U.S. patent application number 11/564990 was filed with the patent office on 2008-06-05 for hypergolic liquid or gel fuel mixtures.
This patent application is currently assigned to United States of America, represented by Secretary of the U.S. Army. Invention is credited to LaShanda D. Felton, Zhu Slocum-Wang, William H. Stevenson, III.
Application Number | 20080127551 11/564990 |
Document ID | / |
Family ID | 39493307 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080127551 |
Kind Code |
A1 |
Stevenson, III; William H. ;
et al. |
June 5, 2008 |
Hypergolic Liquid Or Gel Fuel Mixtures
Abstract
Hypergolic liquid or gel fuel mixtures utilized in bipropellant
propulsion systems are disclosed as replacements for fuels
containing toxic mono-methylhydrazine. The fuel mixtures include
one or more amine azides mixed with one or more tertiary diamine,
tri-amine or tetra-amine compounds. The fuel mixtures include
N,N,N',N'-tetramethylethylenediamine (TMEDA) mixed with
2-N,N-dimethylaminoethylazide (DMAZ), TMEDA mixed with
tris(2-azidoethyl)amine (TAEA), and TMEDA mixed with one or more
cyclic amine azides. Each hypergolic fuel mixture provides a
reduced ignition delay for combining with an oxidant in fuel
propellant systems. The fuel mixtures have advantages in reduced
ignition delay times compared to ignition delay times for each
unmixed component, providing a synergistic effect which was not
predictable from review of each component's composition. Additional
fuel mixtures include various tertiary diamine, tertiary tri-amine
or tetra-amine compounds combined with one or more amine azides or
imidic amide compounds, to provide clean burning, high performing,
and non-toxic fuels.
Inventors: |
Stevenson, III; William H.;
(Huntsville, AL) ; Felton; LaShanda D.;
(Huntsville, AL) ; Slocum-Wang; Zhu; (Huntsville,
AL) |
Correspondence
Address: |
DEPARTMENT OF THE ARMY;LEGAL OFFICE
AMSAM - L - G - I, U.S. ARMY AVIATION & MISSILE COMMAND
REDSTONE ARSENAL
AL
35898-5000
US
|
Assignee: |
United States of America,
represented by Secretary of the U.S. Army
Washington
DC
|
Family ID: |
39493307 |
Appl. No.: |
11/564990 |
Filed: |
November 30, 2006 |
Current U.S.
Class: |
44/320 ;
44/327 |
Current CPC
Class: |
C10L 7/00 20130101; C06D
5/08 20130101; C10L 1/1291 20130101; C10L 1/1208 20130101; C06B
47/02 20130101; C10L 1/146 20130101 |
Class at
Publication: |
44/320 ;
44/327 |
International
Class: |
C10L 1/226 20060101
C10L001/226 |
Claims
1. A hypergolic fuel mixture in a propulsion system comprising: a
first component including a hypergolic amine azide compound; and a
second component including a hypergolic tertiary amine compound;
whereby said first and second components form a liquid or gel fuel
mixture in the propulsion system.
2. The hypergolic fuel mixture of claim 1, further comprising an
oxidizer selected from the group consisting of inhibited red fuming
nitric acid, nitrogen tetroxide, hydrogen peroxide,
hydroxylammonium nitrate, and liquid oxygen.
3. The hypergolic fuel mixture of claim 1 wherein said first
component is selected for the group consisting of:
2-(N,N-dimethylamino)ethylazide; 2-(N-cyclopropylamino)ethylazide;
bis(2-azidoethyl)methylamine; bis(2-azidoethyl)ethylamine;
tris(2-azidoethyl)amine; 2-(N-pyrrolidinyl)ethylazide;
N-(2-azidoethyl)morpholine; and
1,2-bis(N-(2-azidoethyl)-N-methylamino)ethane.
4. The hypergolic fuel mixture of claim 1, further comprising said
second component including a tertiary diamine selected from the
group consisting of: N,N,N',N'-tetramethylethylenediamine;
N,N,N',N'-tetramethyl-1,3-diamino-propane;
N,N,N',N'-tetramethyl-1,4-diamino-butane;
N,N,N',N'-tetramethyl-1,4-diaminobut-2-ene; and
N,N,N',N'-tetramethyl-1,4-diaminobut-2-yne.
5. The hypergolic fuel mixture of claim 1, further comprising said
second component including a tertiary tri-amine or tetra-amine
compound selected from the group consisting of
N,N,N',N'',N''-pentamethyldiethylenetriamine, and
hexamethyl-triethylene-tetra-amine.
6. The hypergolic fuel mixture of claim 1, further comprising said
first component is an amidine compound selected for the group
consisting of: 1,5-Diaza-bicyclo(4.3.0)non-5-ene;
1,8-Diazabicyclo(5.4.1)undec-7-ene;
1-ethyl-2-methyl-1,4,5,6-tetrahydropyrimidine;
1-methyl-2-ethyl-1,4,5,6-tetrahydropyrimidine;
1-ethyl-2-methyl-4,5-dihydroimidazole; and
1-methyl-2-ethyl-4,5-dihydroimidazole.
7. The hypergolic fuel mixture of claim 1, further comprising an
additive gellant added to said first and second components in a
proportion of between about 0.5% to about 10% additive relative to
said first and second components thereby forming a gel fuel
mixture, said additive gellant selected from the group consisting
of silicon dioxide, clay, carbon, and polymeric gel.
8. A hypergolic liquid or gel utilized in a fuel propulsion system
comprising: a hypergolic fuel containing a mixture of a first
component and a second component, including: said first component
includes one or more hypergolic amine azides of the general formula
(R.sub.1)(R.sub.2)(R.sub.3)N, in which the composition of each
R.sub.1, R.sub.2, and R.sub.3 group is selected from the group
consisting of a hydrogen, an aliphatic, alkene, alkyl, alkyne and
cycloalkyl group, and at least one of each R.sub.1, R.sub.2, and
R.sub.3 group contains an azide compound; said second component
includes one or more hypergolic amines of the general formula
R.sub.4R.sub.5N--R.sub.6--NR.sub.7R.sub.8, in which the composition
of each R.sub.4, R.sub.5, R.sub.7, and R.sub.8 group is an
aliphatic group, and said R.sub.6 group is selected from the group
consisting of an aliphatic, alkene, alkyne, or cycloalkyl compound;
and an oxidizer mixed with said first component and said second
component within the fuel propulsion system.
9. The hypergolic liquid or gel of claim 8 wherein said oxidizer is
selected from the group consisting of inhibited red fuming nitric
acid, nitrogen tetroxide, hydrogen peroxide, hydroxylammonium
nitrate, and liquid oxygen.
10. The hypergolic liquid or gel of claim 8 wherein said first
component including a selected first proportion of
2-(N,N-dimethylamino)ethylazide, mixed with said second component
including a selected second proportion of
N,N,N',N'-tetramethylethylenediamine.
11. The hypergolic liquid or gel of claim 8 wherein said first
component including a selected first proportion of
tris(2-azidoethyl)amine, mixed with said second component including
a selected second proportion of
N,N,N',N'-tetramethylethylenediamine.
12. A hypergolic fuel mixture utilized in a propulsion system
comprising: a first component including at least one of a
hypergolic amine azide or an imidic amide compound; a second
component including at least one of a hypergolic tertiary amine
compound; and a source for inducing reaction of said first and
second components, said source being an oxidizer; whereby said
first and second components are provided as a liquid or gel mixture
combined with said oxidizer in the fuel propulsion system.
13. The hypergolic fuel mixture of claim 12, further comprising
said first component is selected from the group consisting of:
2-(N,N-dimethylamino)ethylazide; 2-(N-cyclopropylamino)ethylazide;
bis(2-azidoethyl)methylamine; bis(2-azidoethyl)ethylamine;
tris(2-azidoethyl)amine; 2-(N-pyrrolidinyl)ethylazide;
N-(2-azidoethyl)morpholine; and
1,2-bis(N-(2-azidoethyl)-N-methylamino)ethane.
14. The hypergolic fuel mixture of claim 12, further comprising
said second component is selected from the group consisting of:
N,N,N',N'-tetramethylethylenediamine;
N,N,N',N'-tetramethyl-1,3-diamino-propane;
N,N,N',N'-tetramethyl-1,4-diamino-butane;
N,N,N',N'-tetramethyl-1,4-diaminobut-2-ene;
N,N,N',N'-tetramethyl-1,4-diaminobut-2-yne; and
N,N,N',N'',N''-pentamethyldiethylenetriamine.
15. The hypergolic fuel mixture of claim 12 wherein said source for
inducing reaction is an oxidizer selected from the group consisting
of inhibited red fuming nitric acid, nitrogen tetroxide, hydrogen
peroxide, hydroxylammonium nitrate, and liquid oxygen.
16. The hypergolic fuel mixture of claim 12, further comprising an
additive gellant added to said first and second components in a
proportion of between about 0.5% to about 10% additive relative to
said first and second components thereby forming a gel fuel
mixture, said additive gellant selected from the group consisting
of silicon dioxide, clay, carbon, and polymeric gel.
17. A process for producing a hypergolic propellant utilizable in a
fuel propulsion system comprising: a step of adding a first
component including a hypergolic amine azide compound; a step of
adding a second component including a hypergolic tertiary amine
compound to said first component in a liquid or gel mixture; and a
step of adding an oxidizer for inducing reaction of said first and
second components in said liquid or gel mixture in the fuel
propulsion system.
18. The process of claim 17 wherein said step of adding a first
component includes a step of adding at least one amine azide
compound selected from the group consisting of:
2-(N,N-dimethylamino)ethylazide; 2-(N-cyclopropylamino)ethylazide;
bis(2-azidoethyl)methylamine; bis(2-azidoethyl)ethylamine;
tris(2-azidoethyl)amine; 2-(N-pyrrolidinyl)ethylazide;
N-(2-azidoethyl)morpholine; and
1,2-bis(N-(2-azidoethyl)-N-methylamino)ethane.
19. The process of claim 17 wherein said step of adding a first
component further including an additional step of adding at least
one imidic amide compound selected from the group consisting of:
1,5-Diaza-bicyclo(4.3.0)non-5-ene;
1,8-Diazabicyclo(5.4.1)undec-7-ene;
1-ethyl-2-methyl-1,4,5,6-tetrahydropyrimidine;
1-methyl-2-ethyl-1,4,5,6-tetrahydropyrimidine;
1-ethyl-2-methyl-4,5-dihydroimidazole; and
1-methyl-2-ethyl-4,5-dihydroimidazole.
20. The process of claim 17 wherein said step of adding a second
component including a step of adding at least one tertiary amine
compound selected from the group consisting of:
N,N,N',N'-tetramethylethylenediamine;
N,N,N',N'-tetramethyl-1,3-diamino-propane;
N,N,N',N'-tetramethyl-1,3-diamino-propane;
N,N,N',N'-tetramethyl-1,4-diamino-butane;
N,N,N',N'-tetramethyl-1,4-diaminobut-2-ene; and
N,N,N',N'-tetramethyl-1,4-diaminobut-2-yne.
21. The process of claim 17 wherein said step of adding a second
component further including an additional step of adding at least
one tertiary tri-amine or tetra-amine compound selected from the
group consisting of N,N,N',N'',N''-pentamethyldiethylenetriamine,
and hexamethyl-triethylene-tetra-amine.
22. The process of claim 17 wherein said step of adding an oxidizer
including said oxidizer selected from the group consisting of
inhibited red fuming nitric acid, nitrogen tetroxide, hydrogen
peroxide, hydroxylammonium nitrate, and liquid oxygen.
23. The process of claim 17 further comprising a step of adding an
additive gellant to said first and second components in a
proportion of between about 0.5% to about 10% additive relative to
said first and second components thereby forming a gel fuel
mixture, said additive gellant selected from the group consisting
of silicon dioxide, clay, carbon, and polymeric gel.
24. A hypergolic liquid or gel utilized in a fuel propulsion system
comprising: a hypergolic fuel containing a mixture of a first
component and a second component, including: said first component
including one or more hypergolic imidic amide compounds having a
formula (R.sub.1)(R.sub.2)--N--(R.sub.3)C.dbd.N--(R.sub.4), in
which the composition of each R.sub.1, R.sub.2, R.sub.3 and R.sub.4
group is selected from the group consisting of hydrogen, aliphatic,
alkene, alkyl, alkyne, and cycloalkyl groups, and at least one of
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 groups contains an amidine
group; said second component including one or more hypergolic
amines of the general formula
R.sub.5R.sub.6N--R.sub.7--NR.sub.8R.sub.9, in which the composition
of each R.sub.5, R.sub.6, R.sub.8, and R.sub.9 group is an
aliphatic group, and said R.sub.7 group is selected from the group
consisting of an aliphatic, alkene, alkyne, or cycloalkyl compound;
and an oxidizer mixed with said first component and said second
component within the fuel propulsion system.
25. The hypergolic liquid or gel of claim 24 wherein said first
component including a selected first proportion of said first
component selected from the group consisting of,
1,5-Diaza-bicyclo(4.3.0)non-5-ene, 1,8-Diazabicyclo(5.4.1)
undec-7-ene, 1-ethyl-2-methyl-1,4,5,6-tetra-hydropyrimidine,
1-methyl-2-ethyl-1,4,5,6-tetrahydropyrimidine,
1-methyl-2-ethyl-4,5-dihydroimidazole, and
1-ethyl-2-methyl-4,5-dihydroimidazole; and said second component
including a selected second proportion of
N,N,N',N'-tetramethyl-ethylenediamine or
N,N,N',N'',N''-pentamethyl-diethylenetriamine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] The invention described herein may be manufactured, used and
licensed by or for the Government for governmental purposes without
the payment to the inventors and/or the assignee of any royalties
thereon.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to fuel mixtures utilized in
hypergolic propulsion systems. More specifically, the invention
relates to hypergolic fuel mixtures of tertiary amines and amine
azides, or amines and imidic amides.
[0005] 2. Description of the Related Art
[0006] A liquid or gel bipropellant rocket propulsion system
consists of gas generators, oxidizer and fuel propellant tanks,
plumbing, oxidizer and fuel valves, and an engine. The bipropellant
rocket propulsion unit begins operation when the gas generators
have been initiated and the gases from the gas generator pressurize
oxidizer and fuel propellant tanks. When the oxidizer and fuel
valves open, the pressurized oxidizer and fuel tanks then force the
propellants through the plumbing into the engine where the
propellants are mixed and ignited. The propellants can be ignited
by either ignition aids or by hypergolic (spontaneously
self-igniting) chemical reaction. Since ignition aids can take up
valuable space in the propulsion system, a hypergolic chemical
reaction is the preferred ignition method. Inhibited red fuming
nitric acid (hereinafter, IRFNA) and monomethyl hydrazine
(hereinafter, MMH) have been the preferred hypergolic rocket
oxidizer and fuel for rocket propulsion systems for some time, by
providing a high specific impulse and density specific impulse, and
providing a short ignition delay of approximately 3 milliseconds or
less to approximately 15 milliseconds (depending on test
techniques), before ignition after combining of an oxidizer and
MMH. A short ignition delay characteristic is important since a
long ignition delay of approximately 25 millisecond or longer
causes fuel and oxidizer to accumulate in the combustion chamber,
so that when ignition does take place an overpressurization can
occur with creation of a "hard start." Overpressurization in the
combustion chamber can be severe enough to destroy the rocket motor
and negate achievement of the mission objective.
[0007] A main drawback of MMH is the high toxicity of the compound.
Classified as a suspected human carcinogen, MMH requires
exceptional safety precautions during handling which makes fueling
of rocket motors both time consuming and expensive. A
non-carcinogenic alternative to MMH which can be readily utilized
in hypergolic bipropellant propulsion systems is preferred.
[0008] U.S. Pat. No. 6,013,143, issued to D. M. Thompson and
assigned to the Secretary of the Army, discloses liquid or gel
bipropellant fuel compounds which are alternatives to use of
potentially carcinogenic compound MMH in rocket propulsion systems
similar to a system illustrated in U.S. Pat. No. 5,133,183. The
hypergolic fuel compounds disclosed in the '143 patent include
three tertiary amine azide compounds consisting of
2-N,N-dimethylamino-ethylazide (identified as DMAZ), bis(ethyl
azide) methylamine (identified as BAZ), and pyrrolidinylethylazide
(also identified as 2-(N-pyrrolidinyl)ethylazide, or PYAZ). The
'143 patent disclosed that use of MMH as a fuel mixture with IRFNA
would deliver a specific impulse of 284 lbf sec/Ibm and a density
impulse of 13.36 lbf sec/cubic inch. Under similar operating
conditions, DMAZ delivered a specific impulse of 287 lbf sec/Ibm
and a density impulse of 13.77 lbf sec/cubic inch. To achieve
performance comparable to MMH used in a rocket propulsion system,
the '143 patent disclosed each one of the tertiary amine azides
(DMAZ, BAZ or PYAZ) were combined with an oxidizer selected from
the group of oxidizers consisting of IRFNA, nitrogen tetroxide,
hydrogen peroxide, hydroxylammonium nitrate, and liquid oxygen. The
'143 patent did not disclose alternative oxidizer compounds which
may provide similar or improved performance when combined with
DMAZ, BAZ or PYAZ. A limitation of the compounds disclosed in the
'143 patent included, for each of the three hydrocarbon moieties
attached to the tertiary amine, that at least one but no more than
two moieties contained an azide group. A further limitation of the
'143 patent includes the tertiary amine azide molecule can have no
more than seven carbon atoms for the compound to remain hypergolic,
allowing the tertiary amine azides to produce adequate specific
impulse or density specific impulse results when mixed with
IRFNA.
[0009] U.S. Pat. No. 6,210,504, issued to D. M. Thompson and
assigned to the Secretary of the Army, discloses a gas generator
fuel source for a liquid or gel gas generator system, including the
three tertiary amine azide compounds disclosed in the '143 patent,
specifically DMAZ, BAZ, and PYAZ. The '504 patent discloses that
any one of the three tertiary amine azide compounds is contained
and heated in an iridium catalytic reactor bed to achieve a self
sustaining decomposition reaction to yield gaseous products for
pressurization of the liquid or gel gas generator system. The '504
patent does not disclose alternative tertiary amine azide compounds
which may provide similar or improved performance when used instead
of, or in combination with DMAZ, BAZ or PYAZ. Limitations of the
structure and radicals attached to the tertiary amine azide
compounds are relevant to the '504 patent as also disclosed in the
'143 patent. The '504 patent discloses solid additives and gellant
additives consistent with the additives disclosed in the '143
patent, including use of a gallant such as silicon dioxide, clay,
carbon, and polymeric gallant.
[0010] It is desirable to provide a plurality of hypergolic fuel
mixtures exhibiting minimal toxicity, classified as a
non-carcinogen, and having a short ignition delay when mixed in a
propulsion system. It is also desirable to provide a plurality of
fuel mixtures having a short ignition delay and a density specific
impulse competitive with MMH fuel. It is further desirable to
provide a plurality of hypergolic fuel mixtures containing a
tertiary diamine, tertiary tri-amine or a tetra-amine compound, any
of which is mixed with an amine azide compound, a monocyclic
amidine compound, or a multi-cyclic amidine compound, for use in
propulsion systems as replacements for MMH fuel.
BRIEF SUMMARY OF THE INVENTION
[0011] A fuel mixture is disclosed for use as hypergolic liquid or
gel fuel in bipropellant propulsion systems, with the chemical
compounds preferably having similar ignition characteristics as
MMH, and preferably the compounds not being toxic or classified as
a suspected human carcinogen. One compound disclosed includes
N,N,N',N'-tetramethylethylenediamine (hereinafter, TMEDA), a
tertiary diamine, mixed with any one of a family of hypergolic
amine azides, with one compound being DMAZ. Laboratory test data
for TMEDA provides an ignition delay of approximately 14
milliseconds, and laboratory test data for DMAZ provides an
ignition delay of approximately 26 milliseconds. Combination of
TMEDA and DMAZ in a hypergolic liquid or gel fuel provides an
unexpected reduction for ignition delay values to a range of about
9 milliseconds to about 10 milliseconds depending on the percentage
of DMAZ mixed with TMEDA.
[0012] An alternative compound includes a mixture of a hypergolic
tertiary diamine such as TMEDA, and an amine azide such as
tris(2-azidoethyl) amine (TAEA). Laboratory test data for unmixed
TMEDA provides an ignition delay of about 14 milliseconds, and
laboratory test data for unmixed TAEA provides an ignition delay of
about 43 milliseconds. Combination of TMEDA and TAEA in a
hypergolic liquid or gel fuel provides an unexpected reduction for
ignition delay times to a range of about 8 milliseconds to about 9
milliseconds depending on percentage of TAEA mixed with TMEDA.
[0013] Additional combinations of chemical compounds to form a
hypergolic fuel mixture include numerous cyclic amidine (also
identified as imidic amide) compounds, such as
1,5-diazabicyclo(4.3.0)non-5-ene (hereinafter, DBN), mixed with a
hypergolic tertiary diamine such as TMEDA, or a
1,8-Diazabicyclo(5.4.1) undec-7-ene (hereinafter, DBU), mixed with
a hypergolic tertiary diamine such as TMEDA. A monocyclic analog of
bi-cyclic DBN but having the non-nitrogen containing cyclic
structure opened along with isomers thereof, are additional
compounds utilized to form a hypergolic fuel mixture when mixed
with a hypergolic tertiary diamine such as TMEDA. Compounds
containing one or more tertiary tri-amine structures, such as
N,N,N',N'',N''-pentamethyldiethylenetriamine (hereinafter, PMDETA),
and compounds containing tetra-amine, such as
hexamethyl-triethylene-tetra-amine (HMETA), or larger amine
structures, when mixed with amine azide or imidic amide compounds,
are also capable of providing favorable short ignition delay values
to serve as hypergolic fuel mixtures with minimal toxicity and
lacking suspicion as a human carcinogen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention is disclosed to include mixtures of
chemicals referenced herein, with performance test results
illustrated in graphs of ignition delay in milliseconds (msec) vs.
% ratios of chemicals, including:
[0015] FIG. 1 is a graph of ignition delay time of DMAZ and TMEDA
mixtures, relative to % content DMAZ for laboratory drop testing
and engine testing;
[0016] FIG. 2 is a graph of ignition delay times of TAEA and TMEDA
mixtures, relative to % content of TAEA at about 30.degree. C. for
laboratory drop testing;
[0017] FIG. 3 is a graph of ignition delay times of DBN and TMEDA
mixtures, relative to % content of DBN at about 30.degree. C. for
laboratory drop testing;
[0018] FIG. 4 is a graph of ignition delay times of DBN and PMDETA
mixtures, relative to % content of DBN at about 30.degree. C. for
laboratory drop testing;
[0019] FIG. 5 depicts a structure for
N,N,N',N',-tetramethylethylenediamine (TMEDA);
[0020] FIG. 6 depicts a structure for
N,N,N'',N''-pentamethyl-diethylene-triamine (PMDETA);
[0021] FIG. 7 depicts a structure for 2-N,N-dimethylaminoethylazide
(DMAZ);
[0022] FIG. 8 depicts a structure for tris(2-azidoethyl) amine
(TAEA);
[0023] FIG. 9 depicts a structure for 2-(N-pyrrolidinyl)ethylazide
(PYAZ);
[0024] FIG. 10 depicts a structure for
1,5-diazabicyclo(4.3.0)non-5-ene (DBN);
[0025] FIG. 11 depicts a structure for
1,8-diazabicyclo(5.4.1)undec-7-ene (DBU);
[0026] FIG. 12 depicts a structure for
1-ethyl-2-methyl-1,4,5,6-tetra-hydropyrimidine;
[0027] FIG. 13 depicts a structure for
1-methyl-2-ethyl-1,4,5,6-tetrahydro-pyrimidine;
[0028] FIG. 14 depicts a structure for
1-methyl-2-ethyl-4,5-dihydroimidazole; and
[0029] FIG. 15 depicts a structure for
1-ethyl-2-methyl-4,5-dihydroimidazole.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Referring now to FIGS. 1-15, a plurality of mixtures of
compounds are disclosed for use as hypergolic liquid or gel fuels
in bipropellant propulsion systems. A plurality of combinations of
amine azide compounds and tertiary diamine compounds are disclosed
as providing suitable hypergolic bipropellant fuels with
sufficiently short ignition delay times, including TMEDA (see FIG.
5) when mixed with one of the compounds of DMAZ (see FIG. 7), TAEA
(see FIG. 8), PYAZ (see FIG. 9), BAZ, DBN (see FIG. 10), DBU (see
FIG. 11), or monocyclic compounds similar to DBN. Also disclosed is
the use of tertiary tri-amines such as PMDETA (see FIG. 6), to
achieve sufficiently short ignition delay times when mixed with one
or more of the compounds of DMAZ, TAEA, PYAZ, BAZ, DBU, DBN, or
monocyclic compounds similar to DBN.
[0031] Previously disclosed alternative fuel compounds proposed for
replacement of MMH in fuel, specifically DMAZ, BAZ and PYAZ mixed
with IRFNA, have been investigated and found by laboratory drop
testing of individual compounds to each provide significant longer
ignition delays than that of MMH, as illustrated by data generated
as a result of laboratory testing and provided in Table 1. Testing
to determine ignition delay values of compounds was achieved using
a laboratory drop test known to those skilled in the art involved
in testing, such as drop testing utilized by the U.S. Army
Research, Development and Engineering Command at the Redstone
Arsenal, Ala., and government contractors including ERC,
Incorporated, in Huntsville, Ala. The following ignition delay
results for individual compounds are tested separately as mixtures
with oxidant IRFNA, to allow comparisons with the ignition delay
data for fuel mixtures in various combinations as disclosed herein
(see FIGS. 1-4).
TABLE-US-00001 TABLE 1 Laboratory Drop Test/Ignition Delay of
Hypergolic Fuels with IRFNA Ignition Delay Compound (msec)
MeNNH.sub.2 (MMH) 8 Me.sub.2NCH.sub.2CH.sub.2NMe.sub.2 (TMEDA) 14
(CH.sub.3).sub.2NCH.sub.2CH.sub.2N.sub.3 (DMAZ) 26
--CH.sub.2CH.sub.2CH.sub.2CH.sub.2NCH.sub.2CH.sub.2N.sub.3 28
Pyrrolidinylethylazide (PYAZ) Tris(2-azidoethyl)amine (TAEA) 43
EtN(CHCH.sub.2N.sub.3).sub.2 (BAZ) 52
[0032] Fuel combinations of the present invention consist of one or
more of a family of hypergolic amine azides or hypergolic imidic
amide compounds (also referenced as a first component), mixed with
one or more hypergolic tertiary diamine compound(s) (also
referenced as a second component), and/or one or more tertiary tri-
or tetra-amine compound(s) (an alternate second component). The
hypergolic amine azides have the general structure
(R.sub.1)(R.sub.2)(R.sub.3)N, in which R.sub.1, R.sub.2, and
R.sub.3 is selected from the element of hydrogen, and an aliphatic,
alkene, alkyne, or cycloalkyl group, any of which may or may not
contain heteroatoms or heterocyclic atoms, but where at least one
of the R groups selected contains an azide. The amine azides thus
need not be tertiary amines and may have three azide-containing
groups attached to the amine. The disclosed description of the
amine azide differs from, and is broader than, that prior art
relating to liquid or gel fuels, in which the disclosures of azides
are limited to tertiary amine azides in which a maximum of two
attached groups contain an azide. Examples of hypergolic amine
azides defined by this invention include but are not limited to
2-(N,N-dimethylamino) ethylazide (DMAZ),
2-(N-cyclo-propylamino)ethylazide, bis(2-azidoethyl)methylamine,
bis(2-azidoethyl)ethylamine (BAZ), tris(2-azidoethyl)amine (TAEA),
2-(N-pyrrolidinyl)ethylazide (PYAZ), N-(2-azidoethyl)morpholine,
and 1,2-bis(N-(2-azidoethyl)-N-methylamino)ethane.
[0033] The tertiary diamines have the general formula
R.sub.4R.sub.5N--R.sub.6--NR.sub.7R.sub.8, where R.sub.4, R.sub.5,
R.sub.7, and R.sub.8 are aliphatic groups and R.sub.6 may be an
aliphatic, alkene, or alkyne group. The hypergolic diamines include
but are not limited to, N,N,N',N'-tetramethyl-ethylene-diamine
(TMEDA), N,N,N',N'-tetramethyl-1,3-diaminopropane (TMPDA),
N,N,N',N'-tetramethyl-1,4-diaminobutane (TMBDA),
N,N,N',N'-tetramethyl-1,4-diaminobut-2-ene (cis or trans isomers or
mixtures of cis/trans isomers), and
N,N,N',N'-tetramethyl-1,4-diaminobut-2-yne.
[0034] The relative proportion of the hypergolic amine azide
compound in the fuel may vary from about 1% to about 99%, and the
proportion of the hypergolic tertiary diamine, tria-mine or
tetra-amine compounds in the fuel may vary from about 1% to about
99% (dependent on amount of amine azide compound mixed wherewith).
For optimal motor specific impulse and density specific impulse it
is generally desirable to incorporate into the fuel the maximize
percentage of amine azide compound which will still allow an
acceptably low ignition delay of about 3 milliseconds to about 15
milliseconds. The tertiary diamine component of the fuel will
optimally have a relatively short ignition delay when mixed with
the oxidizer and have a relatively high content of tertiary amine
groups in the molecule. An example of one embodiment is a fuel
containing about 33.3% DMAZ and about 66.7% TMEDA (see FIG. 1), and
providing an ignition delay of about 9.0 milliseconds. Illustrated
in Table 1, laboratory drop ignition delay test results for a DMAZ
and IRFNA mixture include ignition delay of about 26 milliseconds,
and test results for a TMEDA and IRFNA mixture include ignition
delay of about 14 milliseconds. The significantly shortened
ignition delay times for DMAZ and TMEDA mixtures illustrated in
FIG. 1 were not predictable from review of each component's
physical structure or chemical composition.
[0035] An unexpected characteristic of the new fuel combinations is
illustrated by the test data for shortened ignition delay times of
mixtures of an amine azide and a tertiary amine as compared to test
data for ignition delay times for either of the unmixed individual
components. This synergistic effect of shortened ignition delay
times is illustrated in FIG. 1 for mixtures of DMAZ and TMEDA, in
FIG. 2 for mixtures of TAEA and TMEDA, in FIG. 3 for mixtures of
DBN and TMEDA, and in FIG. 4 for DBN and PMDETA. As shown in FIG.
1, a fuel consisting of approximately 33.3% DMAZ mixed with
approximately 66.7% TMEDA was tested in a rocket motor and provided
successful motor ignition, as compared to rocket motor testing with
pure DMAZ fuel which provide "hard starts." The calculated density
specific impulse of approximately 33.3% DMAZ mixed with
approximately 66.7% TMEDA is competitive with and generally
identical to that calculated for MMH (12.6 lbf-sec/in.sup.3). An
additional benefit of the DMAZ and TMEDA mixture was that the fuel
mixture burned cleaner with fewer residues than when pure TMEDA was
used as the fuel.
[0036] A process for producing an improved hypergolic fuel mixture
having shortened ignition delay times includes selecting an optimal
proportion of DMAZ, a cyclic amine azide or an imidic amide
compound, combined with a proportion of TMEDA or a tri- or
tetra-amine, and further includes adding an oxidizer to the fuel
mixture to initiate a reaction which is sufficiently exothermic to
cause spontaneous ignition of the fuel in a propulsion system. The
ignition delay is caused by several factors including production of
sufficient heat by the initial oxidizer when mixed with the first
component and second component to cause ignition of the fuel
mixture. An ideal situation for fast ignition (i.e. shortened
ignition delay) is one in which the fuel gives off a large amount
of heat upon initial reaction with the oxidizer and also has a
relatively low ignition temperature. In the two component mixture
described herein, the amine azide (component one) releases a
relatively low amount of heat upon initial reaction with an
oxidizer because of its relatively low amine content and the
relatively low basicity of the amine, therefore the amine azide has
a relatively low ignition temperature. In contrast, the tertiary
amine (component two) releases a greater amount of heat upon
initial reaction with an oxidizer because of its relatively high
amine content and its relatively high basicity, although the
tertiary amine has a relatively high ignition temperature. A step
of selecting appropriate first and second components, followed by
adding the selected first and second components with an oxidizer in
a propulsion system, allows the process to take advantage of the
favorable characteristics of the first and second components,
namely low ignition temperature of the amine azide, and high
initial heat production of the tertiary amine.
[0037] Examples of test results for proportions of TAEA compound as
a first component of a hypergolic fuel mixture, when mixed with
TMEDA compound as a second component are illustrated in FIG. 2. One
embodiment of the fuel mixture is adding TAEA in the range of about
20% to about 40%, and adding TMEDA in the range of about 80% to
about 60%, to provide a shortened ignition delay of about 9.0
milliseconds. Similar structured non-cyclic hypergolic amine azide
compounds as first component of a hypergolic fuel mixture, which
can be mixed with TMEDA include a compound selected from the group
including the compounds of, 2-(N-cyclopropylamino)ethylazide,
bis(2-azidoethyl)methylamine, bis(2-azidoethyl)ethylamine (BAZ),
2-(N-pyrrolidinyl)ethylazide (PYAZ), N-(2-azidoethyl)morpholine,
and 1,2-bis(N-(2-azidoethyl)-N-methylamino)ethane.
[0038] Examples of test results for proportions of a DBN cyclic
compound used as a first component of a hypergolic fuel mixture,
when mixed with TMEDA compound as a second component are
illustrated in FIG. 3. One embodiment of the fuel mixture is adding
DBN in the range of about 20% to about 80%, and adding TMEDA in the
range of about 80% to about 20%, to provide a shortened ignition
delay of between about 7.0 milliseconds and about 9.0 milliseconds.
Similar structured bicyclic or monocyclic hypergolic amine azide or
imidic amide compounds are utilized as a first component of a
hypergolic fuel mixture. The imidic amide compounds include an
amidine group of
(R.sub.1)(R.sub.2)--N--(R.sub.3)C.dbd.N--(R.sub.4), where the R
substituents could be either hydrogen, alkyls or cycloalkyl groups.
The R.sub.1, R.sub.2, and R.sub.4 groups are attached to nitrogen
atoms, and the R.sub.3 group is attached to the carbon in the
imidic amide compounds. As an example, DBN and DBU are bicyclic
compounds in which the amidine group is contained within a ring
composed of the R.sub.3 and R.sub.4 groups joining. The bicyclic or
monocyclic amine azide or imidic amide compounds which can be
combined in a mixture with TMEDA include a compound selected from
the group of first component compounds of:
1,5-diazabicyclo(4.3.0)non-5-ene (DBN, see FIG. 10),
1,8-diazabicyclo(5.4.1) undec-7-ene (DBU, see FIG. 11),
1-ethyl-2-methyl-1,4,5,6-tetra-hydropyrimidine (see FIG. 12),
1-methyl-2-ethyl-1,4,5,6-tetrahydropyrimidine (see FIG. 13),
1-methyl-2-ethyl-4,5-dihydroimidazole (see FIG. 14), and
1-ethyl-2-methyl-4,5-dihydroimidazole (see FIG. 15). Any of the
above group of first component compounds can be mixed with TMEDA
(second component), in the form of a liquid for use as a fuel in a
propulsion system. If a gelled fuel mixture is preferred, any of
the disclosed group of first component compounds are mixed with
TMEDA (second component), and mixed with an additive to create and
maintain the mixture as a gel. The additive is added in proportions
of between about 0.5% to about 10%, and selected from the group
consisting of, silicon dioxide, clay, carbon, and/or polymeric gel,
or similar additives utilized by those skilled in the art of
maintaining a mixture as a gel.
[0039] Any of the above described hypergolic amine azide compounds
or imidic amide compounds as first components can be mixed with an
alternative second component of
N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA), to provide
favorably short ignition delay times. One embodiment of the fuel
mixture is illustrated in FIG. 4, providing DBN in the range of
about 50% to about 90%, and adding PMDETA in the range of about 50%
to about 10%, to provide shortened ignition delay times of between
about 5.0 milliseconds and about 10.0 milliseconds. Additional
embodiments for a hypergolic fuel mixtures include any of the above
described hypergolic amine azide or imidic amide compounds mixed
with an alternative second component of a tertiary tetra-amine such
as hexamethyl-triethylene-tetra-amine (HMETA), or compounds having
larger tertiary amine structures.
[0040] A source for inducing reaction of the first compound and the
second compound is stored with the fuel propulsion system and is
readily injected in the mixture of the first and second compound at
a time when ignition of the first and second compound is required
for proper operation of the propulsion system. The source for
inducing reaction is an oxidizer selected from the group consisting
of liquid oxygen, hydrogen peroxide, nitric acid, nitrogen dioxide
and inhibited red fuming nitric acid (IRFNA).
[0041] Additives to a fluid mixture of first and second components
are available for forming a gel mixture. The additive gellant is
provided in the mixture in a proportion of between about 0.5% to
about 10% additive selected from silicon dioxide, clay, carbon, and
polymeric gel. The gelled fuel mixture can also include solid
additives which improve the specific impulse and density specific
impulse. The solid additives are known to those skilled in the art
of rocket fuels and include, but are not limited to, carbon,
aluminum, silicon, boron, tungsten, triamino-trinitrobenzene or
tetramethyl-ammoniumazide. The gelled fuel mixtures can include
between about 1% to about 80% solid additives, between about 98.5%
to about 10% amine azide and tertiary amine fuel mixtures in
varying ratios (see FIGS. 1, 2, 3 and 4), and between about 0.5% to
about 10% gellant. Liquid fuel mixtures have between about 98.5% to
about 10% amine azide and diamine fuel mixtures and lack the
gellant.
[0042] While numerous embodiments of mixtures of chemical compounds
and processes for combining the chemical compounds for this
invention are illustrated and disclosed herein, it will be
recognized that various additional embodiments utilizing the
primary chemicals of the invention may be employed without
departing from the spirit and scope of the invention as set forth
in the appended claims. Further, the disclosed invention is
intended to cover all stereoisomer chemical compositions and
alternate processes falling within the spirit and scope of the
invention as set forth in the appended claims.
* * * * *