Two museums in Zlatoust and Penza openly exhibit the RN-28. The developer of the Russian Federal Nuclear Center is the All-Union Scientific Research Institute of Experimental Physics (RFNC-VNIITF). Tactical nuclear munitions were developed in the mid-1960s. According to the information provided by the museum, the product was disassembled in 1969 and discontinued in 1990. The type and power of the charge, overall dimensions and other information about special ammunition are protected information. The bomb has long been removed from the armament, but the regime has not been canceled.
The body of the aerodynamic shape with a low coefficient of resistance. Stamped plumage type "free pen" with four stabilizers. The front part is made of a radio-transparent material for placing the radio altimeter of the detonation system. In the caudal cone there is a container for the brake parachute. In accordance with the terms of reference, the bomb could be suspended on the aircraft of the front-line aircraft MiG-21, MiG-23, MiG-27, Su-7B, Su-17. Bombing is allowed from a height of 500 to 3,000 meters, as with horizontal flight.
Soviet RN-28 tactical nuke has a weight of 250kg; variable yield, either 1-10kt or 5-30kt depending on source. The Soviet educational and propaganda film "Nuclear weapons in readiness for use" captured the process of using the RN-28 special munition from the side of the early modification of the Su-7B aircraft at the nuclear test site.
The magazine "Aviation and Time" #5 for 2011 describes the process of using a bomb: "The aircraft was equipped with a device for bombing from horizontal flight and calibrating PBK-1, as well as equipment for the use of a nuclear bomb type RN-28. It was created on the basis of the smallest charge of that time RDS-9 with a capacity of 5 kiloton. suspended on the left ventral pylon, equipped with a special connector, the RN-28 was adjusted to a blasting height from 0 to 250 m. The bomb did not have a braking parachute.
"PBK-1 was an electromechanical calculator of the moment of airbomb dropping - an analog of the American low-altitude bombing system LABS. In a horizontal flight, the pilot included a PBC at the time of flight of a certain landmark in the target area or by sighting this landmark through the sight. After a predetermined period of time, the device began to transmit sound and light signals, through which the pilot pressed the reset button. The interval of time was established still on the ground according to special tables, depending on the type of ammunition, altitude and speed of flight. The wind was recorded by the pilot directly in flight by introducing an appropriate correction.
"The bombing from the cockpit was more difficult. After the device was switched on, after a predetermined time, the PBK gave a preliminary signal to activate the afterburner and put the aircraft into the half loop, and already during the climb, at the angle of 45-60 ", a signal appeared to press the combat button. inertia continued to fly forward along the ballistic trajectory, while the Su-7B did a half-turn and flew in the opposite direction .In order to increase the accuracy of the bombing, the inclusion of the PBC was to be performed automatically. In this case, the marker was a marker radio beacon, which was delivered to the area of the target by subversive and reconnaissance groups.
"In the "arsenal" of PBK-1 there was also a more exotic bombing technique, which the Americans once called "over the shoulder" or "idiotic loop". In this case, the goal of inclusion was the goal itself. The pilot switched on the instrument above the target and immediately began a sharp climb. The bomb was detached from the aircraft at an angle of 80-130 'and flew almost vertically upwards by inertia. The airplane came out of the half-loop and "scraped" with a dive as quickly and farther as possible. Under the influence of gravity, the bomb changed its direction of movement and began a practically vertical drop. That's where the brake parachute would be useful, but the designers counted on a small ammunition capacity and acceleration characteristics of the Su-7B, which left the pilot a rather high chances of survival."
The nuclear-capable Fishbeds introduced dedicated wiring to enable use of a single nuclear bomb carried on the centerline pylon, together with a control panel in the cockpit, installed on the top of the fixed windscreen frame. The control panel enabled the pilot to arm the bomb, perform its emergency jettisoning and set the desired type of detonation – airburst or upon impact with the ground. The Soviet Air Force’s three squadron fighter-bomber regiments, stationed in the 1970s and 1980s in East Germany and some other East European counties, had one of their component squadrons permanently equipped for the tactical nuclear role, with the nuclear bomb’s control panel always installed. Ground crews regularly practised fitting training rounds, while pilots practised delivery profiles using standard practice bombs.
The nuclear bomb was designed for delivery in either level flight or by the so-called toss-bombing method. The latter called first for acceleration in ultra-level flight at low level to 1,050km/h, then a 45º climb and release of the bomb at about 1,500m (4,900ft), which then impacted the ground some 7km from the release point or detonated in the air at low level in order to deliver a better blast wave destructive effect on surface targets.
There was another, more precise derivative of the toss-bombing method – the so-called over-the-shoulder release – which called for acceleration in level flight to 1,050km/h at 100m (330ft) above the terrain and then commencement of a looping manuver. Bomb release took place when the nose went just beyond the vertical, at a 106º pitch angle, and at an altitude of about 3,000m (9,800ft). In this event, after release the bomb travelled on a ballistic trajectory, initially going sharply upwards and then reversing downwards, hitting the ground immediately beneath the release point. After release, the MiG- 21 pilot had 1–2 minutes to escape from the blast wave at full afterburner before the bomb’s detonation, at a distance of some 10km.
The RN-28 bomb was the main nuclear weapon carried by Soviet tactical aircraft in the 1970s and 1980s, superceding an earlier design known as the RN-25. A low-yield weapon, the RN-28 was equipped with a programmable control unit that allowed the type of desired detonation – airburst or upon impact with the ground – to be set before take-off, while the bomb’s yield was adjustable between 1 and 10 kilotons.
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