CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63/274,143, titled “TANK FOR AN OXIDIZER IN A LIQUID ROCKET PROPULSION SYSTEM”, filed November 1, 2021, the content of which are all incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

[002] The present invention relates generally to an oxidizer tank. More specifically, the present invention relates to tank for bipropellant oxidizer.

BACKGROUND OF THE INVENTION

[003] Liquid rocket bipropellant systems generate thrust by the expulsion of high velocity exhaust gases produced by a reaction between a fuel and an oxidizer. Direct ignition of rocket propellant systems may be achieved using fuels and oxidizers in a hypergolic combination, which ignites spontaneously upon contact with each other. However, hypergolic ignition systems often use a harmful component, fuel or oxidizer.

[004] Fuels, such as MMH (Monomethyl hydrazine) combined with oxidizers, including nitrogen tetroxide or inhibited red fuming nitric acid, have typically been employed in hypergolic bipropellant systems. However, these propellants are considered highly toxic and carcinogenic chemicals to humans, making their implementation in propulsion systems expensive and problematic.

[005] In the last decades, there is a growing interest in the use of hydrogen peroxide as an alternative oxidizer due to its properties such as being non-toxic (“green” propellant), non- cryogenic, storable, and high densityT Several studies have been conducted to investigate the hypergolicity of hydrogen peroxide with different types of fuels.

[006] In liquid-bipropellant engines, the oxidizer is provided from an oxidizer tank while the fuel is provided from a fuel tank. A system of valves controls the synchronized provision of both the fuel and the oxidizer to the combustion chamber. Upon opening flow control valves, determining amounts of fuel and oxidizer are provided to produce a reaction. The flow control valve may be a Normally Closed (NC) solenoid valve, operated in pulses and/or in steady- state. [007] In order to provide the oxidizer and the fuel at the required flows, bi-compartmental tanks may be used upon opening the corresponding flow control valve. Such a tank includes a flexible diaphragm that divides the tank into two compartments, one filled with either the oxidizer (in an oxidizer tank) or fuel (in a fuel tank), and the other with pressurized gas for pushing the oxidizer or the fuel, upon opening of the valves.

[008] However, using hydrogen peroxide as an oxidizer challenges state-of-the-art bicompartment tanks due to its high corrosivity with common elastomeric diaphragms.

[009] Accordingly, there is a need for a bi-compartment oxidizer tank for holding and providing hydrogen peroxide to bi-propellant engine.

SUMMARY OF THE INVENTION

[0010] Some aspects of the invention are directed to an oxidizer tank, comprising: a first shell and a second shell; and a flexible diaphragm separating the first shell from the second shell, thus defining: a first compartment, configured to contain the oxidizer; and a second compartment, configured to contain a pressurized gas. In some embodiments, the flexible diaphragm comprises a fluoro-organic polymeric material.

[0011] In some embodiments, the fluoro-organic polymeric material includes one of, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP) and perfluoroalkoxy alkanes (PFA).

[0012] In some embodiments, the first shell includes a peripheral first diaphragm attachment shoulder comprising at least one first recess or at least one first protrusion or both; and the second shell includes a peripheral second diaphragm attachment shoulder comprising at least one second recess or at least one second protrusion or both. In some embodiments, the at least one first recess is configured to be partially inserted into the at least one second protrusion, and the at least one second recess is configured to partially inserted into the at least one first protrusion, such that a gap is formed between each recess to each corresponding protrusion. In some embodiments, the flexible diaphragm is inserted into, the gap. In some embodiments, the gap’s size is set to provide a seal compression ratio (squeeze) of between 0.02 and 0.15 [mm/mm]. In some embodiments, the size of the gap’s size is set to provide compression stress below the yield point of the fluoro-organic polymeric material.

[0013] In some embodiments, the first shell, the second shell or both have at least one of: a circular cross-section and a rectangular cross-section. In some embodiments, an inlet for liquid oxidizer is located in the first shell. In some embodiments, when the tank is empty and the flexible diaphragm is in contact with the first shell.

[0014] In some embodiments, the tank further comprises the pressurized gas located between the flexible diaphragm and the second shell.

[0015] In some embodiments, the tank further comprises two or more connectors for connecting: (a) the first compartment and the second compartment; and (b) said first shell and said second shell. In some embodiments, the one or more connectors are fasteners. In some embodiments, the first and the second shells are welded to each other.

[0016] In some embodiments, the tank has a diameter of 50 to 2500 mm.

[0017] In some embodiments, the at least one first recess and the at least one second protrusion have: a round shape, a triangular shape, a rectangular or a polygonal shape. In some embodiments, the at least one second recess and the at least one first protrusion have: a round shape, a triangular shape, a rectangular or a polygonal shape.

[0018] In some embodiments, the pressurized gas is provided at a pressure from 0.1 to 100 bars. In some embodiments, the pressurized gas is provided at a pressure from 10 to 50 bars. [0019] In some embodiments, the second shell comprises a pressurized gas inlet.

[0020] Some additional aspects of the invention may be directed to a method of propelling a liquid-propellant engine, comprising: synchronizing a provision of liquid fuel from a fuel tank and an oxidizer from an oxidizer tank into a combustion chamber; and producing a reaction between the fuel and the oxidizer, wherein the oxidizer is provided from an oxidizer tank, comprises: a first shell and a second shell; and a flexible diaphragm separating the first shell from the second shell, thus defining: a first compartment configured to contain an oxidizer; and a second compartment configured to contain a pressurized gas, and wherein the flexible diaphragm comprises fluoro-organic polymeric material.

[0021] In some embodiments, synchronizing the provision comprises opening flow control valves, such that determined amounts of fuel and oxidizer are provided to produce the reaction.

[0022] Some additional aspects of the invention may be directed to a liquid rocket bipropellant system, comprising: a bi-compartmental fuel tank; a bi-compartmental oxidizer tank; and at least two control valves configured to control the provision of a determined amount of fuel from the fuel tank and oxidizer and a determined amount of oxidizer from the oxidizer tank to a reaction chamber, wherein, the bi-compartmental oxidizer tank comprises: a first shell and a second shell; and a flexible diaphragm separating the first shell from the second shell, thus defining: a first compartment configured to contain an oxidizer; and a second compartment configured to contain a pressurized gas, and wherein the flexible diaphragm comprises fluoro-organic polymeric material.

[0023] Some additional aspects of the invention may direct to a flying platform comprising the liquid rocket bipropellant system accoridng to embodiments of the invention, wherein the platform is selected from a rocket, a satellite, a missile and a launcher.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0025] Figs. 1A and IB are illustrations of a front view and a section view of an oxidizer tank according to some embodiments of the invention;

[0026] Figs 2A and 2B are detailed illustrations of a section view of an oxidizer tank and an enlarged section of a diaphragm attachment area of the oxidizer tank according to some embodiments of the invention;

[0027] Fig. 3A is a detailed illustration of a connection between two shells of the oxidizer tank according to some embodiments of the invention;

[0028] Fig. 3B is an enlarged detailed illustration of the diaphragm attachment area of the oxidizer tank according to some embodiments of the invention;

[0029] Fig. 4 which is a flowchart of a method of propelling a liquid-propellant engine, according to some embodiments of the invention; and

[0030] Fig. 5 is a block diagram of a liquid rocket bipropellant system according to some embodiments of the invention.

[0031] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0032] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0033] Some aspects of the invention are directed to a bi-compartment oxidizer tank for providing oxidizer under the application pressure. The applied pressure is applied in order to allow the oxidizer to be provided into the combustion chamber, upon opening of a valve system (e.g., a Flow Control Valve (FCV)).

[0034] An oxidizer tank according to embodiments of the invention may include a first compartment, configured to contain the oxidizer (e.g., a liquid oxidizer) and a second compartment, configured to contain a pressurized gas (e.g., nitrogen, helium, etc.). The first compartment and the second compartment are defined by a flexible diaphragm separating a first shell of the oxidizer tank from a second shell of the oxidizer tank. In some embodiments, the first shell includes a peripheral first diaphragm attachment shoulder and the second shell includes a peripheral second diaphragm attachment shoulder. In some embodiments, either the first diaphragm attachment shoulder or the second diaphragm attachment shoulder, comprises at least one recess and either the corresponding second diaphragm attachment shoulder or the corresponding first diaphragm attachment shoulder, comprises at least one protrusion configured to be partially inserted into the corresponding recess such that at least one edge of the flexible diaphragm is located in a gap between the at least one protrusion and the at least one recesses, thus providing also the diaphragm attachment for the sealed connection between the first and second shells.

[0035] In some embodiments, the oxidizer is hydrogen peroxide, and the flexible diaphragm may be selected to include a hydrogen peroxide compatible (e.g., durable) material, such as a fluoro-organic polymeric material. In a nonlimiting example, the flexible diaphragm may include polytetrafluoroethylene (PTFE). In another nonlimiting example, the flexible diaphragm may include fluorinated ethylene propylene (FEP). In another nonlimiting example, diaphragm may include perfluoroalkoxy alkanes (PFA). In some embodiments, the flexible diaphragm may include any flexible material that may be coated with hydrogen peroxide compatible, for example, fluoro-organic polymeric, material.

[0036] Fluoro-organic polymeric materials are known to provide good sealing, however when subjected to a seal compression (i.e., squeeze) may plastically deform (e.g., above the yield stress). As a result of such plastic deformation, the sealing provided by the flexible diaphragm is lost. In order to avoid this unwanted result when the first and second shells are connected together, a gap is made between the at least one recess and the at least one protrusion. The gap is determined such that for a given thickness of the flexible diaphragm, upon closing and connecting the first shell and the second shell, the flexible diaphragm is subjected to a seal compression ratio (squeeze) of between, 2 % to 15%, for example, between 4% to 8%, between 2% to 8 %, between 3% to 10%, between 4% to 12%, and between 4% to 15%, which provides the required sealing while avoiding yield and deformation of the flexible diaphragm. In a nonlimiting example, the flexible diaphragm is inserted inside an internal gap not exceeding an outer portion of the diaphragm attachment shoulders, thus allowing the first and second shells to be fully closed together, for example, to be welded together.

[0037] As used herein, seal compression ratio (also known in the art as ‘squeeze’) is defined as the relative reduction (e.g., percentage) in the seal thickness [mm/mm] (e.g., the thickness of the flexible diaphragm), required for sealing.

[0038] Reference is now made to Figs. 1A and IB which are illustrations of a front view and a section view of an oxidizer tank according to some embodiments of the invention. An oxidizer tank 100 may include a first shell 11 and a second shell 12. The first shell may be separated from the second shell by a flexible diaphragm 15, thus defining a first compartment 9 and a second compartment 10. In some embodiments, first compartment 9 may be configured to contain the oxidizer and second compartment 10 may be configured to contain a pressurized gas.

[0039] First shell 11 and second shell 12 may be made of any suitable metallic alloy. Flexible diaphragm 15 may be made of any hydrogen peroxide compatible material. For example, the hydrogen peroxide compatible materials may be fluoro-organic polymeric materials, composite materials including fluoro-organic polymer and the like. In some embodiments, flexible diaphragm 15 may be coated with metallic sheaths and/or free standing metallic sheaths. In a nonlimiting example, the flexible diaphragm may include fluoro-organic polymeric material. [0040] First shell 11 and second shell 12 may have a circular cross-section, comprising a cylindrical, hemispherical, or other dome, as illustrated. Alternatively, first shell 11 and second shell 12 may have any other suitable shape and the invention is not limited to tanks having circular cross-section or hemispherical shells, for example, rectangular cross section. In a nonlimiting example, the diameter of the circular cross-section may be 50-2500 mm. In some embodiments, the diameter of the circular cross-section may be 50-200 mm. In some embodiments, the diameter of the circular cross-section may be 50-300 mm. In some embodiments, the diameter of the circular cross-section may be 50-500 mm. In some embodiments, the diameter of the circular cross-section may be 50-1000 mm. In some embodiments, the diameter of the circular cross-section may be 50-1500 mm. In some embodiments, the diameter of the circular cross-section may be 50-1500 mm. In some embodiments, the diameter of the circular cross-section may be 100-2500 mm. In some embodiments, the diameter of the circular cross-section may be 200-2500 mm. In some embodiments, the diameter of the circular cross-section may be 500-2500 mm. In some embodiments, the diameter of the circular cross-section may be 1000-2500 mm.

[0041] In some embodiments, first shell 11 includes peripheral first diaphragm attachment shoulder 21 and second shell 12 includes peripheral second diaphragm attachment shoulder 22. In some embodiments, flexible diaphragm 15 may be held between first diaphragm attachment shoulder 21 and second diaphragm attachment shoulder 22.

[0042] In some embodiments, oxidizer may enter/exit from inlet/outlet 17 in first shell 11 and the pressurized gas may enter form inlet 16 in second shell 12. In some embodiments, flexible diaphragm 15 is located at first shell 12 when oxidizer tank 100 is empty from oxidizer, as illustrated in Figs. IB and 2A.

[0043] In some embodiments, pressurized gas is located/inserted between flexible diaphragm 15 and second shell 12. In some embodiments, the pressurized gas is introduced to second compartment 10 at 0.1 to 100 bars. In a nonlimiting example, the pressurized gas is introduced at 10-30 bar, for example, 24 bar. In some embodiments, the pressurized gas may occupy at least 0.05, for example, 0.1, 0.2, or more, of the volume of tank 100. In such case, outlet 17 may be connected to a pump for providing the oxidizer with the additional required pressure for being provided to the combustion chamber. Therefore, the pressure at tank 100 is the minimal pressure required to provide the oxidizer to the pump. In a nonlimiting example, tank 100 for low pressures (e.g., below 1 or 2 bar) may have a rectangular cross-section. In a nonlimiting example, pressurized gas at 24 bars may occupy 0.25 of the volume of tank 100 and the oxidizer may occupy the rest of the 0.75. Therefore, upon providing the last oxidizer portion from tank 100, the pressure in the tank is reduced to 6 bars, and flexible diaphragm 15 is located in proximity (e.g., touching) first shell 11. In some embodiments, the gas pressure is determined such that upon providing the last oxidizer portion from tank 100, less than 1 vol.% oxidizer is left in the tank.

[0044] Reference is now made to Figs. 2A and 2B which are detailed illustrations of a section view of an oxidizer tank and an enlarged section of a diaphragm attachment area of the oxidizer tank according to some embodiments of the invention. As better shown in Figs. 2 A and 2B flexible diaphragm 15 is mounted in a gap 23 and/or 24 between first diaphragm attachment shoulder 21 and second diaphragm attachment shoulder 22. In some embodiments, first diaphragm attachment shoulder 21 includes at least one first recess 14. In such case second diaphragm attachment shoulder 22 includes a corresponding first protrusion 13. Additionally or alternatively, first diaphragm attachment shoulder 21 may include at least one first protrusion 13’ and therefore diaphragm attachment shoulder 22 includes a corresponding second recess 14’. In some embodiments, at least one first recess 14 is configured to be partially inserted into the at least one second protrusion 13, and at least one second recess 14’ is configured to be partially inserted into at least one first protrusion 13’, such that a gap 23 and/or 24 is formed between each recess to each corresponding protrusion. In some embodiments, tank 100 may include a plurality of recesses 14 and 14’ and corresponding protrusions 13 and 13’, located at first diaphragm attachment shoulder 21 and second diaphragm attachment shoulder 22.

[0045] In some embodiments, at least one first recess 14 and at least one second protrusion 13’ have: a round shape, a triangular shape, a rectangular or a polygonal shape. In some embodiments, at least one second recess 14’ and the at least one first protrusion 13 have: a round shape, a triangular shape, a rectangular, or a polygonal shape. In some embodiments, first and second diaphragm attachment shoulders may include a labyrinth having any number of protrusions and corresponding recesses.

[0046] In some embodiments, gap 23 and/or 24 is configured to fix a distance ‘d’ between first diaphragm attachment shoulder 21 or the second diaphragm attachment shoulder 22 at which flexible diaphragm 15 is to be inserted. In some embodiments, only first diaphragm attachment shoulder 21 includes gap 23 or only second diaphragm attachment shoulder 22 include gap 24. In some embodiments both first and second diaphragm attachment shoulders, 21 and 22 each include gaps 23 and 24, as illustrated. In some embodiments, the size of each gap 23 and/or 24 is determined to create a squeezing force sufficient for sealing the connection between first and second shells 12 and 22 while avoiding plastic deformation (e.g., yield) in flexible diaphragm 15.

[0047] In some embodiments, the size ‘d’ of gap 23 and/or 24 is determined such that for a given thickness of flexible diaphragm 15, upon closing first shell 11 and the second shell 12, the flexible diaphragm is subjected to a seal compression ratio (squeeze) of between 2% (0.02 [mm/mm]) and 15% (0.15 [mm/mm]). In nonlimiting example, when flexible diaphragm 15 includes polytetrafluoroethylene, the size ‘d’ of gap 23 and/or 24 is determined such that for a given thickness of flexible diaphragm 15, upon closing first shell 11 and the second shell 12, flexible diaphragm 15 is subjected to compression stress below the yield point of the fluoro-organic polymeric material.

[0048] In some embodiments, gaps 23 and/or 24 are internal gaps not exceeding the outer surface of shoulders 21 and 22, thus allowing first shell 11 and second shell 12 to be completely closed when connected together, for example, by continuous welding of the outer surface of shoulders 21 and 22 to each other.

[0049] Reference is now made to Fig. 3A which is a detailed illustration of another nonlimiting example, for connecting shell 11 to shell 12, using a connection according to some embodiments of the invention. Oxidizer tank 100 may further include two or more connectors 25 for connecting first shell 11 and second shell 12. In some embodiments, two or more connectors 25 are detachably connected by one of clamps, screws, bolts 28 or both (as illustrated) or any other fastener.

[0050] Reference is now made to Fig. 3B which is an enlarged detailed illustration of the diaphragm attachment area of the oxidizer tank according to some embodiments of the invention. In the nonlimiting example, illustrated in Fig. 3B, each of connectors 25, first diaphragm attachment shoulder 21 and second diaphragm attachment shoulder 22 have a plurality of corresponding holes, at which a plurality of bolts 28 are inserted in order to tighten connectors 25, first diaphragm attachment shoulder 21 and second diaphragm attachment shoulder 21 together. In some embodiments, the tightening holds flexible diaphragm 15 between recess 14 and protrusion 13 to seal tank 100.

[0051] Accordingly, the structure of tank 100 may allow to form a bi-compartment oxidizer tank having a flexible diaphragm, while maintaining the sealing of the tank when a pressurized gas is inserted into the second compartment. [0052] Reference is now made to Fig. 4 which is a flowchart of a method of propelling a liquid-propellant engine, according to some embodiments of the invention. The method may include in step 410, synchronizing a provision of liquid fuel from a fuel tank and an oxidizer from an oxidizer tank, such as, oxidizer tank 100, into a combustion chamber; and in step 420 producing a reaction between the fuel and the oxidizer. In some embodiments, synchronizing the provision comprises opening flow control valves, such that determined amounts of fuel and oxidizer are provided to produce the reaction.

[0053] In some embodiments, in order to provide the oxidizer and the fuel at the required flows, bi-compartmental tanks may be used upon opening the corresponding flow control valve. Therefore, both the fuel tank and oxidizer thank 100 may include a flexible diaphragm (e.g., diaphragm 15) that divides the tank into two compartments (e.g., compartments 11 and 12), one filled with the oxidizer (in an oxidizer tank) or fuel (in a fuel tank) and the other with pressurized gas for pushing the oxidizer or the fuel, upon opening of the valves.

[0054] In some embodiments, the oxidizer may be hydrogen peroxide which is highly corrosive for common elastomeric diaphragms and therefore require the use of flexible diaphragm 150 made from fluoro-organic polymeric material.

[0055] Some additional aspects of the invention may be directed to a liquid rocket bipropellant system 1000, illustrated in Fig. 5, comprising: a bi-compartmental fuel tank 200; and a bi-compartmental oxidizer tank, for example, tank 100 disclosed and discussed herein above. ; and at least two control valves 150 and 250 configured to control the provision of a determined amount of fuel from the fuel tank and oxidizer and a determined amount of oxidizer from the oxidizer tank to a reaction chamber 300, wherein, the bicompartmental oxidizer tank comprises: first shell 11 and second shell 12; and a flexible diaphragm 15 separating the first shell from the second shell, thus defining: a first compartment configured to contain an oxidizer; and a second compartment configured to contain a pressurized gas, and wherein the flexible diaphragm comprises fluoro-organic polymeric material.

[0056] Some additional aspects of the invention may be directed to a flying platform comprising the liquid rocket bipropellant system according to embodiments of the invention, wherein the platform is selected from a rocket, a satellite, a missile and a launcher.

[0057] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all formulas described herein are intended as examples only and other or different formulas may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time.

[0058] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0059] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.