The American defense industry continues to develop the direction of aviation weapons. The promising Raytheon GBU-53 / B Small Diameter Bomb II project is nearing completion, the goal of which is to create a new guided bomb with a number of characteristic features. Due to the use of modified guidance tools, built on the basis of new equipment, this product has noticeable advantages over similar weapons already used by military aviation.
The roots of the current GBU-53 / B SDB II project can be found in the middle of the last decade. In 2005-2006, the US Air Force began to master the newest GBU-39 SDB guided bomb, developed by Boeing Integrated Defense Systems. This product was a gliding bomb with a homing system using inertial instruments and satellite navigation. The 285 lb (129 kg) bomb carried a 206 lb (93 kg) warhead. Depending on the conditions of the drop, the GBU-39 bomb could fly about 100-110 km.
Promotional image of the GBU-53 / B SDB II bomb
Tests and the first cases of combat use have confirmed the design characteristics and the rather high potential of the new weapon. Nevertheless, in its current form, it could not solve some combat missions, and therefore its potential was limited. The homing head with inertial and satellite navigation ensured that the bomb was displayed only at a stationary target with previously known coordinates. The attack of a moving object, for obvious reasons, was excluded.
Realizing the specific problems of the GBU-39 bomb, the Pentagon immediately decided to develop another bomb. In this case, 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 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 determined only in 2008. In accordance with the terms of reference, the new bomb was supposed to be able to independently search for a target and then aim at it. At the same time, it was required to ensure the possibility of attacking moving objects at any time of the day and in any weather conditions. The carriers of the new bomb were to be all the main modern and promising front-line aircraft.
Several aircraft weapons developers have joined the Small Diameter Bomb II program, including Raytheon. To develop her project, she involved the American branch of the European organization MBDA. In accordance with the contract, this company was to take over the development of a wing for a gliding bomb. All other elements of the product were created by the specialists of Raytheon. This company in the future was supposed to establish mass production.
In July 2010, the US military department chose the most successful project from the proposed ones. Analysis showed that the best guided bomb was produced by Raytheon and MBDA. Further work was carried out only on this project. From a certain time in relation to it, the designation GBU-53 / B Small Diameter Bomb II was used. Over the next few years, it was planned to complete the development of the project, set up production and conduct tests. According to the results of the latter, the Pentagon had to make a decision on the adoption of the bomb for service or on the abandonment of it.
Product layout
From the technical point of view, the GBU-53 / B bomb is a gliding product equipped with a relatively large warhead and a whole range of target detection equipment. At the same time, like the SDB bomb, it is relatively small in size. In particular, the small diameter of the body and the absence of large protruding parts (in the transport position) allows several such bombs to be suspended on a compatible holder. Thanks to this, the maximum possible ammunition load of the aircraft is noticeably increased.
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 a casing with straightened surfaces appears above it, containing devices for controlling the wing and hinges for installing it. In the tail section, the protruding casing is smaller. The tapering tail of the bomb is equipped with folding X-shaped rudders. To obtain the maximum possible drop range, a wing that is deployed in flight is used. Two planes of minimum sweep in the transport position are placed on the rear casing of the hull and open after dropping.
The bomb head compartment is given for the installation of guidance systems of several types. In particular, it is for this reason that the characteristic transparent fairing is used. A large central compartment accommodates the warhead. The tail of the body is intended for mounting some elements of the control system and steering machines. Also in this compartment there are narrow niches for placing the rudders in the folded position. The protruding upper casing of the body accommodates the drives for folding the wing.
The GBU-39 SDB guided bomb is equipped with inertial and satellite navigation systems, which allows it to attack only stationary targets with known coordinates. The requirements for the new project led to a noticeable complication of the homing equipment. Unlike its predecessor, the SDB II product has four guidance systems at once, thanks to which it is capable of solving a wider range of combat missions.
To attack stationary targets, you can use guidance from satellite or inertial navigation data. 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 systems allow obtaining a circular probable deviation at the level of 5-8 m - approximately the same characteristics are shown by the GBU-39 bomb.
Warhead tests
To attack moving targets, it is proposed to use other guidance tools. So, the new guided bomb is equipped with an infrared head of the IIR type. 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 able not only to find sources of thermal radiation, but also to create a high-resolution target image used for heading correction. Increased performance is declared when observing small-sized objects such as people.
For operation in adverse weather conditions, the bomb is equipped 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 seeker is intended primarily for the destruction of armored combat vehicles and other targets clearly visible to radars.
Also, the GBU-53 / B Small Diameter Bomb II project provides for the use of a passive laser homing head. The latter requires assistance from the ground or from other aircraft. Ground scouts or UAVs must detect the target and provide its illumination with a laser designator. The bomb, in turn, finds reflected light and is aimed at the indicated target.
An important feature of the Raytheon guided bomb is the original control system, connected to all targeting means. The operating mode of the electronics is set either by the pilot before reset, when entering target parameters, or is determined automatically. In the latter case, the on-board 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 seeker units are connected to work.
Due to the correct simultaneous use of several systems, the bomb is capable of showing fairly high accuracy characteristics. The circular probable deviation, according to the developer, does not exceed 1-5 m.
There are also communications and data transmission facilities on board the bomb. With the help of the Link 16 system, the bomb maintains communication with the carrier and transmits telemetry data to him, as well as receives commands. The possibility of re-targeting the bomb after dropping or transferring its escort to another aircraft has been declared. Also, if necessary, the carrier pilot can issue a command to self-destruct.
Bombs GBU-53 / B on the carrier F-15E
In the central compartment of the hull there is a high-explosive fragmentation warhead. The project provides for the use of a charge weighing 48 kg. According to the idea of the customer and the developer, the relatively small mass of the charge must be compensated for by high accuracy. Such characteristics to a certain extent simplify the use of weapons in difficult conditions, for example, in the city.
The SDB II bomb is not the largest in size, which simplifies its operation. The length of the product 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.
The flight performance and combat characteristics of the product depend on a number of factors. So, the maximum range is determined taking into account the speed and height of the carrier at the time of release. It is also influenced by the type of target. According to known data, when dropped from the maximum permissible altitude and speed, the flight range of the GBU-53 / B reaches 110 km. In this case, it is possible to attack only a stationary target with previously known coordinates. A moving target can be attacked only from 70-72 km. This difference in parameters is due to the need to maneuver when aiming at a moving target.
Several modern aircraft of the American Air Force are considered as carriers of the GBU-53 / B Small Diameter Bomb II. In this case, there is the possibility of obtaining very remarkable results. The F-15E fighter-bomber can carry GBU-53 / B bombs using BRU-61 / A type pendant holders. The aircraft can carry up to seven holders with four bombs on each. F-22 and F-35 fighters are capable of carrying SDB II bombs in internal cargo bays. Their ammunition load can include up to 8-10 such items.
It should be noted that to date, aircraft of the F-35 family do not yet have the ability to use promising bombs. To use such weapons, they need a certain update of the software onboard equipment. The massive introduction of such updates will begin only in the twenties. Other potential carriers, as far as we know, may already use the new weapon.
SDB II bombs on the battlefield as presented by the artist
Previously, it was proposed to introduce 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 fighting qualities.
The tests of the new model bombs started in early 2011. At first, simple removal of inert products on carriers was carried out, and then trial discharges began. Since the summer of 2012, F-15E fighters have been using experimental bombs with full-fledged homing heads at ranges. By the fall of 2014, all major checks had been completed. GBU-53 / B products have shown themselves well, and received a recommendation for adoption. However, specialists from Raytheon and the Pentagon had to carry out some additional work.
By the middle of the current decade, plans for future procurement were identified. In total, it is planned to purchase over 17, 1 thousand promising bombs. Each of them will cost about $ 128.8 thousand in 2015 prices. Taking into account the costs of developing the project, the cost of an individual ammunition increases by about $ 98 thousand.
According to known data, the US Air Force is currently engaged in the gradual introduction and development of new weapons. In the very near future, the SDB II bombs and their carriers in the form of the 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 delayed.
Bombs GBU-53 / B Small Diameter Bomb II have not yet reached full-fledged operation, but have already become the subject of several contracts. First of all, such weapons were ordered by the US Air Force. The Royal Air Force also showed interest in bombs, but in the end they chose to launch their own project. In the fall of 2016, the Republic of Korea announced its desire to purchase the latest American bombs. They are supposed to be used with F-15K aircraft. In the event of the outbreak of war, they should become the main means of combating the DPRK's mobile missile systems. In October 2017, a contract was signed to supply 3,900 SDB II bombs to the Australian Air Force.
In the near future, several American combat aircraft will be able to use the new guided bomb in real operations. Great hopes are pinned on the GBU-53 / B Small Diameter Bomb II product, and so far it justifies them. In what battles this product will be used, against what targets and with what results - time will tell.
