The roots of the current GBU-53 / B SDB II project should be sought in the middle of the last decade. In 2005-2006, the United States Air Force began to master the newest GBU-39 SDB bomb developed by Boeing Integrated Defense Systems. This product was a planning bomb with a homing system using inertial instruments and satellite navigation. A bomb weighing 285 pounds (129 kg) carried an 206-pound (93 kg) warhead. Depending on the discharge conditions, a GBU-39 bomb could fly around 100-110 km.
Tests and the first cases of combat use confirmed the design characteristics and the relatively high potential of the new weapon. However, in its present form, it could not solve some combat missions, and therefore its potential turned out to be limited. The homing head with inertial and satellite navigation provided the withdrawal of a bomb only to a stationary target with previously known coordinates. The attack of a moving object, for obvious reasons, was excluded.
Understanding the specific problems of the GBU-39 bomb, the Pentagon immediately decided to develop another bomb. At the same time, the development of a bomb for attacking moving targets was proposed to be carried out separately. Until a certain time, the military department concentrated all its efforts on the first SBD project, as a result of which the development of a new bomb began only a few years later.
The final requirements for the SBD II bomb were defined only in 2008. In accordance with the terms of reference, the new bomb should have been able to independently search for a target and then aim at it. At the same time, it was required to ensure the possibility of an attack of moving objects at any time of the day and in all weather conditions. The carriers of the new bomb were to be all the main modern and future front-line aircraft.
The Small Diameter Bomb II program has been joined by several aviation weapon developers, including Raytheon. She involved the American branch of the European organization MBDA in the development of her project. In accordance with the contract, this company had to take over the development of the wing for the planning bomb. All other elements of the product were created by Raytheon specialists. This company in the future was supposed to start mass production.
In July, 2010, the US military chose the most successful project of the proposed. The analysis showed that the best version of the guided bomb was created by Raytheon and MBDA. Further work was carried out only on this project. For a certain time, the term GBU-53 / B Small Diameter Bomb II was used in its relation. Over the next few years it was planned to complete the development of the project, to establish production and conduct tests. According to the results of the last Pentagon had to decide on the adoption of a bomb or to abandon it.
From the technical point of view, the bomb GBU-53 / B is a planning product equipped with a relatively large warhead and a whole set of target detection tools. At the same time, like the bomb SDB, it is characterized by relatively small dimensions. In particular, the small diameter of the hull and the absence of large protruding parts (in the transport position) makes it possible to hang several such bombs on a compatible holder. Thanks to this noticeable increase in the maximum possible ammunition of the aircraft.
The SDB II project provides for the placement of all devices in a housing of a fairly simple form. Its head is formed by a hemispherical fairing and a small annular section. Further, the bomb retains the tubular body, but above it appears a casing with straightened surfaces, containing devices for controlling the wing and hinges for its installation. In the tail part of the protruding housing has a smaller size. The tapering tail of a bomb is equipped with folding rudders of an X-shaped design. In order to obtain the maximum possible range of discharge, the wing is used in flight. Two planes of minimal sweep in the transport position are placed on the rear casing of the case and are revealed after a drop.
The head compartment of the bomb is given for the installation of several types of guidance tools. In particular, it is for this reason that the characteristic transparent fairing is used. The large central compartment accommodates the warhead. The tail of the case is intended for the installation of some elements of the control system and steering gears. Also in this compartment there are narrow niches for placing the rudders in the folded position. The protruding upper casing of the housing accommodates the drives for folding the wing.
The GBU-39 SDB controlled bomb is equipped with inertial and satellite navigation systems, which allows it to attack only stationary targets with known coordinates. Requirements for the new project have led to a noticeable complication of homing equipment. Unlike its predecessor, the SDB II product has just four guidance systems, thanks to which it is capable of solving a wider range of combat missions.
To attack stationary targets, you can use the guidance according to satellite or inertial navigation. In this case, the automation continuously monitors the position of the bomb in space and issues commands to the steering cars. According to known data, the satellite and inertial system allows to obtain a circular probable deviation at the level of 5-8 m - approximately the same characteristics are shown by the bomb GBU-39.
Tests of the warhead
To attack moving targets it is proposed to use other means of guidance. So, the new guided bomb is equipped with an infrared head type IIR. This device is based on the components of the larger AGM-154 JOSW bomb, but is smaller. Such a head, built using an uncooled matrix, is capable of not only finding sources of thermal radiation, but also creating an image of a high-resolution target used for course correction. Stated performance when monitoring small objects such as humans.
To work in adverse weather conditions, the bomb is completed with an active radar homing head operating in the millimeter range. After the product reaches the target area, the head begins an independent search for ground objects. This GOS is intended primarily for the destruction of armored fighting vehicles and other targets well visible to radars.
Also, the GBU-53 / B Small Diameter Bomb II project involves the use of a passive laser homing head. The latter requires assistance from the ground or from other aircraft. Ground reconnaissance or UAVs must detect the target and provide its illumination with a laser target designator. The bomb, in turn, finds the reflected light and is aimed at the specified target.
An important feature of the Raytheon guided bomb is the original control system, coupled with all the means of guidance. The mode of operation of the electronics is set either by the pilot before the reset, when the target parameters are entered, or determined automatically. In the latter case, the onboard control system analyzes various data and selects the optimal mode of joint operation of several separate systems. In this case, the exit to the target area is carried out using satellite or inertial navigation, and then three GPS are connected to work.
Due to the correct simultaneous use of several systems, the bomb is capable of displaying fairly high accuracy characteristics. The circular deviation, according to the developer, does not exceed 1-5 m.
On board the bombs are also present means of communication and data transmission. With the help of the Link 16 system, the bomb communicates with the carrier and transmits telemetry data to it, and also receives commands. Declared the possibility of retargeting a bomb after dropping or transferring its tracking to another aircraft. Also, if necessary, the pilot of the carrier can issue a command for self-destruction.
In the central compartment of the corps is a high-explosive fragmentation warhead. The project involves the use of a charge mass 48 kg. As planned by the customer and the developer, a relatively small mass of charge should be compensated for by high accuracy. Such characteristics to a certain extent simplify the use of weapons in difficult conditions, for example in a city.
Bomb SDB II differs not the largest size, which simplifies its operation. Product length is 1,76 m with a maximum diameter of about 180 mm. Wingspan in flight position - 1,67 m. Weight - 93 kg. The explosive charge accounts for just over half of the total mass.
Flight technical and combat characteristics of the product depend on a number of factors. Thus, the maximum range is determined taking into account the speed and height of the carrier at the time of the reset. In addition, it affects the type of goal. According to known data, when resetting from the maximum allowable height and speed, the GBU-53 / B range reaches 110 km. In this case, it is possible to attack only a stationary target with previously known coordinates. A moving target can only be attacked from 70-72 km. Such a difference in the parameters is due to the need for maneuvering when aiming at a mobile target.
As the carriers of the GBU-53 / B Small Diameter Bomb II bombs are considered several modern aircraft of the US Air Force. At the same time there is the possibility of obtaining very remarkable results. The F-15E fighter-bomber can carry GBU-53 / B bombs with BRU-61 / A pendant holders. On the plane you can hang up to seven holders with four bombs on each. The F-22 and F-35 fighters are capable of carrying SDB II bombs in internal cargo compartments. Their ammunition may include up to 8-10 of such products.
It should be noted that, to date, aircraft of the F-35 family do not yet have the possibility of using advanced bombs. For the use of such weapons, they need a certain software update onboard equipment. Mass introduction of such updates will begin only in the twenties. Other potential carriers, as far as is known, can already use new weapons.
Earlier it was proposed to introduce the GBU-53 / B bombs into the armament range of the A-10C attack aircraft and the AC-130 fire support aircraft. However, the study of such issues has shown that this will lead to a significant increase in costs without a tangible gain in combat qualities.
Tests of new model bombs started at the beginning of 2011 of the year. At first, simple removal of inert products on carriers was carried out, and then test dumps began. Since the summer of 2012, the F-15E fighter jets have used test bombs with full-fledged homing heads on the test sites. By the autumn of 2014, all basic checks were completed. Products GBU-53 / B showed themselves well, and received a recommendation for adoption. However, the Raytheon and Pentagon specialists were to carry out some additional work.
By the middle of this decade, plans for future procurement had been determined. In total, it is planned to purchase over 17,1 thousand prospective bombs. Each of them will cost about 128,8 thousand dollars in 2015 prices of the year. Taking into account the cost of developing the project, the cost of a single ammunition increases by about 98 thousand dollars.
According to known data, at present, the US Air Force is engaged in the gradual introduction and assimilation of new weapons. In the very near future, SDB II bombs and their carriers in the form of F-15E should reach the stage of initial operational readiness. Other carriers will receive new weapons in the near future. At the same time, in some cases, the integration of weapons into the existing complex has been significantly postponed.
Bombs GBU-53 / B Small Diameter Bomb II have not yet reached full operation, but have become the subject of several contracts. First of all, such weapons were ordered by the US Air Force. The Royal Air Force of Great Britain showed interest in the bombs, but they eventually chose to launch their own project. In the autumn of 2016, the Republic of Korea announced its desire to purchase the latest American bombs. They are supposed to be used with aircraft F-15K. In the event of a war, they should become the main means of combating DPRK mobile missile systems. In October, 2017, the contract appeared to supply 3900 SDB II bombs to the Australian Air Force.
In the near future, several American combat aircraft will be able to use in real operations a new guided bomb. The GBU-53 / B Small Diameter Bomb II product has high expectations, and so far it justifies them. In what battles this product will be used, against what goals and with what results - time will show.
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