Title:
Methods and systems for laser diode ignition of field weaponry
Kind Code:
A1


Abstract:
Methods and systems for laser diode ignition of field cannons and weaponry. A series of one or more laser diodes or laser diode array, bars or stripes that are configured to optically pump a collimator which may be formed of materials to provide a lasing medium. The energy output of these devices can be combined when configured as an array or a series of redundant laser diodes assemblies to provide safe and reliable ignition systems. The collimator may direct the output from these laser diode assemblies as multiple collimated ignition beams. The laser diode assemblies may optically end pump and/or side pump the collimator or collimating rod to deliver a more directed energy output to artillery propellant. Additionally, the duration of the pulses may be controlled and extended as necessary to help ensure proper ignition of the propellant.



Inventors:
Folsom, Mark (Monterey, CA, US)
Fahey, Wm David (Cupertino, CA, US)
Carvalho, Joseph E. (Hollister, CA, US)
Butterfield, Tom (Hollister, CA, US)
Valenti, Robert M. (Menlo Park, CA, US)
Application Number:
10/165606
Publication Date:
03/13/2003
Filing Date:
06/06/2002
Assignee:
FOLSOM MARK
FAHEY WM. DAVID
CARVALHO JOSEPH E.
BUTTERFIELD TOM
VALENTI ROBERT M.
Primary Class:
International Classes:
F41A19/58; F42B3/113; F42C19/08; (IPC1-7): F42C19/00
View Patent Images:
Related US Applications:



Primary Examiner:
CHAMBERS, TROY
Attorney, Agent or Firm:
WILSON, SONSINI, GOODRICH & ROSATI (PALO ALTO, CA, US)
Claims:

What is claimed is:



1. A laser-ignited cannon comprising: a barrel formed with an interior region; a cannon breech positioned adjacent to the barrel, wherein the breech includes a light-transmissive window for allowing the passage of laser energy into the interior region of the cannon barrel to ignite a propellant contained therein; a laser diode ignition assembly optically coupled to the cannon barrel for directing laser energy through the light-transmissive window of the breech into the interior region of the cannon; and a power management system connected to the laser diode ignition assembly for delivering electrical energy to the laser diode ignition assembly to controllably generate an ignition beam output.

2. The laser-ignited cannon as recited in claim 1 wherein the laser diode ignition system includes a laser diode array and an optically coupled collimator that directs collimated light through the light-transmissive window of the breech into the interior region of the cannon barrel.

3. The laser-ignited cannon as recited in claim 2 wherein the collimator is a laser rod.

4. The laser-ignited cannon as recited in claim 1 wherein the power management system includes a low voltage power storage device and battery charger.

5. The laser-ignited cannon as recited in claim 1 wherein the power management system further includes a controller for controlling the timing and duration of the laser energy pulse.

6. The laser-ignited cannon as recited in claim 5 wherein the controller is programmable to deliver electrical power continuously to the laser diode ignition assembly until ignition of the propellant has occurred.

7. A laser ignition system for a field cannon comprising: a collimator formed of a lasing material for collimating a laser pulse; at least one laser diode disk array formed with a central aperture, wherein at least a portion of the collimator is positioned within the central aperture such that the laser diode disk array may optically side pump the collimator to generate a collimated laser pulse used as an ignition beam for a field cannon; and a power management system connected to the laser diode disk array for controlling the laser pulse length to provide variable ignition times.

8. The laser ignition system as recited in claim 7 wherein the collimator is a laser rod.

9. The laser ignition system as recited in claim 7 wherein the collimator is positioned in a cannon breech such that laser output of the collimator is directed through a light-transmissive window in the breech to a propellant positioned in a cannon barrel interior.

10. The laser ignition system as recited in claim 7 wherein the laser energy is directly optically coupled to a propellant.

11. The laser ignition system as recited in claim 7 wherein the electrical power supply is a battery.

12. The laser ignition system as recited in claim 7 wherein the power management system includes a controller for controlling the timing and duration of the laser energy delivery.

13. The laser ignition system of claim 12 wherein the controller is connected to at least one sensor for monitoring the timing and duration of the laser energy delivery for ignition to provide feedback on system performance and the need for maintenance.

14. A field cannon with a laser diode array comprising: a field cannon that includes a breech portion and a barrel portion, wherein the breech portion and barrel portion are adjoined by a firing window formed with an optically transmissive material to permit the passage of light energy therethrough; a laser diode assembly that is positioned in the breech portion for delivery of a collimated ignition beam through the firing window, wherein the laser diode assembly includes a collimator having an end surface and is formed of a lasing material for collimating a laser pulse; and at least one laser diode array optically coupled to the end surface of the collimator such that the laser diode array optically end pumps the collimator to generate the collimated ignition beam; and a power management system connected to the laser diode assembly for powering and controlling the pulse length of the ignition beam.

15. The field cannon of claim 14 wherein the power management system includes a feedback monitor to detect ignition performance conditions.

Description:
[0001] This patent application claims the benefit of the U.S. Provisional Patent Application Serial No. 60/296,582 filed on Jun. 6, 2001, which is incorporated by reference in its entirety herein.

FIELD OF THE INVENTION

[0002] The present invention relates to methods and apparatus for igniting propellant in field weaponry with laser diode systems. More particularly, the invention relates to laser diode ignition systems for field cannons.

BACKGROUND

[0003] Many field cannons are fired today using a combination of prime charges in cartridges and acceptor charges. A prime charge is initially loaded into the breech portion of a cannon. The prime charge is then fired by electrical or percussive means to thereby ignite the adjacent acceptor charge portions of field cannon artillery or other propellants. After the field cannon is fired, the breech of the cannon is opened so that the expended cartridge of the prime charge can removed and replaced. This approach has worked for decades, but not without certain disadvantages including the significant amount of time that is required to manually replace the prime charges for each round fired by the field cannon.

[0004] In recent years, the use of prime charges in field cannons has been replaced with flashlamp lasers. A flashlamp is basically used as a light source to optically pump a lasing medium such as Nd:glass or Nd:YAG. For example, the United States government has pursued laser ignition of propellants with flashlamps in an attempt to avoid using prime charges. By substituting the firing of prime charges, flashlamp laser ignition systems eliminate the time-consuming process of removing and replacing the prime charge cartridges between each discharge. This consequently reduces the required operating time to fire each round of the cannon, which in turn allows the cannon to effectively fire more projectiles within a specified period of time. Flashlamp-pumped laser rod systems are used in government funded weaponry systems to provide the laser pulse which ignites artillery propellant. The laser head in this type of system is typically mounted directly onto the breech of a field cannon. The pulse of light can be thus fired through a window formed in the cannon breech in order to illuminate and ignite a propellant bag. Assuming a sufficient amount of energy is generated and directed by this laser beam to a suitable portion of the propellant bag, the ignition of the propellant bag in turn causes the artillery propellant to ignite and thereby fire the cannon.

[0005] A variety of disadvantages and associated problems exist however with flashlamp-pumped laser ignition systems. The flashlamps, which are commonly used to optically pump a selected lasing medium, usually operate at high-voltages. Because field cannons are often deployed in harsh environmental conditions including rain, dust, high humidity and damp weather, flashlamps and other high voltage equipment can be difficult to operate and maintain which presents reliability issues. In addition, flashlamp laser ignition systems are generally not energy efficient devices. A significant amount of electrical power must be initially provided at a high voltage level to begin operating the system. The typical level of efficiency observed when this high voltage electrical input is converted into the resulting photons, which illuminate the igniter in the propellant, is estimated to be less than two-percent. This type of inefficiency and high demand for electrical power presents even more challenges to the external power supplies that are needed to recharge these ignition system for multiple firings. Moreover, with the increasing trend toward low voltage digital electronics, high voltage components of the past are also becoming less available as the supplier base and demand decreases. The long-term ability to continually manufacture and rely on these types of flashlamp ignition systems for field use therefore remains uncertain.

[0006] Current flashlamp-based ignition systems also consist of relatively large components that are cumbersome and difficult to mobilize. In order to provide sufficient electrical power to operate the ignition system, relatively large high voltage capacitors must be used to store the significant amount of electrical energy which must be accumulated and subsequently discharged into the electrical circuits rapidly to fire the flashlamp. Moreover, while these large energy storage capacitors can rapidly discharge their retained energy, they have been known to lose a relatively larger percentage of their capacitance when operating at relatively lower surrounding temperatures. As a result, it may be necessary to select capacitors that are even physically larger in order to store enough electrical energy to operate the flashlamp under a wider range of temperatures. These less efficient larger and heavier ignition system components can significantly hamper the mobility and operability of field cannons. Furthermore, available flashlamp laser ignition systems provide laser ignition pulses for relatively small time intervals lasting only approximately five milliseconds. If ignition fails to occur within this small window of time, there is a hang fire. Subsequent attempts to ignite the propellant can be made again, but only after the capacitor bank is allowed to fully recharge for another firing which cause undesirable delays in the field.

[0007] There is a need for a compact and mobile laser ignition system that is a safe alternative to current high voltage flashlamp laser ignition systems. A cost effective and reliable ignition system is also needed that can be easily maintained and constructed from components that are readily available.

SUMMARY OF THE INVENTION

[0008] The present invention provides laser diode ignition systems for field cannons and weaponry. The ignition systems described herein are relatively inexpensive to manufacture and maintain. The laser diodes selected for these systems are generally low-voltage, compact light sources which are energy efficient. In accordance with various aspects of the invention, the energy output of these devices can be combined as an array or a series of redundant laser diodes assemblies to provide safe and reliable ignition systems for field cannons and weaponry. A collimator such as a laser rod may be selected to direct the output from these laser diode assemblies as multiple collimated ignition beams. The particular features of the described embodiments in the following specification may be considered individually or in combination with other variations and aspects of the invention.

[0009] It is an object of the invention to provide methods and systems for laser diode ignition of field cannons and weaponry. A series of one or more laser diodes can be combined to deliver sufficient laser output in the aggregate to effectively and reliably ignite weaponry propellants. The collimated laser beams provided by the laser diode ignition systems herein deliver focused and energy efficient output for field cannons and other weaponry in a safe and reliable manner without the need for high-voltage equipment.

[0010] Another object of the invention is to provide laser diode ignition systems with built-in redundancy and increased reliability. Some embodiments of the invention utilize multiple laser diodes to increase the intensity and/or likelihood of igniting artillery propellant. The laser ignition systems further provide the weaponry operator with valuable control and feedback on the operating performance of the ignition system which can provide extended firing times as needed to avoid hangfires. Continuous and extended laser pulses can be thus provided until ignition to ensure adequate delivery of energy for more reliable field weapon operation.

[0011] With respect to another aspect of the invention, methods are provided herein to operate field cannons and weaponry with laser diode ignition systems. A laser diode array may be initially selected to end pump and/or side pump a collimator or collimating rod which delivers a more directed energy output to artillery propellant. The energy output may consist of collimated ignition beams which can pass through the firing window of a weapon. Additionally, the duration of the pulses may be controlled and extended as necessary to help ensure proper ignition of the propellant. The invention further provides reliable methods of igniting weaponry with built-in redundancy in that multiple ignition beams are delivered across a wider area to provide a greater likelihood of propellant ignition and more reliable operation of the weapon. The ignition systems herein may include multiple diode arrays with multiple diodes per array to provide numerous ignition beams.

[0012] Other objects and advantages of the invention will become apparent upon further consideration of the specification and drawings. While the following description may contain many specific details describing particular embodiments of the invention, this should not be construed as limitations to the scope of the invention, but rather as an exemplification of preferable embodiments. For each aspect of the invention, many variations are possible as suggested herein that are known to those of ordinary skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a simplified cross-sectional view of a field cannon laser diode ignition system provided in accordance with the invention.

[0014] FIG. 2 is a cross-sectional view a laser diode disc array provided herein for optically side pumping an ignition collimator.

[0015] FIG. 3 illustrates an ignition collimator that is optically pumped by one or more laser diode disk arrays to generate sufficient laser output with relatively low divergence to pass through a field cannon firing window.

[0016] FIG. 4 is a simplified block diagram of a laser diode ignition system with a resonator cavity formed with an external mirror or reflector.

[0017] FIG. 5 is a simplified cross-sectional view of yet another embodiment of the invention that provides a field cannon ignition system that generates a highly collimated laser output by optical end pumping of a collimating rod.

[0018] FIG. 6 depicts the optical coupling or combining of laser output from a series of laser diodes and optical fibers to direct a plurality of light beams towards a collimator.

[0019] FIG. 7 is a cross-sectional view of an end pumped collimating (lasing) rod that receives optical output from a plurality of laser diodes to provide a series of collimated light beams.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The invention provides methods and apparatus for ignition of propellants in field cannon and weaponry using laser diode assemblies. Laser diodes are relatively compact semiconductor devices that do not require the use of high-voltage equipment such as those demanded by flashlamp lasers. The availability and versatility afforded by these light sources as described herein can provide more reliable ignition systems that are well suited for use in the field.

[0021] As shown in FIG. 1, a laser diode ignition system 10 may be selected and installed in a field cannon 12 in accordance with the invention. The principles of the invention herein are applicable to Crusader field cannons or other propellant-based field weaponry. The field cannon 12 (not drawn to scale) may be constructed with a cannon breech 14 and a barrel portion 16. The cannon breech 14 may be formed with a firing window 15 leading into the interior region 17 of the cannon barrel 16. Within the cannon barrel 16, a round of artillery 11 can be positioned for firing. The artillery round 11 basically consists of a projectile 13 and a propellant section 18 which can be initiated by the laser ignition system 10 herein. A powder bag 20 may be placed within a relatively rearward compartment of the propellant section 18. The back portion of the propellant 18 may include a prime charge 22 formed with a Mylar disk or back covering 21 which permits laser ignition beams to pass therethrough in order to ignite the propellant bag 20. The bag 20 may contain black powder or other combustible material. The ignition of the propellant bag 20 consequently ignites the adjacent artillery propellant 18 in order to fire the projectile 13 from the field cannon 12.

[0022] The laser diode ignition assemblies herein may be installed in the breech section 14 of the field cannon 12. As shown in FIG. 1, a laser diode assembly or module 10 may be connected to and driven by a variety of power storage and control apparatus. A portable external power source 22 may provide electrical energy to a battery charger 23 for charging a relatively compact and low voltage power storage, i.e. battery 24. The low voltage power storage or battery 24 can be charged as needed by a conventional battery charger and the external power source 22. The power storage 24 may be in turn connected to a controller 25 to drive the laser diode assembly 10. The controller 25 can be configured to control the timing and duration of an energy pulse by regulating the electrical current delivered to the laser diode assembly 10 positioned in the cannon breech 14. Additionally, the laser diode assembly 10 shown may further include a collimating ignition rod 26 with one or more laser diode arrays 28 to optically end pump or side pump the rod. It shall be understood that for purposes of describing the invention, the collimators or collimating rods referenced herein shall include laser rods that are optically pumped by laser diodes to efficiently collimate the laser diode output. In this illustrated embodiment of the invention, the light energy from the laser diode array 28 optically pumps the adjacently positioned collimating rod 26 to generate an ignition beam. The rod 26 is typically formed from a solid state medium and any suitable lasing material known to those in the field including Nd:YAG and YV04:YAG. A variety of diameters may be selected for the collimating rod 26 ranging from 2 to 10 mm or greater. While other configurations may be selected for the lasing medium such as a slab or wafer, a cylindrical shaped laser rod with a predefined length is preferable for the applications described herein. It has been observed that uncollimated laser output from edge emitting low voltage laser diodes is too diffuse to provide propellant ignition within an acceptable time frame or across a large depth of field. The collimated ignition beams provided by the collimating rod assemblies herein however offer more less divergent output that do not spread significantly as they pass through the firing window of the cannon. A relatively higher energy density is thus created by these laser ignition beams which may traverse a relatively large depth of field or gap within the cannon breech to ignite artillery propellant.

[0023] The collimating rod 26 may be positioned just outside the cannon breech 14 so that the laser output passes through the light-transmissive firing window 15 into the cannon barrel interior 17. The firing window 15 may be formed of sapphire or other durable optical material that is suitable for field weapons. The laser energy can thereby initiate a pyrotechnic reaction by passing through the Mylar disc and/or back covering 21 of the propellant 18. The laser ignition beam may first ignite the propellant bag 20, which in turn ignites surrounding artillery propellant 18. The artillery propellant 18 may be formed in a substantially donut-shape around the bag 20 or other appropriate configuration. The expanding gases from the ensuing reaction and complete deflagration of the propellant 18 thereby propels the projectile 13 from the field cannon barrel 16. A series of one or more ignition pulses can be also continuously fired by the laser diode assembly 10 until the propellant 18 is ignited. The pulse length or pulse times can be variably adjusted in accordance with types of weaponry and changes in atmospheric or external conditions which may prolong requisite ignition times. Furthermore, the controller 25 may be connected to a sensor or a feedback monitor to detect and signal ignition of the propellant 18 or other conditions, or even automatically stop the flow of electrical energy to the laser diode 28 when the weapon is successfully fired. The controller 25 may be also programmed to instruct the laser diode array 28 to deliver a predetermined pulse length in accordance with an anticipated time to ignite the propellant. Depending on the types of ammunition and propellants (Zones 1-6) that are used for the field weapon, appropriate ignition pulse lengths may be also selected and programmed by the controller 25 in a predetermined manner. It has been further observed that longer pulse times may be required as the optical quality of firing windows diminishes over extended periods of time and usage. Noting this extension in time provides feedback that the window needs maintenance.

[0024] FIG. 2 illustrates a laser diode disk array 30 which may be selected for the ignition systems provided herein. A series of one or more of these arrays 30 may optically side pump an ignition collimator (laser rod) 33 to generate a collimated output beam. Each laser diode disk array may be in communication with and connected to the field gun controller. Certain applications or types of artillery may require firing of only certain laser diodes, while other types of propellants may require the combined collimated output of all laser diodes within the disk array. The laser diode disc array 30 may be formed with a mounting portion 32 that secures the assembly within a selected portion of the field cannon. The disk array 30 may include multiple individual laser diodes 34 that are spaced apart and positioned to direct their output toward a central region or aperture 35 occupied by the collimating (lasing) rod 33. The measured diameter of the collimating (lasing) rod 33 may range from one-millimeter or greater depending upon certain applications. The central region 35 of the laser diode disk array 30 may be modified accordingly with appropriate clearance to surround and effectively side pump the laser rod 33. In this embodiment of the invention, five laser diode bars were selected for purposes of illustration. It shall be understood however that any number of one or more laser diode bars 34 may be selected for the side pumped collimating rod assemblies provided herein. The output of the individual laser diodes 34 may also optically pump the laser rod at an angle perpendicular to the external surface of the rod 33 or at any other angle to feed the lasing medium with light energy. Furthermore, it has been further observed that the side pumped laser diode arrays herein are often physically smaller than those laser diode assemblies that provide end pumping. A more compact light source to optically pump the ignition collimating rod may therefore reduce costs and save space within the field cannon.

[0025] The ignition collimators or collimating rods herein may be optically pumped by one or more laser diode disk arrays to generate a sufficient ignition pulse which can pass through a field cannon firing window. As shown in FIG. 3, a single side pumped collimating rod assembly 36 may be fitted with one or more laser diodes disk arrays 38 that are slipped over and positioned along the longitudinal axis of the laser rod 39. A series of laser diode arrays (Laser Diode Array #1, Laser Diode Array #2 . . . Laser Diode Array #n) may be selected to optically pump the ignition collimating rod 39 in order to generate the laser output needed to ignite various types of propellants under different operating conditions. Each of the laser diode disk arrays 38 may be wired to the weapon control unit to receive instructions and power to optically pump the rod 39. Moreover, any number of one or more of the laser diode arrays 38 may be fired or not fired in accordance with predetermined ignition requirements. Under certain operating and weather conditions, certain types of propellants may not require operation of all arrays within the laser diode ignition assembly. In other instances where shorter ignition times are required or greater laser output levels are desired, all laser diode arrays within the assembly may be directed to optically pump the ignition collimating rod or collimator. Depending on the optical transmissivity of the firing window or the physical deformities or characteristics of certain propellant bags, more heat energy may be also delivered as needed in certain instances to achieve ignition. A variety of ignition times may be provided herein ranging up to 50 milliseconds or longer. It shall be understood that the laser diode disk arrays illustrated herein for purposes of illustration are donut-shaped light sources. Those of ordinary skill however will understand that other types and shapes of laser diodes may be selected herein in accordance with the invention to side pump the lasing medium in order to generate an ignition beam.

[0026] The collimating rods selected herein may be conventionally formed with a lasing medium that is bound by a pair of mirrors or reflectors as is known in the field. By optically side pumping the collimating (lasing) rod or medium with light energy from laser diodes, the light is reflected back and forth within the resonant cavity formed by the end mirrors. While it may be desirable for many applications to form a collimating rod with a monolithic construction, it may be more preferable in certain systems to select external mirrors to define the laser cavity. In FIG. 4, for example, another embodiment of the invention may be configured with an external mirror 42. The collimating rod 44 may be optically side pumped as described herein with laser diodes to generate collimated laser output. The output may be used as an ignition beam which passes through the firing window 46 of a field cannon to ignite artillery propellant within the barrel region of the weapon. It shall be understood that various ignition beam profiles may be generated herein depending upon certain factors including the output power levels and beam diameters of the laser diodes and collimators. The number of laser diodes with each array, and total number of laser diode arrays selected to optically side pump the lasing medium, may also affect the ignition beam profile and certain concentrations of energy densities. In any event, the collimating rods herein are intended to collimate the light received from the laser diodes with less divergence and greater concentration within a defined area to provide more reliable and efficient laser ignition of field weaponry.

[0027] Another aspect of the invention provides end pumped laser diode ignition systems for field weaponry. As shown in FIG. 5, another embodiment of the invention provides a field cannon ignition system 50 that generates a collimated ignition beam by optically end pumping a collimating rod 56. As described herein, the ignition collimator beam may be directed to pass through a firing window 51 of a field cannon 52 in order to ignite a prime charge 66 having a propellant bag 53 positioned within a relatively rearward portion of an artillery propellant 56 section. The ignition of the propellant bag 53 may in turn ignite surrounding propellant 56 in order to fire a projectile 59 from the interior region 57 of the cannon barrel 54. Furthermore, the end pumping laser diode assemblies described herein may be installed in the cannon breech section 67 of the field cannon 52. A controller 65 may also control the firing sequence and duration of the laser diode assembly 50. The ignition system may include a relatively portable low voltage power storage or battery 64 that can be charged with a batter charger 63 and power source 62. It shall be understood that other power management and control systems may be selected to operate the laser diode ignition systems described herein. In order to generate an ignition beam pulse, a series of one or more laser diodes 58 optically end pump a substantially adjacent collimating rod 56 which may be formed from a lasing material. The collimating rod 56 will collimate the light energy received from the laser diode(s) 58 to form relatively concentrated and less divergent ignition beam(s). For many applications, a collimating rod formed of suitable lasing material may be selected to more quickly generate requisite ignition beams. However, a basic optical collimator or optical device with configured lenses may be used alternatively with adequately powered laser diodes in order to provide desired ignition beam diameters and energy densities in accordance with the invention. Lasing rods are effective collimators which direct light pulses from laser diodes to ignite propellant-based weaponry. It shall be understood that the fundamental principles associated with laser rod operation herein are basically the same for both end pumped and side pumped laser diodes except for the different equipment used and the direction in which light is pumped into the lasing medium.

[0028] FIG. 6 depicts the optical coupling or combining of laser output from a series of laser diodes which is provided by end pumping ignition systems herein. The end pumping laser diode ignition systems herein may include a series of laser diodes (LD1, LD2 . . . LDn) that optically feed into a plurality of optical fiber cables 69. The fiber cables may be formed with various lengths of up to one meter or more so that an adequate degree of free movement may be provided during operation and recoil of a field cannon. All of the transmitted light pulses from the laser diode array may be thus combined with suitable optical couplers or combiners. The number of input ports for the coupler may equal the number of laser diodes or individual emitting laser elements on the laser diode bars selected for the ignition system. The coupler may be formed with a single output port 70 to direct all of the laser diode optical transmissions into a collimating (lasing) rod. The resulting ignition laser beam or series of beams can be formed and directed through a light-transmissive window located in the cannon breech into the interior of a cannon barrel. It shall be understood that lenses and other optical components and coatings may be selected to assist in collimating the combined laser diode output into the cannon breech. As with the other laser diode arrays described herein for either end pumping or side pumping applications, each laser diode within the array may have various power output levels ranging from approximately 1 to 50 watts or higher. The laser diode may be compact and operate at relatively low voltages as low as 5 volts or even lower. These devices are relatively efficient light sources and can convert approximately 50% or more of electrical power into optical power to provide small and durable components for field use. Some laser diodes may be configured to efficiently operate for hundreds or even thousands of ignition cycles from a single charged battery. A variety of commercially available laser diodes may be selected with different power output levels in accordance with the invention such as Coherent Semiconductor FAP-808-60C-1200BL for end pumping and Coherent Seminconductor B1-81-60Q-49-50-A for side pumping. For example, in order to achieve a desired output of 40 watts, an appropriate number of laser diodes with predetermined power levels and efficiency may be selected as known by those of ordinary skill. More than one laser diode may be optically coupled to the laser rod to add to the resultant ignition beam. It has been observed that by increasing the number of laser diodes which optically end pump the collimator (laser) rod, as well as those side pumping, there is a proportional increase in the number of ignition beam spots. Accordingly, multiple ignition beams may be generated by the end pumped laser diode ignition systems herein to provide redundancy and to increase the likelihood propellant ignition.

[0029] For example, as shown in FIG. 7, an end pumped collimating (lasing) rod 72 may transmit multiple ignition beams generated by a plurality of end pumping laser diodes. When viewing the lasing rod from a cross-sectional view, it has been observed that the resultant ignition beam profile basically consists of a number of ignition beam spots which corresponds to the number of particular laser diodes selected for the ignition system. The optical output from the plurality of laser diodes provides a series of collimated light beams producing such spots. The ignition spots have been observed to vary in size ranging from one-half millimeter to four-millimeters or greater, and may be dependent on the size of the input beams and pulse lengths. The geometry and sizes of these spots will also vary according to the optical strength or power (watts) and output diameters (mm) of the selected laser diodes. For certain field cannon ignition assemblies, it may be preferable to select relatively high powered laser diodes with smaller output diameters. Other embodiments of the invention may alternatively include relatively lower powered laser diodes having larger output diameters to ignite propellant.

[0030] Another aspect of the invention provides methods of igniting propellants in field cannons with laser diode assemblies. The laser diode assemblies such as those described herein may include laser diode arrays that either optically end pump or side pump a collimator such as a laser rod. The optical output from the laser diodes are collimated by the laser rod to form an ignition beam pulse. The ignition beam pulse may be sustained as needed to ensure ignition of artillery propellant. Various methods of holding the ignition beam are thus provided with the laser diode ignition systems described herein. A suitable power management and controller may be also selected to communicate and drive the laser diode assemblies. Other methods of igniting field weaponry are provided herein in accordance with the operation of the field cannons and weaponry provided above.

[0031] While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the preferred embodiments herein are not meant to be construed in a limiting sense. It shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. Various modifications in form and detail of the embodiments of the invention, as well as other variations of the invention, will be apparent to a person skilled in the art upon reference to the present disclosure. It is therefore contemplated that the appended claims shall cover any such modifications, variations or equivalents of the described embodiments as falling within the true spirit and scope of the invention.