 1944.]
[Will a missile defense system of] the sort proposed by the Bush administration help or hurt our national security?
You know, at first sight you can argue about the cost, [and] you can argue about the effectiveness. But many people would feel any kind of missile defense is better than no missile defense. That's a natural reaction. But I don't think it's true. I think it may be that we're more vulnerable with a missile defense than we are without it.
This is because we don't have the last move. What we do affects what other countries do. It's pretty clear -- and this has been stated in the national intelligence estimate -- that our building a missile defense system will lead the Chinese to make a large increase in the number of their missiles from about 20 now to perhaps 200. ... So we face a danger from the number of missiles aimed at us, which depends on whether we build a missile defense system. ...
Is the cost of this proposed system another factor in measuring whether we'll be more or less secure?
It's easy to say that we have to defend ourselves whatever it costs. But in fact, we don't, and we never will give ourselves every kind of defense we can possibly imagine. ... If [we're] worried about nuclear threats, we should spend every penny we can usefully spend on reducing the amount of fissionable material, nuclear weapons-grade material that are held by the Russians.
They have about a thousand tons of highly enriched uranium and about a 150 tons of plutonium as byproducts of their nuclear power reactors. This material in the hands of rogue states could furnish an arsenal of very large numbers of nuclear weapons.
Nothing is more important to our safety it seems to me than getting control of this material. We have a program. We're working with the Russians to control this material. But it's being funded at a rate which I think is about a quarter the rate that it should be funded.
It's just the availability of money again. I would much rather see our funds spent on that program than on building a ballistic missile defense system ... that may have some effectiveness a decade from now, perhaps against the very limited sort of implausible threat.
You wrote about a question that you were asked at the Federation of American Scientists press conference, when you were talking about this letter from the Nobel scientists. Can you tell me what that question was?
In the press conference at which the Federation of American Scientists announced the letter ... there was a general discussion of missile defense issues, pro and con. One of the reporters present asked an interesting question.
He said, "Well, the arguments against going ahead with missile defense and walking away from the ABM Treaty seem so strong, why does the administration want to do it?" I was taken aback. I really don't know the answer. A lot of answers come to mind. When you can think of a lot of answers to a question like that, it shows you don't really know the right one.
One is that there are always political pressures in favor of large defense spending projects from contractors who would get the contracts for it, from politicians who find it useful to trade on that sort of apparent patriotism. ...
There's also a natural appeal to the idea of defending ourselves. You have to think about it a little bit to see that, by defending ourselves, we may be worse off than we would be if we didn't. That's not the thing one thinks of immediately. So it has a kind of superficial plausibility to it. ...
I think there's also something else. There's a kind of passion for projecting American power into space. We see this with some of the programs that we pursue like the international space station, which I really have never understood any reason for the United States [to spend] money on.
I remember during the Reagan administration when a much more science fiction kind of defense, the so-called "Star Wars" defense, was being proposed. ... Space brings out ... a kind of passionate attachment. Maybe that's good for some things, but it's a dangerous mood to get in when you're considering matters of national security.
Is another reason ... that there's this conviction that American science will overcome all technological burdens?
... One often hears it asked, why, if the United States could put men on the moon, can't it develop a defense system that will defend our country against attacking missiles? On the face of it, it's a reasonable question. But there are pretty great differences between going to the moon and defending the country.
The moon is a fixed target. We know where it is. With absolute precision, we know where the moon will be at any future time. It's not going to evade us. If we send rockets to the moon, there will be no effort on the part of the moon to prevent them from reaching there. They will just go there. It's completely predictable. When we had developed the rockets that went to the moon, we knew they would get there.
Unfortunately with missile defense, we face human beings on the other side. Whatever we do to defend ourselves, they can take another step. They always have the last move, and [can] deploy decoys or other penetration aids that will defeat our defense. ... Dealing with a human adversary is considerably more tricky.
Building a missile defense system will call forth response on the parts of countries who are not necessarily our enemies, countries like Russia and China, like, for example, the Chinese building up the number of their missiles. ... The only thing wrong with going to the moon is how much it costs. It had no other bad effects.
Someone has said to me that in this whole debate and beyond, the technology is lagging behind the political fervor. Do you think that that's a fair statement?
There have been technological advances. It's really quite an achievement to be able to send a missile up that can hit an incoming missile in space above our atmosphere in mid-course. But the technology isn't there for a credible defense, for a defense that will be able to deal with an adversary that sends decoys along with the warhead. We're not remotely yet in the position of testing against that kind of credible offense. ...
I think the rocket technology is there, or will be there within a reasonable amount of time. But the organization of a defense including the development of sensors, computer capability that would deal with a reasonably competent attack, is just not there. I don't know that it ever will be, because as we improve our technology, the kind of thing the adversary might do can also be improved.
It has been suggested that one of the reasons that there is this current apparent rush to deploy and deploy ... what's called a multi-layered system has more to do with getting rid of the ABM Treaty than with missile defense itself.
It may be that, rather than getting rid of the ABM Treaty in order to test missile defense, we're testing missile defenses in order to get rid of the ABM Treaty. The Bush administration has shown its dislike of having the United States bound by treaty obligations -- not just in regard to missile defenses, but in regard to the comprehensive test ban treaty, with regard to the Kyoto protocol.
I'm afraid one of the unpleasant fallouts of the administration through the decision to abrogate the 1972 ABM Treaty will be a further confirmation of the world view that the United States does not want to be part of an international system of mutually agreed on obligations.
Frankly, that alone wouldn't bother me. If I thought that tomorrow we could deploy a system that would give the United States 100 percent protection against missile attacks. I would say go ahead, and do it at almost any cost.
But that's not what's on our plates. What we have to face is a decade of gradually developing a possible missile defense system that might have some capability against a very limited range of threats, threats that may not be plausible ... and that ... cost[s] enormous amounts of money, and furthermore, will lead countries like China and Russia to adopt policies that are more dangerous to us in the long run than the danger we're trying to defend ourselves against.
Do you fear that doing away with ... the ABM Treaty will start a process that other arms control agreements will begin to fall apart as well? That the whole architecture will begin to fall apart?
I think that getting rid of the ABM Treaty starts a chain of events that we can't really now predict. For example, if it leads China to increase the number of their missiles, as it almost certainly will, what's going to be the reaction on the part of possible Chinese adversaries -- Japan and India?
India of course has a nuclear capability. If India develops its nuclear capability in response to China, what's going to be the effect on Pakistan? We're getting into a downward slope in international relations which I think is very dangerous.
I'm afraid there are too many people who think that the pattern of international treaties and obligations is superfluous. They can see a better future, in which the United States just goes it alone, develops its own technology, doesn't pay any attention to what the rest of the world does. I think that's a very dangerous attitude and dangerous to the United States, which is what I really care about.
What do you say to those people who say ... the ABM Treaty has constrained the technology, [that] had it not been for the ABM Treaty we would have a working anti-missile system now?
The ABM Treaty hasn't prevented research on missile defense technology since 1972. It's continued about as vigorously as it could continue. Even the testing that's being done now could have been done under the ABM Treaty, with slight reorientation of where the launch sites and radars are.
I think we should continue research on missile defense, because we might discover something that we need to know about. In any case, it can't be banned by international treaty, because you can't really police who is doing research on what. What you can police are testing and deployment.
So since it can't be banned, to be safe, we ought to go on doing active research on missile defense. I've done some myself. I don't feel guilty about it. I just don't believe that the treaty has stood in the way of this kind of research. ... I think the treaty gives some assurance that, since we are not testing a system, that we're not going to deploy one overnight. That, I think, is a good thing, because it reassures countries that might otherwise build up their missile and nuclear forces in a way that would be dangerous to us. ...
This sounds like more of a Washington political argument. ...
The ABM Treaty had prevented an active program of testing various components. For example sea-based, air-based, space-based systems not only couldn't be deployed, but couldn't be tested under the treaty. But we really didn't have any systems to test. ...
Space-borne laser systems that could attack enemy missiles as they were boosting up just above the earth's atmosphere, they haven't jelled into anything that we would want to test. There is no system in the wings that would solve the problem of missile defense if only we could test it.
So I find the argument that we have to get rid of the treaty in order to test these things to be a false one. I think getting rid of the treaty does open up the door to lots and lots of testing and development and lots of vigorous activity, which will call for responses that will be very dangerous to us, but which doesn't seem likely to lead to anything in the way of a really workable ABM system.
You've written that it's hard to remember a time when we have not been debating missile defense. Are you seeing the same debates, arguments, even actions/reactions playing out?
The arguments against and for missile defense didn't begin with the Clinton or the Bush administration or even the Reagan administration. It goes way back to the Eisenhower administration. It's the same argument over and over again. On one side people say, "We've got to do something to defend the country. This is the threat. We've got to defend against it."
[Editor's note: See the timeline for more about the history of missile defense since 1944.]
On the other side, people say, "Well, you may be worse off with a defense than you were without it." The arguments about decoy discrimination, telling decoys from warheads, they're the same arguments that people made back in the Kennedy and Johnson administration. It just goes on and on. ...
Government defense planners have learned a few things. They've learned not to use nuclear weapons in the defense, because it causes too many political problems, and it also causes technical problems. It blinds the radars, for example. So we're not talking about exactly the same kind of systems. These are not nuclear-armed systems. So some of the arguments against them have been ameliorated. But apart from that, it's just the same old argument over and over again.
Former Senator Sam Nunn has said that if we're ever going to come to a meeting of the minds of missile defense, we have to stop debating it as a theology, and start looking at it as a technology. Does that make sense to you?
I think there's a terrible tendency to equate issues like missile defense with other issues. If you're for missile defense, you're against gun control, and you're against abortion and so on. The idea is not so much to make a rational decision about these things, but to have an ideologically coherent set of bumper stickers.
I don't think you can argue about these things this way. Being for or against missile defense shouldn't be a test of whether you're some kind of left-wing wimp or a right-wing super patriot. It's a serious issue on which the future of our country may to some extent depend. It has to be argued by people who are willing to look at the particular issues.
What will the defense be? What capabilities will it have? What will other countries do in response to it? What will it cost? What will it defend us against? I don't think that this really should divide Republicans and Democrats or conservatives and liberals. But it sure does.
Back to your article. Has the decision of whether to deploy a national missile defense system been settled?
... Congress is going to have to consider that. Every year that the administration comes to it for appropriations, there are going to be hearings. I hope that the senators and representatives will take a serious look at the system, its capabilities, its dangers, its costs, and think about it in detail, rather than just accepting it as a fait accompli. ...
I think Congress should be very active in resisting the idea that, having withdrawn from the treaty, we are now committed to developing a missile defense system. They should look at what's being offered to them before they appropriate any money for it. The level of requested appropriation is going to rise to the point where this will become a very serious matter to people who worry about the budget. Eventually, I think probably the system will not be built for that reason.
But in the meantime, in the next few years while we see the cost rising, great damage will be done to the United States' international position and to our security because of the response that other countries will make to our withdrawal from the treaty. ...
[Talk about "pure" versus "applied" missile defense.]
In my own field of physics, as in most other areas of science, we like to distinguish between pure physics and applied physics. Applied physics is physics done for some societal purpose -- to develop new technologies, for example. Pure physics is done for its own sake, the search for knowledge, just for the knowledge itself, rather than for any application it might have.
Both kinds of physics are of course worth doing, and both are valuable. I'm not going to put down pure physics. It's what I do. But there are places where you have to be a little suspicious about something being pure.
In trying to develop a missile defense system which would have only a very dubious capability against threats which are not very plausible and which on balance would hurt our security more than help our security, it seems to me that the administration is pursuing a program of pure missile defense. That is, missile defense carried on for its own sake rather than for any application that it might have in defending our country. ...