Laser Guided Bombs (LGB) – The development of the first decades

Guided weapons have always been a requirement of every armed force. The requirement, or the need if we want to put it differently, became even more imperative during World War II, especially for the forces that did not have at their disposal the required volume (power) of fire to hit the enemy. From the years of the First P.P. the Air Weapon was found to provide precision strike capability, coupled with significant operational flexibility.

Despite the very little firepower that light tanks could carry and utilize at the time, they provided the ability to engage targets on enemy soil in a short amount of time. Targets that would require entire campaigns to be hit by ground or naval artillery. Targets beyond the range of conventional large-caliber guns in safe areas, but of great importance, could also be hit. A typical example is Britain, which was completely secured from land and naval attacks.

In the years of the First World War it was therefore recognized that despite the minimal firepower of the Air Force at that time, it was extremely destructive in points. And the increased firepower could only be made much more effective if combined with the airplane. In the Second P.P. the Germans first attempted to offset the massiveness of Allied aerial bombardment and the sheer size and overwhelming power of the Soviet behemoth, with the radio-guided FX cruise bomb. It was mainly used against surface targets.

In the years immediately after the end of the Second World War German technology in this field was not utilized as emphasis was placed solely on the further development of German rocket technology. Both from the Americans and from the Russians (USSR). The revolution brought by the turbo engine and its rapid development combined with the parallel development of rocket technology led to a frantic race to produce new faster and higher flying fighter and bomber jets as well as anti-aircraft missiles to destroy them. The downing of Powers’ U-2 over the USSR (Sverdlovsk) on May 1, 1960, is a typical example of this race.

B-58 Hustler and XB-70 Valkyrie bombers attempted to disable Soviet AA missiles. Because the strategic bombers contained the awesome power of the nuclear bomb. A single plane was sufficient to destroy area targets that previously required the involvement of hundreds of bombers! The ease of penetration of one strategic bomber instead of hundreds is obvious, as is the small importance of accuracy when using nuclear weapons. Of course, this fact did not apply in case of attack on tactical targets.

This is how we got to the period of the Vietnam War. There the targets had to be destroyed with conventional weapons. Their mass release (carpet bombing) was not possible because anti-aircraft missiles (SA-2, SA-3) were particularly dangerous against bombers of any type flying at any height (never higher than 40,000 feet). Also, the multi-target arrangement negated mass bombing. As was the fact that most were point targets. Attacking them accurately was a very difficult task, with accuracy limits well below expectations due to inherent limitations.

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The most important was of course the anti-aircraft guns. Increasing attack accuracy meant descending to a low altitude and thus greater chances of casualties due to the action of anti-aircraft artillery, while avoiding it automatically entailed a dramatic decrease in accuracy.

It was under these conditions that the first mass-produced airborne guided tactical weapons were tested. The first attempts naturally concerned the integration of some sensor, so that it was possible to distinguish the target, but also some aerodynamic control surfaces that would increase the kinetic performance not only to increase the radius of attack, but also to have the margin for corrections (course or trajectory) to engage the target. Control vanes were added to the bombs that were connected to the sensor via a computer system, and to the missiles, the sensor simply “gave” the vanes correction commands to accurately hit the target.

Paveway families laser pointer collections

Early attempts included heavy bombs that would be used to destroy high-value targets (HVUs-HighValueUnits). Laser beam search was adopted as the guidance method because it has great advantages. It is much “sharper” (the radiation) and diffuses more difficult than others, resulting in good reflectivity characteristics and use by remote catalysis systems. The first attempts involved the beastly M-117 bombs (BOLT-117 was the code name of the first attempt, with movable tail fins), where laser beam homing receivers were mounted on tripods protruding from the tail surfaces.

In order to improve the aerodynamic behavior of the weapon (bomb with guided collection), very soon it was chosen to place the sensor in the muzzle, with its rotation mechanism in order to easily track the radiation source. The tail fins were large but fixed, while only the front fins were mobile and were placed near the nose of the bomb. The first weapon was a 2,000 lb (907 kg) version of the Mk-84 bomb, which was natural since the cost of the conversion collection was significant and it was intended for large targets.

The weapon was designated GBU-10 (GBU= Guided bomb Unit) Paveway (Pave: Precision Avionics Vectoring Equipment), as the previous two numbers were GBU-8/-9 HOBOS (electro-optical guidance). In addition to the Mk-84, a guidance collection was developed for the beastly 3,000-pound M-118, a bomb of inferior aerodynamic characteristics, which for its time represented a different approach to the problem of destroying fortified targets than its later counterpart, the armor-piercing BLU-109 (BLU= Bomb Live Unit). The weapon was named GBU-11, and soon after the Benjamin of the family appeared. The GBU-12, based on the Mk-82, so that more targets were hit per exit, a practice that favored attacks against tanks.

The PavewayI family had fixed wings, which made it difficult to carry bombs in large numbers (only two GBU-10s could be carried by an F-4, with a theoretical capacity for four). The family, PavewayII that followed, had the advantage of low production costs, increased reliability, resistance to countermeasures and moderate visibility conditions, and folding wings, which allowed mass transport and storage in confined spaces. It was no accident that it became the favorite version of the US Navy, which had always faced space problems on aircraft carriers.

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Finally, the fins had a greater range of rotation, for greater and more direct course changes. The codes remained the same for the 500- and 2,000-pounder guns, and a subsequent version was to convert the intermediate 1,000-pounder Mk.83 as the GBU-16, especially for use by the USN, whose aircraft could not easily operate with weapons greater than 2000 lbs. The intermediate code GBU-15 referred to the successor to the GBU-8, an electro-optically guided bomb.

The Paveway III family offered two important new features. The release from low heights at a fairly satisfactory distance (18 km), due to larger fixed control vanes and the possibility of selecting a trajectory through a sophisticated computer. The sensor became cylindrical, instead of the small cantilever inside a ring of the previous family, with a wider field of view and increased sensitivity, but also resistance to false reflections due to weather phenomena. The microcomputers used (digital autopilot) allow a much better beam performance and selection of the trajectory and the impact angle on the target, while in combination with the new sensor, they allow an attack from a low height, since the latter does not require a high release height to “see » the reflection and the computers, with the larger, more efficient wings, turn the bomb faster to hit its target.

The first two generations of Paveway (I & II) were weapons that in order to have a decent radius, which in turn would significantly increase the survivability of the fighter-carrier, had to be launched from medium heights. This made it easier for the sensor to lock onto the targets, but also for the wings to offer precision guidance and some relatively increased radius during the glide. However, if there were clouds, then the release had to be made from a low height, so that the laser radiation would not be “hidden” by the clouds. But this limited the range to about three kilometers for the 2,000-pound weapon, which meant the fighter was within range of systems such as the ZSU-23 and SA-7.

Great export success was experienced only by the GBU-24 in two different configurations. The GBU-24B with a Mk-84 warhead and the A/B, with a BLU-109 armor-piercing warhead of the same weight, for piercing important targets. Another version, 2B, is the same type of ammunition (BLU-109), but with mechanical safety/arming systems, for safe use in the electromagnetically charged environment of USN aircraft carriers. The GBU-24C\B (USAF) version and the equivalent but with mechanical arming/locking device GBU-24D\B (USN) use the BLU-116 (known as AUP -Advanced Unitary Penetrator) as their charge. which provides 50 to 100% more penetration than the BLU-109 while maintaining the same flight characteristics and size/weight combination.

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