General Purpose Bombs
The M117 (Figure 25) is a 750-pound general purpose bomb which may be employed in several different configurations. The basic M117 dates from the Korean War and uses a low-drag tail fin for medium and high-altitude deliveries. The M117R (Retarded) uses a special fin assembly providing either high-drag or low-drag release options. For low altitude deliveries, the tail assembly opens four large drag plates which rapidly slow the bomb and allow the aircraft to escape its blast. The M117 (Destructor) looks similar to the M117R but uses a magnetic influence fuze which enables the bomb to function as a mine. The M117D is released in a high-drag configuration for ground implant or shallow water mining. It detonates when an object passing near the bomb triggers the fuze. The M117 series was used extensively during the Vietnam War, and B-52G aircraft dropped thousands of tons of M117 and M117R bombs during Operation Desert Storm.
The MK-83 (Figure 26) is a free-fall, non-guided general purpose [GP] 1,000 pound bomb. The bomb can be fitted either with mechanical nose and tail fuzes or with a proximity fuze. During Desert Storm, this bomb was dropped mainly by Marine aircraft conducting close air support/battlefield air interdiction (CAS/BAl) missions.
The MK83 AIR (Figure 27) is a 1,000 pound bomb modified with a BSU-85/B high drag tail assembly. The "ballute" air bag which deploys from the tail provides a high speed, low altitude delivery capability by quickly slowing the bomb and allowing the aircraft to escape the blast pattern. The tail assembly consists of a low-drag canister unit containing a ballute (combination balloon and parachute), and a release lanyard assembly that opens the canister releasing the ballute. The ballute assembly is made from high strength low porosity nylon fabric. When the bomb is released from the aircraft a lanyard unlatches the back cover which opens, releasing part of the nylon bag/retarder. Air turbulence at the rear of the bomb acts on that portion of the retarder, pulling the remainder out of the housing. Ram air inflation is accomplished through four air inlet ports toward the aft end of the ballute. The weapon can be delivered in the low-drag mode (canister remains closed after release) or in the high drag mode. The pilot may select either a high drag or low drag configuration depending on mission requirements.
The MK-80 (Figure 28) series was developed in the 1950s in response to the need for bombs producing less aerodynamic drag. All MK-80 series bombs are similar in construction. MK-80 series bombs are cylindrical in shape and are equipped with conical fins or retarders for external high-speed carriage.
Laser-Guided Bombs
In World War II it could take 9,000 bombs to hit and completely destroy a target the size of an average factory on the ground. Today, because of precision, accuracy, and modern ordnance like the laser-guided bomb, the military can do that with one bomb launched from an F-115.
The development of laser cadette weapons has dramatically improved the accuracy of weapon guidance and delivery. With the assistance of build-up guidance kits, general GP bombs are turned into laser-guided bombs (LGBs). The kits consist of a computer-control group (CCG), guidance canards attached to the front of the warhead to provide steering commands, and a wing assembly attached to the aft end to provide lift. Laser guided bombs are maneuverable, free-fall weapons requiring no electronic interconnect to the aircraft. They have an internal semiactive guidance system that detects laser energy and guides the weapon to a target illuminated by an external laser source. The designator can be located in the delivery aircraft, another aircraft, or a ground source.
All laser guided weapons have a CCG, a warhead (bomb body with fuze), and an airfoil group. The computer section transmits directional command signals to the appropriate pair(s) of canards. During the ballistic phase, the weapon continues on the unguided trajectory established by the flightpath of the delivery aircraft at the moment of release. In the ballistic phase, the delivery attitude takes on additional importance, since maneuverability of the UGB is related to the weapon velocity during terminal guidance. Therefore, airspeed lost during the ballistic
phase equates to a proportional loss of maneuverability. The transition phase begins at acquisition. During the transition phase, the weapon attempts to align its velocity vector with the line-of-sight vector to the target. During terminal guidance, the UGB attempts to keep its velocity vector aligned with the instantaneous line-of- sight. At the instant alignment occurs, the reflected
laser energy centers on the detector and commands the canards to a trail position, which causes the weapon to fly ballistically with gravity biasing towards the target.
An airborne detector can provide steering information to the pilot, via his gunsight, for example, and lead him on a direct heading to the target, finally giving him an aim point for a conventional
weapon. Alternatively, a laser guided "smart" bomb or missile may be launched when a pilot is satisfied that the detector head has achieved lock-on and the launch envelope requirements are satisfied. In either of these cases, the pilot may never see the actual target, only the aim point as indicated by the laser.
Guided Bomb Unit-10 Paveway II
The Guided Bomb Unit-10 (GBU-10) utilizes the 2,000-pound general purpose or penetrating warhead. The operator illuminates a target with a laser designator and then the munition guides to a spot of laser energy reflected from the target. The GBU-10 consists of an MK-84 2,000 pound bomb with an added laser guidance package. The GBU-1OI mates a BLU-109B weapon with a Paveway II laser guidance kit. This improved 2,000-pound bomb is used against targets requiring deeper penetration.
The munition was used during Operation Desert Storm, and, according to the Air Force, hit 78 percent of its targets. In Operation Desert Storm, GBU-10/10Is were used extensively by F-15Es and F-111Fs mainly against bridges, Scuds, C3I (command, control, communications, intelligence) nodes, and bunkers. Of the 2,637 expended,'44 over one- third were dropped by F-111Fs, and the rest by F-117s, F-15Es, and Navy and Marine Corps aircraft. There are two generations of GBU-10 LGBs: Paveway I with fixed wings and Paveway II with folding wings. Paveway II models have the following improvements: detector optics and housing made of injec- tion-molded plastic to reduce weight and cost; increased detector sensitiv- ity; reduced thermal battery delay after release; increased maximum canard deflection; laser coding; folding wings for carriage, and increased detector field of view. (Paveway II's instantaneous field of view is thirty percent greater than that of the Paveway I's field of view).
Weight (lbs.) 2562
Length (in.) 172
MK 84; Blast/Fragmentation
Explosive: 535 pounds or 945 pounds of Tritonal
Range 8 nautical miles
