LASER-GUIDED MISSILES

An Accurate and Efficient Weapon

Stacy Rousseau EE Ď03




Guided missile systems have evolved at a tremendous rate over the past four decades, and recent breakthroughs in technology ensure that smart warheads will have an increasing role in maintaining our military superiority. On ethical grounds, one prays that each warhead deployed during a sortie will strike only its intended target, and that innocent civilians will not be harmed by a misfire. From a tactical standpoint, our military desires weaponry that is reliable and effective, inflicting maximal damage on valid military targets and ensuring our capacity for lightning-fast strikes with pinpoint accuracy. Guided missile systems help fulfill all of these demands.


The world's first laser-guided bomb, the BOLT-117.

BOLT-117

Laser-guided missiles were first developed during the Vietnam War. The Army began to research laser guidance systems in 1962. The first laser-guided bomb, the BOLT-117, was developed by the Air Force in 1967; however, it was not used in combat until 1968. The BOLT-117 worked using two planes. One plane was used to keep a laser illuminating the intended target, while the otherís job was to drop the missile by following the reflected laser bean and directing the missile by sending signals to its control fins. For high efficiency, there was a very narrow region within which the pilot could release the missile. Laser-guided missiles of this time were generally made of standard iron and were simply dumb bombs with a laser guidance and control system attached. They commonly had a range of three to four kilometers.

Diagram of an aircraft approaching a target to be destroyed by a laser-guided missile.

MODERN LASER-GUIDED MISSILES

Modern laser-guided missiles can be self-detonated, thus requiring only a single aircraft, and their range has increased significantly. The laser-guided missiles use a laser of a specific frequency bandwidth to locate the target. The pilot must line up the crosshairs and lock successfully onto target. This laser creates a heat signature on the target. The weapon must be released during a certain window of opportunity. After it is launched, the missile uses its onboard instrumentation to find the heat signature. The target is acquired when the missile locates the heat signature. The missile is able to secure the target even if the target is moving.

Laser-guided missiles work by following the reflected light of a laser beam, which can either be shone on the target by the aircraft itself, by another airplane, or by ground troops with a handheld laser designator. Therefore, once the missile has been launched its own instrumentation is able to remain on target, rather than older laser-guided missiles that required the pilot to continually sight the target with the laser.

Laser-guided missiles are used for those targets that need pinpoint accuracy. A disadvantage of laser-guided missiles is that their guidance systems do not work well in all weather conditions. If it is cloudy, the water droplets in the air cause the laser to diffract. Because the laser only operates within a certain bandwidth, the laser can be completely diffracted if it is too cloudy and the missile will not be able to locate its target. Rain has a similar effect on the laser because each raindrop serves to diffract the laser beam, once again deterring the missile from its target.

OTHER GUIDED MISSILES

The precise work required by pilots sparked the development of other forms of guided missiles that do not require the pilotís guidance. Additionally, the weather limitations mentioned previously spawned a new breed of missiles that allow for accurate deployment in adverse weather conditions. Such missiles are guided using Global Positioning Satellite (GPS) technology. To guide such missiles, three coordinates are necessary: the latitude, longitude, and elevation. Developed by NASA in 2000, C-band and X-band interferometric synthetic aperture radars (ISFARs) are used to collect the topographic data required to employ this technology. NASA used these ISFARs to create the most complete and high resolution topography of the Earth available today within ten days, with guided weapons being its primary application. These missiles have a longer range than typical laser-guided missiles.


JDAM missiles have the advantage of functioning even in adverse weather conditions.

Joint Direct Attack Munition (JDAM) missiles are based on a relatively new technology. JDAM is attached to the tail of the missile to change it from a conventional weapon to a GPS guided smart bomb. Accurate guidance is accomplished through a new tail section that contains a GPS aided Inertial Navigation System (INS) which guides the bomb from the release point to the intended target by the use of three coordinates. The INS with GPS updates allow control fins to correct trajectory until the moment of impact. These coordinates are sent to the bomb by way of an interface from the delivery aircraft. The missiles can be released up to fifteen miles from the target. JDAM also works in the adverse weather conditions that create difficulties in firing laser-guided missiles.



New technology continually increases the accuracy of guided missiles. As weapon technology continues to evolve, this increased accuracy will help our armed forces to spare innocent lives while inflicting maximal damage on enemy targets.







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