The invention relates generally to gun-launched projectiles. In particular, this invention relates to submunition-dispensing rounds without incorporation of energetic materials.
As the United States Navy transitions from a “Blue Water” Combat Posture to a “Littoral” Combat Posture, naval warships become more susceptible to attack from non-conventional surface weapon platforms from shore-launched threats, such as coastal boats. The Mk 45-5″ 54/62 Gun Mount serves as one of the primary surface warfare weapons aboard these vessels. Although there are multiple 5″ (five-inch) diameter projectiles available for use against small boat threats, their fuzing safe and arm devices preclude their use at close ranges.
Additionally, rules of engagement often permit potential small boat threats to enter within the minimum fuzing safe and arm ranges, thus eliminating any potential self-defense contributions from the Mk 45-5″ 54/62 caliber Gun Mount. Cruiser CG-47 (USS Ticonderoga) and destroyer DDG-51 (USS Arleigh Burke) class ships employ the Mk 45-5″ 54/62 Gun Mount as a primary surface warfare weapon. The Mk 45 5″ 54/62 Gun Mount is a fully automated, rifled, single-barrel weapon that stows and fires 5″ 54/62-caliber ammunition. The weapon is capable of firing 70-lb projectiles at surface craft, low altitude aircraft, and shore targets.
Conventional gun-launched projectiles yield disadvantages addressed by various exemplary embodiments of the present invention. Although there are multiple 5″ (5-inch) diameter projectiles available for use against small boat threats, their fuzing safe and arm devices preclude their use at close ranges, eliminating any potential self-defense contributions from Mk 45-5″ 54/62 Gun Mount. In particular, various exemplary embodiments provide an inert axisymmetric projectile for launching from a shipboard gun and dispersing submunitions at a target.
The projectile features include a base plug, a sabot housing, a submunitions package, a retainer ring, and a slip obturator. The sabot housing includes a plurality of sabot petals angularly arranged and attached to the plug. The housing includes a payload portion and a nose portion, with a passage corridor between these portions. The submunitions package is contained within the payload portion and constrained radially by the housing. The retainer ring constrains the petals for joining together. Upon launch the ring fractures from aerodynamic pressure and rotational forces. This causes the petals to unfurl, thereby releasing the submunitions package for dispersal.
The slip obturator engages the lands and grooves of the barrel rifling and seals the explosive gases behind the projectile, preventing them from advancing further up the projectile and potentially causing damage. The projectile “slips” at the interface between the slip obturator and the base plug, reducing the spin on the projectile that would have otherwise been induced by the barrel rifling. As the projectile progresses down the barrel, the structure of the sabot petals resist undesired deformations under the gun launch loadings of axial inertial setback and rotational inertia. The forward retaining band is restrained from deformation or failure by the radial restraint of the gun barrel itself.
Once the projectile exits the muzzle of the gun, the retaining band is no longer restrained by the barrel and fractures. The band suffers a controlled fracture by means of stress concentrations at geometric cross-section reductions along its circumference due to the combined loadings of axial inertial setback, rotational inertia, and aerodynamic stagnation pressure. Thus, absent restraint at their forward ends, the sabot petals begin to “peal” away from the projectile's central axis due to the centrifugal forces caused by rotation, as well as pressure resulting from petal contact with the ambient air. The petals then discard from the projectile and expose the interior submunitions package. The submunitions immediately begin to disperse radially due to their rotational inertia and their interaction with the ambient air. The dispersed payload is then disposed to engage the intended target. The remaining non-payload projectile components in flight are considered sacrificial materials.
These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which:
In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
Various exemplary embodiments provide an inert gun-launched projectile actuated by gun-launch induced pressures, or “pressure actuated projectile-inert” (PAPI) for standoff ship defense against proximate threats. The PAPI dispenses an internal payload of multiple fragments over an extended area without the use of a conventional fuze or energetic material. The PAPI uses the propelling gasses and acceleration-induced forces from gun launch to initiate internal mechanisms that release housing petals and dispense an internal payload towards a target.
PAPI is being developed to significantly increase the self-defense capabilities of warships against small, fast, asymmetric watercraft threats. Being inert renders the PAPI more convenient and safer to store, manufacture, and maintain. In this context, the term “inert” means without energetic material, such as an explosive or chemical propellant to disperse submunitions from the projectile upon reaching the target.
The PAPI increases capacity provided to the fleet for proximate ship self defense by providing a near-field projectile to be fired from a 5″ (5-inch, e.g., Mk 45) diameter ship-board gun. As such the PAPI constitutes an axisymmetric munitions round. The PAPI is unique less due to its objective, but because of features related to achieving that objective. There are existing “shotgun” type rounds in use by the United States Army. However, these rounds disperse their payloads by means of projectile bodies that shatter apart at or near muzzle exit from the gun.
The PAPI dispenses its payload using mechanisms actuated by gun launch forces. These mechanisms employ controlled fracture of a retaining ring or the channeling of propellant gasses into the interior of the projectile during gun launch. Current research reveals no existing projectile that dispenses a multiple fragment payload by channeling propellant gas to actuate a mechanical device. The novelty of these embodiments can also be extended by the use of a slip obturator to retard spread of the submunitions by reducing spin when fired out of a rifled gun barrel. Exemplary embodiments use the slip obturator to reduce spin (i.e., angular rotation about the PAPI's longitudinal axis) to limit the distribution of the payload to a smaller area. Alternatively, the PAPI can use a regular obturator, thereby achieving full spin, and enabling the round to accurately traverse to the target.
Most shotgun type rounds are fired out of a smoothbore barrel. PAPI can be used on ships wielding large-caliber rifled barrels to engage close range, asymmetric surface threats. The inner spring and pressure actuation mechanism of PAPI can be used for other types and sizes of projectile or as a release mechanism initiated by inertial forces. The principle embodiments described herein include an aerodynamic design and a mechanical design. Each configuration is described in further detail.
Exemplary balls 430 can be composed of a dense metal, such as ⅜ (0.375 inch) diameter tungsten spheres. The base plug 360 features an angular groove 440 for receiving bottom edges of the petals.
Assembly of the retainer ring PAPI can be described in the following illustrations.
In order for the PAPI to be used effectively in the fleet, the interface with the Mk 45 Gun Mount's loading system should be considered.
The detail view 1820 in
Upon muzzle exit, the propelling gasses evacuate the pressure chamber at the rear of the projectile and the upper internal spring 1885 decompresses, drawing the pressure plate back to its original position, along with the latched pushrod 1855. The downward motion of the pushrod withdraws it from a series of tabs within the forward portion of petals 1845, enabling the petals to separate under the residual forces of gun launch. The petals would then be discarded, enabling the payload 1850 contained within to spread and disperse on target.
The delayed opening serves to produce a tight spread pattern for the internal payload 710. Exemplary embodiments facilitate fine tuning into the system. By adjusting the size of the holes 1890 enabling pressure into and out of the system, or altering the size and spring stiffness of the springs 1880 and 1885, the time required for the projectile to open can be customized to the optimal opening time.
The modified mechanical pressure PAPI functions in essentially the same manner as the mechanical pressure PAPI shown in
In summary, the external structure for the general PAPI concept includes detachable envelopes, referred to as petals 310, 320, 330, 340, and a base plug 360. The petals are restrained at the bottom of the projectile by the base plug 360, which is surrounded by a gas-sealing obturator 620, and restrained at the top of the projectile by a frangible retainer ring 610 or a mechanical retaining pin as the pushrod 1855.
The PAPI embodiments can employ either the ring 610 or the pushrod 1855. Both PAPI designs share the same mission and are completely inert and without conventional fuzes. However, the retaining ring PAPI actuates payload dispersion by creating fractures at areas of stress concentration in the retainer ring 610 due to the resulting forces of gun launch. The mechanical pressure PAPI actuates payload dispersion by enabling gun propelling gases into a rear chamber and using this pressure increase to elevate the plate 1875 and engage the pushrod 1855, which is then disengaged from the sabot petal structure 1845, enabling payload dispersion.
Returning to the view 2000, upon launch from the gun 2020, the projectile exits the muzzle and becomes subject to various aerodynamic forces. In general the projectile will experience about 110 psi of pressure due to aerodynamic forces at the nose of the projectile and about 288 psi of pressure due to the spin of the PAPI. The pressure on the nose portion 110 of the PAPI acts on the angled nose cone, and the angular velocity pulls the petals 310, 320, 330 and 340 of the projectile away from the center of rotation. These forces separate the petals being held together by the ring 610.
Assembly of the PAPI includes the procedures described as follows. First as in view 1400, the petals connect together by the dowel pins 1360 with silicone between each petal for environmental sealing purposes. This petal assembly slides into a groove in the retainer ring 610 and is secured in place with standard 4-40 screws. Hose clamps can be used at several locations along the payload portion 120 to keep the petals together until attaching the base plug 360. The upper plate 410 acts as a forward constraint for the payload 710 and features the groove 1330 to fit an o-ring to environmentally and pneumatically seal the PAPI from the nose portion 120.
Second as in view 1420, the plate 410 with o-ring slides inside the petal assembly until reaching the groove 1330 on the petals. The snap ring 1440 can then be inserted into the groove 1330 in the petals to keep the plate 410 from falling out of the projectile. This snap ring 1440 also provides support for the petals to be torqued to the base plug 360.
Third as in view 1450, upon installing the upper plate 410, the tungsten ball payload 710 can be installed. The precise number of balls is determined by the overall weight of the projectile, with the intent of keeping the PAPI to the standard 70±1 pounds-mass. For the volume considered, this configuration has room for just under 50 pounds-mass worth of payload which can equate to about 2800θ⅜″ tungsten spheres or balls 430.
The rod 510 is inserted before the payload 710 is poured into the payload portion 120. This all-thread feature enables use of nuts 520 to torque and compress the payload 710 against the lower plate 420, and enables threading into the base plug 360. The lower plate 420 is somewhat more robust than the upper plate 410 to support the payload 710 during setback acceleration upon launch. The lower plate 420 also features an o-ring groove 1030 for environmental and pneumatic sealing.
Fourth as in view 1460, the lower plate 420 slides into the payload portion 120 and contacts the payload 710. The nut 520 (e.g., locknut and lockwasher) are threaded behind the lower plate 420 to enable torque to be applied. The entire assembly continues a process of vibrating and torquing down the nuts 520 until the payload 710 is sufficiently compacted. This compaction restrains the balls 430 from rattling around, but also acts to inhibit the payload 710 from pushing the petals radially outward by hydrostatic pressure setback forces upon firing. This hydrostatic pressure gradates from negligible at the upper plate 410 to a maximum at the lower plate 420, causing premature separation of the petals. By compressing the load, these forces can be normalized and enabling the payload 710 to act as a unitary item instead of several individual balls 530.
Under the pressures and temperatures experienced during shooting aluminum has been shown to melt and burn, causing small particles of aluminum to be deposited on rifle grooves of the gun barrel. The proceeding shot rips this aluminum from these grooves. With the aluminum comes the chrome plating intended to protect the inside of the barrel. Upon removal of the chrome plating, subsequent shots cause pitting in the rifling of the barrel. This pitting causes blow-by reducing the efficiency and accuracy of future rounds. To avoid such deposits, the base plug 360 is composed of steel.
Fifth as in view 1480, the petals slide into the groove 440, and the rod 510 threads into the hole 1140 of the base plug 360. The two holes 1150 enable use of a spanner wrench to thread the base plug 360 onto the rod 510. A bead of silicone will be applied to the groove in the base plate prior to assembly to provide an environmental seal. The base plug 360 turns into the rod 510 until the sides of the petals mate with the top surface of the inner flange 1110.
Sixth as in view 1490, the obturator 620 is prepared by heating in an oven to allow the nylon to expand, as is commonly accomplished with nylon bands. After heating, the obturator 620 is pressed onto the base plug 360 and permitted to cool and thereby shrink into position. This is a practice carried out on the M1040 in addition to multiple other munitions with similar band designs. After installation of the obturator 620 onto the base plug 360, the PAPI is completed and ready for load and launch in the gun 2020.
While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.
The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
Number | Name | Date | Kind |
---|---|---|---|
3444813 | Bird | May 1969 | A |
3847082 | Feldmann | Nov 1974 | A |
3981242 | Shurtleff | Sep 1976 | A |
4140061 | Campoli | Feb 1979 | A |
6779463 | Mutascio et al. | Aug 2004 | B2 |
8171838 | Heitmann | May 2012 | B2 |
8250988 | Heitmann | Aug 2012 | B2 |
8333153 | Caillat | Dec 2012 | B2 |
20120144712 | Rostocil | Jun 2012 | A1 |
Number | Date | Country | |
---|---|---|---|
20140251173 A1 | Sep 2014 | US |