In November 2011 the U.S. Air Force announced the successful test (on 17 May) of a new cruise missile, CHAMP (Counter-Electronics High Microwave Power). CHAMP may have been the first missile designed specifically to carry what is more usually called an HPM (high-power microwave) device, the non-nuclear (and short-range) equivalent of the electromagnetic pulse (EMP) created by a high-altitude nuclear burst. It is widely supposed that such pulses are particularly dangerous to modern industrial societies because they can wipe out microelectronic devices, not merely computers and cell phones but also the computers that control most critical infrastructure. In this sense the EMP threat is not altogether different from various cyber-threats, the latter most recently demonstrated in the November 2011 attacks on municipal water systems in Texas and Illinois.
EMP and HPM differ from electronic jamming in that they operate at much higher power and across a broad frequency spectrum; their users do not need intimate knowledge of how their targets function in order to disable them. An Air Force video released when CHAMP was revealed shows the missile approaching a building in which an office is lit. When the HPM payload goes off, the lights go out and the computers fail (one stops, restarts, and then stops for good).
The 17 May test flight proved that CHAMP, which was developed by the Boeing Phantom Works, could navigate to its target, orient itself (the weapon is apparently directional), and trigger its payload; the payload itself was not demonstrated, and it is not clear whether it is on the verge of becoming operational. The payload was developed by Raytheon, which reportedly bought the Ktech company (which develops HPM warheads) specifically to provide such a warhead for its entire range of missiles. The Air Force has stated that the CHAMP warhead is scalable, and that the customer decides which frequency range is desired. A video shows a missile dropped by a B-52, but there are presumably other ways of delivering an HPM warhead.
The potential of such warheads is immense, because virtually the entire modern world depends on microprocessors. For example, jet fighters and attack aircraft are inherently unstable, relying on computer flight-control systems (“fly by wire”) simply to stay in the air. That is particularly true of many stealthy aircraft, like the recently retired F-117, whose radar-evading shapes are poorly adapted to flight. It seems likely that an HPM warhead would have a greater lethal radius than the usual blast warhead, hence might be particularly well adapted to attacking a stealthy aircraft whose track was not precisely known. Such aircraft conceivably might be attacked by a subtle form of jamming that would upset their flight controls, but that would require very intimate knowledge of the target system. HPM offers effectiveness without any such subtlety.
HPM might change the way we attack enemy air defenses. Currently we attempt to destroy each enemy radar, and that takes missiles that can get close enough. One of the countermeasures is to keep most of the key equipment far enough from the radar antenna that a blast that wipes out the antenna does not touch the rest of the radar. Anti-radar missiles are sometimes rated by the length of time before their effects can be repaired. An HPM attack might cover a wide enough area that nothing would survive, and the wires connecting antenna and radar might themselves serve as antennas attracting HPM radiation. Much would of course depend on just how much power an HPM warhead developed within a given package.
Consider, similarly, an HPM attack on a building. Most modern buildings use microelectronics to control their air conditioners, water supplies, and elevators. Imagine knocking all of them out at one blow. The results for those inside such a building might be far more devastating than merely seeing lights blow out or desktop computers crash. HPM might be even more effective; it could disrupt or disable a buried command center.
All of this might suggest that the future of warfare lies with HPM weapons, which would seem to offer much greater payoffs than current explosives, and probably in much smaller packages. There is, however, a rub. It is impossible, without testing (by attacking), to be sure that a target really is vulnerable. Many years ago, in connection with proposals for such weapons, a U.S. naval officer put the problem simply: He would never be sure that his own ships and aircraft could survive EMP attack (despite considerable effort expended), but equally he could not be sure, without tests, that an enemy was fatally vulnerable to such attacks. HPM may be a blunter instrument than a jammer, but it still depends on many details of the target, including exactly how it is arranged. For years, one of the most basic defenses against EMP has been to enclose the target in a Faraday cage, meaning a wire cage. What if a target building had wire mesh over its windows? Would that be enough of a protection? Or would other paths into the building suffice to keep it vulnerable?
Assessing the Effects
Quite aside from the question of whether an HPM warhead should be able to produce a desired level of damage is the question of how to tell how well it has done: battle (or bomb) damage assessment (BDA). BDA often seems to attract remarkably little attention. For example, current Western antiship missiles have relatively small warheads. They are often advertised as sufficient to put a target out of action, but admittedly they will rarely sink a ship, at least directly. Certainly a small warhead in the right place will have the desired effect, but someone firing far beyond the horizon cannot see the results of an attack. Has the warhead hit in the right place?
During the Cold War, the U.S. Navy estimated that it would take high numbers of Harpoons to sink large Soviet warships. It might take far fewer to disable those ships, but it is remarkably difficult to go from the effect of a single warhead at a particular place on a ship to an assessment of how much combat power the ship loses. A great deal depends on subtle details of the ship’s construction and operation—and also on how well the crew has been trained for damage control. For instance, a radar system can be degraded considerably if the air compressor at the foot of a mast is destroyed (the radar waveguide cannot carry as much energy). It seemed significant that the Soviets enclosed their masts and therefore protected their waveguides. We still have no idea of whether that was an attempt to improve survivability or a matter of structural design to support heavy gyro-stabilized antennas. Incidentally, visits to Russian ships after the end of the Cold War suggested that their ability to resist hull and fire damage had been overestimated.
Imagine what information would be available during combat. Would it be enough to see that the target has ceased transmitting, or that it is apparently dead in the water? Or should the attacker demand positive proof that the attack has succeeded, in the form of a sinking target? If that is the only satisfactory proof of damage, then the Western trend toward small warheads is delusionary. One might be tempted to add that the Cold War-era Soviets had it right with their large missiles and warheads, but the Russians are now building missiles with Western-size warheads, because it took very large and unaffordable ships to accommodate the old massive missiles.
BDA can be (and probably in future will be) very much a cat-and-mouse game, in which each side turns off emitters to make it appear that attacks have succeeded. The ability to net sensors makes it easier to turn off any particular emitter without sacrificing system capability. Compared with the subtlety of HPM, physical destruction has the enormous advantage that it produces clear evidence. In a few cases, such as fly-by-wire aircraft, HPM might have unambiguous consequences: an airplane flying into the ground because its flight control system was gone. In many more cases, however, a target might play possum. The HPM warhead in the Air Force video might well have turned off lights and knocked out computers, but it might also be possible for an enemy to turn out the lights deliberately (and who could know what was happening with the computers?). The answer may be that the missile carrying the HPM payload is itself so stealthy that the target could not know it was coming, hence could not simulate damage.
However, the point remains. With cyber attack and then with HPM, we are moving into a new world of non-kinetic weapons with considerable potential. Because BDA is now so much more difficult, we may also be entering a world of tactics and deception well beyond anything we now know. Take the report of cyber-attack on a Texas water system. It may be true. However, it might also be false, an attempt to force a failed cyber-attacker out into the open. The attacker might feel compelled to assess damage, and that attempt in turn might make identification possible.