ROCKET-POWERED SIGNALING DEVICE
United States Patent 3749019
In the embodiments of the subject device shown and described herein, a rocket casing is disclosed which is designed to separate during operation into two sections. The point of separation is predetermined. At separation, the device changes over from a rocket to a flare, smoke marker, or other type of signaling means. The grain functions as a propellant initially and then as the signaling means following casing separation.
US Patent References:
Self-propelling projectile
Damblanc - April 1938 - 2114214
Pyrotechnic device
Fisher - June 1938 - 2120246
Rocket propelled illuminating flare
Hickman - April 1950 - 2503269
Hand-operated rocket type device for signaling and other purposes
Dwyer et al. - August 1950 - 2519123
Toy rocket
Carlisle - July 1958 - 2841084
Self-propelling projectile
Damblanc - April 1938 - 2114214
Pyrotechnic device
Fisher - June 1938 - 2120246
Rocket propelled illuminating flare
Hickman - April 1950 - 2503269
Hand-operated rocket type device for signaling and other purposes
Dwyer et al. - August 1950 - 2519123
Toy rocket
Carlisle - July 1958 - 2841084
Inventors:
Hancock, Earl A. (Clifton, VA)
Macpherson, James R. (Falls Church, VA)
Macpherson, James R. (Falls Church, VA)
Application Number:
05/178580
Publication Date:
07/31/1973
Filing Date:
09/08/1971
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
102/357
International Classes:
F42B4/12; F42B12/50; F42B4/00; F42B12/02; F42B13/38
Field of Search:
102/49.4,34.1-34.5,35.6,37.6
US Patent References:
| 3102477 | Rocket signal device | September 1963 | Stefan et al. |
Primary Examiner:
Stahl, Robert F.
Claims:
What I claim is
1. A rocket-powered signaling device comprising:
2. said grain being a gas generating thrust source in an initial phase of operation and then a signal flare source in a subsequent phase of operation;
3. A device as claimed in claim 1 further comprising:
4. A device as claimed in claim 2 wherein:
5. A device as claimed in claim 2 wherein:
6. A device as claimed in claim 2 wherein:
7. A device as claimed in claim 2 wherein said grain is composed of a plurality of grain sections bonded together and supported in said casing.
8. A device as claimed in claim 3 wherein:
9. a plurality of blades normally held in a folded position by said confining means and being released upon separation of said casing sections.
10. A rocket-powered signaling device comprising:
11. said grain being a gas generating thrust source in an initial phase of operation and then a signal source in a subsequent phase of operation;
12. A device as claimed in claim 8 further comprising:
13. A device as claimed in claim 8 wherein:
1. A rocket-powered signaling device comprising:
2. said grain being a gas generating thrust source in an initial phase of operation and then a signal flare source in a subsequent phase of operation;
3. A device as claimed in claim 1 further comprising:
4. A device as claimed in claim 2 wherein:
5. A device as claimed in claim 2 wherein:
6. A device as claimed in claim 2 wherein:
7. A device as claimed in claim 2 wherein said grain is composed of a plurality of grain sections bonded together and supported in said casing.
8. A device as claimed in claim 3 wherein:
9. a plurality of blades normally held in a folded position by said confining means and being released upon separation of said casing sections.
10. A rocket-powered signaling device comprising:
11. said grain being a gas generating thrust source in an initial phase of operation and then a signal source in a subsequent phase of operation;
12. A device as claimed in claim 8 further comprising:
13. A device as claimed in claim 8 wherein:
Description:
BACKGROUND OF THE INVENTION
The present invention relates to a rocket-powered signaling device of the general type in which the signaling means becomes detached from the rocket motor in flight and is then suspended from a drag device, such as a parachute or rotor vanes, as it is lowered to earth. Examples of signaling means which are used are pyrotechnic candles and smoke generators.
In the prior art of rocket-propelled signaling devices, it is generally the practice to construct the device with the propellant formed separate from the composition forming the signaling means so that the combustion of the former can not adversely affect the latter. Once the propellant has been consumed or the device has reached a predetermined altitude, the signaling means is mechanically expelled from the rocket body or alternatively, the two parts are detached such as by an explosive charge. The end result is that the signaling means is freed to enable it to return to earth by a parachute, rotor vanes, or other suitable drag device.
While certain of these devices might operate satisfactorily, their designs entail unnecessary manufacturing cost, complexity, and weight for what should ideally be a functionally simple, lightweight, and economical device.
SUMMARY OF THE INVENTION
The present invention improves upon state-of-the-art, rocket-powered signaling devices by utilizing the same grain both as a propellant for powering or thrusting the device during the initial combustion phase and then as the signaling means during the subsequent combustion phase.
The casing which houses the grain is designed to become separated at a predetermined point by the temperature of the burning grain, thereby permitting the device to change from a rocket into a signaling device with attendant deployment of a drag means for lowering the device to earth.
The present invention provides for simplicity in design, ruggedness in construction and economical manufacture. The various features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of this invention, its operating advantages and specific objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a preferred embodiment of the present invention in a longitudinal cross-sectional view;
FIG. 1a is a partial plan view of a drag rotor used in the present invention;
FIG. 2 shows an alternative embodiment in quarter section; and
FIG. 3 shows a partial view of another embodiment in partial cross-section.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With particular reference to FIG. 1 showing a preferred embodiment of the present invention, there is shown a rocket-powered signaling device indicated generally by the numeral 10. This device 10 includes an elongated, cylindrical casing 12 made of a suitable material, such as aluminum, which will burn through in response to the high combustion temperatures experiecned during combustion of a grain 14 housed therein. The grain 14 is bonded to the forward, closed end 16 of casing 12. A conventional inhibitor 18 lines the outer periphery of the grain 14 throughout its length, and during operation, this inhibitor prevents the ignition of the grain 14 forward of the end-burning flame front. The inhibited grain 14 fits tightly within what is here termed the forward section 20 of casing 12.
The open aft end 22 of casing 12 is closed by nozzle closure 24 made preferably of graphite or a reinforced phenolic material which can withstand the temperature of the combustion gases. A plurality of nozzle apertures 26 is formed in nozzle closure 24. Casing 12 is crimped over the aft end of nozzle closure 24 as shown at 28 to retain this closure in the assembly.
The aft end of grain 14 is spaced from closure 24 by a tube 30 and an annular washer 32. Washer 32 is preferably made of a material such as spring steel which will serve to cushion the grain 14 during transportation and launch. Grain 14 is here shown as having a shaped uninhibited end face 34 to provide a larger initial burning surface than that of a flat face; however, the particular shape of the initial burning surface is not critical to the present invention.
As shown in FIG. 1, the periphery of inhibited grain 14 and the periphery of tube 30 are in substantial alignment within the device 10. A sleeve 36 surrounds and closely contacts the lower part of this grain 14 and the tube 30. At its periphery, sleeve 36 is in tight engagement with the inside of casing 12, and at its aft end abuts and is retained by nozzle closure 24. Sleeve 36 is an insulator and is used to insulate the casing 12 from the high-temperature combustion gases generated by the burning of grain 34 during operation of the device, as later described. It can be made of a phenolic impregnated paper or other suitable insulating material.
Casing 12 is of a substantially constant diameter in its forward section 20, but as shown has an enlarged diameter toward its aft end 22 to accommodate sleeve 36. This enlarged portion is here termed the aft section 38 of the casing 12. A shoulder 40 is formed between the forward section 20 and the aft section 38. Within casing 12, the forward end of sleeve 36 terminates adjacent to this shoulder 40.
Connected at the forward end 16 of casing 12 is a drag device whose function is to slow or retard the return to earth of the rocket-powered signaling device 10 while this device is in its signaling phase. As depicted here, the drag device is a rotor 42 made of spring steel or other suitable material which permits it to be folded into the position shown where its blades 44 are alongside the casing 12.
With reference also now to FIG. 1a, the unfolded or deployed rotor 42 is shown in partial plan view. Rotor 42 is depicted as having four blades 44 extending outwardly from a central hub 46. This hub is provided with a centrally-located hole 48 which is designed to receive a retaining button 50 in a losse fit. Button 50 is welded to the forward end 16 of casing 12. When the device 10 is at altitude and rotor 42 is unfolded, the blades 44 are so designed that the flow of air through the rotor as the device falls causes windmilling rotation, thus braking or retarding the velocity of the fall and thereby extending the signaling time.
Rotor 42 is maintained in a folded position on device 10 by a thin tubular sheath 52. At its aft end, sheath 52 is crimped at several points 54 about the end of casing 12, and this crimping in combination with the outward pressure of the rotor blades 44 and the generally close fit about aft section 38 is sufficient to hold sheath 52 in place.
In the operation of the FIG. 1 embodiment, the device 10 is first inserted in a conventional launcher tube (not shown) having a dimaeter sized to receive this device in a close fit. Such a launcher tube would include conventional firing means such as a trigger, striker, percussion cap and igniter. Alternatively, the igniter can be included in the device 10 by positioning it in an appropriate recess formed on the inside face of nozzle closure 24. As shown, the igniter 56 is retained by an igniter cup 58 made of a material such as cellulose acetate which will readily be consumed by the burning of the igniter. Igniter 56 is initiated by the blast of the primer or percussion cap (not shown) through aperture 60 formed in the nozzle closure 24. Upstream of the igniter 56, the space within the spacer tube 30 and any recess formed in the grain 14, such as shown at 34, forms the initial combustion chamber 62 for the burning of grain 14.
In operation, the igniter 56, when initiated, ignites the exposed surface 34 of grain 14, and the gases which are generated by this combustion are vented through nozzles 26 to launch and propel device 10. In this initial combustion phase, device 10 functions as a rocket; and assuming that the initial launch was from a ground position, the device 10 is propelled to altitude. As combustion of the grain continues, the flame front proceeds forward consuming both the grain 14 and the inhibitor 18. However, the insulation sleeve 36 protects the aft section 38 of the casing 12 against the high combustion temperatures within chamber 62.
When the flame front reaches shoulder 40, which as described previously is where sleeve 36 terminates, the inside wall of casing 12 becomes exposed to the high combustion temperatures. As a result, casing 12 melts or burns through at shoulder 40.
When burn-through occurs, casing 12 is thereby divided into separate forward and aft sections 20 and 38, respectively. The pressure within combustion chamber 62 at this time aids in moving these two component sections rapidly away from each other. Aft section 38 takes with it nozzle closure 24 and the remaining components within combustion chamber 62, namely, sleeve 36, spacer 30 and washer 32. Additionally, aft section 38 takes sheath 52 with it, freeing blades 44 of rotor 42. Rotor 42 now unfolds.
Since thrusting of forward section 20 has terminated, it now slows down, aided additionally by the braking effect of the unfolded rotor 42. Upward movement ceases and section 20 now descends to earth. Rotor 42 revolves to brake or retard the descent velocity. The grain 14 which has continued to burn during separation of the casing, now acts as a signaling source. For example, grain 14 can be a pyrotechnic candle or flare whose combustion emits light of great brilliancy to illuminate a vast area.
As the grain 14 burns, the forward section 20 of casing 12 is preferably also consumed so that it cannot shield the output of the signal source as might occur should the grain be permitted to burn up into the inside of the casing. The inhibitor 18 prevents the unscheduled combustion of the grain 14 upstream of the flame front so that the grain will burn as scheduled.
With reference now to FIG. 2, there is presented a longitudinal quarter-sectional view of an alternative embodiment of the rocket-powered signaling device 10. In this embodiment, the enclosed casing 12 is shown as having a loop 70 formed at its forward end. To this loop 70 is attached a parachute 72 which is used to lower the signaling device to earth following casing separation as hereinafter described.
The parachute 72 resides in a folded and compressed manner within a compartment defined at one end by the forward end of casing 12 and at the other by a flexible cap 74. Cylindrical sheath 52 forms the wall of the compartment. In this embodiment, sheath 52 is crimped to form an outwardly projecting ridge near its forward end, as shown at 76, to retain cap 74 in a snap fit. The aft end of this thin sheath 52 is joined to casing 12 by crimping around its entire periphery, as shown at 78. Other suitable forms of attachment can be used such as welding or soldering, the result being to ensure that the sheath is removed when the casing separates. The aft end of casing 12 is again closed by a nozzle closure 24 which is shown as being threaded into this casing. Nozzles 26, of which only one is shown in this view, are provided in closure 24, and a cup 56 is also formed for the igniter.
Within the casing 12, the grain 14 and its inhibitor 18 are bonded to the interior surface of the grain. A preformed initial burning surface 34 is again provided at the aft end of grain 14.
Casing 12 is made of a material, such as a molded plastic, which will melt and burn due to the high temperatures experienced in the combustion chamber 62 during the burning of grain 14. As shown, this casing is unitary in construction but has between its forward and aft ends a circumferential groove 80 formed thereon. This groove forms a weakened zone on the casing and permits control of the failure point of the casing 12 so that during operation the casing will separate into forward and aft sections 20 and 38, respectively, at approximately this predetermined zone.
In operation, the device of FIG. 2 is launched from a suitable launching mechanism (not shown). As described previously with regard to FIG. 1, the grain 14 is initially in its propellant phase and serves to propel the device along its in-flight course by exhausting the combustion gases through nozzles 76. The high temperature within combustion chamber 62 begins to melt the exposed interior of casing 12. Once sufficient melting has occurred, the casing will fail at its weakest point, namely, at the groove 80 as planned. The casing, of course, has a sufficient thickness to ensure that the desired distance or altitude has been attained prior to failure.
At failure, casing 12 separates into forward section 20 and aft section 38; and these two sections rapidly fall away from one another, aided by the high pressure within chamber 62. Aft section 38 carries with it sheath 52. At the forward end of the device 10, cap 74 is freed and falls away, permitting parachute 72 to deploy. Combustion of grain 14 in forward section 20 continues; and as this section is lowered to earth, the burning grain functions as a signaling device, e.g., flare or smoke signal. During this signaling phase, it is preferred that the forward section of the casing continues to melt or burn so as not to hunder the signaling function.
While the grains shown in FIGS. 1 and 2 are of unitary construction, it is to be understood that the grain can also be built up from individual segments. This arrangement is shown in a partial cross-sectional view in FIG. 3. The grain within casing 12 is composed of a plurality of cylindrical sections 14a, 14b, 14c and 14d. Sections 14a and 14b can be, as an example, composed of the signaling composition while sections 14c and 14d can be formed of propellant compositions. By building up the grain in this fashion, it permits different loading configurations to be obtained. For example, assuming that 14a and 14d are the basic signaling and propellant charges, respectively, then for further or extended signaling, section 14b is added while for greater altitude, section 14c of the propellant is also added. To accommodate this ability to tailor altitudes and signaling times to fit a desired mission, it will be convenient to have on hand a range of casing sizes, having various lengths and thicknesses. Each of the grain segments 14 is preferably formed with its own inhibitor 18 about its outer surface. During formation of the grain, each segment is bonded or otherwise attached to the interior of the casing 12 to ensure its retention therein during flight, and each interior segment face is preferably bonded or attached to the interior face which abuts it.
External of the casing 12 is formed a sheath 36, the purpose of which is again to retain the drag means against deployment until separation of the casing into two sections during operation. The particular drag device partially depicted in FIG. 3 is the rotor of FIG. 1 and is represented here by one of the blades 44 shown in folded position; however, it is obvious that a parachute or other convenient drag device can be utilized as well.
The casing 12 is again designed to be separated into two sections during operation. The casing in this embodiment, for purposes of illustrating the versatility of the present invention, is actually formed in two separate sections 20 and 38, which are then mated by a threaded joint 82. The aft section 38 is made of a flame-resistant material such as castable carbon while the forward section 20 is made of plastic or other suitable material which will melt and burn under the temperature of grain combustion. Thus, after launch, when the burning of grain 14 regresses to the point of joint 82, the plastic of forward section 20 melts and burns and permits rapid separation of these two casing sections. The aft section 32 falls away and carries with it the outer sheath 36 which releases the drag device as described in the earlier embodiments. The device thus changes over from a rocket to a signaling source.
During manufacture, the grain of FIGS. 1 and 2 and the grain sections of FIG. 3 can be either extruded or cast, depending on the characteristics of the composition. Other methods of manufacture can be followed; for example, the composition can be formed as a powder and then tightly packed into what becomes essentially a solid grain. If the composition of the grain or a grain section is homogeneous, then extrusion is an economical form of manufacture since the grain is continuously extruded and then cut to size. The actual initial burning surface configuration employed can be other than shown since the particular preformed surface design 34 is not critical to successful operation.
The propellant used can be composed of any of a number of compositions well-known in the published art. The propellant can be of the composite type comprising an organic binder and oxidizer. The binder can be, for example, polyvinyl chloride, polyester, polybutadiene, acrylate, polyamide, polyurethane, cellulose acetate with or without conventional plasticizers. The oxidizer can be, for example, ammonium, alkali metal (e.g., Na, K, Li) or alkaline earth metal (e.g., Ca, Sr) chlorate, perchlorate or nitrate. The propellant can also be of the double-base type, e.g., nitrocellulose plasticized with a nitrated binder such as nitroglycerine. Conventional additives, such as burning-rate modifiers, coolants, stabilizers, and the like can also be incorporated into the composition. Metal fuels, such as A1, Mg, Zr, and B, can also be incorporated. An example of a suitable solid propellant is a plastisol composed primarily of an ammonium perchlorate oxidizer, polyvinyl chloride binder, and an organic ester plasticizer; however, other propellant compositions are equally suitable.
The addition of the signaling device composition can be accomplished in several ways. Certain compositions, such as those for creating colored flares, can be added to the propellant during manufacture. For example, a suitable red flare additive is strontium nitrate which can replace a portion of the propellant oxidizer, e.g., ammonium perchlorate in the plastisol propellant example of the preceding paragraph. For a green flare, barium nitrate would be substituted. In both cases, the chlorine which reacts with the additive to produce the emitter having the desired color is found in the source of remaining ammonium perchlorate. Where feasible, the grain can be tailored during manufacture to have it substantially void of any signaling composition in its aft region which is intended to burn during the rocket propulsion phase, thereby having only the forward end of the grain loaded with a signaling composition. Another method of grain manufacture is as defined previously with regard to FIG. 3 where the signaling composition and the propellant are made separately and then joined together to form the grain 14. For example, for colored smoke generation, a suitable composition is an intimate mix of fuel (e.g., sulfur or sugar), vaporizable organic dye, chlorate (e.g, potassium perchlorate) oxidizer, and perhaps a coolant such as sodium bicarbonate. This powdery composition is then tightly pressed, and the resulting solid grain section is combined with the solid propellant grain section to form the grain 14. If the generation of white smoke is desired, an example of a suitable composition is a pressed grain of a conventional HC composition. For illuminating candles, the grain can be made, for example, by pressing a conventional sodium nitrate metal fuel composition, although there are other known and suitable compositions that can be cast as well.
While the present invention has now been described with respect to particular embodiments thereof, it is evident that changes may now be made by someone skilled in the art to the construction, composition, and arrangement of parts without departing from the spirit and scope of the present invention as defined by the appended claims.
The present invention relates to a rocket-powered signaling device of the general type in which the signaling means becomes detached from the rocket motor in flight and is then suspended from a drag device, such as a parachute or rotor vanes, as it is lowered to earth. Examples of signaling means which are used are pyrotechnic candles and smoke generators.
In the prior art of rocket-propelled signaling devices, it is generally the practice to construct the device with the propellant formed separate from the composition forming the signaling means so that the combustion of the former can not adversely affect the latter. Once the propellant has been consumed or the device has reached a predetermined altitude, the signaling means is mechanically expelled from the rocket body or alternatively, the two parts are detached such as by an explosive charge. The end result is that the signaling means is freed to enable it to return to earth by a parachute, rotor vanes, or other suitable drag device.
While certain of these devices might operate satisfactorily, their designs entail unnecessary manufacturing cost, complexity, and weight for what should ideally be a functionally simple, lightweight, and economical device.
SUMMARY OF THE INVENTION
The present invention improves upon state-of-the-art, rocket-powered signaling devices by utilizing the same grain both as a propellant for powering or thrusting the device during the initial combustion phase and then as the signaling means during the subsequent combustion phase.
The casing which houses the grain is designed to become separated at a predetermined point by the temperature of the burning grain, thereby permitting the device to change from a rocket into a signaling device with attendant deployment of a drag means for lowering the device to earth.
The present invention provides for simplicity in design, ruggedness in construction and economical manufacture. The various features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of this invention, its operating advantages and specific objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a preferred embodiment of the present invention in a longitudinal cross-sectional view;
FIG. 1a is a partial plan view of a drag rotor used in the present invention;
FIG. 2 shows an alternative embodiment in quarter section; and
FIG. 3 shows a partial view of another embodiment in partial cross-section.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With particular reference to FIG. 1 showing a preferred embodiment of the present invention, there is shown a rocket-powered signaling device indicated generally by the numeral 10. This device 10 includes an elongated, cylindrical casing 12 made of a suitable material, such as aluminum, which will burn through in response to the high combustion temperatures experiecned during combustion of a grain 14 housed therein. The grain 14 is bonded to the forward, closed end 16 of casing 12. A conventional inhibitor 18 lines the outer periphery of the grain 14 throughout its length, and during operation, this inhibitor prevents the ignition of the grain 14 forward of the end-burning flame front. The inhibited grain 14 fits tightly within what is here termed the forward section 20 of casing 12.
The open aft end 22 of casing 12 is closed by nozzle closure 24 made preferably of graphite or a reinforced phenolic material which can withstand the temperature of the combustion gases. A plurality of nozzle apertures 26 is formed in nozzle closure 24. Casing 12 is crimped over the aft end of nozzle closure 24 as shown at 28 to retain this closure in the assembly.
The aft end of grain 14 is spaced from closure 24 by a tube 30 and an annular washer 32. Washer 32 is preferably made of a material such as spring steel which will serve to cushion the grain 14 during transportation and launch. Grain 14 is here shown as having a shaped uninhibited end face 34 to provide a larger initial burning surface than that of a flat face; however, the particular shape of the initial burning surface is not critical to the present invention.
As shown in FIG. 1, the periphery of inhibited grain 14 and the periphery of tube 30 are in substantial alignment within the device 10. A sleeve 36 surrounds and closely contacts the lower part of this grain 14 and the tube 30. At its periphery, sleeve 36 is in tight engagement with the inside of casing 12, and at its aft end abuts and is retained by nozzle closure 24. Sleeve 36 is an insulator and is used to insulate the casing 12 from the high-temperature combustion gases generated by the burning of grain 34 during operation of the device, as later described. It can be made of a phenolic impregnated paper or other suitable insulating material.
Casing 12 is of a substantially constant diameter in its forward section 20, but as shown has an enlarged diameter toward its aft end 22 to accommodate sleeve 36. This enlarged portion is here termed the aft section 38 of the casing 12. A shoulder 40 is formed between the forward section 20 and the aft section 38. Within casing 12, the forward end of sleeve 36 terminates adjacent to this shoulder 40.
Connected at the forward end 16 of casing 12 is a drag device whose function is to slow or retard the return to earth of the rocket-powered signaling device 10 while this device is in its signaling phase. As depicted here, the drag device is a rotor 42 made of spring steel or other suitable material which permits it to be folded into the position shown where its blades 44 are alongside the casing 12.
With reference also now to FIG. 1a, the unfolded or deployed rotor 42 is shown in partial plan view. Rotor 42 is depicted as having four blades 44 extending outwardly from a central hub 46. This hub is provided with a centrally-located hole 48 which is designed to receive a retaining button 50 in a losse fit. Button 50 is welded to the forward end 16 of casing 12. When the device 10 is at altitude and rotor 42 is unfolded, the blades 44 are so designed that the flow of air through the rotor as the device falls causes windmilling rotation, thus braking or retarding the velocity of the fall and thereby extending the signaling time.
Rotor 42 is maintained in a folded position on device 10 by a thin tubular sheath 52. At its aft end, sheath 52 is crimped at several points 54 about the end of casing 12, and this crimping in combination with the outward pressure of the rotor blades 44 and the generally close fit about aft section 38 is sufficient to hold sheath 52 in place.
In the operation of the FIG. 1 embodiment, the device 10 is first inserted in a conventional launcher tube (not shown) having a dimaeter sized to receive this device in a close fit. Such a launcher tube would include conventional firing means such as a trigger, striker, percussion cap and igniter. Alternatively, the igniter can be included in the device 10 by positioning it in an appropriate recess formed on the inside face of nozzle closure 24. As shown, the igniter 56 is retained by an igniter cup 58 made of a material such as cellulose acetate which will readily be consumed by the burning of the igniter. Igniter 56 is initiated by the blast of the primer or percussion cap (not shown) through aperture 60 formed in the nozzle closure 24. Upstream of the igniter 56, the space within the spacer tube 30 and any recess formed in the grain 14, such as shown at 34, forms the initial combustion chamber 62 for the burning of grain 14.
In operation, the igniter 56, when initiated, ignites the exposed surface 34 of grain 14, and the gases which are generated by this combustion are vented through nozzles 26 to launch and propel device 10. In this initial combustion phase, device 10 functions as a rocket; and assuming that the initial launch was from a ground position, the device 10 is propelled to altitude. As combustion of the grain continues, the flame front proceeds forward consuming both the grain 14 and the inhibitor 18. However, the insulation sleeve 36 protects the aft section 38 of the casing 12 against the high combustion temperatures within chamber 62.
When the flame front reaches shoulder 40, which as described previously is where sleeve 36 terminates, the inside wall of casing 12 becomes exposed to the high combustion temperatures. As a result, casing 12 melts or burns through at shoulder 40.
When burn-through occurs, casing 12 is thereby divided into separate forward and aft sections 20 and 38, respectively. The pressure within combustion chamber 62 at this time aids in moving these two component sections rapidly away from each other. Aft section 38 takes with it nozzle closure 24 and the remaining components within combustion chamber 62, namely, sleeve 36, spacer 30 and washer 32. Additionally, aft section 38 takes sheath 52 with it, freeing blades 44 of rotor 42. Rotor 42 now unfolds.
Since thrusting of forward section 20 has terminated, it now slows down, aided additionally by the braking effect of the unfolded rotor 42. Upward movement ceases and section 20 now descends to earth. Rotor 42 revolves to brake or retard the descent velocity. The grain 14 which has continued to burn during separation of the casing, now acts as a signaling source. For example, grain 14 can be a pyrotechnic candle or flare whose combustion emits light of great brilliancy to illuminate a vast area.
As the grain 14 burns, the forward section 20 of casing 12 is preferably also consumed so that it cannot shield the output of the signal source as might occur should the grain be permitted to burn up into the inside of the casing. The inhibitor 18 prevents the unscheduled combustion of the grain 14 upstream of the flame front so that the grain will burn as scheduled.
With reference now to FIG. 2, there is presented a longitudinal quarter-sectional view of an alternative embodiment of the rocket-powered signaling device 10. In this embodiment, the enclosed casing 12 is shown as having a loop 70 formed at its forward end. To this loop 70 is attached a parachute 72 which is used to lower the signaling device to earth following casing separation as hereinafter described.
The parachute 72 resides in a folded and compressed manner within a compartment defined at one end by the forward end of casing 12 and at the other by a flexible cap 74. Cylindrical sheath 52 forms the wall of the compartment. In this embodiment, sheath 52 is crimped to form an outwardly projecting ridge near its forward end, as shown at 76, to retain cap 74 in a snap fit. The aft end of this thin sheath 52 is joined to casing 12 by crimping around its entire periphery, as shown at 78. Other suitable forms of attachment can be used such as welding or soldering, the result being to ensure that the sheath is removed when the casing separates. The aft end of casing 12 is again closed by a nozzle closure 24 which is shown as being threaded into this casing. Nozzles 26, of which only one is shown in this view, are provided in closure 24, and a cup 56 is also formed for the igniter.
Within the casing 12, the grain 14 and its inhibitor 18 are bonded to the interior surface of the grain. A preformed initial burning surface 34 is again provided at the aft end of grain 14.
Casing 12 is made of a material, such as a molded plastic, which will melt and burn due to the high temperatures experienced in the combustion chamber 62 during the burning of grain 14. As shown, this casing is unitary in construction but has between its forward and aft ends a circumferential groove 80 formed thereon. This groove forms a weakened zone on the casing and permits control of the failure point of the casing 12 so that during operation the casing will separate into forward and aft sections 20 and 38, respectively, at approximately this predetermined zone.
In operation, the device of FIG. 2 is launched from a suitable launching mechanism (not shown). As described previously with regard to FIG. 1, the grain 14 is initially in its propellant phase and serves to propel the device along its in-flight course by exhausting the combustion gases through nozzles 76. The high temperature within combustion chamber 62 begins to melt the exposed interior of casing 12. Once sufficient melting has occurred, the casing will fail at its weakest point, namely, at the groove 80 as planned. The casing, of course, has a sufficient thickness to ensure that the desired distance or altitude has been attained prior to failure.
At failure, casing 12 separates into forward section 20 and aft section 38; and these two sections rapidly fall away from one another, aided by the high pressure within chamber 62. Aft section 38 carries with it sheath 52. At the forward end of the device 10, cap 74 is freed and falls away, permitting parachute 72 to deploy. Combustion of grain 14 in forward section 20 continues; and as this section is lowered to earth, the burning grain functions as a signaling device, e.g., flare or smoke signal. During this signaling phase, it is preferred that the forward section of the casing continues to melt or burn so as not to hunder the signaling function.
While the grains shown in FIGS. 1 and 2 are of unitary construction, it is to be understood that the grain can also be built up from individual segments. This arrangement is shown in a partial cross-sectional view in FIG. 3. The grain within casing 12 is composed of a plurality of cylindrical sections 14a, 14b, 14c and 14d. Sections 14a and 14b can be, as an example, composed of the signaling composition while sections 14c and 14d can be formed of propellant compositions. By building up the grain in this fashion, it permits different loading configurations to be obtained. For example, assuming that 14a and 14d are the basic signaling and propellant charges, respectively, then for further or extended signaling, section 14b is added while for greater altitude, section 14c of the propellant is also added. To accommodate this ability to tailor altitudes and signaling times to fit a desired mission, it will be convenient to have on hand a range of casing sizes, having various lengths and thicknesses. Each of the grain segments 14 is preferably formed with its own inhibitor 18 about its outer surface. During formation of the grain, each segment is bonded or otherwise attached to the interior of the casing 12 to ensure its retention therein during flight, and each interior segment face is preferably bonded or attached to the interior face which abuts it.
External of the casing 12 is formed a sheath 36, the purpose of which is again to retain the drag means against deployment until separation of the casing into two sections during operation. The particular drag device partially depicted in FIG. 3 is the rotor of FIG. 1 and is represented here by one of the blades 44 shown in folded position; however, it is obvious that a parachute or other convenient drag device can be utilized as well.
The casing 12 is again designed to be separated into two sections during operation. The casing in this embodiment, for purposes of illustrating the versatility of the present invention, is actually formed in two separate sections 20 and 38, which are then mated by a threaded joint 82. The aft section 38 is made of a flame-resistant material such as castable carbon while the forward section 20 is made of plastic or other suitable material which will melt and burn under the temperature of grain combustion. Thus, after launch, when the burning of grain 14 regresses to the point of joint 82, the plastic of forward section 20 melts and burns and permits rapid separation of these two casing sections. The aft section 32 falls away and carries with it the outer sheath 36 which releases the drag device as described in the earlier embodiments. The device thus changes over from a rocket to a signaling source.
During manufacture, the grain of FIGS. 1 and 2 and the grain sections of FIG. 3 can be either extruded or cast, depending on the characteristics of the composition. Other methods of manufacture can be followed; for example, the composition can be formed as a powder and then tightly packed into what becomes essentially a solid grain. If the composition of the grain or a grain section is homogeneous, then extrusion is an economical form of manufacture since the grain is continuously extruded and then cut to size. The actual initial burning surface configuration employed can be other than shown since the particular preformed surface design 34 is not critical to successful operation.
The propellant used can be composed of any of a number of compositions well-known in the published art. The propellant can be of the composite type comprising an organic binder and oxidizer. The binder can be, for example, polyvinyl chloride, polyester, polybutadiene, acrylate, polyamide, polyurethane, cellulose acetate with or without conventional plasticizers. The oxidizer can be, for example, ammonium, alkali metal (e.g., Na, K, Li) or alkaline earth metal (e.g., Ca, Sr) chlorate, perchlorate or nitrate. The propellant can also be of the double-base type, e.g., nitrocellulose plasticized with a nitrated binder such as nitroglycerine. Conventional additives, such as burning-rate modifiers, coolants, stabilizers, and the like can also be incorporated into the composition. Metal fuels, such as A1, Mg, Zr, and B, can also be incorporated. An example of a suitable solid propellant is a plastisol composed primarily of an ammonium perchlorate oxidizer, polyvinyl chloride binder, and an organic ester plasticizer; however, other propellant compositions are equally suitable.
The addition of the signaling device composition can be accomplished in several ways. Certain compositions, such as those for creating colored flares, can be added to the propellant during manufacture. For example, a suitable red flare additive is strontium nitrate which can replace a portion of the propellant oxidizer, e.g., ammonium perchlorate in the plastisol propellant example of the preceding paragraph. For a green flare, barium nitrate would be substituted. In both cases, the chlorine which reacts with the additive to produce the emitter having the desired color is found in the source of remaining ammonium perchlorate. Where feasible, the grain can be tailored during manufacture to have it substantially void of any signaling composition in its aft region which is intended to burn during the rocket propulsion phase, thereby having only the forward end of the grain loaded with a signaling composition. Another method of grain manufacture is as defined previously with regard to FIG. 3 where the signaling composition and the propellant are made separately and then joined together to form the grain 14. For example, for colored smoke generation, a suitable composition is an intimate mix of fuel (e.g., sulfur or sugar), vaporizable organic dye, chlorate (e.g, potassium perchlorate) oxidizer, and perhaps a coolant such as sodium bicarbonate. This powdery composition is then tightly pressed, and the resulting solid grain section is combined with the solid propellant grain section to form the grain 14. If the generation of white smoke is desired, an example of a suitable composition is a pressed grain of a conventional HC composition. For illuminating candles, the grain can be made, for example, by pressing a conventional sodium nitrate metal fuel composition, although there are other known and suitable compositions that can be cast as well.
While the present invention has now been described with respect to particular embodiments thereof, it is evident that changes may now be made by someone skilled in the art to the construction, composition, and arrangement of parts without departing from the spirit and scope of the present invention as defined by the appended claims.