The weapons referred to in this study under the generic title of cruise missiles can be ground- or air-launched. Ground-launched cruise missiles are generally multistage missiles, with the first stage being a rocket. At some predetermined altitude, the rocket booster is discarded and wings or canards are deployed to provide aerodynamic lift. Simultaneously, a motor is activated to provide propulsion. Air-launched cruise missiles are carried to launch altitude by an aircraft. In this case, too, tail fins, wings, and/or canards may be deployed to provide trajectory control surfaces.
A cruise missile may be accelerated to cruise speed by a rocket booster and might be designed to employ rocket thrust for a high-speed terminal attack. For most of its flight, a cruise missile is propelled by air-breathing turbojet or ramjet engines and relies on aerodynamic lift to carry its weight and maintain altitude. Cruise missiles remain within the atmosphere and under power during their cruise phase. Hence, their range and general flight characteristics are similar to those of an airplane.
Payloads carried by cruise missiles may include large, unitary, high-explosive warheads, submunitions, runway penetrators, or weapons of mass destruction (nuclear, chemical, or biological). In the past, successful cruise missile attacks succeeded in sinking warships or causing severe, mission-limiting damage to them. Cruise missiles that are configured to carry and dispense submunitions constitute a particularly severe threat to troops in the field and to nonarmored vehicles such as trucks. When the submunitions that are dispensed by a cruise missile are high-performance, self-propelled devices that are equipped with terminal engagement sensors, they can even constitute a significant threat to armored vehicles. Thus, cruise missiles are a significant threat both to plat-forms at sea and to forces ashore.
Cruise missiles can be classified according to the altitude and velocity of their cruise segment, as well as their launch-to-target range. Cruise altitudes fall into three categories: high altitude, low altitude, and surface skimming. High-altitude cruise extends the range by improving fuel-use efficiency, but it makes the cruise missile more likely to be detected. At lower altitudes, such missiles can take advantage of the decreased line-of-sight horizon for trackers in the vicinity of the target and of terrain features that mask the approach path. Surface skimmers, which are practical only over the ocean or extremely flat and desolate terrain, descend to within a few meters of the surface and may go undetected until very close to the target. Cruise missiles may cruise at subsonic, supersonic, or hypersonic velocity. Because lift-to-drag ratios decrease with increasing speed above the maximum endurance speed, a range penalty is paid for supersonic or hypersonic flight. However, since the time of flight is inversely proportional to speed, the intercept problem becomes more difficult as the speed of the target missile is increased. Of course, a cruise missile's flight path may be broken into