Abstract:
A laser ignition/ablation propulsion system that captures the advantages of both liquid and solid propulsion. A reel system is used to move a propellant tape containing a plurality of propellant material targets through an ignition chamber. When a propellant target is in the ignition chamber, a laser beam from a laser positioned above the ignition chamber strikes the propellant target, igniting the propellant material and resulting in a thrust impulse. The propellant tape is advanced, carrying another propellant target into the ignition chamber. The propellant tape and ignition chamber are designed to ensure that each ignition event is isolated from the remaining propellant targets. Thrust and specific impulse may by precisely controlled by varying the synchronized propellant tape/laser speed. The laser ignition/ablation propulsion system may be scaled for use in small and large applications.

Description:
FEDERAL RESEARCH STATEMENT 
     The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. 
    
    
     TECHNICAL DESCRIPTION OF THE INVENTION 
     The present invention relates generally to the field of rocket propulsion, and more specifically to a device utilizing a pulsed, variable, high precision laser ignition/ablation thruster for propulsion. 
     BACKGROUND OF THE INVENTION 
     Aerospace propulsion systems are known in the art. Rockets are propelled using either liquid or solid fuel chemical propulsion or some combination of both. Each system has unique advantages and disadvantages. Liquid fuel chemical propulsion systems can be throttled and are capable of being turned on and off. In addition, the thrust levels can be varied resulting in greater efficiency and flexibility during operation. Liquid propulsion systems, however, generally have a higher mass and require more complex and costly components than do solid rocket systems. 
     Solid rocket propulsion systems have a lower level of controllability than liquid rocket propulsion systems. Unlike liquid rocket propulsion systems, solid rocket propulsion systems cannot be turned off once lit. Once the propulsion system is turned on, it will continue to burn until all fuel is used up. The inability to be turned off limits the operational envelope and presents a potential safety hazard. 
     Solid rocket propulsion systems respond more quickly than liquid fuel propulsion systems once turned on. In addition, solid rocket propulsion systems generally have higher performance than liquid fuel propulsion systems, providing a greater thrust/specific impulse per fuel weight. The weight and performance of the fuel is a significant factor for aerospace craft as it is estimated that each additional pound adds $10,000 to the cost of putting a payload into space. 
     Propulsion systems are usually tailored to meet certain mission requirements and specifications and may have to start and stop a limited number of times. As space applications continue to diversify, scalability in propulsion systems is important and allows rocket builders to more effectively tailor their designs to a given application. 
     Depending on the mission, liquid propulsion systems also may have inconvenient storage requirements or limited shelf life and may be inconvenient for modular packaging. For example, liquid systems may require the continued cooling for cryogenic fuels with associated insulation and storage tanks while solids would only need a “room temperature” environment. 
     It is very desirable to have a propulsion system that captures the controllability of liquid propulsion and the high performance of solid propulsion. 
     It is very desirable to have a propulsion system that is scalable and able to be tailored to a variety of applications, which allows for variable thrust or specific impulse levels. 
     It is very desirable to have a propulsion system that can be started, stopped and restarted as needed, and which aids in providing high precision performance. 
     It is very desirable to have a propulsion system with modular design for convenient resupplying, refueling and modifying of ignition/ablation material. 
     It is further desirable to have a propulsion system that allows multiple systems to be integrated into a single craft. 
     SUMMARY OF THE INVENTION 
     The present invention is a pulsed, variable, high precision laser ignition/ablation thruster, which captures the advantages from both liquid and solid propulsion. A reinforced, transparent tape in back carries a volume of propellant or ablation material into the ignition/ablation chamber. A sufficiently intense laser pulse passes through a transparent, high temperature, high pressure laser window and through the transparent carrier tape, striking the back surface of the target propellant/ablation material. If a propellant is used, it is ignited and the expanding gas passing through a rocket nozzle generates thrust. If an ablative material such as paraffin is used, the substance is converted to an expanding gas that passes through a rocket nozzle producing thrust. 
     Once this event is complete, the tape then moves a new target element into the ignition/ablation chamber and the event is repeated. Many events may take place per second creating high average thrust and specific impulse. Tape speed for a given propellant or ablative substance determines thrust level. This process can be employed on size scales ranging from very small to very large, and may be synchronized with a computer control. 
     GLOSSARY 
     As used herein, the term “containment border structure” refers to a component of a transport structure that encloses ignition or ablation material. 
     As used herein, the term “flammable” means subject to burning when exposed to heat. 
     As used herein, the term “highly resilient material” refers to a material that is tolerant of high temperatures, pressure, and tension, is able to withstand vacuum environments and environments with an extreme range of temperatures, and which is resistant to tangling. Examples of highly resilient material include, but are not limited to para-aramid synthetic fiber (e.g., Kevlar®) and polyimide (e.g., Kapton®). 
     As used herein, the term “nonconductive” means not capable of conducting an electrical current. 
     As used herein, the term “opaque” means a material that absorbs a laser beam rather than allowing it to pass through. 
     As used herein, the term “propellant material” refers to a substance capable of being ignited or ablated. 
     As used herein, the term “reel” refers to a rotating component used for storing, dispensing, and/or protecting a transport structure. 
     As used herein, the term “reinforcing members” refers to material added to a layer of propellant tape to add strength. Reinforcing members may include, but are not limited to wire mesh, metallic wires, wire ribbon, wire threads, Kevlar® threads, and nylon threads. 
     As used herein, the term “synthetic fiber” refers to a material that is stronger than steel and which is tolerant to high pressure and temperature. Examples of synthetic fibers include, but are not limited to para-aramid fibers (e.g., Kevlar® and Twaron®), polymer fibers, polyethylene fibers, nylon fibers, carbon fibers, and glass fibers. 
     As used herein, the term “transport structure” or “propellant tape” refers to a component that moves propellant material through an ignition/ablation chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary embodiment of a laser ignition/ablation propulsion system. 
         FIG. 2   a  illustrates a top view of a first exemplary embodiment of propellant tape for a laser ignition/ablation propulsion system. 
         FIG. 2   b  illustrates a side view of a first exemplary embodiment of propellant tape for a laser ignition/ablation propulsion system. 
         FIG. 2   c  illustrates a top view of a second exemplary embodiment of propellant tape for a laser ignition/ablation propulsion system. 
         FIG. 2   d  illustrates a top view of a third exemplary embodiment of propellant tape for a laser ignition/ablation propulsion system. 
         FIGS. 3   a  through  3   d  illustrate perspective views of exemplary shapes of propellant targets. 
         FIG. 4   a  illustrates a back view of an exemplary embodiment of a propellant tape storage feed reel for a laser ignition/ablation propulsion system. 
         FIG. 4   b  illustrates a front view of an exemplary embodiment of a propellant tape storage feed reel for a laser ignition/ablation propulsion system. 
         FIG. 5   a  illustrates a back view of an exemplary embodiment of a propellant tape storage takeup reel for a laser ignition/ablation propulsion system. 
         FIG. 5   b  illustrates a front view of an exemplary embodiment of a propellant tape storage takeup reel for a laser ignition/ablation propulsion system. 
         FIG. 6  illustrates a cross sectional view of an exemplary embodiment of an ignition/ablation chamber for a laser ignition/ablation propulsion system. 
         FIG. 7  illustrates an exemplary embodiment of a fiber optic transmission of a laser pulse of a laser ignition/ablation propulsion system. 
         FIG. 8  illustrates an exemplary embodiment of a packaging option for an ignition/ablation propulsion system. 
         FIG. 9   a  illustrates an exemplary embodiment of a configuration of a plurality of packaged ignition/ablation propulsion systems. 
         FIG. 9   b  illustrates a second exemplary embodiment of a configuration of a plurality of packaged ignition/ablation propulsion systems. 
         FIG. 10  illustrates an exemplary embodiment of an ignition/ablation propulsion system having multiple ignition chambers. 
     
    
    
     DETAILED DESCRIPTION 
     For the purpose of promoting an understanding of the present invention, references are made in the text to exemplary embodiments of a laser ignition/ablation propulsion system, only some of which are described herein. It should be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent materials, components, and placement may be used. The inclusion of additional elements may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present invention. 
     It should be understood that the drawings are not necessarily to scale; instead, emphasis has been placed upon illustrating the principles of the invention. In addition, in the embodiments depicted herein, like reference numerals in the various drawings refer to identical or near identical structural elements. 
     Moreover, the terms “substantially” or “approximately” as used herein may be applied to modify any quantitative representation that could permissibly vary without resulting in a change to the basic function to which it is related. 
       FIG. 1  illustrates an exemplary embodiment of laser ignition/ablation propulsion system  100  comprised of laser  10 , laser window  35 , target containment walls  42   a ,  42   b , ignition chamber  40 , storage feed reel  20 , storage takeup reel  22 , and propellant tape  25 . Laser  10  is positioned so that laser pulse  12  passes through laser window  35  between target containment walls  42   a ,  42   b.    
     Propellant tape  25  contains propellant targets  30  (See  FIG. 2   a ), comprised of ignition/ablation material, at regular intervals. Propellant tape  25  is wound on storage feed reel  20 , which unwinds, feeding propellant tape  25  under laser  10 . Propellant tape  25  is rewound on storage takeup reel  22  after propellant targets  30  have been ignited/ablated. 
     When a propellant target  30  is positioned between target containment walls  42   a ,  42   b , propellant tape  25  pauses and laser  10  fires sending laser pulse  12  through laser window  35 . Laser pulse  12  strikes the surface of propellant target  30  igniting or ablating it, resulting in a thrust impulse. Propellant tape  25  then carries another propellant target  30  over ignition chamber  40 . 
     The movement of propellant tape  25  is synchronized to the firing of laser  10  so that a new propellant target is in position each time laser  10  fires. The resulting thrust/specific impulse may be precisely controlled by varying the speed of propellant tape  25  and the firing of laser  10 . 
     In addition, the frequency of laser pulse  12  will be a direct function of the burn rate of propellant target  30 . The burn of propellant target  30  must be complete prior to moving a new propellant target into ignition chamber  40 . The ignition transient time, steady-state burn-time, and tail-off transient for each propellant target  30  needs to be considered. Heat transfer must also be considered. 
     In the embodiment shown, laser window  35  is integrated with ignition chamber  40 , which is comprised of a material that is tolerant of high temperatures and high pressure, and is transparent to the wavelength of laser pulse  12 . Laser window  35  prevents the hot gas which results from ignition/ablation from escaping through the top of ignition chamber  40  helping to control the outflow of gas by forcing it to pass through nozzle  85 . Laser window  35  may be comprised of a material including, but not limited to polycarbonate resin thermoplastic (e.g., Lexan®), glass, plastic, resin, quartz, silicon, or any other material(s) that is transparent to a laser beam and is tolerant to high temperatures and pressure. 
       FIG. 2   a  illustrates a top view of a first exemplary embodiment of propellant tape  25  for laser ignition/ablation propulsion system  100 . Propellant tape  25  is comprised of a plurality of discrete propellant targets  30  positioned at regular intervals between transparent back cover  26  and transport layer  27 . Propellant tape  25  is positioned so that transparent back cover  26  faces upward toward laser pulse  12  (see  FIG. 2   b ). 
     The design of propellant tape  25  is crucial. Propellant tape  25  must protect propellant targets  30  during storage and when a propellant target is ignited/ablated. Propellant tape  25  must prevent the contingency of other propellant targets igniting/ablating in an uncontrolled chain reaction. 
     In the embodiment shown, transparent back cover  26  is a transparent, heavy duty, relatively thick foundation tape layer that is transparent to the wavelength of laser pulse  12  (not shown). Transparent back cover  26  must be comprised of a material that is robust and thick enough to tolerate the transient temperature and pressure that occurs during ignition/ablation. 
     Openings are cut in transport layer  27  to the desired size of ignition/ablation material. The openings are then covered with a nonflammable membrane  31 , which is secured to transport layer  27 . The membrane  31  may be bonded, glued, or sewn to the front of transport layer  27 . Containment border structures  29  are mounted to transport layer  27  so that they surround the openings. Ignition/ablation material is then attached to transport layer  27  forming propellant targets  30 . 
     In various embodiments, propellant targets  30  may be comprised of ignition or ablation material. Examples of ignition material include, but are limited to shuttle solid rocket booster propellant, Ammonium Perchlorate Composite Propellant, or another solid rocket propellant known in the art. For lower thrust levels, ablation material, such as paraffin may be used. Propellant targets  30  may be attached to transparent back cover  26  via adhesive properties of the ignition/ablation material or may be glued to transparent back cover  26  using adhesive. 
     Transport layer  27  is secured to transparent back cover  26  so that propellant targets  30  are secured between transparent back cover  26  and transport layer  27 . Transport layer  27  and transparent back cover  26  may be secured together by bonding, gluing, sewing, or another attachment means known in the art to form propellant tape  25 . 
     Transport layer  27  faces toward ignition chamber  40  (not shown). When propellant target  30  is ignited/ablated, propellant target  30  bursts through the membrane  31  into ignition chamber  40 . 
     In the embodiment shown, transparent back cover  26 , transport layer  27 , and the membrane  31  may be comprised of conductive materials, nonconductive materials, or a combination thereof. For example, transparent back cover  26  and transport layer  27  may be comprised entirely of nonconductive materials including, but not limited to para-aramid synthetic fiber (e.g., Kevlar®) and polyimide (e.g., Kapton®). The use of nonconductive materials prevents an electrical current from traveling through propellant tape  25  causing propellant targets other than the one in the ignition chamber to ignite. In various other embodiments, transparent back cover  26  and/or transport layer  27  may further contain reinforcing members which are nonconductive (e.g., para-aramid synthetic fibers, nylon threads) or nonconductive (e.g., metallic threads). The use of only nonconductive materials may be desirable to maximize safety and reliability; however, metallic reinforcement may be required for maximum performance. 
     Similarly, the membrane  31  may be comprised of a relatively thin nonconductive material including, but not limited to plastic film, polyimide film, or other plastic film, and/or a conductive material including, but not limited to aluminum foil or another type of metallic foil. 
     The membrane  31  enhances the storage life of propellant targets  30 . In various embodiments, the membrane  31  is comprised of aluminum foil or another type of foil, and/or may be comprised of multiple layers (e.g., a conductive layer and a nonconductive layer). In various embodiments, an additive may be added inside the membrane  31  to further increase the storage capability of propellant targets  30 . 
     Transport layer  27  is the primary drive tape and must be thick enough to allow propellant tape  25  to be driven at a high rate of speed. In addition, transport layer  27  must be impervious to being burned cutting propellant tape  25  in multiple pieces, which would affect the movement of propellant tape  25 . 
     Transparent back cover  26  and transport layer  27  hold propellant targets  30  firmly in position during movement of propellant tape  25  and further enables propellant targets  30  to be accurately aligned between laser widow  35  (not shown) and ignition chamber  40 . 
     In the embodiment shown, propellant tape further includes sprocket holes  28 , which correspond to inner gear sprockets  66  of takeup reel  20  (not shown) and aid in the unraveling of propellant tape  25 . 
     In the embodiment shown, propellant targets  30  are circular, but in other embodiments may be of another shape including, but not limited to doughnut-shaped, oval, square, rectangular, star-shaped, or may have an undefined shape or be randomly shaped. In other embodiments, propellant targets  30  have an array pattern so that one element of the array pattern is ignited and subsequently ignites other elements of the array. The cross section of propellant target  30  may also vary. For example, propellant target  30  may be concave or convex in order to optimize performance and cost. In various embodiments, propellant tape  25  may further include optional filler material  33  to smoothen propellant tape  25  so it is better adapted for winding/unwinding on storage feed reel  20  and storage takeup reel  22 . 
     In embodiments where ablation material, rather than ignition material, is used, the ablation material may be located continuously along the propellant tape. 
     In various embodiments, one or more additional layers of transparent layers with square or circular openings may be joined continuously to the transparent back cover  26  for additional positioning and support of propellant tape  25 . In still other embodiments, inserts are attached to transparent back cover  26  and are used to surround propellant targets  30 . These inserts may be opaque to the wavelength of laser pulse  12 . 
     In various embodiments, transparent back cover  25  and transport layer  27  materials may vary depending on the ignition/ablation material used for propellant targets  30  and the associated ignition/ablation temperatures and pressures. 
     The spacing and size of propellant targets  30  on propellant tape  25  is dependent upon a number of factors including, but not limited to the ignition/ablation material being used, the amount of ignition/ablation material in each propellant target, the length of propellant tape  25 , the speed that propellant tape  25  moves through the ignition chamber, operation time, and the application for which laser ignition/ablation propulsion system  100  is being used. Propellant targets  30  should be located far enough apart so that one propellant target can be ignited without the risk of igniting adjacent propellant targets. If the propellant targets are located too close together, igniting/ablating one propellant target may cause a second propellant target to ignite/ablate outside of the ignition chamber. 
     In an exemplary embodiment, propellant targets are uniformly spaced. In embodiments where the desired thrust variations for a mission application are known in advance, non-uniformed spacing of propellant targets may be desired. 
       FIG. 2   b  illustrates a side view of a first exemplary embodiment of propellant tape  25  showing the direction that laser pulse  12  passes through propellant tape  25 . 
       FIG. 2   c  illustrates a top view of a second exemplary embodiment of propellant tape  25 . In the embodiment shown, propellant tape  25  further includes wires  50  between propellant targets  30  and sprocket holes  28 . Wires  50  provide additional reinforcement for extremely energetic events and only minimally affect the flexibility of propellant tape  25 . 
       FIG. 2   d  illustrates a top view of a third exemplary embodiment of propellant tape  25 . In the embodiment shown, propellant tape  25  further includes wire ribbon  52  for additional reinforcement. In various embodiments, propellant tape  25  may be reinforced by embedding steel, para-aramid synthetic fiber, or other high tensile strength wires or threads which run the length of propellant tape  25 . A mesh matrix may also be used to reinforce propellant tape  25 . 
     The addition of metallic elements (e.g., threads, wires, wire ribbon) provides a strong border for propellant tape  25  decreasing the likelihood that propellant tape  25  will be cut by ignition/ablation. The width and thickness of propellant tape  25  may also be adjusted to decrease the likelihood of propellant tape  25  being cut. 
       FIGS. 3   a  through  3   d  illustrate perspective views of exemplary shapes of propellant targets.  FIG. 3   a  illustrates propellants that are convex,  FIG. 3   b  illustrates propellant targets that are concave,  FIG. 3   c  illustrates donut-shaped propellant targets and  FIG. 3   d  illustrates propellant targets that are arranged in an array. Propellant targets may be shaped and arranged in order to optimize performance and cost for each application. 
       FIG. 4   a  illustrates a back view of an exemplary embodiment of propellant tape storage feed reel  20 . Propellant tape  25  is wound on storage feed reel  20  and fed into ignition chamber  40  (not shown) and then rewound on storage takeup reel  22  ( FIGS. 3   a  and  3   b ). 
     In the embodiment shown, storage feed reel  20  is driven by gearbox  60  and motor  62 , which is controlled by controller  64  (e.g., a computer). Controller  64  is isolated outside of the contained area where ignition/ablation occurs. Controller  64  may be hard-wired or wireless and a single controller may be capable of controlling multiple laser ignition/ablation propulsion systems. In an exemplary embodiment, controller  64  controls all aspects of thruster operation and communicates with reel motors and laser  10  (not shown), as well as the spacecraft controller. One controller may operate several reels depending on the mission application. 
       FIG. 4   b  illustrates a front view of an exemplary embodiment of propellant tape storage feed reel  20  showing propellant tape  25 , the direction of unraveling, and inner gear sprockets  66 . Inner gear sprockets  66  correspond to sprocket holes  28  (not shown) in propellant tape  25  aiding in the placement and unraveling of propellant tape  25 . 
       FIG. 5   a  illustrates a back view of an exemplary embodiment of propellant tape storage takeup reel  22 . In the embodiment shown, storage takeup reel  22  is driven by gearbox  60  and motor  62 , which is controlled by controller  64 . In the embodiment shown, controller  64  controls all aspects of thruster operation. 
     In the embodiment shown, both storage feed reel  20  and storage takeup reel  22  are comprised of light, tough, heat-resistant materials. Storage feed reel  20  and storage takeup reel  22  may be comprised of nonconductive material including, but not limited to high strength plastic such as Kapton®, or carbon composite, and/or a conductive material including, but not limited to aluminum, beryllium, and combinations thereof. In addition, storage feed reel  20  protects propellant tape  25  from outside contamination and humidity. 
     In various embodiments, one or both reels may be powered. For example, only storage takeup reel  22  is driven by an electric motor and the tension from storage takeup reel  22  is used to unwind propellant tape  25  from storage feed reel  20 . In an exemplary embodiment, both storage feed reel  20  and storage takeup reel  22  have gearing which allows them to be driven by a single electric motor. Driving both reels allows for precise control of the tension of propellant tape  25 . The controller would sense this level of tension and manage it accordingly to minimize the chance of pulling apart the tape. 
       FIG. 5   b  illustrates a front view of an exemplary embodiment of propellant tape storage takeup reel  22  showing propellant tape  25  and inner gear sprockets  66  which correspond to sprocket holes  28  (not shown) on propellant tape  25 . 
       FIG. 6  illustrates a cross sectional of an exemplary embodiment of ignition chamber  40  showing laser window  35 , target containment walls  42   a ,  42   b , tape containment walls  74   a ,  74   b , synchronizing mechanism  78   a ,  78   b , propellant tape  25 , propellant target  30 , expended propellant target  32 , and laser pulse  12 . 
     Target containment walls  42   a ,  42   b  and tape containment walls  74   a ,  74   b  isolate the ignition/ablation event from the rest of propellant tape  25 , from other propellant targets  30 , and from storage feed reel  20  and storage takeup reel  22 . Target containment walls  42   a ,  42   b  seal off the ignition chamber  40  during an ignition/ablation event. During the ignition/ablation event, the only escape path for expanding gases is through nozzle  85  (not shown). 
     Synchronizing mechanisms  78   a ,  78   b  are movable and are used to place additional pressure on propellant tape  25 . Synchronizing mechanisms  78   a ,  78   b  are lowered creating an additional barrier between the ignited/ablated propellant target  30  and the adjacent propellant targets and reels  20 ,  22  (not shown) helping to maintain the structure of propellant tape  25  and to force the resulting hot gas into through nozzle  85  (not shown). Synchronizing mechanisms  78   a ,  78   b  are then retracted to allow propellant tape  25  to carry another propellant target  30  into ignition chamber  40 . In the embodiment shown, synchronizing mechanisms  78   a ,  78   b  are lowered and retracted using a spring; however, in other embodiment another mechanism, such as movable pistons, may be used. 
     In the embodiment shown, tape containment walls  74   a ,  74   b  are fixed and target containment walls  42   a ,  42   b  are movable and are synchronized to lift away from propellant tape  25  prior to propellant tape  25  moving, allowing a new propellant target  30  to be brought into ignition chamber  40 . Propellant tape  25  also carries away all post-ignition/ablation contaminants preventing them from clouding laser window  35 . 
       FIG. 7  illustrates an exemplary embodiment of fiber optic transmission of laser pulse  12 . In the embodiment shown, laser  10  is not located in the proximity of propellant target  30  and fiber optic cable  90  is used to transmit laser pulse  12  from laser  10  to propellant target  30 . 
     Fiber optic cable  90  is capable of carrying a sufficiently intense laser pulse to achieve ignition/ablation, enabling many packaging options for laser  10 . Utilizing fiber optics enables the use of remote lasers from either the ground, space, internal to the ignition/ablation propulsion system  100 , or from anywhere with a suitable environment to power the thruster. 
       FIG. 8  illustrates a second exemplary embodiment of a packaging option for ignition/ablation propulsion system  100  showing controller  64 , laser  10 , ignition chamber  40 , storage feed reel  20 , storage takeup reel  22 , and nozzle  85 . The direction in which nozzle  85  points determines the direction of thrust. Nozzle  85  is controlled by controller  64 . 
     In the embodiment shown, ignition/ablation propulsion system  100  has one nozzle; however, in other embodiments, ignition/ablation propulsion system  100  may include more than one nozzle pointed in the same or in varying directions. 
     The packaging option for ignition/ablation propulsion system  100  shown in  FIG. 8  enables convenient packing into thruster modules with relatively long storage life. In addition, modular packaging allows for replenishment of attitude control propulsion subsystems (e.g., for a return mission). If scaled up, these modules could be used to push a potentially hazardous asteroid, meteoroid, or comet away avoiding a potential impact with Earth. 
       FIG. 9   a  illustrates an exemplary embodiment of a configuration of a plurality of packaged ignition/ablation propulsion systems  100 . In the embodiment shown, ignition/ablation propulsion systems  100  are stacked to achieve greater performance. 
       FIG. 9   b  illustrates a second exemplary embodiment of a configuration of a plurality of packaged ignition/ablation propulsion systems  100  combined to thrust in several directions. In another embodiment, a movable mirror may be used to ignite/ablate all modules using a single laser pulse. 
       FIG. 10  illustrates an exemplary embodiment of an ignition/ablation propulsion system having multiple ignition chambers  40  positioned along a single propellant tape  25 . In various embodiments, multiple ignition chambers  40  may share one or more pairs of storage feed and storage takeup reels, one laser, and one controller.