Separate pressure vessels for oxidizer and fuel components in a combustion/decomposition system add weight and complexity to the system. The fuel and oxidizer can be pre-mixed within a single pressure vessel, but can be unacceptably volatile in a mixed configuration. Providing separate fuel and oxidizer compartments within a singular pressure vessel reduces the weight and complexity of the system, while maintaining the non-volatility of separately stored fuel and oxidizer. The fuel and oxidizer can be selectively mixed within the pressure vessel when desired.

DETAILED DESCRIPTIONS

Disclosed herein is a system and method of separately storing a fuel and an oxidizer within one pressure vessel (or tank) to decrease the weight and expense requirements of providing and maintaining two separate pressure vessels while maintaining the safety benefit of separately storing fuel and oxidizer.

FIG. 1is a cross-sectional perspective view of an example vessel100utilizing an in-tank propellant mixing system102. The vessel100could be a rocket, thruster, or other engine that converts decomposition and/or combustion of propellant into thrust or work. The mixing system102includes a fuel storage tank114within an oxidizer storage tank116. A valve118is actuated to release the stored fuel into the oxidizer storage tank116when a mixed fuel/oxidizer is desired. In other implementations, a mixing trigger other than the valve118(e.g., the multiple valves ofFIG. 3, the burst disk418ofFIG. 4, the explosive charge517/piston515/cap518combination ofFIG. 5, and/or the puncturing device or explosive change618and barrier634ofFIG. 6). In yet another implementation, all or a portion of the fuel storage tank114is dissolvable over time by the fuel and/or the oxidizer. The dissolving fuel tank wall(s) is the mixing trigger. Further, the dissolvable portion of the fuel storage tank114may be located within the oxidizer storage tank116such that it is partially or fully submerged in oxidizer to facilitate dissolving of the fuel storage tank114.

The mixed fuel/oxidizer (i.e., propellant) is discharged from the tank116via an outlet104into lines106. One or more valves (e.g., valve108) and other equipment may also be located at the discharge of the tank116. The lines106lead to an ignition interface110where the propellant is ignited and propelled out of an expansion nozzle112. Due to conservation of momentum, the discharge of the combusted propellant out of the nozzle112from right to left causes the vessel100to be propelled from left to right inFIG. 1. In one implementation, the vessel100is a part of a larger vessel (e.g., vessel100is a thruster on a space station).

In an example implementation, the vessel100could be first located near a large quantity of people (e.g., in a city) or in a high-risk area (e.g., a combat zone). The fuel and oxidizer are stored in separate tanks114,116, respectively, to minimize the risk of explosion. An explosion could cause injury to the nearby population and/or destruction of the vessel100should energy sufficient to ignite mixed propellant be inadvertently applied to the tank116. Once the vessel100is relocated away from the people or high-risk area (e.g., in lower Earth orbit after a successful launch of the vessel100), the fuel and oxidizer stored in the tanks114,116, respectively, may be mixed so that the combined propellant may be combusted and/or decomposed to extract thrust or work from the vessel100.

In one implementation, the fuel and the oxidizer are each stored at vapor pressure in the tanks114,116respectively, with quantities of both gaseous-phase and liquid-phase oxidizer in the oxidizer tank116and quantities of both gaseous-phase and liquid-phase fuel in the fuel tank114. In other implementations, the vapor pressures of the fuel in the fuel tank114and oxidizer in the oxidizer tank116differ sufficiently to create an all gaseous-phase or all liquid-phase fluid in one or both of the tanks114,116.

In an implementation where both the oxidizer and the fuel are relatively high vapor pressure fluids (e.g., typically significantly greater than 101 kPa at 25° C.). The storage tank114can be designed to withstand a relatively small differential pressure between the two stored fluids rather than a much larger pressure differential between the vapor pressure of the oxidizer in the oxidizer tank116and an external environment (e.g., underwater, atmosphere, space, and other external environments) ambient pressure. As a result, the storage tank114may be designed lighter and cheaper than the storage tank116, which may store the oxidizer at a higher pressure relative to the outside of storage tank116. For example, the storage tank114may merely be a bladder within a rigid storage tank116.

In another implementation, the vapor pressure of the fuel may be significantly higher than the vapor pressure of the oxidizer (or vice versa), which facilitates rapid mixing of the fuel with the oxidizer when the valve118is opened. More specifically, the higher-pressure fuel is forced out of the storage tank114into the lower-pressure oxidizer within the storage tank116when the valve118is opened. The higher-pressure fuel continues to exhaust into the storage tank116until the pressure equalizes between the storage tanks114,116. In a further implementation, a relatively long period of time is available to mix the oxidizer and fuel. Even if the vapor pressures of the oxidizer and fuel are the same or nearly the same, mixing of the oxidizer and fuel through diffusion and/or convective fluid motion will occur over time. In another implementation, one or more areas of the storage tanks114,116may be heated with sufficient energy to initiate and sustain convective currents within the storage tanks114,116to facilitate mixing of the fuel and oxidizer, but insufficient energy to initiate a chemical reaction between the fuel and oxidizer.

The in-tank propellant mixing system102may work with a variety of oxidizers and fuels, each with a variety of vapor pressures (e.g., nitrous oxide, various hydrocarbon fuels, ammonia, oxygen, nitrogen tetroxide, nitric oxide, and methane). In some implementations, two or more smaller tanks are stored within a larger tank in systems that mix three or more individual component fuels/oxidizers. Further, while the storage tanks114,116are both depicted as spherical, the storage tanks114,116may be of any size and shape. Still further, storage tank114may be a flexible bladder. Further yet, while fuel storage tank114is depicted inside of the oxidizer storage tank116, the oxidizer storage tank116may be inside of the fuel storage tank114depending on the desired mixing ratio of fuel to oxidizer. In various implementations, the desired volumetric ratio may vary from 1% to 50% fuel. Still further, multiple fuel storage tanks may be oriented inside of the oxidizer storage tank116, or vice versa. Further yet, the storage tanks114,116may store two separate working fluids other than an oxidizer and a fuel (e.g., two fuels, two oxidizers, a fuel and a non-oxidizer additive, an oxidizer and a non-fuel additive, or two non-oxidizer, non-fuel working fluids). In one implementation, the two separate working fluids form a monopropellant when mixed. In another implementation, the two separate working fluids form a non-energetic working fluid when mixed.

FIG. 2is a cross-sectional elevation view of an example in-tank propellant mixing system200with an internal single-discharge fuel tank214releasing fuel224into an encompassing oxidizer tank216. The fuel tank214is suspended or otherwise secured within the oxidizer tank216using one or more supports (e.g., support220). In other implementations, the fuel tank214is not suspended within the oxidizer tank216and is allowed to move freely within the oxidizer tank216. The oxidizer tank216acts a pressure vessel for both oxidizer226and the fuel224stored within the fuel tank214.

The fuel tank214is equipped with a release mechanism (e.g., a valve218) that when actuated releases the fuel224into the oxidizer tank216as illustrated by arrows222. In other implementations, the release mechanism ruptures the fuel tank214to release the fuel224into the oxidizer tank216(see e.g.,FIGS. 4 and 5). The released fuel224mixes with the oxidizer226stored within the oxidizer tank216. Further, any movement of the released fuel224and/or oxidizer226causes an increased rate of mixing, as illustrated by circulation arrows (e.g., arrows228). In one implementation, a separate mixing mechanism (e.g., a vortex generator, vanes adjacent outlet204, etc. (not shown)) is used to induce movement of the fuel224and the oxidizer226and facilitate convective and/or diffusive mixing.

In one implementation, a mixing monitor219is incorporated within the oxidizer tank216. The mixing monitor219includes any sensing and signaling device that is capable of monitoring for the release of the fuel224into the oxidizer226and alerting a user if and when the fuel224is released into the oxidizer226. For example, the mixing monitor219may monitor for an unintentional or unexpected release of fuel224into oxidizer226(e.g., if the valve218leaks or unexpectedly fails). The mixing monitor219may alert the user to an unintentional or unexpected release by sounding visual and/or audio alerts, in some implementations through a computerized monitoring interface.

In one implementation, the mixing monitor219monitors for a minor pressure change when the fuel224is released into the oxidizer226. In another implementation, the mixing monitor219includes a chemical or infrared sensor that detects the presence of the fuel224. If the mixing monitor219is located in the oxidizer tank216, as soon as the fuel224is released into the oxidizer226, the mixing monitor219is triggered. In other implementations, the mixing monitor219is located in the fuel tank214and includes a chemical or infrared sensor that detects the presence of the oxidizer226in the fuel tank214.

Once the fuel224and the oxidizer226are adequately mixed into a single propellant, the propellant may be discharged from the oxidizer tank216via the outlet204(as illustrated by arrows232) with a control valve208that leads to a gas generator, a work-generating engine, or a device for generating thrust (not shown). In an example implementation utilizing an engine, the mixed propellant flows from the outlet204of the oxidizer tank216, through the valve208(as illustrated by arrow230), and into the engine, where work is extracted from the propellant. The control valve208may vary the flow rate of the propellant out of the oxidizer tank216to provide a desired work output from the engine. In other implementations, the control valve208is used to provide a desired gas generation rate or a desired level of thrust from a thruster. In other implementations, the storage tanks214,216store two separate working fluids other than the fuel224and the oxidizer226, which when combined may or may not produce a monopropellant.

FIG. 3is a cross-sectional elevation view of an example in-tank propellant mixing system300with an internal multi-discharge fuel tank314releasing fuel324into an encompassing oxidizer tank316. The fuel tank314is suspended or otherwise secured within the oxidizer tank316using one or more supports (not shown). In other implementations, the fuel tank314is not suspended within the oxidizer tank316and is allowed to move freely within the oxidizer tank316. The oxidizer tank316acts a pressure vessel for both oxidizer326and the fuel324stored within the fuel tank314.

The fuel tank314is equipped with one or more release mechanisms (e.g., valve318) that when actuated release the fuel324into the oxidizer tank316(e.g., as illustrated by arrows322). The multi-discharge system300ofFIG. 3may be significantly more efficient at mixing than the single discharge system200ofFIG. 2due to the multiple outlets from the fuel tank314. The multiple discharges release the fuel324into the oxidizer tank316at multiple locations throughout the tank316, expediting release of the fuel324and mixing throughout the oxidizer tank316. The number of fuel discharges, shape and orientation of the manifold for releasing the fuel324into the oxidizer tank316, and number of valves controlling the release of the fuel324may vary significantly depending on time constraints on how fast the fuel324and oxidizer326should mix and be ready to be discharged as a single propellant and cost and weight constraints for the system300, for example. Further, the manifold may also serve as support for the fuel tank314within the oxidizer tank316. Any movement of the released fuel324and/or oxidizer326causes an increased rate of mixing, as illustrated by circulation arrows (e.g., arrows328). In one implementation, a separate mechanism (not shown) is used to induce movement of the fuel324and oxidizer326and facilitate mixing.

Once the fuel324and the oxidizer326are adequately mixed as a single propellant, the propellant may be discharged from the oxidizer tank316via an outlet304(as illustrated by arrows332) with a control valve308that leads to a gas generator, a work-generating engine, or a device for generating thrust (not shown). In an example implementation utilizing an engine, the propellant flows from the outlet304of the oxidizer tank316, through the valve308(as illustrated by arrow330), and into the engine, where work is extracted from the propellant. The control valve308may vary the flow rate of the propellant out of the fuel tank316to provide a desired work output from the engine. In other implementations, the control valve308is used to provide a desired gas generation rate or a desired level of thrust from a thruster. In other implementations, the storage tanks314,316store two separate working fluids other than the fuel324and the oxidizer326, which when combined may or may not produce a monopropellant.

FIG. 4is a cross-sectional elevation view of an example in-tank propellant mixing system400with a burst-disk fuel tank414releasing fuel424into an encompassing oxidizer tank416. The fuel tank414is suspended or otherwise secured within the oxidizer tank416using one or more supports (e.g., support420). In other implementations, the fuel tank414is not suspended within the oxidizer tank416and is allowed to move freely within the oxidizer tank416. The oxidizer tank416acts a pressure vessel for both oxidizer426and the fuel424stored within the fuel tank414.

The fuel tank414is equipped with a burst disk418that when ruptured releases the fuel424into the oxidizer tank416as illustrated by arrows422. In one implementation, a puncturing device (not shown) is used to selectively rupture the burst disk418. In another implementation, an explosive change is selectively detonated to release sufficient energy to rupture the burst disk418but insufficient energy to ignite the oxidizer426and fuel424. Other systems and methods for rupturing the burst disk418without igniting the oxidizer426and the fuel424are contemplated herein.

The released fuel424mixes with the oxidizer426stored within the oxidizer tank416. Further, any movement of the released fuel424and/or oxidizer426causes an increased rate of mixing, as illustrated by circulation arrows (e.g., arrows428). In one implementation, a separate mechanism (not shown) is used to induce movement of the fuel424and the oxidizer426and facilitate convective and/or diffusive mixing.

Once the fuel424and the oxidizer426are adequately mixed into a single propellant, the propellant may be discharged from the oxidizer tank416via an outlet404(as illustrated by arrows432) with a control valve408that leads to a gas generator, a work-generating engine, or a device for generating thrust (not shown). In an example implementation utilizing an engine, the mixed propellant flows from the outlet404of the oxidizer tank416, through the valve408(as illustrated by arrow430), and into the engine, where work is extracted from the propellant. The control valve408may vary the flow rate of the propellant out of the oxidizer tank416to provide a desired work output from the engine. In other implementations, the control valve408is used to provide a desired gas generation rate or a desired level of thrust from a thruster. In other implementations, the storage tanks414,416store two separate working fluids other than the fuel424and the oxidizer426, which when combined may or may not produce a monopropellant.

FIG. 5is a cross-sectional elevation view of an example in-tank propellant mixing system500with a cylindrical fuel tank514releasing fuel524into an encompassing oxidizer tank516. The fuel tank514is suspended or otherwise secured within the oxidizer tank516using one or more supports (e.g., support520). In other implementations, the fuel tank514is secured to an interior surface of the oxidizer tank516within the use of one or more supports (i.e., the fuel tank514is directly attached to the interior surface of the oxidizer tank516). In other implementations, the fuel tank514is not suspended within the oxidizer tank516and is allowed to move freely within the oxidizer tank516. The oxidizer tank516acts a pressure vessel for both oxidizer526and the fuel524stored within the fuel tank514.

The fuel tank514is equipped with a piston515that separates the fuel524within the fuel tank514from an explosive charge517. Further, the fuel524within the fuel tank514may be separated from oxidizer526within the oxidizer tank516by a cap518. In other implementations, the fuel524may be separated from oxidizer526by a burst disk, or membrane, for example. The explosive charge517may be a liquid or solid propellant, which when detonated releases sufficient energy to rupture and/or remove the cap518and move the piston515outward, forcing the fuel524out of the fuel tank514, as illustrated by arrows522. However, the explosive charge517releases insufficient energy to ignite the mixing oxidizer526and fuel524. In another implementation, a puncturing device (not shown) is used to selectively rupture the cap518. Further, use of a solid or liquid propellant to forcibly discharge the fuel514from the fuel tank514into the oxidizer tank516is contemplated herein.

In some implementations, the explosive charge517may be replaced with a high-pressure gas or liquid. Further, the piston515may be selectively ruptured and/or removed. In such a case, a puncturing device (not shown) is used to selectively rupture the piston515separating the high-pressure gas or liquid from the fuel514, which sufficiently pressurizes the fuel524to rupture and/or remove the cap518from the tank514and discharge the fuel524into the oxidizer526.

The released fuel524mixes with the oxidizer526stored within the oxidizer tank516. Further, any movement of the released fuel524and/or oxidizer526causes an increased rate of mixing, as illustrated by circulation arrows (e.g., arrows528). In one implementation, a separate mechanism (not shown) is used to induce movement of the fuel524and the oxidizer526and facilitate convective and/or diffusive mixing.

Once the fuel524and the oxidizer526are adequately mixed into a single propellant, the propellant may be discharged from the oxidizer tank516via an outlet504(as illustrated by arrows532) with a control valve508that leads to a gas generator, a work-generating engine, or a device for generating thrust (not shown). In an example implementation utilizing an engine, the mixed propellant flows from the outlet504of the oxidizer tank516, through the valve508(as illustrated by arrow530), and into the engine, where work is extracted from the propellant. The control valve508may vary the flow rate of the propellant out of the oxidizer tank516to provide a desired work output from the engine. In other implementations, the control valve508is used to provide a desired gas generation rate or a desired level of thrust from a thruster. In other implementations, the storage tanks514,516store two separate working fluids other than the fuel524and the oxidizer526, which when combined may or may not produce a monopropellant.

FIG. 6is a cross-sectional elevation view of an example in-tank propellant mixing system600with a ruptured barrier634releasing stored fuel624into stored oxidizer626within a storage tank616. The storage tank616has separated sections storing fuel624and oxidizer626. The storage tank616acts a pressure vessel for both the fuel624and the oxidizer626, while the barrier634merely separates the fuel624from the oxidizer626. In one implementation, the barrier634is a thin flexible non-permeable membrane that is designed to withstand an expected pressure difference between the stored fuel624and the stored oxidizer626. The barrier634may be constructed of rubber, plastics, and/or various composite materials. In other implementations, the barrier is a relatively non-flexible structure (e.g., made of metal alloys, plastics, composites, etc.).

When it is desired that the fuel624and the oxidizer626be mixed, the barrier634is ruptured. If the fuel624is stored at a higher pressure than the oxidizer626(as depicted inFIG. 6), the fuel624primarily moves through the ruptured barrier634to mix with the oxidizer626(as illustrated by arrows622). In another implementation when the oxidizer626is stored at a higher pressure than the fuel624, the oxidizer626primarily moves through the ruptured barrier634to mix with the fuel624. In various implementations, the oxidizer626and the fuel624move both directions through the ruptured barrier634to diffuse thoroughly together. Further, any additional movement of the fuel624and/or the oxidizer626causes an increased rate of mixing, as illustrated by circulation arrows (e.g., arrows628). In one implementation, a separate mechanism (not shown) is used to induce movement of the fuel624and the oxidizer626and facilitate mixing.

In one implementation, a puncturing device (not shown) is used to selectively rupture the barrier634. In another implementation, an explosive change618is selectively detonated to release sufficient energy to rupture the barrier634but insufficient energy to ignite the oxidizer626and the fuel624. Other systems and methods for rupturing the barrier634without igniting the oxidizer626and the fuel624are contemplated herein.

Once the fuel624and the oxidizer626are adequately mixed as a single propellant, the propellant may be discharged from the storage tank616via an outlet604(as illustrated by arrows632) with a control valve608that leads to a gas generator, a work-generating engine, or a device for generating thrust (not shown). In an example implementation utilizing an engine, the propellant flows from the outlet604of the storage tank616, through the valve608(as illustrated by arrow630), and into the engine, where work is extracted from the propellant. The control valve608may vary the flow rate of the propellant out of the storage tank616to provide a desired work output from the engine. In other implementations, the control valve608is used to provide a desired gas generation rate or a desired level of thrust from a thruster. In other implementations, the storage tank616stores two separate working fluids other than the fuel624and the oxidizer626, which when combined may or may not produce a monopropellant.

FIG. 7illustrates example operations700for using an in-tank propellant mixing system. A providing operation705provides a pressure vessel with separated fuel and oxidizer compartments (or tanks). The separated fuel and oxidizer compartments provide some protection against inadvertent combustion of the stored fuel and oxidizer. The separated fuel and oxidizer compartments may be arranged in a variety of manners. For example, the fuel compartment may be one or more interior bladders or tanks stored with an outer oxidizer tank, or vice-versa. In a further example implementation, the fuel and oxidizer may be separated within a tank by a flexible membrane or rigid barrier. The interior tank, flexible membrane, or rigid barrier may be designed to withstand at least a pressure difference between the vapor pressure of the fuel and the oxidizer. In other implementations, the pressure vessel stores two separate working fluids other than the fuel and the oxidizer, which when combined may or may not produce a monopropellant. A monitoring operation708monitors the pressure vessel for mixing of the separated fuel and oxidizer components is incorporated within the providing operation705. The monitoring operation708may also include alerting a user if the fuel and oxidizer components are inadvertently or unexpectedly mixed.

An opening operation710opens a fluid communication channel between the fuel compartment and the oxidizer compartment. The opening operation710may be accomplished by opening one or more valves on fluid lines connecting the fuel compartment and the oxidizer compartment, for example. Further, the opening operation710may be accomplished by rupturing the flexible membrane or rigid barrier separating the fuel compartment and the oxidizer compartment using a mechanical puncturing device or an explosive device, for example.

A mixing operation715mixes the fuel and oxidizer within the pressure vessel. In an example implementation where a long period of time is available for the fuel and oxidizer to mix, the fuel and oxidizer may mix via diffusion and/or convection without any mixing aids. In implementations where less time is available, mechanical or jetted agitation mechanisms may stir the fluid within the pressure vessel to expedite mixing of the fuel and the oxidizer. In various implementations, the time required or available for mixing can range from seconds to years. Further, a manifold with various shapes may distribute the fuel released into the oxidizer compartment or vice versa to expedite mixing of the fuel and the oxidizer.

Once the fuel and the oxidizer are mixed, the pressure vessel is at a greater risk of inadvertent combustion of the stored fuel and oxidizer. It may be desired to mix the fuel and oxidizer immediately prior in time to combustion of the mixed fuel and oxidizer propellant to minimize the risk of inadvertent combustion of the stored fuel and oxidizer.

A discharging operation720discharges the mixed fuel and oxidizer propellant from the pressure vessel. The mixed fuel and oxidizer propellant may be discharged to a gas generator, an engine that extracts work, or a rocket motor or thruster that generates thrust (all of which chemically react the mixed fuel and oxidizer). A reacting operation725exothermically reacts the discharged fuel and oxidizer in order to extract work or thrust from the reacting fuel and oxidizer. The reacting fuel and oxidizer may be combusting and/or decomposing, for example.

The logical operations making up the embodiments of the invention described herein are referred to variously as operations, steps, objects, or modules. Furthermore, not all described operations are required and additional operations may be performed, unless explicitly claimed otherwise or the claim language inherently necessitates a specific order.

The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Furthermore, structural features of the different embodiments may be combined in yet another embodiment without departing from the recited claims.