Patent Application
20150226525
1. Technical Field of the Invention
The invention is in the field of aerial vehicles with time-delay release mechanisms.
2. Description of the Related Art
Aerial vehicles such as projectiles or missiles have had parts that are releasable in flight, such as covers for sensor systems. In the past pyrotechnic devices have been used in separating covers, but initiating circuits for squibs or other pyrotechnic devices increase cost and complexity. Explosives also cause vibrations in the vehicle that may disrupt operations of systems in the aerial vehicle, for example temporarily disrupting operation of an inertial measurement unit. Further, safety precautions are required for handling during manufacture, storage, and transportation of the aerial vehicle.
An aerial vehicle includes a combustible time-delay fuse for releasing a part of the vehicle during flight.
According to an aspect of the invention, an air vehicle includes: a combustible propellant that propels the air vehicle; and a retention device for retaining a part of the air vehicle. The retention device is part of a combustible time-delay fuse, combustion in which is initiated by combustion of the combustible propellant, and which after a time delay from initiation of combustion of the fuse, releases the retention device.
According to another aspect of the invention, a method of releasing a part of an air vehicle during flight includes the steps of: launching the air vehicle, where in the launching includes igniting a combustible propellant of the air vehicle, with the part of the air vehicle retaining during launching by a retention device of the air vehicle; initiating combustion of a combustible time-delay fuse by combustion of the propellant; and releasing the retention device by sufficient combustion of the fuse, thereby releasing the part of the air vehicle.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
The annexed drawings, which are not necessarily to scale, show various features of the invention.
An air vehicle includes a combustible fuse that is used for time-delayed release of a retention device. Combustion of a combustible propellant for propelling the air vehicle initiates combustion of the fuse. After a time delay following initiation of the combustion of the fuse, a retention device of air vehicle is released. In one embodiment, the air vehicle is a projectile which is fired from a propellant in a cartridge that is behind the projectile. The retention device may be used to release a cover for a sensor of the air vehicle, such as a cover for an optical sensor or seeker.
The projectile 10 is propelled using a combustible propellant 20 that is located in a cartridge case 22 of the projectile 10. The propellant 20 is ignited using an ignition primer 24 at a base 28 of the case 22.
A tail 30 of the fuse 12 extends back from the cover 14 into the propellant 20. Combustion of the propellant 20 initiates combustion of the fuse tail 30. The fuse 12 burns forward from the propellant 20, toward a retention portion or device 34 of the fuse 12, such as a retention band, that is engaged with the cover 14, and that keeps the cover 14 from being prematurely released. There is a time delay between the initiation of combustion of the fuse tail 30, and when the combustion reaches the fuse retention portion 34, which causes release of the cover 14. This time delay is a function of the material characteristics of the fuse tail 30, and the dimensions of the fuse tail 30, among other possible factors. By proper configuration of the fuse 12, a desired time delay between initiation of propellant combustion and release of the cover 14 may be achieved.
The fuse 12 may be made of any of a wide variety of combustible materials. For example, the fuse 12 may include a fabric, such as canvas or a synthetic fabric, that is impregnated with gunpowder or potassium nitrate, similar to materials used for cannon fuse. With reference to
The entire fuse 12 may be made of combustible material. Alternatively, only part of the fuse 12 may be combustible, with for instance the fuse tail 30 being combustible, and the retention portion 34 being combustible only to the degree necessary to release the cover 14 after combustion of the combustible parts of the fuse 12. The noncombustible retention portion 34 may be made of any of a variety of suitable materials, for instance suitable plastic materials.
The fuse 12 may have any of a variety of suitable shapes. The fuse tail 30 may have a substantially circular cross section. The tail 30 may be straight, longitudinally oriented along an inner surface of the case 22, as shown in
The retention portion 34 may have a flattened shape, and may be connected to the cover 14 by any of a variety of suitable methods, such as by being adhesively attached to the cover 14. The retention portion 34 may be on the inside of the cover 14, or alternatively may be on the outside of the cover 14, with the tail 30 passing through a hole in the cover 14. If the retention portion 34 is on the outside of the cover 14, it may be in a suitable groove in the cover 14, perhaps with an epoxy covering to protect it from ablation and/or to reduce drag.
As noted above, the fuse 12 is a combustible retention device that relies on combustion to release the retention portion 34. This is in contrast to pyrotechnic explosive devices, which use an explosive force to cause separation.
The time delay provided by the fuse 12 may be set to any of a wide variety of times. For example, the time delay may be from 1 second to 30 seconds, although other time delays are possible. The time delay may be controlled by selection and configuration of the fuse 12 using any or all of the variables described above.
The fuse 12 may be used to keep the cover 14 in place for a predetermined time after combustion of the propellant 20 commences. The cover 14 may protect the sensor 16 during launching, as well as during the initial phase of flight of the projectile 10. For example the cover 14 may protect the sensor 16 from objects in the air, such as dust or sand, that may otherwise ablate or otherwise damage the sensor 16. In addition, the cover 14 may provide better aerodynamic performance (e.g., less drag) than the uncovered sensor 16.
The sensor 16 may be any of a variety of types of sensors. The sensor 16 may be an optical sensor, such as an optical seeker. Alternatively, as shown in
The projectile 10 may be fired from a gun or other suitable launcher, with the propellant 20 used to propel the projectile 10 out of the launcher. Alternatively or in addition, the propellant 20 may power the air vehicle (the projectile or the missile, for example) during flight.
The retention portion 34 holds the cover parts 52 and 54 against a separation force from a resilient device 58, illustrated as a spring. The resilient device 58 provides an initial force to aid in separating the cover parts 52 and 54 after release of the retention portion 34, as discussed below. In addition the resilient device 58 may provide an outward force that helps hold the retention portion 34 in place, prior to release. In the illustrated embodiment the cover parts 52 and 54 are held together at a releasable hinge 60, allowing the cover parts 52 and 54 to pivot outward when released.
The resilient device 58 may be a spring or other resilient device, in any of a variety of forms, to provide a preloaded force to initiate separation of cover parts 52 and 54, once the retention device 34 is released. The device 58 may be a coil spring, as is illustrated in
The cover parts 52 and 54 may separate in other ways than are shown in
In the illustrated embodiment there are only two cover parts 52 and 54. Alternatively there may a different number of cover parts and/or a different configuration of the cover parts. For example, there may be four or six cover pieces. Making the cover pieces smaller has the advantage that lighter pieces falling away from the projectile 10 form less of a hazard to people or devices on the ground, such as friendly personnel in the area of the projectile 10.
The retention device 34 is shown as a retention band that breaks in order to release the cover parts 52 and 54. Many alternative types of retention devices are possible. For example the retention device may be some sort of releasable mechanical latch that is released by combustion of a fuse such as all or part of the fuse 12.
Many variations are possible. The air vehicle may be a missile, or a powered or unpowered projectile, to give a few examples. Propellant used to initiate combustion of a time-delay fuse may be part of a solid-fuel rocket, or a gun cartridge that provide pressurized gasses within a launcher. The time-delay fuse mechanism described above may be used to retain other parts of an air vehicle, which may be separated, deployed, or otherwise changed in configuration following release of a retention mechanism.
The fuses described above provided numerous advantages over prior release mechanisms such as explosives, for example in the form of one or more explosive bolts. The fuses described above avoid use of explosives that may cause vibrations that interfere with operations of components of the sensor or other parts of the aerial vehicle, such as an inertial measurement unit. Also, explosives have relied upon electrical ignition, which adds weight and complexity, and may require running a wire between the vehicle main body and a cover or other item to be released. Further, using combustible materials instead of explosive materials avoids the precautions that are associated with explosives, for example during manufacture, transportation, and storage of devices that include explosive materials.
Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.
