Title:
Iridium-catalyzed hydrogen peroxide based monopropellant system
Kind Code:
A1


Abstract:
Rocket propulsion or rapid response gas generation systems and methods are disclosed in which a novel one component, single tank storable, low toxicity, low detonation sensitivity liquid monopropellant containing a mixture of aqueous 70% hydrogen peroxide, alcohol, and water is catalytically decomposed with an iridium based catalyst. The resulting rapidly formed gaseous decomposition products consisting substantially of carbon dioxide and water vapor are used for rocket propulsion, satellite propulsion, divert attitude control systems for interceptor missiles, and other power control systems where a re-start capability is desired.



Inventors:
Lundstrom, Norman H. (Fox Island, WA, US)
Gribben, Edward S. (Amherst, NY, US)
Marvin, Mayne D. (Gowanda, NY, US)
Application Number:
10/402139
Publication Date:
11/04/2004
Filing Date:
03/31/2003
Assignee:
Atlantic Research Corporation (Gainsville, VA, US)
Primary Class:
International Classes:
C06B47/00; C06D5/04; (IPC1-7): C06B47/00
View Patent Images:



Primary Examiner:
FELTON, AILEEN BAKER
Attorney, Agent or Firm:
NIXON & VANDERHYE, PC (ARLINGTON, VA, US)
Claims:

What is claimed is:



1. A gas generation system comprising: a liquid monopropellant comprising a solution of hydrogen peroxide, alcohol, water, and optionally a stabilizer, and an iridium catalyst for providing rapid catalytic decomposition of the monopropellant solution.

2. The system of claim 1, wherein the catalyst comprises iridium and at least one of ruthenium, iridium, palladium and platinum.

3. The system of claim 1, in which the monopropellant is a class 1.3 one component liquid propellant formulation comprising a solution of stabilized hydrogen peroxide, alcohol, and water; which when catalytically decomposed; forms gaseous products consisting substantially of carbon dioxide and water vapor.

4. The system of claim 1, in which the monopropellant is a class 1.3 one component liquid propellant formulation comprising a solution of stabilized hydrogen peroxide, alcohol, and water; which when catalytically decomposed; forms gaseous products consisting substantially of carbon dioxide, water vapor, and a low concentration of oxygen.

5. The system of claim 1, in which the monopropellant is a class 1.3 one component liquid propellant formulation comprising a solution of stabilized hydrogen peroxide, alcohol, and water; which when catalytically decomposed; forms gaseous products consisting substantially of carbon dioxide, water vapor, and a low concentration of carbon monoxide.

6. The system of claim 1, wherein the alcohol in the liquid monopropellant comprises at least one of methanol and ethanol.

7. The system of claim 1, wherein the alcohol in the liquid monopropellant comprises an ethanol/water mixture.

8. The system of claim 1, wherein the alcohol in the liquid monopropellant comprises a methanol/water mixture.

9. The system of claim 1, wherein the hydrogen peroxide is a stabilized hydrogen peroxide/water mixture.

10. The system of claim 1, wherein the hydrogen peroxide is a water solution containing 60-90 wt % stabilized hydrogen peroxide.

11. The system of claim 10, wherein the water solution contains about 70 wt % hydrogen peroxide.

12. The system of the system in claim 1, in which the water is purified or unpurified.

13. The system of claim 1 in which the liquid monopropellant is catalytically decomposed on a supported or unsupported iridium-based catalyst.

14. The system of claim 1 in which the liquid monopropellant is catalytically decomposed on a supported or unsupported iridium based catalyst containing ruthenium.

15. The system of claim 1, wherein the catalyst is in the form of granules.

16. The catalyst of claim 15, wherein the size of the granules is about 14-18 mesh.

17. The system of claim 1, wherein the catalyst is deposited onto a porous carrier.

18. The system of claim 17, wherein the porous carrier is comprised of a refractory.

19. The system of claim 18, wherein the refractory comprises at least one of alumina, silica, zirconia, clays, silicates, aluminates and mixtures thereof.

20. The system of claim 1, wherein the stabilizer comprises tin in the form of an alkali metal stannate.

21. The system of claim 1, wherein the stabilizer comprises a nitrogen containing phosphonic acid.

22. The system of claim 1, wherein the stabilizer comprises a phosphonic acid.

23. The system of claim 1, wherein the stabilizer comprises an organophosphonic acid.

24. The system of claim 23, wherein the stabilizer comprises amino tris(methylenephosphonic acid) (ATMP), ethylenediamine tetra(methylenephosphonic acid) (EDTMP), 1-hydroxyethyl-1, 1-diphosphonic acid (HEDP); or mixtures thereof.

25. The system of claim 1, wherein the stabilizer comprises a mixture of a primary stabilizer in the form of an alkali metal stannate with a pyrophosphate of a phosphate for improving the stability of the colloidal stannic oxide formed from the alkali metal stannate.

26. The system of claim 1, wherein the stabilizer comprises a mixture of a primary stabilizer in the form of an alkali metal stannate with a pyrophosphate or phosphate for improving the stability of the colloidal stannic oxide formed from the alkali metal stannate and an organophosphonic acid.

27. A gas generation method which comprises combusting a gas generant system comprised of: a liquid monopropellant comprising a solution of hydrogen peroxide, alcohol, water, and optionally a stabilizer, and an irridium catalyst for providing rapid catalytic decomposition of the monopropellant solution.

28. The system of claim 27, wherein the catalyst comprises iridium and at least one of ruthenium, iridium, palladium and platinum.

29. The system of claim 27, in which the monopropellant is a class 1.3 one component liquid propellant formulation comprising a solution of stabilized hydrogen peroxide, alcohol, and water; which when catalytically decomposed; forms gaseous products consisting substantially of carbon dioxide and water vapor.

30. The system of claim 27, in which the monopropellant is a class 1.3 one component liquid propellant formulation comprising a solution of stabilized hydrogen peroxide, alcohol, and water; which when catalytically decomposed; forms gaseous products consisting substantially of carbon dioxide, water vapor, and a low concentration of oxygen.

31. The system of claim 27, in which the monopropellant is a class 1.3 one component liquid propellant formulation comprising a solution of stabilized hydrogen peroxide, alcohol, and water; which when catalytically decomposed; forms gaseous products consisting substantially of carbon dioxide, water vapor, and a low concentration of carbon monoxide.

32. The system of claim 27, wherein the alcohol in the liquid monopropellant comprises at least one of methanol and ethanol.

33. The system of claim 27, wherein the alcohol in the liquid monopropellant comprises an ethanol/water mixture.

34. The system of claim 27, wherein the alcohol in the liquid monopropellant comprises a methanol/water mixture.

35. The system of claim 27, wherein the hydrogen peroxide is a stabilized hydrogen peroxide/water mixture.

36. The system of claim 27, wherein the hydrogen peroxide is a water solution containing 60-90 wt % stabilized hydrogen peroxide.

37. The system of claim 36, wherein the water solution contains about 70 wt % hydrogen peroxide.

38. The system of the system in claim 27, in which the water is purified or unpurified.

39. The system of claim 27 in which the liquid monopropellant is catalytically decomposed on a supported or unsupported iridium-based catalyst.

40. The system of claim 27 in which the liquid monopropellant is catalytically decomposed on a supported or unsupported iridium based catalyst containing ruthenium.

41. The system of claim 27, wherein the catalyst is in the form of granules.

42. The catalyst of claim 41, wherein the size of the granules is about 14-18 mesh.

43. The system of claim 27, wherein the catalyst is deposited onto a porous carrier.

43. The system of claim 43, wherein the porous carrier is comprised of a refractory.

44. The system of claim 44, wherein the refractory comprises at least one of alumina, silica, zirconia, clays, silicates, aluminates and mixtures thereof.

45. The system of claim 27, wherein the stabilizer comprises tin in the form of an alkali metal stannate.

46. The system of claim 27, wherein the stabilizer comprises a nitrogen containing phosphonic acid.

47. The system of claim 27, wherein the stabilizer comprises a phosphonic acid.

48. The system of claim 27, wherein the stabilizer comprises an organophosphonic acid.

49. The system of claim 48, wherein the stabilizer comprises amino tris(methylenephosphonic acid) (ATMP), ethylenediamine tetra(methylenephosphonic acid) (EDTMP), 1-hydroxyethyl-1,1-diphosphonic acid (HEDP); or mixtures thereof.

50. The system of claim 27, wherein the stabilizer comprises a mixture of a primary stabilizer in the form of an alkali metal stannate with a pyrophosphate of a phosphate for improving the stability of the colloidal stannic oxide formed from the alkali metal stannate.

51. The system of claim 27, wherein the stabilizer comprises a mixture of a primary stabilizer in the form of an alkali metal stannate with a pyrophosphate or phosphate for improving the stability of the colloidal stannic oxide formed from the alkali metal stannate and an organophosphonic acid.

52. A hydrogen peroxide-based liquid gas generant system which comprises: (i) an aqueous liquid monopropellant comprising a solution of hydrogen peroxide and alcohol, and (ii) a catalytically effective amount of an iridium catalyst.

53. The system of claim 52, wherein the iridium catalyst includes iridium metal deposited onto a porous carrier.

54. The system of claim 53, wherein the catalyst is supported on a porous refractory carrier.

55. The system of claim 54, wherein the porous carrier is comprises at least one of alumina, silica, zirconia, clays, silicates, aluminates and mixtures thereof.

56. The system of claim 52, wherein the monopropellant comprises a stabilizer.

57. The system of claim 56, wherein the stabilizer comprises tin in the form of an alkali metal stannate.

58. The system of claim 56, wherein the stabilizer comprises a phosphonic acid.

Description:

FIELD OF INVENTION

[0001] The present invention relates generally to a method and system for rocket propulsion or gas generation comprising the catalytic decomposition or ignition of non-hypergolic premixed monopropellant mixtures or solutions based on hydrogen peroxide and organic fuels. The catalyzed decomposition of these one-component propellant mixtures or solutions results in extremely rapid formation of gaseous reaction products applicable to various types of rocket propulsion, satellite propulsion or other types of rapid response gas generation systems. In preferred forms, the present invention comprises a supported or unsupported catalytic surface consisting of iridium or a mixture of iridium with other reactive catalytic metals such as ruthenium and/or platinum which results in a repeatable start-stop capability for the gaseous decomposition of a single component non-hypergolic monopropellant mixture consisting of hydrogen peroxide, alcohol, and water.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates to methods and systems for repeatable, start-stop, multipulse, high response gas generation for use in rocket propulsion and other applications involving the catalytic decomposition of novel relatively insensitive single component liquid monopropellant compositions based on mixtures or solutions of aqueous hydrogen peroxide with various low carbon alcohols, or mixtures thereof. Low carbon alcohols are defined as those containing not more than four carbon atoms within the selected alcohol molecular structure. Preferred low carbon alcohols include ethyl alcohol (ethanol), methyl alcohol (methanol), or mixtures thereof. A preferred water solution of hydrogen peroxide consists of a commercial/industrial grade containing a 70% concentration of hydrogen peroxide, either stabilized or unstabilized.

[0003] The methods and systems of the present invention generally comprise two major components or subsystems, including: (1) a catalyst pack and (2) a single component liquid monopropellant composition. A preferred catalyst pack in the form of a supported or unsupported catalyst comprises either the use of iridium or an iridium/ruthenium based mixture commercially available as SHELL 405 or its equivalent. The single component liquid monopropellant composition most preferably comprises a mixture of a aqueous solution of 70 wt % hydrogen peroxide and methyl or ethyl alcohol. A preferred single component liquid monopropellant solution comprises a mixture of 80 wt % commercially available 70% aqueous hydrogen peroxide, 12 wt % ethyl alcohol, and 8 wt % water. The above preferred composition equates to a solution containing 56 wt % of 100 wt % hydrogen peroxide, 12 wt % ethyl alcohol, and 32 wt % water. This composition is preferred because of certain advantages over the prior art such as class 1.3 low detonation sensitivity and lowered toxicity. Such preferred compositions are disclosed further in copending commonly owned U.S. application Ser. No. 09/363,013 filed Jul. 29, 1999 entitled “PREMIXED LIQUID MONOPROPELLANT SOLUTIONS AND MIXTURES”, the entire content of which is expressly incorporated hereinto by reference.

[0004] Solid silver catalysts are known to be the most accepted with regard to promoting the rapid decomposition of highly concentrated aqueous solutions of hydrogen peroxide ranging in concentrations of 85-9 8 wt %. U.S. Pat. No. 5,711,146 to Armstrong et al1 discloses that silver catalysts are not attractive for use over long periods with hydrogen peroxide concentrations greater than about 93% because of the loss of strength which silver undergoes at the high adiabatic decomposition temperatures resulting from the use of the more concentrated peroxide. In addition, U.S. Pat. No. 5,711,146 indicates that an alternative catalyst system based on a mixture of ruthenium with iridium or platinum is acceptable for decomposition of hydrogen peroxide in concentrations of greater than 95 wt %. 1 The entire content of each prior-issued U.S. Patent cited herein is expressly incorporated hereinto by reference.

[0005] At an 85-98 wt % concentration, hydrogen peroxide is referred in the industry as “rocket grade” or “high performance grade” and involves more extensive, time consuming, hazardous, and costly manufacturing operations. In the past, aqueous hydrogen peroxide was used by itself at these high concentrations as a single constituent liquid monopropellant for power generation and propulsion and deemed to dangerous for direct incorporation of non-hypergolic organic fuel ingredients for improving the performance as a monopropellant system. Also, in the past, 70 wt % aqueous hydrogen peroxide was not considered a viable monopropellant candidate due to its low energy output and poor response to catalytic decomposition resulting from its high concentration of water.

[0006] Hydrazine monopropellant fuels are known to be usefully catalyzed by iridium as disclosed, for example, in U.S. Pat. Nos. 3,846,339 to Blumenthal et al and 5,485,721 to Steenborg. However, hydrazine based monopropellants and bipropellants do not conform to recent requirements for more environmentally friendly and less toxic chemical ingredients for use in rocket systems. Hydrazine is an extremely toxic material and scientific investigation suggests that it may be a human carcinogen. Combustion of other monopropellant formulations, such as hydroxylanimonium nitrate-based compositions have also been proposed to be catalyzed by iridium, as evidenced by U.S. Pat. Nos. 5,485,722 to Schmidt et al and 5,608,179 to Voecks et al. In addition, iridium catalysts of the type disclosed more fully in U.S. Pat. No. 4,124,538 to Armstrong et al have been suggested to be useful in a catalytic combustor for generating a working fluid (i.e., steam) from the combustion of high pressure hydrogen and oxygen.

[0007] It has now been discovered that a system comprising a novel monopropellant composition based on a mixture or solution containing 70 wt % aqueous hydrogen peroxide, ethyl alcohol, and water in the proper stoichiometric combination can be catalytically and rapidly decomposed repeatedly on a supported or unsupported iridium based catalyst, such as of SHELL 405 or a variant thereof, to yield certain desired gaseous decomposition products for use in rocket propulsion, satellite thrusters, divert attitude control systems for interceptor missiles, and other power generation systems. No methods or systems are currently known for the rapid and repeatable decomposition, using an iridium based catalyst, of a high water content hydrogen peroxide/ethyl alcohol mixture or solution, the inexpensive and commercially available oxidizer and fuel ingredients of which can be readily and safely blended together and stored in one propellant tank, and used as a monopropellant for rocket propulsion applications.

[0008] These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0009] For the purpose of this invention, a monopropellant, in contrast to a bipropellant, is one in which the oxidizer and fuel components are physically mixed or blended together to provide a compatible non-hypergolic liquid composition or solution of ingredients which requires only one storage tank for the propellant. A bipropellant requires two storage tanks, a separate storage tank for each of the oxidizer and fuel components, because the oxidizer and fuel ingredients are incompatible, and generally are highly reactive materials which are hypergolic (autoignite) on contact with each other.

[0010] A liquid monopropellant rocket or thruster propulsion system generally consists of a pressurization system, one propellant tank, a fuel valve, and a chamber containing a catalytic reactor with a nozzle. The system commences operation when the pressurization is activated, and the monopropellant is pressurized in the propellant storage tank of the flight vehicle. When the fuel valve is opened, the pressurized low toxicity monopropellant composition of the present invention containing the solution of hydrogen peroxide, alcohol, and water is expelled into the chamber, onto the catalyst bed, where the composition is exothermically decomposed into low molecular weight gases consisting of carbon dioxide and water vapor.

[0011] As discussed above, the methods and systems of the present invention generally comprise two subsystems, namely (1) a catalyst for providing catalytic decomposition of the liquid monopropellant composition, and (2) the monopropellant composition itself for providing the desired gaseous decomposition products resulting from contact with the catalyst surface, the gaseous products of which provide the thrust and energy for use in a rocket propulsion or other power generation device.

[0012] For the purpose of this invention, as used herein in the accompanying claims and discussed briefly above, the term “monopropellant” and like terms such as “gas generant” is meant to refer to a liquid mixture in which the oxidizer and fuel ingredients are dissolved in one another to form a miscible liquid solution thereof. The liquid monopropellants of this invention, moreover, are aqueous—that is, contain a significant amount of water. Preferably, the liquid monopropellants will contain at least about 20 wt % water, more preferably between about 20 wt % to about 45 wt % water, and most preferably about 28 wt % to 36 wt % water.

[0013] The method and system of the present invention will include iridium as a partial or total constituent of the catalyst used for the catalytic decomposition of the monopropellant composition or solution comprising hydrogen peroxide, ethanol, and water. Catalysts based on the use of iridium are well known in the art for hydrazine monopropellant decomposition and to a very limited extent, as discussed above, with 95 wt % and greater concentrations of aqueous hydrogen peroxide as disclosed in U.S. Pat. No. 5,711,146 to Armstrong et al. However, what is unknown in the art is the use of an iridium based catalyst for the catalytic decomposition of a one tank storable, compatible liquid oxidizer/alcohol/water monopropellant composition or solution in which the composition is a solution of fuel, oxidizer, and a high concentration of water for controlling the decomposition temperature and detonation sensitivity of the propellant. In fact, as noted briefly above, for the catalytic decomposition of hydrogen peroxide, the art generally discloses the use of silver based catalysts.

[0014] The iridium may be coated and/or applied to a particulate substrate, for example, alumina or variations thereof, and mixed with the other components. Although various forms of iridium and mixtures of iridium with other materials and on various substrates may be used, a preferred form for the iridium catalyst is in the form of 1.0% iridium on high purity 4 mm gamma alumina spheres, reduced, anhydrous, and available under stock number 11735 from Alfa Aesar, Ward Hill, Mass. 01835. Another preferred form for the iridium catalyst is the iridium stock number 11735, discussed above, combined with elemental palladium powder of less than 7.5 microns with an average particle size of 1.1-2.0 microns available from Alfa Aesar as stock number 14622. In accordance with this invention, other preferred forms of the iridium catalyst are described in the above-cited U.S. Pat. No. 4,124,538 to Armstrong et al, a most preferred variety described as catalyst B in Example II of U.S. Pat. No. 4,124,538. Another even more preferred iridium based catalyst is that which is commercially available in its different forms from the Shell Oil Company as “SHELL 405” catalyst. The various iridium based catalysts may be incorporated as powders, granules, pellets, wires, and mixtures thereof. The catalyst may be used with or without various substrates either supported or unsupported. However, the catalyst is preferably used with other substrates in a supported mode. In general, although not required, a preferred iridium based catalyst of the Armstrong et al or SHELL 405 type will have iridium or iridium based metal mixtures containing, for example, ruthenium and/or palladium deposited on a carrier having a pore volume of at least 0.1 cubic centimeters per gram and a specific surface area, measured in square meters per gram, equal to 195 (Cp+0.013+0.736 Vp) where Cp is the specific heat capacity of the carrier at about 25 degrees centigrade in calories per gram per degree, and Vp is the pore volume of the carrier in cubic centimeters per gram.

[0015] The iridium-containing material may be iridium metal per se, or a mixture of iridium with another active metal such as ruthenium or palladium. The iridium metal or metal mixture may be deposited onto the carrier in an amount between about 10% to about 60% by weight of the catalyst. However, the iridium metal or metal mixture is most preferably deposited onto the carrier in an amount between about 20% to about 40% by weight of the catalyst and distributed through the pores thereof in discrete particles sufficiently separated from each other so that they do not sinter or fuse together when the catalyst is at the monopropellant decomposition temperature. In accordance with the present invention, it is highly desirable that the iridium, iridium/ruthenium, and iridium/palladium active metal based catalysts and mixtures thereof be properly dispersed on the surface of the carrier if the catalyst is to have the required activity and stability, for many successive starts using the one component premixed monopropellant solution disclosed herein, and assure repeated operation of the propulsion system as required.

[0016] In the various combinations of iridium with other metals such as ruthenium and or palladium, it is desirable to employ the iridium at a level of about 20 to 80 atom % when incorporated into either an iridium/ruthenium, iridium/palladium, or iridium/ruthenium/palladium mixture. Preferably, the iridium based catalytic metal or mixture containing iridium with the other active metals such as ruthenium and/or palladium is uniformly distributed over the surface of the carrier in particles of about 10 to 100 angstroms in diameter and separated from each other by an average of about 20 angstroms to 250 angstroms. Most preferably, the catalyst particles will be about 20 to 30 angstroms in diameter and spaced about 50 to 60 angstroms apart from each other. The spacing or separation distances of the particles are similar as disclosed in U.S. Pat. No. 4,124,538 to Armstrong et al, and to be understood as idealized distances measured along surfaces, and not direct distances cutting across pore walls.

[0017] The novel one component liquid monopropellant formulation used in conjunction with the catalyst system described above contains a compatible mixture or solution of liquid ingredients which are miscible with each other, storable in a single tank, and when catalytically decomposed with a catalyst, such as SHELL 405 or a variation thereof, provide gaseous products consisting of carbon dioxide and water vapor for use as a propelling medium for a rocket, satellite, or missile propulsion or control system.

[0018] The monopropellant used in this invention contains three subcomponents consisting of an oxidizer, fuel, and coolant-desensitizer. The oxidizer is hydrogen peroxide preferably of a readily available inexpensive commercial non-rocket industrial grade consisting of a 70 wt % aqueous solution with or without the various stabilizers used in the high strength commercial grades of material. The liquid fuel is a readily available inexpensive industrial grade, low carbon alcohol, preferably methanol or ethanol. The final sub-component is water which acts as a coolant and desensitizer to decrease the detonation susceptibility and sensitivity of the mixed sub-components.

[0019] Upon mixing the three liquid sub-components, the novel low toxicity, low detonation susceptibility monopropellant solution may be used with the iridium based catalyst discussed above to provide an effective propulsion or rapid response gas generation system with a start-stop capability. A preferred monopropellant composition or solution (99323-1) consists of 56 wt % hydrogen peroxide, 12 wt % ethanol, and 32 wt % water. It is more preferred that the above monopropellant solution be prepared using an inexpensive readily available industrial grade 70 wt % aqueous solution of hydrogen peroxide with or without stabilizers. When an aqueous 70 wt % grade of hydrogen peroxide is used, the above preferred monopropellant solution (99323-1) containing 56 wt % hydrogen peroxide, 12 wt % ethanol, and 32 wt % water equates to 80 wt % of an aqueous 70% concentration of hydrogen peroxide, 12 wt % ethanol, and 8 wt % water.

[0020] The optimum operation of certain types of rockets, for example, vernier control rockets, thrust vector control motors and the like, requires maximum thrust control. The present invention pertains to a novel system which is an improvement over the prior art which combines an iridium based active metal catalyst with a low toxicity and low detonation sensitivity liquid monopropellant solution, which contains no hydrazine, and results in a throttable rapidly responsive and temperature controllable propulsion or gas generation system, that can be successively turned on and off at will. In addition, the mixed hydrogen peroxide/ethanol/water monopropellant solution of the present invention provides a significant improvement in performance, with respect to boost velocity (Compositions C, E, and F in Table I below) when theoretically compared to a state of the art hydrazine system. Even though the most preferred mixed monopropellant solution (Composition C of Table I) of the present invention provides significantly greater performance than a hydrazine system, explosive sensitivity tests indicate that the formulation meets the requirements for a class 1.3 propellant based on results of the Naval Ordnance Laboratory NOL card gap test at 70 cards. Tests with #8 blasting caps were negative and impact, friction, and electrostatic tests were acceptable.

[0021] In the case of a spill, the monopropellant system of the present invention is much safer to clean up. Whereas prior art mono and bipropellant systems containing anhydrous hydrazine, hydrazine hydrate, or organic hydrazine derivatives such as unsymmetrical dimethylhydrazine and monomethylhydrazine are extremely toxic and considered potential human carcinogens, the ingredients used in the monopropellant solution of the present invention are considered to be significantly less toxic and not carcinogenic. As discussed above, a catalyzed monopropellant based upon a method or system of the present invention which includes hydrogen peroxide/alcohol/water and iridium based catalyst, and preferably 70% aqueous hydrogen peroxide/ethanol/water and SHELL 405 catalyst, looks very attractive as a replacement for anhydrous hydrazine because it is less toxic, non-carcinogenic, and provides improved performance over hydrazine. The 70% aqueous hydrogen peroxide component is inexpensive, commercially available, and less hazardous than “Rocket Grade” 90-98% hydrogen peroxide.

[0022] Low to higher levels of various proprietary and nonproprietary stabilizers may be incorporated into the hydrogen peroxide solution as desired. Stability is usually achieved by using a mixture of stabilizers and the generally accepted primary stabilizer is tin supplied in the form of an alkali metal stannate which forms colloidal stannic oxide. Pyrophosphates or phosphates are added for improving the stability of the colloidal stannic oxide. Other stabilizers are known in the art and include various phosphonic acids, boric acids, oxalic acids, hydroxyquinoline, and acetanilide. Ethanol is commercially available, inexpensive, non-toxic, readily miscible with the other ingredients, and exhibits a low freezing point. Water is used for tailoring or control of decomposition temperature and resistance to detonation. In accordance with the present invention, a preferred monopropellant (99323-1 blend) catalyzed to decomposition, containing 80 wt % of an aqueous solution of 70% hydrogen peroxide, 12 wt % ethanol, and 8 wt % water theoretically results in a low signature exhaust containing 22.9wt % carbon dioxide, 1.3 wt % oxygen, and 75.7 wt % water vapor.

[0023] The present invention will be further described with reference to the following non-limiting example.

EXAMPLE

[0024] Table I below shows particularly preferred examples of premixed liquid monopropellant solutions and mixtures employed in the present invention. 1

TABLE 1
Examples of Premixed Liquid Monopropellant
Solutions and Mixtures
CompositionABCDEFG
70% H2O259.8684.0080.0080.0077.0077.0036.67
AND51.20
AN25.00
Ethanol15.1416.0012.0020.0020.0018.0012.13
Water8.003.005.00
Freezing Point ° C.<−10<−10<−10<−10<−10
Flame Temp. ° K.2000200019001817171317562542
IVAC276.0279.6273.1270.0264.8266.9307.7
Density (rho).0450.0422.0423.0413.0410.0412.0503
PERFORMANCE COMPARED TO NTO/MMH:
Relative Boost Velocity Compared With
Baseline Bipropellant (NTO/MMH)
mf = 0.10.710.770.710.721.00
mf = 0.50.800.770.720.730.96
mf = 0.90.790.780.730.740.92
PERFORMANCE COMPARED TO ANHYDROUS HYDRAZINE:
Relative Boost Velocity Compared With
Baseline Monopropellant (ANHYDROUS HYDRAZINE)
mf = 0.11.531.461.421.381.341.361.88
mf = 0.51.451.411.381.341.301.321.75
mf = 0.91.361.341.311.291.261.271.58
HAZARDS
(Imapct, Friction,Accept-Accept-Accept-Accept-Accept-
Electrostatic)ableableableableable
Detonation #8yesyesnoyes
Cap
NOL card gap testNegative
@ 70 cards
ExplosiveClass 1.3
Classification

[0025] A full scale test of the system and methodology disclosed in the present invention, which includes the preferred iridium based SHELL 405 catalyst subsystem and the preferred blended 99323-1 monopropellant solution subsystem shown below, was conducted in a six (6) lbf monopropellant thruster. The take-apart monopropellant thruster assembly consisted of a thrust chamber assembly, SHELL 405 catalyst, a thermal standoff, and a solenoid valve. The thruster design had previously been designed, fabricated and tested as a six (6) lbf hydrazine monopropellant thruster. In accordance with the present invention, the thruster design was modified for use with the low toxicity hydrogen peroxide based 99323-1 monopropellant blend and incorporated a 1.25″ long catalyst bed containing the SHELL 405 catalyst. A flat bed plate was used to maximize catalyst bed volume and a heat shield was utilized to maximize the heat input to the catalyst bed. In addition a gaseous nitrogen (GN2) purge was used to minimize the potential for catalyst oxidation during preheat. A summary of the test results is provided in Table II below. 2

TABLE II
Full Scale Test
(1) Nominal Thruster Operating Characteristics.
Monopropellant:99323-1
Chamber Pressure:200 psia
Feed Pressure:320 psia
Thrust, Vacuum:6 lbf
Bed Loading0.04 lbm/sec/sq. in.
Catalyst:SHELL 405 (14-18 mesh)
Catalyst Bed Length:1.25 inches
Catalyst Bed Preheat Temperature:600° F.
ValveSolenoid
IngredientPercent by Weight
(2) 99323-1 Monopropellant Solution:
70 wt % aqueous hydrogen peroxide80.00
Ethanol12.00
Water 8.00
(3) Catalyst Bed and Conditions:
Catalyst:SHELL 405
Bed Size:1.25 inches
Temperature600° F.
DurationC* Efficiency
(4) Monopropellant Feed Pressure Tests @ 350 psia:
6 second test˜94%
5 second test˜94%
3 second test˜94%
(5) Comments:
Tests considered success.
Two longer duration tests completed.
Series of pulse tests completed.
Steady state achieved in ˜3 seconds.
Catalyst bed in good condition.
Some deterioration of catalyst bed plate.
When pulsed, variability of Pc Ibit decreases as # of
pulses increase.
Demonstrated high efficiency.

[0026] The relationship between feed pressure and chamber pressure (Pc) was generally linear. When the 99323-1 monopropellant solution was catalytically decomposed on the 1.25 inch SHELL 405 catalyst bed at 600° F., a rapid decomposition into gaseous components resulted. In fact, all of the tests, long duration and pulsing, resulted in rapid catalytic decomposition of the 99323-1 monopropellant blend with the chamber pressure tending to drift upward over time to a steady state value. The transient to reach steady state chamber pressure was about three seconds. The time to reach 90% chamber pressure was longer than that exhibited for a hydrazine monopropellant. The test results indicated a relatively linear relationship between chamber pressure and flow rate but were slightly offset from the predicted performance. The offset was due to a lower than anticipated characteristic velocity (C*). The longer duration tests exhibited a definite shift in performance (i.e. higher C*) at steady state conditions. Predicted C* efficiency for the 99323-1 monopropellant blend was 4181 ft/sec, assuming a combustion efficiency of 95%. Depending on duration, approximately 85 to 95% of theoretical C* was achieved in the test series.

[0027] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.