19. Pyrobolts: types, design, development. Shear type pyrobolt developed at Yuzhnoye SDO

Annotation: The pyrobolts, or explosive bolts, belong to the pyrotechnical devices with monolithic case consisting o f the cap, as a rule with hexagonal surface, and of cylindrical part with thread. The pyrobolts are separated into parts using the pyrotechnical charge placed inside the case. Owing to the simple design, reliability and short action time, the pyrobolts have found wide application in aerospace engineering for separation of assemblies and bays, in particular, stages, head modules, launching boosters, etc. So, for example, about 400 pyrobolts are used in the Proton launch vehicle. The designs of pyrobolts are markedly different. By method of explosive substance action on case structural elements, the pyrobolts are divided into two types: the pyrobolts using the shock wave formed at detonation of brisant explosive substance for case wall destruction and the pyrobolts using the pressure of gases arising at pyrotechnical charge blasting. By method of separation into parts, they are divided into fragmenting pyrobolts with ridge-cut, with piston, and shear pyrobolts. The paper deals with the design of various types of pyrobolts, their disadvantages are considered. The Yuzhnoye SDO-developed pyrobolt of shear type with segments is presented that uses radial shear forces of segments located in the hole of cylindrical part to separate the case parts. The above segments a re actuated using a rod with sealing rings and a piston connected to the rod through a rubber gasket; the piston moves under pressure of gases formed during pyro cartridge action. The following calculations are presen ted: strength analyses with determination of case load-carrying capacity; power analyses with justification of pyro cartridge selection for pyrobolt actuation. In the developed pyrobolt of shear type with segments, the case parts are separated without considerable shock loads and without high-temperature gases and fragments release into environment, ensuring reliable separation of bays and assemblies without damaging sensitive equipment.