U.S. patent application number 14/299889 was filed with the patent office on 2015-02-19 for electrode ignition and control of electrically ignitable materials.
The applicant listed for this patent is Digital Solid State Propulsion, Inc.. Invention is credited to Charles GRIX, Wayne N. SAWKA.
Application Number | 20150047526 14/299889 |
Document ID | / |
Family ID | 41319082 |
Filed Date | 2015-02-19 |
United States Patent
Application |
20150047526 |
Kind Code |
A1 |
SAWKA; Wayne N. ; et
al. |
February 19, 2015 |
ELECTRODE IGNITION AND CONTROL OF ELECTRICALLY IGNITABLE
MATERIALS
Abstract
Apparatus for providing electrically initiated and/or controlled
combustion of electrically ignitable propellants is provided. In
one example, the apparatus includes a volume of electrically
ignitable propellant (liquid and/or gas) capable of self sustaining
combustion, and electrodes operable to ignite the propellant. The
apparatus may further include a power supply and controller in
electrical communication with the electrodes for supplying a
potential across the electrodes to initiate combustion of the
propellant and/or control the rate of combustion of the propellant.
Various configurations and geometries of the propellant,
electrodes, and apparatus are possible. In one example, the
electrodes are supplied a direct current, which causes combustion
of the propellant at the positive electrode. In another example,
the electrodes are supplied an alternating current, which initiates
combustion of the propellant at both electrodes.
Inventors: |
SAWKA; Wayne N.; (Reno,
NV) ; GRIX; Charles; (Citrus Heights, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Digital Solid State Propulsion, Inc. |
Reno |
NV |
US |
|
|
Family ID: |
41319082 |
Appl. No.: |
14/299889 |
Filed: |
June 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12989639 |
Jan 7, 2011 |
8857338 |
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PCT/US09/44206 |
May 15, 2009 |
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14299889 |
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61053971 |
May 16, 2008 |
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61053900 |
May 16, 2008 |
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61053916 |
May 16, 2008 |
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Current U.S.
Class: |
102/374 ;
102/202 |
Current CPC
Class: |
F02K 9/95 20130101; F41A
1/04 20130101; E21B 43/263 20130101; F42C 19/08 20130101; E21B
43/248 20130101; F23R 7/00 20130101; F42C 19/0819 20130101 |
Class at
Publication: |
102/374 ;
102/202 |
International
Class: |
F42C 19/08 20060101
F42C019/08; F41A 1/04 20060101 F41A001/04 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0004] Certain aspects described herein were made in part during
work supported by a Small Business Innovative Research contract
from the United States Navy (N65538-07-M-0119) "Miniaturized
Safe-Fuel Electrically Controlled Divert & Attitude Control
System" and Office of Naval Research, DE Technologies Inc.
subcontract #A630-1341, Tactical Urban Strike Weapon: Safe
Fire-From-Enclosure the Marine Alternative to Double-base
Propellants. The government may have certain rights in the
inventions.
Claims
1-30. (canceled)
31. Apparatus for providing electrically initiated and/or
controlled combustion, the apparatus comprising: a volume of
electrically ignitable propellant, wherein the electrically
ignitable propellant is ignitable in response to the application of
electrical power there through, and is further capable of self
sustaining combustion; and two wire electrodes operable to ignite
the propellant.
32. The apparatus of claim 31, wherein the electrically ignitable
propellant comprises liquid propellant.
33. The apparatus of claim 32, wherein the apparatus is operable to
urge the liquid propellant into contact with the electrodes for
combustion.
34. The apparatus of claim 31, wherein applying direct current to
the electrodes causes combustion of the electrically ignitable
propellant at the contact of a positive electrode with the
electrically ignitable propellant.
35. The apparatus of claim 31, wherein applying alternating current
to the electrodes causes combustion of the electrically ignitable
propellant at the contact of both electrodes with the electrically
ignitable propellant.
36. The apparatus of claim 31, wherein the electrically ignitable
propellant is ignited by passing current there through via the
electrodes.
37. The apparatus of claim 31, wherein at least one of the
electrodes includes an insulator material insulating a portion of
the electrode from the electrically ignitable propellant.
38. The apparatus of claim 31, further comprising a power source
coupled to the electrodes and operable to vary current passing
through at least a portion of the electrically ignitable
propellant.
39. The apparatus of claim 31, further comprising a pressurization
device for increasing pressure on the electrically ignitable
propellant, wherein the current required for igniting the
electrically ignitable propellant is reduced with increased
pressure.
40. The apparatus of claim 39, wherein the current required for
igniting the electrically ignitable propellant is not met by the
apparatus absent the increase in pressure from the pressurization
device.
41. The apparatus of claim 39, wherein the pressurization device
includes one or more of an explosive charge, shock impact,
compressed gas, pneumatic pressurization, or valve device.
42. The apparatus of claim 31, wherein the two electrodes comprise
coaxially disposed electrodes.
43. The apparatus of claim 31, wherein the volume of electrically
ignitable propellant comprises a cylindrical ring of propellant
defining a core region, the core region operable to channel exhaust
gasses from the assembly during combustion.
44. The apparatus of claim 31, further comprising a nozzle for
passing combustion gases.
45. The apparatus of claim 44, wherein the electrodes extend
through the nozzle for causing ignition of propellant passing there
through.
46. The apparatus of claim 31, further comprising an exhaust region
for passing combustion gases form the structure, wherein the
electrodes extend through the exhaust region for causing ignition
of propellant passing there through.
47. The apparatus of claim 31, further comprising a projectile
operable to be propelled by combustion of the electrically
ignitable propellant.
Description
RELATED APPLICATIONS
[0001] This application claims priority from U.S. provisional
patent application Ser. Nos. 61/053,971, filed May 16, 2008,
entitled "Electrode Ignition and control of electrically ignitable
materials", U.S. Ser. No. 61/053,916, filed May 16, 2008, entitled
"Family of Metastable Intermolecular Composites Utilizing Energetic
Liquid Oxidizers with NanoParticle Fuels In Gel-Sol Polymer
Network", and U.S. Ser. No. 61/053,900, filed on May 16, 2008,
"Family of Modifiable High Performance Electrically Ignitable Solid
Propellants" (Attorney Docket No. 280.01), all of which are hereby
incorporated by reference herein in its entirety for all
purposes.
[0002] This application is further related to previously filed U.S.
patent application Ser. No. 11/305,742, filed Dec. 16, 2005,
entitled "CONTROLLABLE DIGITAL SOLID STATE CLUSTER THRUSTERS FOR
ROCKET PROPULSION AND GAS GENERATION", which is hereby incorporated
by reference herein in its entirety for all purposes. Further, this
application is related to three U.S. provisional patent
applications filed on May 16, 2008, U.S. Ser. No. 61/053,916,
entitled "Family of Metastable Intermolecular Composites Utilizing
Energetic Liquid Oxidizers with NanoParticle Fuels In Gel-Sol
Polymer Network", U.S. Ser. No. 61/053,900, "Family of Modifiable
High Performance Electrically Ignitable Solid Propellants"
(Attorney Docket No. 280.01), and U.S. Ser. No. 61/053,956,
"Physical Destruction of Electrical Device and Method for
Triggering Same", all of which are hereby incorporated by reference
herein in their entirety. This application is further related to
the following PCT application and US application filed on an even
date herewith: U.S. Ser. No. ______ [[attorney docket no. 280.03]],
"Family of Metastable Intermolecular Composites Utilizing Energetic
Liquid Oxidizers with NanoParticle Fuels In Gel-Sol Polymer
Network," and PCT Ser. No. ______ [[attorney docket no. 280.07]]
"Family of Modifiable High Performance Electrically Controlled
Propellants and Explosives," filed on an even date herewith, both
of which are incorporated herein by reference.
SECRECY ORDER
[0003] The present application incorporates by reference U.S.
patent application Ser. Nos. 11/305,742 and 10/136,786, both of
which were previously under a secrecy order under 37 CFR 5.2.
BACKGROUND
[0005] 1. Field:
[0006] The present invention relates generally to electrode
ignition and control of combustible materials, and in one
particular example to electrode ignition and control of an
electrically ignitable propellant which may be used for thrusters,
motors, gas generators, explosives, igniters, electric matches,
pyrotechnic displays, oil field down hole gas generators, fire
suppression devices, air bags, electric guns, and the like.
[0007] 2. Description of Related Art
[0008] Digital propulsion systems, and in particular, arrays of
microthrusters are known. Generally, a digital propulsion system
includes a two-dimensional array of individually addressable
thrusters, which may be selectively fired for purposes of
propulsion or gas generation. In one example, described generally
in "Digital MicroPropulsion", by Lewis et al., Sensors and
Actuators A, Physical, 2000, 80(2) pp 143-154, and which is
incorporated by reference, an array of microthrusters are formed,
where each microthruster includes a micro-resistor, thrust chamber,
and rupture diaphragm. A propellant is disposed in the thrust
chamber and may be ignited by energizing (and thus heating) the
micro-resistor to a sufficient temperature to ignite the
propellant. When the propellant is ignited the pressure in the
chamber rises until the diaphragm is ruptured, resulting in the
ejection of material from the chamber. The ejection of material
results in a thrust imparted to the microthruster. Such
microthrusters may be manufactured as dies or chips including an
array of varying number and sized microthrusters. Further, the
microthrusters may be selectively addressed to ignite and impart
varying amounts of thrust.
SUMMARY
[0009] In one aspect of the present invention an apparatus for
providing electrically initiated and/or controlled combustion of
electrically ignitable propellants is provided. In one example, the
apparatus includes a volume of electrically ignitable propellant
(solid and/or liquid), which is capable of self sustaining
combustion, and two (or more) electrodes operable to ignite the
propellant. The apparatus may further include a power supply and
controller in electrical communication with the electrodes for
supplying a potential across the electrodes to initiate combustion
of the propellant and/or control the rate of combustion of the
propellant. For instance, by increasing or decreasing the power and
current supplied through the propellant the rate of combustion may
be varied.
[0010] Various configurations and geometries of the propellant,
electrodes, and apparatus are described. In one example, the
electrodes are in electrical contact with the electrically
ignitable propellant and are supplied a direct current, which may
cause combustion of the electrically ignitable propellant at the
contact location of the positive electrode with the electrically
ignitable propellant. In another example, the electrodes are
supplied an alternating current, which may initiate nearly
simultaneously combustion of the electrically ignitable propellant
at the contact locations of the electrodes with the electrically
ignitable propellant. In some examples, one or more of the
electrodes may include an insulator material insulating a portion
of the electrode from the electrically ignitable propellant (which
may burn away with combustion of the propellant).
[0011] In some examples, the volume of electrically ignitable
propellant includes liquid propellant such as hydroxylammonium
nitrate (HAN) propellants. The propellant may be urged (e.g.,
flowed, streamed, or pumped) to the electrodes for ignition. The
liquid propellant may be urged to the electrodes by pumping
pressure.
[0012] In one example, the apparatus further comprises a
pressurization device for increasing pressure on the electrically
ignitable propellant, where the current required for igniting the
electrically ignitable propellant is reduced with increased
pressure thereon. Further, in one example, the current required for
igniting the propellant cannot (or will not) be met by the
apparatus absent the increase in pressure from the pressurization
device. Such an apparatus may provide for a safe, two-stage
ignition, e.g., requiring both the pressurization device and the
electrodes to be activated to initiate combustion. The
pressurization device may include one or more of an explosive
charge, shock impact, compressed gas, pneumatic pressurization, or
valve operable to at least temporarily increase the pressure on the
propellant.
[0013] In other examples, multiple volumes of propellant (or
"grains") may be included in a common assembly to provide a two or
three dimensional array of combustion volumes. Such an assembly may
include a plurality of grain elements, each grain element
comprising a volume of electrically ignitable propellant capable of
self sustaining combustion, and electrodes associated with the
plurality of grain elements, the electrodes adapted for selectively
igniting at least one of the plurality of grain elements. In one
example, the electrodes may include a common ground and multiple
positive electrodes for selectively or entirely combusting the
plurality of grain elements.
[0014] The present inventions and various aspects are better
understood upon consideration of the detailed description below in
conjunction with the accompanying drawings and claims.
BRIEF DESCRIPTION OF THE FIGURES
[0015] FIGS. 1A and 1B illustrate cross-sectional side and top
views, respectively, of a first exemplary structure including
electrodes and an electrically ignitable propellant.
[0016] FIGS. 2A-2C illustrate an exploded view, perspective
cross-sectional side view, and cross-sectional side view,
respectively, of a second exemplary structure including electrodes
and an electrically ignitable propellant.
[0017] FIGS. 2D and 2E illustrate cross-sectional side views of
another exemplary structure including an electrically ignitable
propellant and an electrode extending through the nozzle/exhaust
region of the structure.
[0018] FIGS. 3A and 3B illustrate exemplary ignition processes of
electrical propellant for different electrode configurations.
[0019] FIGS. 4A and 4B illustrate exemplary ignition processes of
electrical propellant for different electrode configurations.
[0020] FIGS. 5A-5D illustrate exemplary structures and geometries
for electrodes and electrically ignitable propellant.
[0021] FIG. 6 illustrates perspective and cross-sectional views of
an exemplary "core burning" structure including wire electrodes and
electrically ignitable propellant.
[0022] FIG. 7 illustrates perspective and cross-sectional views of
an exemplary "slot burning" structure including wire electrodes and
electrically ignitable propellant.
[0023] FIG. 8 illustrates perspective and cross-sectional views of
an exemplary "star" geometry structure including wire electrodes
and electrically ignitable propellant.
[0024] FIG. 9 illustrates an exemplary "straw" structure including
wire electrodes and electrically ignitable propellant.
[0025] FIG. 10 illustrates an exemplary "end-burner" structure
including wire electrodes and electrically ignitable
propellant.
[0026] FIGS. 11A and 11B illustrate two exemplary methods of
initiation of electrically ignitable propellant using pressure and
electrical power.
[0027] FIG. 12 illustrates an exemplary structure for initiation of
electrically ignitable liquid propellant.
[0028] FIG. 13 illustrates an exemplary structure and device for an
electrically ignitable projectile or gun.
[0029] FIG. 14 illustrates an exemplary structure for initiation of
electrically ignitable propellant.
DETAILED DESCRIPTION
[0030] The following description is presented to enable a person of
ordinary skill in the art to make and use various aspects and
examples of the present invention. Descriptions of specific
materials, techniques, and applications are provided only as
examples. Various modifications to the examples described herein
will be readily apparent to those of ordinary skill in the art, and
the general principles defined herein may be applied to other
examples and applications without departing from the spirit and
scope of the invention. Thus, the present invention is not intended
to be limited to the examples described and shown, but is to be
accorded the scope consistent with the appended claims.
[0031] In one aspect of the present invention, structures and
systems for electrical ignition and/or control of solid or liquid
propellants are described. In one example, a structure includes
energetic materials that may be broadly described as electrically
ignitable propellants (for example, as described in Ser. Nos.
10/136,786, 10/423,072, 11,787,001, and 08/758,431 to Katzakian et
al., and in "Family of Modifiable High Performance Electrically
Controlled Propellants and Explosives" and "Family of Metastable
Intermolecular Composites Utilizing Energetic Liquid Oxidizers with
NanoParticle Fuels In Gel-Sol Polymer Network," incorporated herein
by reference, which can be ignited and controlled, at least in
part, by the application of electrical power as an electrical
circuit (and not an uncontrolled pyrotechnic). For example, passing
electrical current through the propellant causes
ignition/combustion to occur at/along electrode surfaces. The use
of an electrically ignitable propellant obviates the need for
igniters (e.g., spark or other thermal igniters such as resistor
elements or the like) to initiate propellant combustion.
Accordingly, in examples described herein, combustion of a specific
volume of propellant (referred to herein as a "grain" or "grain
element" of propellant) is initiated and/or controlled by
electrical power between electrodes and through the propellant.
Generally, electrical power from a direct current (DC) source can
be operated to cause combustion to occur at and/or along the
positive electrode, and DC power and electrode polarity can be used
to spread the flame front across an end surface of the propellant.
Additionally, electrical power from an alternating current (AC)
power source can be controlled to cause combustion to occur at both
electrodes.
[0032] In some examples, electrical ignition of the material
occurring along one or more electrodes can be modified or
controlled using burn-away electrical insulators such as Teflon,
polyethylene, or the like. Further, by varying the number of
ignition electrodes, polarities, and/or their geometry, the
propellant burn rate can be altered, up to and including the
explosive yield, efficiency, or rate. Exemplary geometries include,
but are not limited to, coaxial grains, sheets and plates, rolled
sheets or jellyrolls, core burning grains, slot burning grains,
star burning grains, straw burning grains, single or
multi-electrode end-burning grains, wired end-burners, and the
like.
[0033] Further, in some examples, a controller or power source may
be operable to control the electrodes to ignite the propellant as
well as control the burn rate of the propellant. For instance, by
varying the electrical power and current passing through the
propellant, the burn or combustion rate can be varied and increased
above the self sustained combustion rate of the propellant up to
and including supersonic-explosive rates. Further, stored
electrical charge supplied by the electrodes can be used to vary
the burning rate up to and including the explosive yield,
efficiency, or rate of the energetic material.
[0034] In some examples, the exemplary structures and propellant
can be used in combination with a compression device such as a
pyrotechnic/explosive charge (e.g., squibs, electric matches,
blasting caps, detonators, or the like), shock impact, compressed
gas pneumatic pressurization and/or valve, including pressure burst
disks to increase reaction pressures and cause faster ignition of
the energetic material at and along the electrodes. For instance,
the threshold current for initiating combustion of some of the
exemplary propellants decreases with increasing pressure. The
structure including the propellant may be included with a
compression device to form a safe two-stage ignition system for the
propellant. For example, a power supply may provide the propellant
with insufficient electrical power to ignite at normal environment
pressures, but sufficient to ignite when the compression device is
also activated. Likewise, the pressure increase (and/or heat) from
the compression device will not cause ignition of the energetic
material with the electrical power being supplied.
[0035] Exemplary structures described herein may be applicable to
various fields including, but not limited to, defense, aerospace,
liquid (monopropellant) rocket engines, automotives, air bags,
electronics, blasting (mining/oil field services, e.g., oil field
down hole gas generators for rock fracturing and enhanced oil/gas
recovery), electric guns, industrial tools, fire suppression,
entertainment-special effects, and the like. In one particular
example, the structures may be used to ignite, throttle,
extinguish, and re-start the combustion of high performance solid
or liquid rocket propellants. Additionally, exemplary methods and
systems may be used as gas generators in a variety of applications.
Various examples described herein may be used in rockets, missiles,
spacecraft, aircraft, sea-craft, oil/gas field services, and land
vehicles for propulsion or as an on-demand gas generator. The
ability to control propellant burn rate further allows tailoring of
the pressure wave to specific rock lithology for maximum facture
propagation as described in R. A. Schmidt, N. R. Warpinski and P.
W. Cooper: In Situ Evaluation of Several Tailored-pulse
Well-shooting Concepts, SPE/DOE 8934 pp 105-116 Symposium on
Unconventional Gas Recovery, Pittsburgh, Pa. May 18-21, 1980, which
is incorporated herein by reference.
[0036] Apparatus described herein, including an electrically
ignitable propellant, may be desirable because they are
electrically controllable and in many examples have no moving
parts. Grain elements can also be stacked into three-dimensional
arrays, without the need to separate or channel hot combustion
gases away from adjacent unused propellant grains. Scaling of
manufacturing methods spans from those of the semiconductor
industry for microchips, such as photo etching and chemical vapor
deposition, upwards to drill, stamped, or molded dies layered
together for larger devices. These manufacturing methods may allow
mass production of these devices at relatively lower cost compared
to conventional thruster devices.
[0037] FIGS. 1A and 1B illustrate cross-sectional side and top
views, respectively, of a first exemplary structure 100 including
an electrically ignitable propellant 102. In this example,
structure 100 includes a single grain element or volume of
electrically ignitable propellant 102 to be ignited and/or
controlled by electrodes 101a and 101b. In operation, electrodes
101a and 101b conduct current through the electrically ignitable
propellant 102 causing combustion thereof. In this particular
example, the center electrode 101b includes an insulator 103 to
control the combustion of propellant 102; in particular, the
application of voltage to electrodes 101a and 101b initiates
combustion at the end of the structure 100 (to the right in FIG.
1A). As combustion of propellant 102 begins insulation 103 burns
away. As described in greater detail below, the polarities and
configuration of electrodes 100a, b, and insulation 103 may be
varied to ignite and control the combustion in various
fashions.
[0038] Propellant 102 may be disposed with electrode 101a (or a
suitable housing, not shown) in any manner, for example, cast,
poured, vacuum poured or the like into electrode 101a or other
suitable housing. The separation between electrodes 101a and 101b
may be varied for efficient combustion of propellant 102, which may
include HIPEP propellant (High Performance Electric Propellant).
HIPEP propellant is described, for example, in
AFRL-PR-ED-TR-2004-0076, "High Performance Electrically Controlled
Solution Solid Propellant," Arthur Katzakian and Charles Grix,
Final Report, the entire content of which is incorporated by
reference herein. Further, suitable propellants include those
described in "U.S. Ser. No. ______ [[attorney docket no. 280.03]],
"Family of Metastable Intermolecular Composites Utilizing Energetic
Liquid Oxidizers with NanoParticle Fuels In Gel-Sol Polymer
Network," and PCT Ser. No. ______ [[attorney docket no. 280.07]]
"Family of Modifiable High Performance Electrically Controlled
Propellants and Explosives," filed on an even date herewith and
incorporated by reference. In some examples, the propellant is
generally flexible when cured (e.g., is the case for HIPEP
propellant) and can be used with flexible foils or thin metal
layers for electrodes 101a and 101b to form various configurations,
such as spiral shapes or jelly roll designs.
[0039] The material of electrodes 101a and 101b, e.g., aluminum or
other suitable material, may be consumed during combustion of
propellant 102, thereby increasing the specific impulse of the
thruster or other device. In other examples, electrodes 101a and
101b may include stainless steel or the like so as to not be
consumed by the combustion. Additionally, insulation layer 103,
which may include Teflon or Phenolic coatings, may also be
combusted with propellant 102. As seen in FIG. 1A, insulation 103
does not extend to the end of electrode 101a such that a portion of
propellant 102 contacts opposing electrodes 101a and 101b near the
axial face of structure 100. The insulation layer 103 burns away in
front of the flame front, thereby sustaining a contact between
electrodes 101a and 101b and propellant 102. The power supplied to
electrodes 101a and 101b may be stopped or varied as described
herein to control the rate of combustion of propellant 102.
[0040] An exhaust port can be positioned generally at the axial top
and/or bottom axial face of structure 100. In one example, a
housing (not shown) may be included to cover the bottom axial
surface of structure 100 such that as propellant 102 is ignited and
combusted from the top axial surface and proceeds downward.
Further, multiple structures 100 may be grouped or clustered
together using a common electrical ground to provide individual
combustion control (via controller 120, which may or may not
include a power source) with fewer wires. Such clusters may be
potted in a suitable matrix forming a unified solid-state
device.
[0041] In other examples, such as described below with respect to
FIG. 12, propellant may include a liquid propellant. Such a device
may operate similar to that described for a solid propellant.
Further, in some examples, the liquid propellant may be flowed,
streamed, pumped, or otherwise urged to electrodes 101a and 101b
for combustion thereof.
[0042] FIGS. 2A-2C illustrate an exploded view, perspective
cross-sectional side view, and cross-sectional side view,
respectively, of a second exemplary structure 200 including
electrodes and an electrically ignitable propellant. In this
example, structure 200 includes stainless steel electrodes 201a and
201b, electrode 201b formed of a stainless steel case enclosing an
aluminum encased propellant 202.
[0043] Further, structure 200 includes a nozzle 212, which may be
made of graphite. Nozzle 212 may be designed and used to control
combustion or gas generation of structure 200 as will be understood
by those of ordinary skill in the art. Further, in configurations
where combustion occurs at two or more openings, two or more
nozzles may be used. In another example, not shown, electrode 201a
may extend within nozzle 212, which may assist in combusting any
propellant particles which are ejected without being ignited and
come into sufficient electrical contact with electrode 201a and
nozzle 212 and/or electrode 210b to pass current there through.
[0044] FIGS. 2D and 2E illustrate cross-sectional side views of
another exemplary structure 201, which include an electrically
ignitable propellant 202 and an electrode 201a extending through a
nozzle or exhaust region of the structure, e.g., through an
afterburner throat region. The extension of electrode 201a through
the end region prevents may reduce clogging (and potentially
subsequent explosion) by causing the (re)ignition of any
incompletely combusted propellant.
[0045] FIGS. 3A and 3B illustrate exemplary ignition processes of
electrical propellant for different apparatus configurations. FIG.
3A illustrates the combustion process for a structure similar to
that of FIG. 1, having an insulated center anode configuration.
This particular structure and configuration results in combustion
of propellant to spread across the grain-end to the outer cathode.
The combustion of the propellant propagates to the left along the
axis of the structure, in a generally uniform manner as
illustrated.
[0046] In contrast, and with reference to FIG. 3B, with a reverse
polarity and with an un-insulated axial electrode, the propellant
is broadly ignited along much of or the entire length of the
positive electrode as shown (it is noted that that for clarity only
one side of the outer case/electrode is shown). Accordingly, by
varying the polarity and apparatus (e.g., with or without burn-away
insulation), various combustion processes may be achieved.
[0047] FIGS. 4A and 4B illustrate exemplary ignition processes of
electrical propellant for different polarities of the electrodes
(it is again noted that for clarity only one side of the outer
case/electrode is shown). Reversing the polarity of the electrodes
for an exemplary structure including burn-away insulation alters
the burn geometry from end-burning to core burning.
[0048] FIGS. 5A-5D illustrate exemplary structures including
electrodes 501a and 501b and electrically ignitable propellant for
various polarities and physical configurations. In these examples,
electric burn strand types are illustrated to indicate ignition and
propagation using inert electrodes (e.g., stainless steel). In
these examples, electrode 501a is positive and electrode 501b is
grounded, where electrical power conducts through the propellant to
ignite at the positive electrode.
[0049] FIG. 6 illustrates an exemplary "core burning" structure 600
including wire electrodes 601a, b and electrically ignitable
propellant 602 having a core region 604 for combustion gases to
escape (it is noted that insulation, e.g., on the positive
electrode 601a, has been excluded here for clarity). In other
examples, electrodes 601a, b can also be in the form of flat sheets
or foils to create a higher surface area of ignition (not shown).
The core region 604 may be formed after the propellant is disposed
in the structure by drilling, etching, milling, laser milling, or
other suitable material removal processes. Further, as will be
recognized by those of ordinary skill in the art, a casing or
housing, nozzle(s), controller, powers supply, compression device,
and other structures may be included with the exemplary structure
shown. The core region 604 may be aligned at least partially with
an aperture in a housing to assist in channeling gas and heat
through a port or nozzle.
[0050] FIG. 7 illustrates an exemplary "slot burning" structure 700
including wire electrodes 701a, b and electrically ignitable
propellant 702 including a slot 704 formed therein. Slot 704 may
provide for combustion gases to escape the structure. Slot 704 may
be formed after the propellant is disposed in the structure by
drilling, etching, milling, laser milling, or other suitable
material removal processes. Further, as will be recognized by those
of ordinary skill in the art, a casing or housing, nozzle(s),
controller, powers supply, compression device, and other structures
may be included with the exemplary structure shown.
[0051] FIG. 8 illustrates an exemplary "star" geometry structure
800 including wire electrodes 801a, b and electrically ignitable
propellant 802 having an open "star" region 804 formed therein. The
exemplary geometry can use one or more ignition electrodes, e.g.,
one or more positive electrodes 801a, with a single grounded
electrode 801b. Region 804 may be formed after the propellant is
disposed in the structure by drilling, etching, milling, laser
milling, or other suitable material removal processes. Further, as
will be recognized by those of ordinary skill in the art, a casing
or housing, nozzle(s), controller, powers supply, compression
device, and other structures may be included with the exemplary
structure shown.
[0052] FIG. 9 illustrates an exemplary "straw" structure 900
including wire electrodes 901a, b (901a positive and 901b negative
in this example) and a plurality of electrically ignitable
propellant grains 902. Positive electrodes 901a are illustrated
extending substantially or completely along the length of a straw
grain 902 such that combustion begins at the far end of positive
electrode 901b (where electrode 901b includes insulation, not
shown, extending nearly to the end thereof). One or more straw
grains 902 may include electrodes, where during operation igniting
one grain may cause the remaining grains 902 to combust. Multiple
positive and negative electrodes can be used to vary the combustion
process and ensure uniform and complete combustion of grains
902.
[0053] FIG. 10 illustrates an exemplary "end-burner" structure 1000
including wire electrodes 1001a, b (1001a positive and 1001b
negative in this example) and electrically ignitable propellant
1002. In this example, the structure may include only a single
ground electrode 1001b and one or more positive electrodes 1001a.
The wired end-burner design also has fewer wires, requiring only
one ground. For example, with respect to FIG. 9, each grain 902 may
be separately encased or isolated from other grains 902 such that
each may be selectively and individually ignited and combusted.
[0054] FIGS. 11A and 11B illustrate two exemplary methods of
initiating combustion of electric solid propellant 1100, which may
include any structure described herein, using pressure and
electrical power. For instance, the exemplary structures and
propellant can be used in combination with a compression device
such as a pyrotechnic/explosive charge (e.g., squibs, electric
matches, blasting caps, detonators, or the like), shock impact,
compressed gas pneumatic pressurization and/or valve, including
pressure burst disks to increase reaction pressures and cause
faster ignition of the energetic material at and along the
electrodes. For instance, the threshold current for initiating
combustion of some of the exemplary propellants decreases with
increasing pressure. The structure including the propellant may be
included with a compression device to form a safe two-stage
ignition system for the propellant. For example, a power supply may
provide the propellant with insufficient electrical power to ignite
at normal environment pressures, but sufficient to ignite when the
compression device is also activated. Likewise, the pressure
increase (and/or heat) from the compression device will not cause
ignition of the energetic material with the electrical power being
supplied. As the pressure is increased from a shockwave (FIG. 11A)
or increase in pressure within a pressure chamber (FIG. 11B)
combustion is initiated.
[0055] FIG. 12 illustrates an exemplary structure for initiation of
electrically ignitable liquid propellant. In this particular
example, liquid propellant 1202 is contained within the structure
1200 and urged to flow past the electrodes 1201a and 1201b.
Electrode 1201a may further include an insulator 1203 disposed
therewith that will not burn away, in one example, such that liquid
propellant 1202 will only be combusted when urged past the
electrodes 1201a and 1201b at the distal or nozzle end of structure
1200.
[0056] In one example, pressure may be introduced to structure 1200
to urge or pump the liquid propellant 1202 to and past electrodes
1201a and 1201b. The liquid propellant may be urged to flow to
electrodes 1201a and 1201b in various other manners including
mechanical (e.g., a plunger or other mechanical devices), gravity,
pressure differentials, magnetic fields, or the like. Further, the
rate at which liquid propellant 1202 is urged to electrodes 1201a
and 1201b may be controlled or ceased by a controller to vary the
rate of combustion thereof.
[0057] In some examples, the volume of electrically ignitable
propellant includes liquid propellant such as hydroxylammonium
nitrate (HAN) propellants, propellants described in the
applications referenced herein, and other pyroelectric materials
such as polyvinylidene fluoride, poly vinylidene
fluoride-trifluoroethylene copolymers, and the like.
[0058] Electrically ignitable solid and liquid propellants may have
various advantageous uses in oil and gas field applications. For
instance, the use of small, electrically controllable explosives
may provide advantages for fracturing oil and gas wells in terms of
safety and predictability, and without excessive wellbore damage
relative to traditional high explosives such as nitroglycerine or
gelatin. Further, the use of liquid propellants, as described
herein, may be used to enter small diameter cracks and holes and
detonated to create reservoirs. In particular, liquid propellant
may be pumped or flowed into cracks (which may be created initially
by hydraulic or explosives methods) associated with a well or well
region and electrically ignited. The explosion may stimulate the
well and increase the oil or gas reservoir for extraction.
[0059] Another exemplary application of the structures and methods
described herein includes an electronic projectile or gun
apparatus. For instance, FIG. 13 illustrates an exemplary structure
1300 for an electrically ignitable projectile or gun. As
illustrated, a volume of electrically ignitable propellant is
suitable connected to electrodes and disposed within the structure
to propel a projectile when ignited, e.g., the combustion of the
propellant propelling the projectile from the barrel.
[0060] According to another aspect described herein, multiple
structures for igniting electrically ignitable propellant (e.g.,
structures 100, 200, 600, 700, 800, 900, 1000, 1200, or other
structures described), may be combined into arrays of individually
addressable grain elements. For example, FIG. 14 illustrates yet
another exemplary structure 1400 for initiation of an electrically
ignitable propellant, the structure including a series of
propellant strips separated by insulation. Further, multiple grain
elements or structures similar to those illustrated may be combined
or stacked into a variety of thruster arrays suitable for various
propulsion or gas generation devices. Additionally, various
structures described with respect to solid propellants may
generally be adapted for use with liquid propellants, and vice
versa (of course, additionally structure such as seals may be
needed to store liquid propellants).
[0061] Various other structures and configurations of electrodes,
exhaust ports or cavities, multiple grain arrangements (including
vertically stacked structures) are further described in copending
patent application Ser. No. 11/305,742, which is incorporated
herein by reference. Exemplary methods and structures described
here allow for multiple thruster units to be manufactured
simultaneously, reducing costs while providing redundancy. The
examples are generally scalable and allow several different size
thrusters to be included in a single assembly. The grain elements
may be in direct contact with one another or separated by
conductive electrodes or insulating layers as shown and described.
Further, the electrodes may include conductive materials such as
copper, aluminum, stainless steel, zirconium, gold, and the like.
Insulator materials for the dies, casing, or to separate grains may
include rubber, phenolic, Teflon.RTM., ceramic, and the like. The
electrode geometries may be configured to allow specific volumes or
surfaces of propellant to be ignited individually and/or in
combination to achieve desired thrust/gas generation control.
Electrode geometry and/or conductive surface coatings can control
propellant combustion either proceeding inward from surfaces or to
instantaneously ignite specific volumes. Electrode surfaces may be
varied from smooth to porous mesh changing the surface area in
contact with the propellant. Once the hardware assemblage/stack is
formed, the propellant can be added by casting with or without
vacuum depending on scale. Additionally, mandrels may be used to
control propellant casting as is known in the art.
[0062] It will be further appreciated that various additional
features may be included or associated with the described
structures, such as power supplies, controllers, electrical pins,
connectors, housings, electrode structures, and the like. It will
be appreciated that one may use a chamber die having a
two-dimensional array of propellant chambers and stacking or
layering grain elements as described herein to form a
three-dimensional thruster array. Additionally, various other
processing techniques may be used and the processing techniques
described may be carried out in other orders or in parallel.
[0063] The above detailed description is provided to illustrate
exemplary embodiments and is not intended to be limiting. It will
be apparent to those skilled in the art that numerous modifications
and variations within the scope of the present invention are
possible. For example, various examples described herein may be
used alone or in combination with other systems and methods, and
may be modified for varying applications and design considerations.
Accordingly, the present invention is defined by the appended
claims and should not be limited by the description herein.
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