US20140137539A1 - Thrust-producing device with detonation motor - Google Patents

Abstract

A detonation thrust-producing device includes an explosive located in a recess in an external surface of a body. Detonation of the explosive expels material out of the recess, providing thrust to the body in an opposite direction. A mass, such as a metal disk, may be placed blocking or covering the external opening. The body may be a part of a vehicle, such as an airborne projectile. The thrust-producing device may include multiple detonation motors arrayed around the body, capable of being individually or multiply detonated. Such thrust-producing devices may be used for attitude adjustment, steering, or other control of the flight of the projectile or other air vehicle. The detonation thrust-producing devices have the advantage of a faster-response time than propellant-based devices, and do not need the nozzles that are used with many propellant-based devices.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The invention is in the field of thrust-producing devices.
• 2. Description of the Related Art
• Many sorts of devices are used for producing thrust for a variety of purposes. Traditional rocket motors use sustained combustion of solid or liquid propellants in combination with a supersonic nozzle to accelerate the exhaust products to high velocities, creating a reaction force. However such rocket motors are not suitable for providing reaction forces over very short timeframes.
SUMMARY OF THE INVENTION
• A thrust-producing device uses one or more detonation motors with explosives, to generate thrust over very short timeframes.
• According to an aspect of the invention, a thrust-providing device includes: a body; and a detonation motor. The detonation motor includes an explosive in a recess in an external surface of the body. Detonation of the explosive provides thrust to the body opposite to the direction that material is expelled from the recess, through an external opening in the body.
• According to another aspect of the invention, an aircraft includes: a body; and detonation motors circumferentially spread around a perimeter of the body. Each of the detonation motors includes an explosive in a recess in an external surface the body, wherein detonation of the explosive provides thrust to the body opposite to a direction that material is expelled from the recess, through an external opening in the body.
• According to yet another aspect of the invention, a method of steering an object includes the steps of: detonating an explosive in a recess in a body of the object; and expelling gasses generated by the explosive, thereby creating thrust on the object.
• 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.
BRIEF DESCRIPTION OF THE DRAWINGS
• The annexed drawings, which are not necessarily to scale, show various aspects of the invention.
• FIG. 1 is an oblique view of a thrust-producing device in accordance with an embodiment of the invention, as part of an aircraft.
• FIG. 2 is a cross-sectional fragmentary view of part of the device ofFIG. 1, showing details of a detonation motor of the device.
• FIG. 3 is an oblique view of the device ofFIG. 1, showing a first step in a method of using the device to change course.
• FIG. 4 is an oblique view illustrating a second step of the method.
• FIG. 5 is an oblique view illustrating a third step of the method.
• FIG. 6 is a cross-sectional fragmentary view, showing details of an alternate embodiment detonation motor.
• FIG. 7 is a view of a device in accordance with another alternate embodiment of the present invention.
DETAILED DESCRIPTION
• A detonation thrust-producing device includes an explosive located in a recess in an external surface of a body. Detonation of the explosive expels material out of the recess, providing thrust to the body in an opposite direction. A mass, such as a metal disk, may be placed blocking or covering the external opening, such as in the recess between the explosive and the external opening. The body may be a part of a vehicle, such as an airborne projectile. The thrust-producing device may include multiple detonation motors arrayed around the body, capable of being individually or multiply detonated to provide thrust to the body in different amounts and/or in different directions. Such thrust-producing devices may be used for attitude adjustment, steering, or other control of the flight of the projectile or other air vehicle. The detonation thrust-producing devices have the advantage of a faster-response time than propellant-based devices, and do not need the nozzles that are used with many propellant-based devices.
• FIG. 1 shows a detonation thrust-producingdevice10 that is part of an airborne vehicle or aircraft12 (intended to broadly include all types of flying things or devices, including space vehicles), such as a projectile or missile. Thedevice10 may be used to steer theaircraft12, producing small bursts of thrust fromdetonation motors14 around the perimeter or circumference of abody16 of theaircraft12. The small bursts of thrust may be produced in any of various directions to cause a corresponding reaction in theaircraft12. As described in greater detail below, small explosive devices in thedetonation motors14 are ignited to produce the bursts of thrust.
• The thrust-producingdevice10 may havedetonation motors14 able to provide thrust in any of a variety of directions. Thedetonation motors14 may be circumferentially spread around a perimeter of thebody16, and/or there may be multiple rows ofdetonation motors14 at the same circumferential locations, separated in a direction of alongitudinal axis20 of thedevice10. The devicelongitudinal axis20 may also be the longitudinal axis of theaircraft12, as in the illustrated embodiment. Thedetonation motors14 may be arrayed in a limited number of circumferential locations about the perimeter of thebody16. For example, thedetonation motors14 may be at four circumferential locations equally spaced about the perimeter of thebody16, or eight equally-space locations, or any other number of suitable locations of suitable spacing.
• Thedetonation motors14 are coupled to acontroller24 that controls selective activation of thedetonation motors14. Thecontroller24 may detonate one or more of thedetonation motors14 as needed, to provide thrust to change the course and/or orientation of theaircraft12. Thecontroller24 may be used to activatedetonation motors14 to provide thrust in a desired direction, and may control the number ofdetonation motors14 activated in order to control the level of thrust provided. Thecontroller24 may include integrated circuits or other suitable devices, to be used in making a determination or otherwise controlling activation of thedetonation motors14. Thecontroller24 may be in communication to other devices external to theaircraft12, such as ground stations or aircraft that fire or simply control theaircraft12, to receive signals regarding movements of a target to be intercepted by theaircraft12, or another desired location to be achieved by theaircraft12.
• One possible use of the thrust-producingdevice10 is in altering course of theaircraft12 to intercept a moving target, such as an incoming projectile. For such a purpose rapid course correction is greatly desired, since little time may be available for correcting course in order to intercept the incoming projectile.
• Other uses are possible for the thrust-producingdevice10. It may be used on any of a variety of aircraft for any of a variety of purposes. The thrust-producingdevice10 may also be used on other sorts of devices, for a variety of purposes. Examples of other such devices include satellites and torpedoes. Instead of havingdetonation motors14 with different orientations, as an alternative all of the detonation motors14 (or even asingle detonation motor14 that is the only detonation motor, in another embodiment of the device10) may provide thrust in only a single direction. An example of such an embodiment is in a small missile or munition, which may involve control over thrust in a single axis, for example as a means of throttling. Instead of smoothly or continuously modulating thrust of a motor, a thrust-producing device can produce small increments of thrust.
• Turning now toFIG. 2, details are shown of one of thedetonation motors14. Thedetonation motor14 includes an explosive32 that is located in arecess34 in thebody16. In the illustrated embodiment therecess34 is a cylindrical recess, with a circular cross section shape, and oriented substantially perpendicular to anouter surface35 of thebody16. Alternatively therecess34 may have any of a variety of other shapes and/or orientations.
• Therecess34 has anexternal opening36 where it is open to aregion38 external to thebody16. Therecess34 also may have aninternal opening42 that puts therecess34 into communication with aninterior cavity34 that is enclosed by thebody14. Theinternal opening42 may allow access from the bottom of therecess34 to adetonator44 that is used to detonate the explosive32. Theinternal opening42 is blocked by afiller48 that is in a bottom portion of therecess34, in order to prevent egress from theinternal opening42 of pressurized gasses or other products of the detonation of the explosive32. Thefiller48 may be a suitable potting material.
• Acasing50 surrounds explosive32 and thefiller48. Thecasing50 holds the explosive32 and thefiller48 in place and aligned. Thecasing50 may be made of suitable metal, for example being made of bronze gilding metal, or aluminum.
• Thedetonator44 may havewires52 or other communication devices for connection to the controller24 (FIG. 1). Thewires52 may pass through theinternal opening42. Alternatively thecontroller24 may communicate with the detonator using various other sorts of communication methods, for example using fiber optic cables or wireless communication methods, such as the sending and receiving of suitable radio frequency (RF) signals.
• Theexternal opening36 may also be blocked or covered, preventing direct communication between the explosive32 and theexternal region38. In the illustrated embodiment this is accomplished by a projectile ormass58 that is in a part of therecess34 that is closest to theexternal opening36. Alternatively the projectile58 may be outside of therecess34, covering theexternal opening36. Detonation of the explosive32 expels the projectile ormass58 clear of thebody16, into thesurrounding region38.
• The use of theprojectile mass58 may aid in maximizing thrust output from thedetonation motor14. The projectile58 may have a mass that is about half the mass of the explosive32. More broadly, the projectile58 may have a mass that is from 0.1 to 2 times the mass of theexplosive charge32, although other ratios are possible. Such a charge mass (explosive) may provide a specific impulse (thrust integral divided by propellant mass) of at least 175 seconds, with projectile/explosive mass ratio of about 0.5 providing a specific impulse of 220 seconds. It is possible that higher projectile/explosive mass ratios may be used, producing a lower specific impulse, where volume efficiency considerations are important.
• The projectile58 may be made of any of a variety of suitable materials, such as metal or plastic, and may have any of a variety of characteristics, such as being solid or being pressed powder. The projectile58 may have a disk shape, or another shape with a circular cross section, to fit the circular-cross-section recess34. Alternatively the projectile58 may have a different cross-section shape, particularly one that corresponds to a non-circular-cross-shape of an alternative recess.
• Advantageously, there may be no need for any sort of sealing between the projectile58 and the walls of therecess34. The explosive32 detonates, as opposed to burning, so it generates pressurized gasses very quickly, for instance in 10% or less of the time to burn a corresponding amount of propellant.
• Thedetonation motor14, with its explosive32, provides many other advantages over propellant-based thrusters. Explosives detonate, in contrast to the burning that occurs in propellants. Burning of a solid propellant is governed by chemical kinetics and reaction rates. These kinetics are specific to the propellant formulation being used. The gas generated by burning of a solid propellant is then generally accelerated through a nozzle to supersonic exit velocities. Since the momentum thrust generated by a propellant-based thruster is equal to the mass flow rate times the velocity, the higher the velocity, the higher the thrust generated by a given mass flow. Therefore a nozzle is an important part of a propellant-based thruster. Dispensing with the nozzle in a propellant-based thruster significantly reduces performance, since the velocity is significant lower if there is no nozzle present.
• In contrast operation of thedetonation motor14 involves detonation of the explosive32. Detonation is not burning, but instead is a reaction that propagates through an explosive material, such as the explosive32, at the speed of sound for the medium. When the explosive32 is detonated, it provides enough momentum for the pressurized gasses to be expelled from therecess34 at a velocity at least that of a traditional rocket motor (the propellant-based nozzle-using thruster described above), but with the advantage that no nozzle is needed. Being able to achieve good performance without a nozzle means a smaller, lighter, and less expensive thruster motor.
• In addition, explosives that are detonated have higher densities than solid rocket motor propellants. This results in thedetonation motor14 having a higher volumetric efficiency than an equivalent propellant-based thruster. Thedetonation motor14 also has the advantage of greater impulse per unit volume. For instance, density specific impulse may be greater than a factor of two or more using thedetonation motor14. Typical propellants have a density specific impulse of about 400 g-sec/cc, while in an embodiment of thedetonation motor14, the density specific impulse was over 1800 g-sec/cc.
• Detonations occur at least one order of magnitude faster than even fast-acting thrusters that use solid propellants. For example thedetonation motor14 can act in microseconds, as opposed to seconds. This faster action allows for finer control, and smaller impulse quanta. For example, 100 detonation micro-thrusters can be activated in the time it takes to fire 10 traditional solid-propellant-based thrusters. The firing of multiple micro-thrusters may be sequential, rather than simultaneous, due to the amount of energy required to fire multiple thrusters. A firing circuit used to file multiple thrusters may need time to recharge between firings of individual or groups of thrusters.
• The explosive material for the explosive32 may be any of a variety of suitable explosives. Examples of suitable explosive materials include CL-20, DBX-1, HNS-IV, and lead styphnate. Other high explosive materials, such as RDX, HMX, TATB, LX-14, LX-17, LX-19, or PBXN explosives, may also be used.
• As noted, thefiller48 may be a suitable potting compound. Examples of suitable potting compounds are epoxies and glasses.
• FIGS. 3-5 show the thrust-producingdevice10 in operation.FIG. 3 shows theaircraft12 traveling afirst direction70. InFIG. 4 several of thedetonation motors14 on one side of the thrust-producingdevice10 are fired, expelling pressurized gasses and their projectile58 in the region around theaircraft12. This produces areaction force74 on theaircraft12, which changes the course of theaircraft12 to thedirection78 shown inFIG. 5.
• Theaircraft12 may have other common structures, some of which may also be used for maintaining or changing course. For example theaircraft12 may include any or all of wings (or other lift-producing devices), canards, ailerons, rudder(s), elevators, and elevons. Theaircraft12 may include a propulsion system, such as rocket motor, jet engine, or other thrust-producing device. Alternatively the aircraft may be unpowered.
• FIG. 6 shows an alternate embodiment thrust-producing device110, which has adetonation motor114. Thedetonation motor114 is in arecess134 in a body112. Therecess134 is packed with an explosive132 that is free, when detonated, to expel pressurized gasses substantially unhindered through anexternal opening136 to anexternal region138 that is outside of the body112. In contrast to thedetonation motor14 shown inFIG. 2, thedetonation motor114 does not have anything corresponding to the projectile58 (FIG. 2) of thedetonation motor14. Thedetonation motor114, when compared with thedetonation motor14, has less weight and fewer parts, and does not expel any solid items when detonated. However, thedetonation motor114 may not perform as well (e.g., produce as much thrust) as thedetonation motor14.
• FIG. 7 shows still another embodiment, aspherical device210 that has a series ofdetonation motors214 placed around its surface. Thedevice210 is “spherical” in the sense that it has a generally round shape, which may have facets, such as circular or polyhedral flat portions. Thedetonation motors214 are located all along the surface of thespherical device214, and may be symmetrically spaced about the spherical surface.
• Thedetonation motors214 may have the characteristics of thedetonation motors14 and114 (FIGS. 1 and 5, respectively) described above. Thedetonation motors214 may be able to provide thrust to steer thedevice210 in any of a wide variety of directions.
• Thedevice210 may have any of a variety of suitable sizes, and may be used for accomplishing any of a variety of goals. In one embodiment, thespherical device214 may be a throwable object, for example about the size of a softball or large hand grenade, which could be maneuvered after throwing toward a target. For example thedevice210 may be a thrown munition that could be maneuvered around a corner, while in flight, by firing appropriate of thedetonation motors214. Suitable communication and control systems could be used to guide thedevice210 in this way.
• The above description only discusses a few of the possible configurations and potential uses of the thrust-producing devices and detonation motors described. Many other variations are possible.
• 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.

Claims (20)

1. A thrust-providing device comprising:

a body; and

a detonation motor;

wherein the detonation motor includes an explosive in a recess in an external surface the body; and

wherein detonation of the explosive provides thrust to the body opposite to a direction that material is expelled from the recess.

2. The thrust-producing device ofclaim 1, further comprising a detonator operatively coupled to the explosive to detonate the explosive.

3. The thrust-producing device ofclaim 2, wherein the detonator is operatively coupled to a control system that controls triggering of the detonator.

4. The thrust-producing device ofclaim 1, wherein the body has an interior opening that puts the recess into communication with an interior cavity of the body.

5. The thrust-producing device ofclaim 4, further comprising a filler between the explosive and the opening.

6. The thrust-producing device ofclaim 5, wherein the filler includes a potting compound.

7. The thrust-producing device ofclaim 1, further comprising a projectile operatively coupled to the explosive, wherein the projectile is expelled clear of the body when the explosive is detonated.

8. The thrust-producing device ofclaim 7, wherein the explosive weighs from1 to3 times what the projectile weighs.

9. The thrust-producing device ofclaim 7, wherein the projectile is a disk.

10. The thrust-producing device ofclaim 7, wherein the projectile is made of metal.

11. The thrust-producing device ofclaim 7, wherein the projectile is in the recess.

12. The thrust-producing device ofclaim 1, wherein the recess has a circular cross-section shape.

13. The thrust-producing device ofclaim 1, wherein the detonation motor is one of a multitude of detonation motors that are part of the thrust-producing device.

14. The thrust-producing device ofclaim 13,

wherein the thrust-producing device is part of an aircraft; and

wherein the thrust-producing device is used to steer the aircraft.

15. The thrust-producing device ofclaim 14, wherein the body of the thrust-producing device is part of an external surface of the aircraft.

16. The thrust-producing device ofclaim 14, wherein the detonation motors are circumferentially spread around a perimeter of the aircraft.

17. An aircraft comprising:

a body; and

detonation motors circumferentially spread around a perimeter of the body;

wherein each of the detonation motors includes an explosive in a recess in an external surface the body, wherein detonation of the explosive provides thrust to the body opposite to a direction that products from the detonation are expelled from the recess.

18. A method of steering an object, the method comprising:

detonating an explosive in a recess in a body of the object; and

expelling gasses generated by the explosive from the recess, thereby creating thrust on the object.

19. The method ofclaim 18, wherein the expelling gasses includes expelling a solid projectile using the gasses.

20. The method ofclaim 18, wherein the object is an aircraft, and the creating thrust is used for steering the object.

Images