The return of Star Wars: How to protect air space from missiles

Long ago, long before we had any hope of actually building one, science fiction writers were starting to talk about “death rays”. On the big screen, Flash Gordon and his friends began to fire death rays at each other with giddy abandon and there were some in high office who decided to take it seriously. Before the Second World War had even kicked off, the British government decided to spend time and money trying to develop a death ray (aka – a “directed energy weapon”) to be used by the Royal Air Force. Within a matter of months, it became obvious that it would take decades to overcome the technical obstacles involved and the design was largely abandoned. On a more positive note, some of the scientists assigned to the project picked up on the possibility of using radio signals to detect the position of enemy aircraft.

In effect, radar was born out of the very first death ray project and this same system would serve the Allies well in the Battle of Britain and beyond. This sequence of events would be repeatedly be played out again and again in many countries over the next few decades with one government after another trying to develop the mythical “directed energy weapon”. Each project in turn would begin with a spirit of optimism and end when the scientists involved decided to submit a report saying “no, we still don’t know how to do it”. Now, in the third decade of the 21st century, a viable laser based system is about to be introduced. The Israeli government plans to deploy just such a system in the near future. A laser system will be used to augment the existing “Iron Dome” system already used by the IDF. In recent years, Israel has been hit by multiple missile strikes. A stream of relatively low tech rockets are fired from several miles outside their own border and start to fall on populated areas.

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The rockets themselves can be fired from the back of a small truck and this kind of attack has proved difficult to anticipate or to counter. The large number of incoming missiles makes it difficult to achieve a 10 per cent kill rate although – in contrast to a nuclear exchange – the actual damage created by each missile is relatively mild. The Arab groups involved often lack the R&D capabilities of the Israeli government but that doesn’t mean they are powerless to oppose them. In this situation, putting up a mass of targets at the same time is a key strategy for any attacking force since tracking and firing upon such a force is particularly difficult to do. Remember that this kind of missile will lack discernible wings, dramatically reducing its cross sectional area and making a successful hit on the incoming missile even more of a challenge.

Other than dumb missiles, the intelligence services are beginning to worry about the possibility of drone attacks. Some strategists are worried about being attacked by a “swarm of drones”, all of them attacking at once. It is now possible to buy a reasonably convincing drone on Amazon and learn to control its flight path in just a few hours. Given that a drone that is capable of carrying a hand grenade is entirely realistic, the potential for mischief by extremists is clear. A sophisticated opponent, attacking with a swarm of drones in a sudden rush could knock out an entire squadron of tanks or armoured cars long before the ground forces involved have time to react. Given the narrow cross sectional area of a drone, the task of actually hitting the incoming weapon it becomes even greater than usual.

Faced with this kind of threat, defence using machine gun bullets is the first idea that comes to mind, consumes a lot of bullets very quickly and, in practice, almost all of the bullets fired will miss the target. By its very nature, a machine gun bullet has to physically strike the target in order to achieve a kill. In contrast, a missile with a proximity warhead need only pass reasonably close to the target in order to detonate. The resulting explosion and surrounding shroud of shrapnel may be enough to damage the incoming drone or missile. Proximity warheads were developed in the Second World War and are still in use but all of these systems come with problems of their own. The economic cost of such a defence is substantial and the forward defensive troops need to be continuously resupplied with specialist ammunition in order to hold out.

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All these problems have led some scientists to believe that some sort of directed energy weapon is the solution. A laser beam can hit an incoming target at much lower cost than a bullet. In principle at least, it does not consume a physical supply of ammunition. For this reason, proponents of the laser based system argue that it can be fired indefinitely (and be effective against a swarm of drones). Unfortunately, this isn’t entirely true. A laser will consume electrical energy so there are always some consumables, especially for a system that is isolated from the National Grid such as a ship at sea, an aircraft, a satellite in outer space. The actual economic cost of each shot is, however, expected to be much less than for a missile. People are quoting a figure of $2,000 a pop rather than $100, 000 for a small rocket-propelled interceptor.

The laser system developed for the new Iron Dome system in Israel will be more analogous to a bullet than a proximity shell. A laser – or some other directed energy weapon – has to physically strike its target in order to achieve a kill. As far as laser weapons go, a miss is as good as a mile. Once the laser beam makes contact with the target, it will have to maintain contact for several seconds in order for the temperature of the incoming missile to become critical. Contact for a few milliseconds may not be enough to complete the task. Remember that the incoming missile will be moving at fantastic speed and is likely to pass through areas of mist and cloud that will take a lot of energy out of the laser beam.

Early studies into the feasibility of laser beams were able to show that the effect of the beam could be completely negated by something as low tech as fog, a smoke screen or by wrapping the target with baking foil. A highly reflective surface will be a lot less likely to catch fire with a beam of light than a matte black one. In spite of this, a number of research groups have advocated for anti-aircraft systems that are based on laser science. Technology demonstrators in the United States used infrared lasers to hit radio controlled targets in the desert and the sales video is reasonably convincing. Needless to say, the engineers involved had been careful to paint the targets red to make sure that they would absorb the infrared rays and disintegrate on camera. A malicious and determined opponent might not be so thoughtful.

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Conscious of the potential of laser weapons but conscious also of their limitations, some in the military have looked at the potential of using lasers to blind an opponent. Given that existing laser technology is incapable of knocking out an incoming aircraft, why not disable the pilot instead? A relatively low powered laser beam could knock out a man’s retina in a split second and some military vessels have been equipped by lasers that could be aimed at incoming bomber crews. For many, the concept is so alarming that some governments have attempted to ban “blinding” laser weapons as part of some kind of alternative arms limitation treaty. Whether or not the world’s military organisations will be subject to this kind of self-restraint is hard to know.

Then, in the 1980s, President Reagan famously fell for the laser beam spell (just as the British had in the 1930s). So certain was Reagan that laser guns were the future that he decided to make a major televised announcement about laser and other directed energy weapons. In the next war, he claimed, the Americans would attempt to defend themselves using a laser beam based weapons system (not dissimilar to the new Israeli Iron Dome concept) that would shoot down incoming nuclear missiles, thus saving the country from annihilation. The same military industrial complex that had brought mankind so close to self destruction would now release us from that threat. Many within the scientific community were severely critical of this new “Strategic Defence Initiative” (SDI) and within a few years, the project had largely ground to a halt. I have to say that conceptually, SDI had a lot to be said for it. Here was a way to stop nuclear war without killing everybody on the planet.

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One of the most popular weapons systems considered by SDI was the X-ray laser. From a scientific perspective, it was a remarkable device. Supporters of the X-ray laser were convinced that it could be used to successfully shoot down a swarm of incoming nuclear missiles. If their other Allies were nice to them, it might just protect them too.

However, from the outset, there were problems associated with the system. The only way to fire the laser was to detonate an atomic bomb in the centre of the weapon. In practice, this would be done in outer space since the system was designed to be deployed in low Earth orbit. Nano seconds before the entire satellite breaks into a million splinters, a system of glass rods would be activated by the initial burst of gamma rays. In turn, these would fire a series of very high energy laser beams towards the incoming missiles. Unfortunately, the United States had already signed up to a binding international treaty that made it impossible to test a nuclear weapon in space. Even if they’d decided to throw caution to the wind and do it anyway, the reaction from the American public would have been severe. In the event, they decided to test it underground, which is where all modern nuclear weapons systems are tested anyway and the results were disappointing.

What was good about the X-ray laser was the intensity of energy that could be directed into the beam (an atom bomb makes for a generous fuel source) and the fact that it could be fired from above the target. Nuclear missiles blast off from the surface of the Earth and quickly ascend under rocket propulsion. They soon soar above the atmosphere and then – quite suddenly – they run out of fuel. This is the initial boost phase of a nuclear missile’s path and from that moment on it follows a passive trajectory, soaring to a peak altitude under its own momentum and then gently falling back through the atmosphere towards its final destination.

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Aware that the west was likely to develop countermeasures against nuclear attack, the Soviets had already equipped their missiles with both real and dummy warheads. The warheads separate from the main rocket in outer space and spread themselves out, with each warhead heading towards a different target. Since it was impossible to tell the difference between a real and a dummy H-bomb, any attempt to shoot down the incoming arsenal would require the defending force to hit each of several warheads, a formidable technical challenge. However, if the missile could be detected before it reached outer space, while the rocket engines are still firing and all the warheads are still contained within the tip of the missile, then one hit ought to wipe out the whole lot. Open discussion of this approach led the Soviets to look at ways to increase the thrust of their rockets, abbreviating the boost phase and reducing the chances of them being hit at an early stage of the attack. However, by placing many X-ray lasers in low Earth orbit, the Americans felt confident that at least some of the lasers would be over the Soviet launch sites whenever the Soviets chose to attack. The down side of this tactic is that the Soviets were massively over-insured against both launch failures or defensive acts. Even if per cent of the incoming missiles reach their targets, most of the nicer areas in the United States would cease to exist. SDI was a project for a real optimist.

Aside from X-ray lasers, much research has been focused on particle beam accelerators. When we speak of directed energy weapons, we are usually talking about either lasers or a particle beam accelerator like system. If you want to accelerate subatomic particles you usually need an electric or magnetic field. Similarly, the particles themselves need to be electrically charged in order to respond to the applied electromagnetic field. For an isolated weapons system like a satellite in outer space, even the briefest negatively charged electron beam firing will leave the satellite massively positive, drawing the actual electron beam back towards the target and effectively committing suicide. Isolated, space based particle accelerators would have to be capable of firing electrically neutral beams over great distances and with great precision. It took several years and tens of billions of dollars for the American scientific community to accept that the technical challenges involved were unsurmountable.

However, that isn’t to say that nothing useful came out of the SDI programme. There is such a thing as spin off and massive R&D expenditure by the US Department of Defence continues to be effective as a means of national advancement in science and engineering as a whole. While an effective anti-ICBM system remains a pipe dream, prototype weapons systems are beginning to emerge. Some years ago, the American Air Force built a laser beam system in a Boeing 747 (a very large jet) and used it to shoot down a sidewinder missile in mid-flight.

Other experts have suggested that by flying close to an enemy missile base such a system could be used to shoot down a nuclear tipped missile during the initial boost phase (remember, the boost phase only lasts a few minutes – it’s a very narrow window). Again, this kind of thing is easier to do in the sales video than it is in real life. Nobody’s going to ring you up and warn you when they intend to fire a nuclear tipped missile in your direction. In the short term, this kind of technology may yet prove effective against a rogue state like North Korea, which might struggle to launch more than a few missiles at the United States but which could probably wipe out several population centres on the west coast if it wanted to. How much of North Korea would be left by the following day is difficult to say but in the aftermath of 9/11, many intelligence officers were forced to completely rethink their strategies. Acts that we might regard as insane can no longer be regarded as impossible. Similarly, some assailants won’t bother to follow the rules.

Even if the west could construct an infallible laser shield against ICBM, a foreign power could simply overcome this by putting live nuclear war heads on scheduled cargo aircraft bound for the United States. Given that hundreds of such flights occur every day, such a weapons system would be cheap, accessible to anyone and very difficult to differentiate from the routine, inbound tourist traffic. By timing the weapons on board to detonate just before landing (most airports are near large cities) the attacking organisation wouldn’t even need to find suicidally fanatical air crew. They could just wave them off with the promise of a monthly wage cheque that need never be seen.

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How would such a system perform if it were deployed in a real conflict? Perhaps even the conflict now emergent in the Ukraine or the one that might come after that, if Putin made good on his threat to unleash nuclear Armageddon? There’s no question that technology has moved on since the 1990s and a number of countries are on the threshold of introducing a laser like weapons system into their militaries, albeit with a very limited role.

In some respects, the “laser gun” remains at home in a laboratory and not a battlefield. A battlefield is a dangerous, dirty and unpredictable environment and the people operating a weapons system in time of war lack the patience and the finesse to set up a laser beam system. Last September, the British Ministry of Defence announced a £70m investment in a laser-like weapon that might be used by the army or navy in the near future. Such sums are puny in comparison to the sort of budget that Reagan threw at SDI although the British do intend to rely on the American company Raytheon for some of the key components.

The new systems might be effective as an aerial denial weapon, driving conventional jet aircraft from the skies and forcing an enemy air force to concentrate on the use of “stand-off” missiles without exposing the attacking aircraft and pilots to the possibility of a laser attack. The Reagan era seems a long time ago now and until recently, his Strategic Defence Initiative (AKA “Star Wars”) seemed consigned to the ash heap of history. Now, in the space of just a few days, his ideas look set to be re-examined.

Whilst Ronald Reagan was widely lampooned for his SDI concept, it should be remembered that a laser is a defensive rather than offensive weapon. If there was a time when Nato felt capable of defending its eastern borders with directed energy weapons, they wouldn’t be much use for an actual attack on Russia (something that Putin seems to fear) but they would make an aerial intrusion of western airspace more difficult.

As the spectre of nuclear annihilation returns, it seems likely that western governments will soon revisit the option of a defensive system against Russian ICBMs, rather relying on our traditional policy of massive retaliation. My guess is that in this context, laser guns will remain a fantasy weapons system that a determined opponent could circumvent quite easily using an improvised delivery system.

Watch this space.