Cole Highlights Survivability
On 11 October, terrorists attacked the USS Cole (DDG-67) in the port of Aden, Yemen, at the mouth of the Gulf. About two hours after she moored, a small boat approached the U.S. guided-missile destroyer carrying a large explosive charge, which the two men on board detonated close to the ship's side. It tore a 40 x 40 foot hole in the destroyer's side abeam her auxiliary machinery space, above which was a crowded mess deck. The blast killed 17 sailors, some of whom were on the deck above. In addition, distortion of the deck above affected the adjacent bulkheads, so the ship flooded beyond the initial hole. Eventually both the auxiliary machinery space and the adjacent engine room were knocked out. The destroyer's crew shored up the affected bulkheads and maintained onboard power. The Cole's survival was a tribute both to her crew and to her designers and builders.
Early reports as to the size and nature of the explosive disagreed sharply; they ranged from a 75-pound shaped charge (as in an antitank missile) up to a thousand-pound shaped or mass charge using military explosives (one report claimed that the material was Octol, which is more powerful than TNT). Destroyers such as the Cole essentially are unarmored because, given their size, it is impossible to cover any significant area with armor likely to keep out modern antiship missiles. Instead, the strategy is to limit the extent of damage by compartmentation. The Arleigh Burke (DDG-51) class, of which the Cole is a unit, was designed to be tougher than earlier surface combatants. Measures to that end include some specially armored bulkheads that would limit the lengthwise extent of damage from the sort of internal explosion a big antiship missile would usually produce. Moreover, even an armored ship would suffer extensive skin damage from a big contact explosion such as that the Cole suffered. That the Cole did not succumb, and perhaps even more significantly that she maintained onboard power, testifies to the success of her design. We do not of course know whether the shock of the explosion disabled the ship's combat systems.
The larger issue is whether this sort of terrorism was to have been expected, and whether much could have been done to prevent it. The Middle East always has been quite volatile, and for a number of reasons (not limited to U.S. support of Israel) the United States is a convenient scapegoat. We are the foremost agent of a modernization that many people resent, and we cannot abandon that position without ourselves sinking into some sort of morass. We are, moreover, an important prop of regimes, such as those in Saudi Arabia and in Yemen, who have real internal enemies. Attacking the United States is a very good way of attacking a regime whose secret police may make more direct attacks impractical. That probably explains the destruction of the U.S. Air Force barracks in Saudi Arabia some years ago, perhaps the first major attack perpetrated by Osama bin Laden.
Obviously emotions throughout the Arab world are running high because of the explosion in Israel; the United States is more of a target now than six months ago. Reportedly there was a warning that Osama bin Laden planned to attack a U.S. target. He is hardly the only Middle Eastern exponent of terrorism. If it turns out that the bomb was not very large, and that it was not very elaborate, it may even have been a private attack. As this column was being written, the Yemeni police had found evidence of the two perpetrators, who had traveled to the port specifically to attack. One or both may have been foreign nationals, and reportedly they kept to themselves during the run-up to the attack. There also was a claim that, as the attackers approached, other boats cleared away, and that an unusually large number of spectators lined the shore. That report may be accurate, or it may reflect nothing more than heightened memories of the event itself. Aden was regarded as potentially dangerous, but it was also described as safer than many alternative fueling ports in the area. Later there was a report that the ship did not really have to refuel, that her visit to Aden was at the behest of the State Department. If so, it was a classic example of naval presence, and the attack on the USS Cole is a good indication that presence carries real dangers.
It seems unlikely that the United States received a warning so specific that the ship could have dealt with the threat. Any ship going into a foreign port finds herself surrounded by small craft, and virtually all of them are harmless. To keep all of them away would destroy the goodwill associated with a port visit, perhaps even display the sort of fear that would repay the attackers. After all, one reason for deploying the fleet overseas is to make contact with the local populations. It is conceivable that some sort of remote sensing device can be developed to detect large concentrations of explosives at, say, a 100-foot range, but right now nothing like that exists. Without such a device, it is unlikely that any patrol around a moored ship can be altogether effective—or even worthwhile.
In a larger sense, the United States has a vital interest in maintaining a degree of world order. A forward-deployed Navy, which regularly visits foreign ports, is our best way of doing so. Many others in the world reject the current order, and thus will attack U.S. forces overseas. If some attacks are unavoidable, Americans may reflect that a ship such as the Cole is likely to be vulnerable for only a very small percentage of the time, whereas fixed ground bases (which may be difficult to establish in the first place) are always available to attackers. Moreover, when a base ashore has to be evacuated after an attack, as the Marines were forced out of Beirut in 1983, U.S. prestige is badly damaged. Since that prestige helps maintain the order we seek, it matters. By way of contrast, when the Cole comes home for repairs, it will have little or no effect on our standing in Yemen; ships come and go.
The rules of engagement inevitably favor an initial attacker. They cannot be otherwise, unless we invent some sort of ESP scanner that detects the intent to attack. In our designs, however, we often tacitly assume that we can shoot first. For example, we require our active antimissile defense to be capable of destroying all weapons directed at us, the implication being that any that leak through are likely to disable the ship. Incidentally, no other navy does any better, and in ships such as the Cole we probably do better than others in providing a serious level of passive protection. Even so, we may well be missing the point. The other fellow will often, perhaps always, get to shoot first. Our ships should be designed so that they can absorb the damage and shoot last. That inevitably means large surface combatants.
A given attack damages a ship over a given length. The larger the ship, the smaller the percentage of her overall size that covers. For about 30 years the published U.S. Navy criterion for survivability has been a 15% damaged length, which for a 500-foot destroyer is 75 feet—which explains why the Cole survived. This has not been a criterion for the combat survivability of the ship, because when it was stated, electronics was unlikely to survive any serious shock anywhere on a ship's hull. That no longer is true, as all readers must know: you can drop your home computer, and it will keep working (and military electronics is packaged better than a home computer). We know we are doing better; for example, when the USS Princeton (CG-59) was mined during the Gulf War, her combat system, or at least her radar/computer system, apparently continued to function.
Navy Purchases Ducted Rocket
In June, Orbital Sciences Corp. won the Navy contract for a supersonic low-altitude target. From a weapons point of view, the most interesting aspect of the design was its use of a new kind of engine, a ducted rocket. For years Atlantic Research Corp. has tried to sell such engines, and visitors to the various annual defense shows will have seen its strike missile, a high-speed antiradiation missile modified with the new engine. Thus far the target is the first application.
Although it might be mistaken for a ramjet, a ducted rocket is more like a rocket with a jet-type afterburner. In a conventional solid-fuel rocket, sufficient oxidizer is provided to burn all the fuel. Some may go unburned into the exhaust, but that is only an inefficiency. In a ducted rocket, the mix is deliberately fuel heavy, so that the exhaust gas contains a considerable fraction of unburned fuel. It burns in the air sucked in through the rocket's ducts. Thus, for a given weight of propellant, the ducted rocket carries significantly more fuel, so it can burn much longer at full thrust than a conventional rocket.
That is an important virtue. It is relatively easy to boost a missile to high speed, but that may take all of the propellant. Once the fuel stops burning, drag takes over and the missile quickly loses energy. That is why several foreign missiles, beginning with some Russian weapons, combine very powerful boosters with small "darts," The dart, which may be unpowered, has much lower drag and thus loses its speed more slowly. Another alternative is to add a slow-burning sustainer, so that speed is lost even more slowly; but in this case, typified by the Standard missile, the initial boost is limited because space and weight have to be reserved for the sustainer.
The alternative ducted rocket is clearly attractive for air-to-air applications. For some years it seemed likely that the current AMRAAM missile eventually would have a ducted-rocket version. A motor of this type was tested late in 1998. At the time, the ducted rocket was rejected because it could not fit easily into the weapons bay of the stealthy F-22 fighter. Note, however, that the Europeans plan to use a ducted rocket in their Meteor, which they adopted instead of the U.S. AMRAAM.