Concrete-piercing aerial bombs (BetAB) are designed to effectively destroy reinforced concrete pavements and airfield runways. Structurally, they are represented by two main types of bombs: free fall and with jet boosters. Free-fall concrete-piercing bombs are designed for bombing from high altitudes and are structurally very close to standard thick-walled high-explosive bombs. Concrete-piercing bombs with a parachute and a jet booster are used for bombing from any altitude (including low). Due to the parachute, the angle of fall of the bomb increases to 60 degrees, after which the parachute is shot back and the jet accelerator is launched.
Most often, the mass of concrete-piercing bombs is 500-1000 kg, while bombs of a larger caliber can also be encountered. This type of weapon is designed to destroy objects with solid concrete or reinforced concrete protection or heavily armored objects. For example, fortifications (such as bunkers), bunkers, coastal batteries, runways or large warships.
American concrete-piercing bomb GBU-28 (BLU-113)
Currently, the most massive American concrete-piercing bomb known in the world is the GBU-28 (BLU-113), which was created before Operation Desert Storm and was designed to destroy Saddam Hussein's bunkers. The assignment for the development of such bombs in October 1990 was issued to the ASD Development Planning group, located at Eglin Air Force Base in Florida. Specialists from Space Company and Lockheed Missile were also involved in the work on this project.
In order to successfully penetrate soil, concrete floors and armor, the bomb must be heavy enough, and also have a small cross-section (in order not to "spread" its kinetic energy over a large area), in addition, it must consist of a hard alloy. This is necessary so that when it touches an obstacle, the warhead does not fire on a hard surface, but penetrates it. At one time in the United States, they racked their brains over how to find and create a suitable case for a concrete-piercing bomb. The way out of the situation was suggested by a former army officer who worked at Lockheed. He recalled that a large number of barrels from 203-mm M201 SP howitzers were stored in artillery warehouses.
GBU-28
These barrels were made of a suitable alloy and were found in sufficient quantities in artillery arsenals, in particular at the Watervliet arsenal located in New York state. It was in the workshops of this arsenal that the artillery barrels were brought to the required size. To make bombs, they were cut to fit the specified dimensions, after which all protruding elements on the outside were removed. The barrels were specially reamed from the inside, and their diameter was increased to 10 inches (245 mm). This was done so that the tip from the old BetAB BLU-109 could be applied to the new "body" of the bomb.
From the Watervliet arsenal, the assembled bomb cases were transported to Eglin base, where they were to be filled with explosives. At the same time, there was simply no special equipment for a bomb of this size at the air base, and the military had to work with almost artisanal methods. So, in particular, the insulating layer, which was applied to the inner surface of the bombs, had to undergo a heat treatment procedure in a special oven, but instead, engineers at the military base were forced to use a homemade external electric heater. Having dug the body of the bomb into the ground, hot molten tritonal was poured into it by hand with buckets. For the bomb guidance system, a laser sighting device from the GBU-24 was used. The result of all the work was a warhead called BLU-113, and the entire bomb was designated GBU-28.
Since time was running out for the creators, they did not conduct a series of 30 required test launches, limiting themselves to only two. On February 24, 1991, the first GBU-28 bomb was dropped from an F-111 aircraft at a desert training ground in the United States. The concrete-piercing bomb went into the ground to a depth of 30 meters - it was even decided not to dig it from this depth. Another 2 days later, the bomb was dispersed on a reactive rail cart and fired at a vertically standing pile of reinforced concrete slabs. As a result, the bomb pierced all the plates and flew another 400 meters.
Another 2 corps, which were prepared at the Eglin air base, were loaded with explosives, equipped and sent for combat tests to Iraq. Taking advantage of complete air superiority, on February 23, 1991, 2 tactical F-111 fighters reached their target without any difficulties - one of the underground bunkers belonging to the Iraqi army. While one of the F-111s was illuminating the target, the other went into the bombing. As a result, one of the bombs passed by, and the other hit right on target, leaving no visible traces of damage on the surface. Only 7 seconds later, thick black smoke escaped from the ventilation shaft of the bunker, which could only mean one thing - the bunker was hit and destroyed. It took only 4 months from the mission statement to the combat tests of the new GBU-28 aerial bomb.
Resetting GBU-28 from F-15
Foreign developments in this area
Back in the early 90s, the defense ministries of a number of NATO countries: the USA, Germany, Great Britain, France, formed requirements for ammunition with increased penetration. It was planned to use such bombs against well-protected underground targets of the enemy (overlap thickness up to 6 meters). Currently, only one type of aerial bombs are produced in sufficient quantities, which are capable of destroying such objects. This is the American BLU-113 aerial bomb, which is part of the GBU-28 and GBU-37 guided aerial bombs (UAB) (total weight 2300 kg). Such concrete-piercing bombs can be placed in the armament compartment of the B-2A strategic bomber or on the ventral suspension point of the F-15E tactical fighter. Based on this, the military is thinking about creating lighter ammunition of this type, which would make it possible to use them from other carrier aircraft, which have restrictions on the size and weight of bombs placed on pylons.
American and European experts have put forward 2 concepts for the creation of new concrete-piercing ammunition weighing no more than 1,000 kg. According to the concept created in Europe, it is proposed to create a new type of tandem concrete-piercing warheads (TBBCH). Currently, the British Air Force is already armed with concrete-piercing submunitions with a tandem arrangement of shaped-charge and high-explosive charges - SG-357, which are part of the equipment of the non-dropable aviation cassette JP-233 and is intended to destroy the runways of airfields.
But due to its small size and low power, the SG-357 charges are not able to destroy objects located deep underground. The proposed new TBBCH consists of an optical proximity explosive device (ONVU), as well as one or more shaped charges, which are located directly in front of the main warhead of the bomb (OCH). In this case, the body of the main warhead of the bomb is made of high-strength materials based on tungsten steel with the use of other heavy metals with similar properties. There is an explosive charge inside, and a programmable explosive device in the bottom of the bomb.
According to the developers, the loss of OBCH kinetic energy as a result of interaction with detonation products will not exceed 10% of the initial value. The undermining of the shaped charge occurs at the optimal distance from the target according to the information coming from the ONVU. The free space that appears as a result of the interaction of the cumulative jet of the bomb with the obstacle is directed by the OCH, which, after hitting the remaining part of the obstacle, explodes already inside the object. Laboratory studies have shown that the depth of penetration of concrete-piercing bombs into an obstacle depends mainly on the impact velocity, as well as the physical parameters of the interacting bodies (such as hardness, density, ultimate strength, etc.), as well as the ratio of the warhead mass and cross-sectional area, and for bombs with TBBCh also on the diameter of the shaped charge.
Bomb hitting concrete airplane shelter
During tests of bombs with TBBCHs weighing up to 500 kg (impact velocity with an object 260-335 m / s), it was revealed that they can penetrate into the soil of average density to depths of 6-9 meters, after which they can pierce a concrete slab with a total thickness of 3 -6 meters. In addition, such ammunition can successfully hit targets at lower kinetic energy than conventional concrete-piercing bombs, as well as at less acute angles of attack and sharper angles of approach to the target.
In turn, American specialists took the path of improving the existing unitary concrete-piercing warheads (UBBC). A feature of the use of such bombs is that they need to be given a large kinetic energy before collision with a target, as a result of which the requirements for their body significantly increase. When creating new ammunition, the Americans conducted a series of scientific studies to develop particularly strong alloys for the production of the hull, as well as to find the optimal geometric dimensions (for example, the nose of the bomb).
To increase the ratio of the warhead mass and the cross-sectional area, which provides greater penetration, it was proposed, while maintaining the same overall dimensions of the existing ammunition, to increase the thickness of their shell by reducing the amount of explosive in the warhead of the bombs. The advantages of the new UBBCh can be confidently attributed to the simplicity of their design and a lower price, especially in comparison with tandem ammunition. As a result of a series of tests, it was found that a new type of UBBCH (weighing up to 1,000 kg and a speed of 300 m / s) can penetrate into the soil of average density to a depth of 18 to 36 meters and punch through reinforced concrete floors with a thickness of 1, 8- 3, 6 meters. Work on improving these indicators is still ongoing.
Russian concrete bombs
Currently, the Russian army is armed with 2 types of concrete-piercing bombs weighing 500 kg. The BETAB-500U free-fall concrete-piercing bomb is designed to destroy underground ammunition depots, fuels and lubricants, nuclear weapons, communication centers, command posts, reinforced concrete shelters (including for aircraft), highways, taxiways, etc. This bomb is capable of penetrating 1, 2 meters of reinforced concrete or up to 3 meters of soil. It can be used from heights from 150 meters to 20,000 meters at speeds from 500 to 2,300 km / h. The bomb is equipped with a parachute to ensure an angle of incidence of 90 degrees.
Russian concrete-piercing bomb BetAB 500ShP in section
BetAB 500U
Diameter: 450 mm.
Length: 2480 mm.
Bomb weight: 510 kg.
Explosive weight: 45 kg. in TNT equivalent
The second concrete-piercing aerial bomb is the BETAB-500ShP, an assault bomb with a jet booster. This bomb is designed to destroy the runways of airfields and taxiways, reinforced concrete aircraft shelters, highways. This ammunition is capable of penetrating armor up to 550 mm thick. In the soil of medium density, the bomb is capable of forming a crater with a diameter of 4.5 meters. When a bomb hits the runway, the concrete pavement is damaged over an area of up to 50 square meters. meters. This bomb is used from aircraft at a speed of 700 - 1150 km / h and at altitudes from 170 to 1000 meters (in horizontal flight). When diving bombing at an angle of no more than 30 degrees and at an altitude of at least 500 meters.
BetAB 500ShP
Diameter: 325 mm.
Length: 2509 mm.
Bomb weight: 424 kg.
Explosive weight: 77 kg.
