The Department of Defense is at the leading edge of a transition to unmanned vehicles, with nearly all of its attention on unmanned aircraft. There is little real interest in the unarmed unmanned aerial vehicle (UAV) except as a learning tool, but no consensus about the features of its combat-capable cousin, the unmanned combat aerial vehicle (UCAV). For the Navy, much of the promise of UCAVs hinges on their deployment from smaller surface combatants, not just carriers.
UCAVs could give every surface combatant area-defense capability, expanding the range of response that a single combatant represents in a crisis, and allowing it to take on some of the lower-end missions of a battle group. More important, ships, aircraft, and crews have been operating for a decade far beyond sustainable paces. Adding a UCAV air-wing offers added flexibility.
Every surface combatant needs air and missile defenses when not part of a carrier battle group. Each must be capable of detecting and defeating surprise attack, whether from the air, swarming small boats, or from underwater, as well as contribute to a group or area defense. Today's ships achieve that with powerful shipboard radars and overlapping engagement zones of missiles backed by automated gun systems for threats surviving to close range.
As missiles and targeting evolve, however, achieving area theater air and missile defense (TAMD) from the surface becomes more challenging. Gaining sufficient battlespace for multiple engagement opportunities requires over-the-horizon targeting and first engagements at long ranges. This creates the need for a layer of TAMD at higher altitudes than the ship's mast can offer, and farther forward—a need which can be filled by surface-deployed UCAVs.
Aside from sensing a threat, combatants require the ability to do something about a detected threat at sufficiently extended ranges to allow multiple engagement opportunities. The greatest reach for a surface combatant today comes in the form of missiles weighing around 3,000 pounds, more than 20-feet long, costing several million dollars each, and of which we cannot buy or carry enough. Adding the elevated, around-the-clock forward sensors of the UCAV extends the reach of these missiles considerably, but it does not increase their numbers.
A shorter-range missile can be designed for the UCAV with a range of 50 to 100 miles, and by exploiting both a hit-to-kill approach and micro-electromechanical systems designs wherever possible, can achieve excellent kill probabilities with a much lighter missile. China Lake and the Air Force's Space and Missile Command worked on a missile concept named Peregrine in the mid-1990s which could do this with a weight of potentially under 350 pounds. Three to four such missiles on each UCAV would provide an effective first layer of defense against aircraft, low altitude and overland cruise missiles, and even theater ballistic missiles and some surface targets.
Between the advanced gun systems and missiles in development for our ships, we will soon be able to strike large numbers of targets deep inland. We will still, however, often be dependent on episodic, late, and not very accurate satellite targeting for those weapons. Organic airborne around-the-clock surveillance assets allow a ship to project power to the limits of her reach by solving one of the major problems of surface power projection-continuous targeting beyond line of sight. The sensors, contact/target recognition logic, and precision geolocation capabilities of the proposed UCAVs complete the surface-based strike capability.
The availability of UCAVs overhead will also extend a ship's communications capability, especially to assets ashore. With satellite relays, a ship usually can maintain high-rate communications to points on the other side of the planet. Paradoxically, communications with assets less than 100 miles away in difficult or urban terrain can be problematic. An airborne relay can make these more reliable.
Putting UCAVs on Surface Combatants
To meet its missions, an airwing would have to consist of dozens of UCAVs per ship, which requires that the vehicle and its weapons and sensors be small. Fortunately, the ability of the UCAV to operate close to targets and threats allows reductions in the ranges of their weapons and the size of their sensors. Concurrently, the tiered, often collaborative targeting of the UCAVs delivers very small target location errors, allowing weapons placement with precision that would not embarrass a sniper.
Delivering the weapon to the chosen aimpoint with such precision allows reductions in the size of the warhead, and even elimination in some cases. This leads to reductions in the size, weight, and cost of UCAV weapons, as well as the UCAV itself.
Other opportunities for lessening impacts on a surface combatant include near-total automation for nearly all shipboard UCAV operations: deck handling and stowage, refueling, rearming, test and repair, and, most important, the launch and recovery.
What Kind of UCAV?
The concepts drawn up by the Chief of Naval Operations' Studies Group (SSG) indicate that the UCAV probably will be a fixed-wing conventional take off and landing jet aircraft of surprisingly small size. If we want to launch and recover dozens of these vehicles around the clock with extensive automation, a strong argument is created to add a modest bit of weight and complexity to the ship if in so doing it would be capable of operating a significantly more useful aircraft.
One key attribute of UCAVs is that they can maintain good control authority at lower airspeeds than current tactical aircraft. This should allow the aircraft to be launched and recovered at around 50 to 70 knots indicated airspeed, possibly even a bit lower.
The SSG concept strove to allow launch and recovery no matter what the ship was doing. The launch approach that appeared most attractive was an electromagnetic aircraft launch system identical (except for scale) to that for the CVNX. Unlike the CVNX, though, the SSG proposed to launch the UCAV aftward from the helicopter flight deck. With the low-speed flight characteristics predicted for their UCAV concepts, this should be possible even if the ship is making maximum speed downwind at the time of launch. In this concept, the electromagnetic aircraft launch system (EMALS) would be integrated into the flight deck and could possibly double as the helo recovery track (with some reliable lockouts and limits when a helo is being recovered).
To put some scale to this, if the UCAV can be launched reliably at 50 knots, the ship is doing 30 knots into a 20-knot headwind, and the EMALS launcher is 60-feet long, the average acceleration required is only 7.4 Gs. If the ship were at anchorage in no wind, the acceleration could be reduced to less than 2 Gs. One of nice things about the EMALS is that it can deliver a programmed ramp-up to a constant acceleration for the remainder of the stroke—a much easier ride for the aircraft than a steam catapult produces for the same end velocity.
Recovering the UCAV in the SSG concept is even more different. The SSG envisioned an articulated arm anchored to the side of the ship in a recess in the edge, or just off the edge, of the helo deck, with the "shoulder joint" about even with the aft end of the helo hangar. At the other end of the arm would be an analog of a hand (though "hook" might be a closer analogy). This hand would be designed in conjunction with a matching lug or receptacle on the UCAV to lock the two together. An analog of a bomb lug latching mechanism is a possibility, with the physical interfaces designed to be self-centering.
The aircraft would make its approach parallel to the ship axis from either forward or aft, offset to the side enough to allow a wave-off without undue risk to the ship in the event a recovery is aborted. As the aircraft acquires the beacon in the hand and vice-versa, the two would pass data supporting the recovery as well as performing simple tracking. When the aircraft engages the hand and is latched to it, the arm flexes, absorbing the energy of the relative motion.
For precisely the same reasons discussed under launching the UCAV, recovery should require no more than about a 20- to 40-foot total stroke of the arm. If more stroke is practical, the system could also be designed to have the hand/arm nearly match the velocity of the UCAV for the last fraction of a second prior to trap, minimizing impact forces on both and reducing the latch offsets. Similar to EMALS, forces applied to the UCAV can be programmed to be uniform throughout the trap, easing loads on both.
There will be many lessons to be learned via experimentation with launch and recovery designs and ship operations to accommodate them. Since these are certain to be influential in the design of the systems, early experimentation would be desirable. As recovery carries the greater technical and schedule risk, that should be a key focus of the earliest practical experiments with whatever UCAV we can acquire that can approximate the recovery air speeds and G-tolerances.
Watchbill Impacts
One of the major—perhaps even mandatory—keys to deploying UCAVs from surface combatants is developing the tools to do so with little or no increase in manning. Near-total automation of the UCAVs shipboard functions will take care of much of this, but some of it must be accommodated by freeing up manpower from other ship functions by automating those functions. In a few instances, manpower-intensive functions can be replaced by capabilities of the UCAV. In most cases, however, the UCAV appears capable of only replacing a portion of a manpower-intensive function, still leaving a net watchbill impact.
For instance, the UCAV can take over nearly all of the helo role of airborne search and surveillance and remote targeting, but it will be useless at rescue or taxi duties. Helos will not rack up the flight hours as quickly with UCAVs on board, and can perhaps be reduced to a single, smaller, simpler, and lighter aircraft. Eventually helo flight hours and maintenance hours per flight hour may both drop enough to remove most helicopter maintenance capability from the ship.
The use of sensors, software, and intelligent agents to detect incipient faults prior to failure is one of the tools that might reduce the UCAV workload. Such systems can also detect battle damage to an aircraft, assist in getting it back to the ship, and in repair once there. They can also serve in determining while still airborne whether the damage is too extensive to warrant repair or risk recovery.
Much of a ship's long-range engagement capability is in the form of large, heavy, and very expensive missiles. By moving some weapons farther forward and guiding them from sensors on the collaborating UCAVs, both the size and the cost can be reduced. We certainly will not want to remove completely the shipboard missile capability in favor of an all-UCAV approach. Even when the UCAV is accompanied on the ship by a gun with the SSG's predicted range of 400 nautical miles and several thousand very low cost guided rounds on board, there will still be some jobs the missiles are sufficiently better at to warrant their cost.
Mr. Yates is a civilian engineer at the Naval Air Warfare Center, China Lake, California.