PROPELLING DEVICE FOR A PROJECTILE IN A MISSILE

Abstract: A propelling device for a projectile (1) that is lying in a standby position within a rocket motor (10) in a missile is disclosed. The projectile (1) is translated in respect of the rocket motor (10) by means of a pyrotechnic charge (2) before the rocket motor (10) is initiated. The projectile (1) is lying within a translation tube (12) centrally located in the rocket motor (10). The projectile (1) comprises a power piston (9) in the rear end thereof. The power piston (9) encloses a pyrotechnic power charge (2) and a pyrotechnic squib (3). The translation tube (12) is sealingly closed behind the power piston (9) and forms a closed expansion chamber (7) for the pyrotechnic charges, which by ignition generate gas pressure that activates the power piston (9) and thus propells the projectile (1) forward within the translation tube (12).

Description: PROPELLING DEVICE FOR A PROJECTILE IN A MISSILE The present invention relates to a propelling device for a projectile that is lying in a standby position within a rocket motor in a missile, where the projectile is translated in respect of the rocket motor by means of a pyrotechnic charge before the rocket motor is initiated. The propelling device according to the invention is developed for use in missiles, and in particular, but not exclusively, in rocket accelerated penetrators. Rocket accelerated penetrators are often kept in their storing and standby state with the main parts thereof not assembled. This means that the part having control fins, the fin cone, and the rocket motor proper is assembled to the penetrator at the moment before the missile is launched from the launcher. The penetrator, which is in form of an arrow like body having substantial mass, is lying in standby position in a translation tube within the rocket motor and with the pointed end thereof supported in the control fin part. How the assembly operation happens is described in detail in the priority founding Norwegian patent application no. 19992739. During launching preparations the penetrator is translated through the translation tube and the control fin part, and the rear end of the penetrator is interlocked to the control fin part immediately before the rocket motor is ignited. It is common practise that the rocket motor is separated from the penetrator during the flight thereof as soon as the rocket motor is burned out and has lost its propelling force. It is the device for the forward propelling of the penetrator, and more generally the projectile, within the rocket motor until the rear end of the projectile locks to the rocket motor, the present application deals with. According to the invention, a propelling device of the introductorily described kind is provided, which is distinguished in that the projectile is lying within a translation tube located centrally in the rocket motor, that the projectile comprises a power piston in the rear end thereof, that the power piston encloses a pyrotechnic igniter charge and a pyrotechnic squib and that the translation tube is sealingly closed behind the power piston and forms a closed expansion chamber for the pyrotechnic charges, which by ignition generates gas pressure that activates the power piston and thus the projectile. In one embodiment the translation tube is sealingly closed behind the power piston by means of an end closure, which end closure is movable axially forward within the translation tube after the ignition of the pyrotechnic charges and translation of the power piston and the penetrator. At which moment of time the end closure moves forwards is dependent of the difference between the pressure in the chambre in the translation tube and the pressure that is generated within the rocket motor when initiated. The motional freedom of the end closure provides a possibility to balance this pressure differential. Thus fragmentation, collapse of or deformation of the translation tube during launching is avoided. At any costs, it is to be avoided that fragments from the inner parts of the rocket are getting into the nozzels of the rocket motor. As a first alternative, the end closure is abutting an internal shoulder in the rear end of the translation tube. As a second alternative, the end closure is abutting a perforated plate integrated to the rear end of the translation tube. Preferably, a sealing means, such like an O-ring, can be provided between the end closure and the translation tube. In one embodiment, the rear end of the projectile can be an integrated power piston that follows the projectile during the flight thereof. In a second embodiment, the power piston can be relesable from the projectile together with the rocket motor. The propelling charge proper can be any suitable pyrotechnic charge, such like leadazide, BKNO3 or gunpowder and be in form of moulded pellets, granules or powder charge (pyrogenic igniter). It is to be understood that the propelling device has completed its mission before the rocket motor is initiated and launched. Other and further objects, features and advantages will appear from the following description of one for the time being preferred embodiment of the invention, which is given for the purpose of description, without thereby being limiting, and given in context with the appended drawings where: Fig.1 shows schematically a rocket accelerated penetrator, Fig.2 shows in longitudinal section a penetrator in the standby position thereof within the forward end of a rocket motor, Fig.3 shows in longitudinal section a partly translated penetrator within a rocket motor, Fig.4 shows in longidutinal section the rear part of the penetrator when the penetrator is completely translated within the translation tube, and Fig.5 shows one embodiment of the rear end of the translation tube and the power piston. The description is related to a missile in form of a penetrator and a rocket motor, but the invention is not limited to a penetrator only. Any projectile, with or without warhead, can together with a rocket motor use the propelling device according to the invention. We firstly refer to fig.l that illustrates a missile in flight. The missile comprises a penetrator 1, a control fin part 5 and a rocket motor 10 as main components. The penetrator 1 is an arrow like body having substantial mass, preferably of tungsten or depleted uranium. A penetrator is a projectile omit warhead and do achieve its destructive effect owing to the kinetic energy thereof. Fig.2 shows the penetrator 1 in the way it is lying in standby position within a translation tube 12 centrally located in the rocket motor 10 during storage until launching, or ready for launching from a launching pipe or launcher (not shown). The penetrator 1 is held axially in place within the rocket motor 10 by a closure means (not shown) having a cap that can be opened or burst away. The reference number 8F refers to one of four control fins that are located circumferentially about a centre and having equal pitch or angular distance from each other. The number of fins 8F can vary according to desire. The rocket motor 10 is, as mentioned, releasable fixed to the control fin part 5. The rocket motor 10 is released and does separate from the control fin part 5 during the flight of the missile when a propellant charge 13 within the rocket motor 10 is burned out and retardation occur. The release mechanism between the control fin part and the rocket motor is described in closer detail in copending Norwegian patent application no. 19995140. The mechanism for translation of the projectile and subsequent locking to the rocket motor is described in closer detail in copending Norwegian patent application no. 19995141. Fig.3 shows the rear end of the penetrator 1 when the penetrator is partly translated through the translation tube 12 in the rocket motor 10 and the control fin part 5. The rear end of the penetrator 1 interlocks to the control fin part 5 after this translation. How this happens is, as mentioned, described in closer detail in Norwegian patent application no. 19992739. The penetrator 1 is, as mentioned, lying within a translation tube 12 within the rocket motor 10 and is translated, or propelled, by means of a pyrotechnic power charge 2, or a pyrogen igniter, that is received within a power piston 9. The pyrotechnic power charge 2 is ignited by a pyrogenic squib 3 that initiates the entire translating and launching operation. The pyrogenic squib 3 is lying rearmost in the translation tube 12 and ignites the power charge 2 in the power piston 9. The pyrotechnic charge in the squib 3 is ignited by means of electric power that is supplied via wires 14 to a thin glow filament that is embedded in the pyrotechnic charge in the squib 3. As one alternative, a laser igniter can be used. Here the laser light is transferred through an optical leader of glass and the light is amplified or consentrated through a prism just ahead of a transfer charge so that this is extremely rapidly heated and ignited. The pyrotechnic charge, or igniter, can be in form of compressed or moulded powder, alternatively moulded pellets or granules and constitute leadazide labelled BKNO3. As mentioned, the power piston 9 envelopes a pyrotechnic power charge 2 that by ignition generates gas pressure that is able to expand rearwards through one or more apertures 4 in the rear wall 6 of the power piston 9. The pyrogenic squib 3 having the pyrotechnic charge, is left behind in the rear end of the translation tube 12. The translation tube 12 is initially sealingly closed behind the power piston 9 and forms a closed expansion chamber 7 for the pyrotechnic charges that by ignition generate gas pressure and activates the power piston 9 and thus propells the projectile 1 forward within the translation tube 12. In fig.3 is the power charge 2 shown partly burnt out. In one embodiment is the translation tube 12 sealingly closed behind the power piston 9 by means of an end closure 8. The end closure 8 can, however, move axially forward in the translation tube 12 after ignition of the pyrotechnic charges and translation of the power piston 9. At which moment of time the end closure 8 moves forward is dependent of the pressure differential of the expansion chamber 7 within the translation tube 12 and the pressure that is generated by the propellant charge 13 in the rocket motor 10 when initiated. The motional freedom of the end closure 8 provides a means to balance this pressure differential. Thus fragmentation, collapse of or deformation of the translation tube 12 during launching is avoided. The end closure 8 can in one variant (not shown) abut against an internal shoulder in the rear end of the translation tube 12. In the shown alternative the end closure 8 abuts a perforated plate 11 that is integrated to the rear end of the translation tube 12. Further is a sealing means, such like an O-ring, arranged between the end closure 8 and the translation tube 12. Fig.4 shows when the penetrator is completely translated in the translation tube 12 and the power piston 9 has been locked to the forward end of the rocket motor 10. Simoultaneously, the rear end of the penetrator 1 has been locked to the control fin part 5 as discribed in NO 19992739. Fig.5 shows another embodiment of the rear end of the translation tube 12. The rear end has an internal shoulder 12'. The end closure 8' has a corresponding complementary shoulder 8", which initially abuts the shoulder 12'. An O-ring 15 is arranged in an external groove 16 on the end closure 8' and seals against an internal circumferential surface on the shoulder 12'. A squib 3' is mounted to the end closure 8'. The power piston 9' retains a power charge 2', in form of pellets, or more generally a pyrogen igniter charge, that are enclosed by a foam substance 17. Another O-ring 18 is provided in a groove 19 in the external surface of the piston 9' and seals against the internal surface of the translation tube 12. As in the one embodiment above, the translation tube 12 is sealingly closed behind the power piston 9' by the end closure 8'. The end closure 8' can move axially forwards in the translation tube 12 after ignition of the pyrotechnic charges and translation of the power piston 9'. As with the other embodiment will the moment of time that the end closure 8' moves forward be dependent of the difference between the gas pressure within the expansion chamber 7 in the translation tube 12 and the pressure that generates by the propellant charge 13 within the rocket motor 10 when initiated. The motional freedom of the end closure 8' balances this pressure differential. As before, this will avoid fragmentation, collapse of or deformation of the translation tube 12 during translation and launching. As a non illustrated alternative, the rear end of the projektile 1 can be an integrated power piston that follows the projectile 1 during the flight thereof. Then the power piston 9, in stead of locking to the front end of the rocket motor 10, will lock to the rear and central extension of the control fin part 5. The translation tube 12 can be made of any suitable material, such like titanium, steel, aluminum, composite, i.e. carbon fibre in epoxy, and lined with aluminum, steel or titanium. The power piston 9 can also be made of any suitable material, such as titanium, aluminum, steel or ceramics. The translation tube 12 may preferably be coated with a lubricating agent, such like graphite or molycote.

Claims: P a t e n t c l a i m s 1. A propelling device for a projectile (1) that is lying in a standby position within a rocket motor (10) in a missile, where the projectile (1) is translated in respect of the rocket motor (10) by means of a pyrotechnic charge (2), or pyrogen igniter, before the rocket motor (10) is initiated, c h a r a c t e r i s e d i n that the projectile (1) is lying within a translation tube (12) centrally located in the rocket motor (10), that the projectile (1) comprises a power piston (9) in the rear end thereof, that the power piston (9) encloses a pyrotechnic power charge (2) and a pyrogenic squib (3) and that the translation tube (12) is sealingly closed behind the power piston (9) and forms a closed expansion chamber (7) for the pyrotechnic charges, which by ignition generate gas pressure that activates the power piston (9) and thus the projectile (1). 2. A propelling device according to claim 1, c h a r a c t e r i s e d i n that the translation tube (12) is sealingly closed behind the power piston (9) by means of an end closure (8), which end closure (8) is movable axially forward within the translation tube (12) after the ignition of the pyrotechnic charges and translation of the power piston (9). 3. A propelling device according to claim lor2, c h a r a c t e r i s e d i n that the end closure (8) is abutting an internal shoulder in the rear end of the translation tube (12). 4. A propelling device according to claim lor2, c h a r a c t e r i s e d i n that the end closure (8) is abutting a perforated plate (11) integrated to the rear end of the translation tube (12). 5. A propelling device according to any of the claims 2-4, c h a r a c t e r i s e d i n that a sealing means, such like an O-ring (15), is arranged between the end closure (8) and the translation tube (12). 6. A propelling device according to any of the claims 2-5, c h a r a c t e r i s e d i n that a sealing means, such like an O-ring (18), is arranged between the power piston (9) and the translation tube (12). 7. A propelling device according to any of the claims 1-6, c h a r a c t e r i s e d i n that the power piston (9) is an integrated part of the projectile (1). 8. A propelling device according to any of the claims 1-6, c h a r a c t e r i s e d i n that the power piston (9) is releasable together with the rocket motor (10). 9. A propelling device according to any of the claims 1-8, c h a r a c t e r i s e d i n that the power charge (2) is inform of moulded pellets, comprimated or moulded powder or granules, mixed, casted and cured composite propellant. 10. A propelling device according to any of the claims 1-9, c h a r a c - t e r i s e d i n that the projectile (1) is a penetrator.

Inventors: BISEROED HANS B, BISEROED, HANS, B.
Applicants: BISEROED HANS B, NAMMO RAUFOSS AS, BISEROED, HANS, B.
Application year: 2000
Main classification: F42B15
IPC codes: F15B15, F42B12, F42B15