CRYOGENICALLY COMPATIBLE ROCKET PROPELLANT

Info

Publication number: 20190270685
Type: Application
Filed: Feb 7, 2019
Publication Date: Sep 5, 2019
Applicant: TGV Rockets (Washington, DC)
Inventor: Earl Renaud (Glouster)
Application Number: 16/270,016

Abstract

Propellants for rockets, space transportation vehicles, launch vehicles and systems, crew escape vehicles and systems, launch escape towers, and space vehicle systems are disclosed. Some embodiments provide a rocket propellant comprising a mixture of a small chain alkane from 1 to 4 carbons and a small chain alkene from 3 to 4 carbons. The mixture of the small chain alkane and small chain alkene is in a proportion that lowers the melting of the mixture below the melting point of both the small chain alkane and small chain alkene.

Description

Description

CROSS-RELATED APPLICATIONS

This application claims the benefits of and priority to U.S. patent application Ser. No. 15/275,336, filed Sep. 2016, entitled “Cryogenically Compatible Rocket Propellant”, which claims the benefits of and priority to U.S. Provisional Patent Application Ser. No. 62/222,390, filed Sep. 23, 2015, entitled “Reduced-Temperature Propellant for Rockets and the Like,” which is incorporated by reference.

GOVERNMENT RIGHTS

Some embodiments of this invention were made with government support under contract W911NF-16-0097 awarded by the Department of Defense. The government has certain rights in some embodiments of this invention.

BACKGROUND

Propellants for rockets, space transportation vehicles, launch vehicles and systems, crew escape vehicles and systems, launch escape towers, and space vehicle systems and devices are known in the art.

With the rise of the chemical industries of the 19^thcentury, combustion of liquid fuels and oxidizers enabled practical implementation of rocket propulsion systems. Starting with acid/analines and liquid oxygen (LOX)/alcohol and hydrazine/peroxide combinations, the industry rapidly settled on LOX/liquid hydrogen (LH) and LOX/kerosene. While numerous potential combinations, such as LOX/hydrazine, LOX/methane, were studied, kerosene (RP-1) provided the most energetic combination and the greatest experience base. However, thermal incompatibility of kerosene to liquid oxygen continue to require complex engineering solutions.

The chemical properties of LOX with almost every practical hydrocarbon (HC), such as methane, butane, benzene, gasoline, alcohol, and ether, have been researched as candidates as a rocket propellant, with mixed results. While these fuels are economical, the low densities of small HCs, such as, methane and butane, yield a propellant that is not very efficient. Recent studies have produced a prototype rocket, which uses propylene as a fuel, however, the studies ended without a viable engine.

In the 1960s, mixtures of methane, ethane, and propane were studied, however, the fuels mixtures required a fluorine-based oxidizer. The density of these mixtures were low, which lowered efficiency, and created problems for storage. These fuel mixtures were abandoned, in favor of RP-1.

Although RP-1 with LOX is the preferred rocket propellant, there are still drawbacks to this combination. For example, after the burn of RP-1, residue coats the inside of the engine, which needs to be removed to reuse the engine. The residue consists of coke, paraffin, and oils, which are difficult and expensive to remove. If this residue is not completely removed, the engine most likely will fail upon reuse.

According to the literature, there has not been a completely new liquid propellant used in flight in over 30 years. A new rocket propellant, which is economical, burns clean, and has a high density that is similar to RP-1, and has specific impulse equal to or greater than RP-1, is needed.

SUMMARY

Various embodiments of the present invention, a mixture of propane and propylene makes an improved rocket fuel by lowering the melting point (freezing point) and improving the bulk density of the fuel. In one aspect, the mixture of propane and propylene is a mixture of a mole fraction of about 50% propane and a mole fraction of about 50% propylene. In some embodiments, the rocket fuel is a mixture of a mole fraction of between 40% and 60% propane and a mole fraction of between 60% and 40% propene.

Various embodiments provide a rocket propellant comprising a eutectic mixture of a small chain alkane from 1 to 4 carbons and a small chain alkene from 3 to 4 carbons. In some embodiments, the rocket propellant comprises a eutectic mixture of a small chain alkane from 1 to 3 carbons and a small chain alkene having 3 carbons. The mixture of the small chain alkane and the small chain alkene is in a proportion that lowers the melting of the mixture below the melting point of both the small chain alkane and small chain alkene.

For example, the rocket propellant can be a eutectic mixture of a mole fraction of 67% methane and a mole fraction of 33% propene. In some embodiments, the rocket propellant is a eutectic mixture of a mole fraction of between 75% and 60% methane and a mole fraction of between 25% and 40% propene. In some embodiments, the rocket propellant is a eutectic mixture of a mole fraction of between 40% and 60% ethane and a mole fraction of between 60% and 40% propene.

Some embodiments provide a rocket propellant comprising a eutectic mixture of a small chain alkane from 1 to 4 carbons and a small chain alkane from 2 to 4 carbons. In some embodiments, the rocket propellant comprises a eutectic mixture of a small chain alkane having 1 carbon and a small chain alkene having 2 or 3 carbons. The mixture of the small chain alkanes is in a proportion that lowers the melting of the mixture below the melting point of each of the small chain alkanes.

For example, the rocket propellant can be a eutectic mixture of a mole fraction of about 46% methane and a mole fraction of about 54% ethane. In some embodiments, the rocket propellant is a mixture of a mole fraction of between 25% and 75% methane and a mole fraction of between 75% and 25% ethane. In some embodiments, the rocket propellant is a mixture of a mole fraction of between 20% and 60% methane and a mole fraction of between 80% and 40% propane.

These and other novel eutectic mixtures for use as rocket propellants and in rocket engine systems are described in detail and claimed in the following Drawings, Description, and Claims.

DRAWINGS

The present disclosure will become more fully understood from the description and the accompanying drawings, wherein:

FIG. 1 is a table, which illustrates a comparison of the melting points and the boiling points of various fuels to coolant sources, in accordance to various embodiments;

FIG. 2 is a table, which illustrates a comparison of various physical properties of various fuels, in accordance with various embodiments;

FIG. 3 is a phase diagram for a mixture of propane and propene, in accordance with various embodiments;

FIG. 4 is a graph illustrating the change in density of propane and propene in a eutectic mixture over a change in temperature, in accordance with various embodiments;

FIG. 5 is a phase diagram for a mixture of ethane and propene, in accordance with various embodiments;

FIG. 6 is a phase diagram for a mixture of methane and propene, in accordance with various embodiments;

FIG. 7 is a graph illustrating the change in density of methane and propene in a eutectic mixture over a change in temperature, in accordance with various embodiments;

FIG. 8 is a bar graph illustrating the values of specific impulse and density impulse for 4 different propellants, in accordance with various embodiments;

FIG. 9 is a bar graph illustrating the values of specific impulse and density impulse for 5 different propellants at a 20:1 expansion ratio, in accordance with various embodiments;

FIG. 10 is a bar graph illustrating the values of specific impulse and density impulse for 5 different propellants at a 4000:1 expansion ratio, in accordance with various embodiments;

FIG. 11 is a phase diagram for a mixture of methane and ethane, in accordance with various embodiments;

FIG. 12 is a graph illustrating the change in density of methane and ethane in a eutectic mixture over a change in temperature, in accordance with various embodiments;

FIG. 13 is a phase diagram for a mixture of methane and propane, in accordance with various embodiments;

FIG. 14 is a table, which illustrates a comparison of the melting point of various light hydrocarbons and eutectic mixtures thereof, in accordance to various embodiments;

FIG. 15 is a table, which illustrates a comparison of the ideal specific impulse of various light hydrocarbons and eutectic mixtures thereof, in accordance to various embodiments;

FIG. 16 is a table, which illustrates a comparison of the density of various light hydrocarbons and eutectic mixtures thereof, in accordance to various embodiments;

FIG. 17 is a bar graph illustrating the values of specific impulse and density impulse for 5 different propellants at a 20:1 expansion ratio, in accordance with various embodiments;

FIG. 18 is a schematic drawing illustrating a cross-section of an exemplary rocket system, in accordance with various embodiments.

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of any of the exemplary embodiments disclosed herein or any equivalents thereof. It is understood that the drawings are not drawn to scale. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements.

DESCRIPTION

The following description is merely exemplary in nature and is in no way intended to limit the exemplary embodiments, their application, or uses. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. For example, various embodiments may be described herein in terms of various functional components and processing steps. It should be appreciated that such components and steps may be realized by any number of hardware components configured to perform the specified functions.

Various embodiments provide compositions, which are propellants for rockets, space transportation vehicles, launch vehicles and systems, crew escape vehicles and systems, launch escape towers, and space vehicle systems and devices. The compositions can be a reduced-temperature propellant for improving performance of a rocket stage, a rocket, a space vehicle, and the like. Some embodiments provide a system, which can be employed as a rocket engine.

Some embodiments provide a rocket propellant mixture comprising a small chain alkane mixed with a small chain alkene. The small chain alkane can comprise from 1 to 4 carbons and the small chain alkene can comprise from 3 to 4 carbons. The mixture of the small chain alkane and small chain alkene is in a proportion that lowers the melting of the mixture below the melting point of both the small chain alkane and small chain alkene. In other words, the mixture of the small chain alkane and small chain alkene is in a proportion, which allows the mixture to be a liquid at a temperature that each of the small chain alkane and the small chain alkene are solids. The rocket propellant mixture can be combined with an oxidizer, such as, liquid oxygen (LOX), in a rocket engine.

The rocket propellant mixture, as described herein, can be cryogenically chilled to the boiling point of liquid nitrogen (LN) and remain in a liquid state. The rocket propellant mixture can remain in a liquid state while in thermal communication with a cryogenic source.

In some embodiments, the rocket propellant mixture comprises propane and propene (propylene). In one example, the rocket propellant mixture consists of propane and propene at a mole fraction 50% for each component. However, the mixture can consist of propane a mole fraction of between 40% and 60% and propene a mole fraction of between 60% and 40%.

In other embodiments, the rocket propellant mixture comprises ethane and propene. In one example, the rocket propellant mixture consists of ethane and propene at a mole fraction 50% for each component. However, the mixture can consist of ethane in a mole fraction of between 40% and 60% and propene in a mole fraction of between 60% and 40%.

In still other embodiments, the rocket propellant mixture comprises methane and propene. In one example, the rocket propellant mixture consists of methane in a mole fraction of 67% and propene in a mole fraction of 33%. However, the mixture can consist of methane in a mole fraction of between 75% and 60% and propene in a mole fraction of between 25% and 40%.

Some embodiments provide a rocket propellant comprising a mixture of a small chain alkane having 1 carbon and a small chain alkene having 2 or 3 carbons. The mixture of the small chain alkanes is in a proportion that lowers the melting of the mixture below the melting point of each of the small chain alkanes.

In some embodiments, the rocket propellant mixture comprises methane and ethane. In one example, the rocket propellant mixture consists of methane in a mole fraction of about 46% and ethane in a mole fraction of about 54%. However, the rocket propellant mixture can consist of methane in a mole fraction of between 25% and 75% and ethane a mole fraction of between 75% and 25%. In other embodiments, the rocket propellant mixture can consist of methane in a mole fraction of between 20% and 60% and propane in a mole fraction of between 80% and 40%.

Turning to FIG. 1, Table 1 is comparison of the melting points and boiling points of various fuels to cooling sources. Although most of these fuels can be combined with an oxidizer other than LOX, the focus of this discussion will only on LOX as the oxidizer. As illustrated in Table 1, available coolants are LOX and LN, which can be used to cool the LOX. In some rocket designs, LOX may not be cooled by LN but rather LOX is vented to atmosphere and topped off as the level drops. In these designs only LOX is available as a coolant.

As a note to Table 1, RP-1 is Rocket Propellant 1 or Refined Petroleum 1, as is well known those skilled in the art. RP-1 is a refined form of kerosene, which is cheaper than liquid hydrogen (LH) and is stable at room temperature. Although RP-1 has lower specific impulse (“Isp”) than LH, RP-1 is far higher density than LH, therefore it is far more powerful than LH by volume.

Other than LH, all of the listed fuels are solids at the boiling point (77K) of LN. Since the rocket propellant needs to flow from a tank to the combustion chamber and mix with the LOX, a solid fuel cannot to used. In addition to LH, propane, propene, ethane and maybe even methane are liquids at the boiling point (90K) of LOX, while all of the other fuels are solid at the boiling point of LOX. Please note that the density of LH is far less than the density of all of the other fuels listed in Table 1.

From the comparison in Table 1, none of the hydrocarbon (HC) based fuels can be used as a rocket propellant while in thermal communication with LN. Of the HC fuels listed, most of the small chain HC fuels can be used can be used as a rocket propellant while in thermal communication with LOX.

In very unexpected results, the inventors discovered that certain small chain alkane from 1 to 4 carbons and certain small chain alkene from 3 to 4 carbons can be mixed in certain proportions that lowers the melting of the mixture below the melting point of both the small chain alkane and small chain alkene. These mixtures are cryogenically compatible with various cryogenic coolants and have increased density near the melting point of the mixture. The inventors determined that these mixtures can be used for rocket propellants.

Now moving to FIG. 2, Table 2 is a performance comparison of various fuels. In very unexpected results, the inventors discovered that a mixture of methane and propene has a eutectic point at certain mixtures, which below the boiling point of LN. This mixture of methane and propene has an increased density and has physical properties that make it superior to RP-1 as a rocket propellant, as shown in FIG. 2.

In very unexpected results, the inventors discovered that a mixture of propene and propene has a eutectic point at certain mixtures, which below the boiling point of LN. This mixture of propane and propene has an increased density and has physical properties that make it superior to RP-1 as a rocket propellant, as shown in FIG. 2.

A brief review of the table above shows that LOX is thermally compatible with both propane and propylene (propene) and that nominally LN is thermally incompatible with methane, propane and propylene. It is not commonly appreciated that the density of propane and propylene at the melting point makes them excellent rocket fuels, because most property tables for propane and propylene are calibrated to the normal boiling point (NBP) of propane and propylene. Most practicing engineers look at the density of propane as 0.49 g/cc at the NBP, not the effective density of propane at the melting point of 1.01 g/cc, and fail to appreciate the dramatic density rise of propane as it is subcooled towards the melting point. The even better density of a propane mix such as about 50%/50% blend of propane/propylene (Pro/Poly 50) subcooled to near the NBP of LN where it increases towards 1.06 g/cc, which grants a 5% density impulse gain over subcooled propane.

A eutectic mixture of propane and propylene provides over 372 seconds of theoretical specific impulse, while having a freezing point margin of 10K (80K) below the normal atmospheric boiling point of LOX. This fuel combination then will provide a high specific impulse, and hence a reasonable structural mass fraction (SW) and propellant mass fraction (PMF), while keeping tank design simple, tank weights low, and overall stage manufacturing costs reasonable.

In one aspect of the present invention, mixtures of propane/propylene, preferably about a 50%/50% mixture (Pro/Poly 50), exhibit strong reduction in melting point, while a eutectic mixture should exhibit a melting point (about 75 Kelvin (K)) compatible with exposure to liquid nitrogen (LN). Mixtures of propane/propylene can be cooled with LN, LOX, liquid helium or by active mechanical coolers or other methods known to one of ordinary skill in the art.

An enhanced Pro/Poly mix can be mixed at any ratio of propane/propylene which results in a reduced melting point down to the eutectic point. The eutectic point is a mixture of approximately 50% propane/50% propylene +/−5%, and is below the boiling point for LN and calculations indicates should have a melting point of about 75 K.

A colder, denser propellant provides a higher density impulse than the same propellant at the normal boiling point (NBP). A liquid pro/poly 50 mixes as liquid phase with LOX providing complete blending before ignition giving a potential for about 100% combustion efficiency. A denser propellant reduces pump power requirements to the pump for the equivalent mass flow.

An increase of density impulse increases the performance of a rocket stage, thus lowering the temperatures and freezing points of propellants results in higher performance even above the engineering improvements engendered by thermal compatibility. Pro/Poly 50 will exhibit a bulk density of about 1.06 G/cc, and, at about 77 K, LOX increases in density to about 1.21 g/cc

Some embodiments provide mixtures of propane/propylene and to lower the melting point into the working ranges for LN. This ultimately approaches the eutectic point wherein the freezing (melting) point of a propane/propylene mixture can be lowered and the viscosity engineered to meet the requirements of passage through fine cooling passages and through a high speed turbopump.

FIG. 3 is a phase diagram for a mixture of propane and propene, which has temperature in K on the y-axis and the increasing mole fraction of propene on the x-axis. This phase diagram illustrates that any mixture of propane and propene has a lower melting point (in degrees K) than the melting point for either pure propane or pure propene. The point at which a mixture has lowest melting (eutectic point) is indicated on the phase diagram. In addition, the NBP of LN and LOX have been added to this phase diagram. From an analysis of the phase diagram, the eutectic point is at a mole fraction of 50% propane and a mole fraction of 50% propene, which has a melting point of 75.0K. As illustrated on the phase diagram, the eutectic point is below the boiling point of LN and this mixture will remain in a liquid state while in thermal communication with LN. As indicated on the phase diagram, other mixtures of propane and propene have a melting point below the NBP of LN.

Based on the data that generated the phase diagram, at a mole fraction of 45% propane and a mole fraction of 55% propene, the melting point of this mixture is 76.27K, which is below the NBP of LN (77.3K). Furthermore, at a mole fraction of 55% propane and a mole fraction of 45% propene, the melting point of this mixture is 76.27K, which is also below the NBP of LN (77.3K). These mixtures provide the termini of a range of mixtures of propane and propene that can be used a cryogenically LN compatible rocket propellant.

However, at a mole fraction of 60% propane and a mole fraction of 40% propene, the melting point of this mixture is 77.48K, which is slightly above the melting point of the NBP of LN (77.3K). At a mole fraction of 40% propane and a mole fraction of 60% propene, the melting point of this mixture is 77.48K, which is slightly above the melting point of the NBP of LN (77.3K). Since the LN, while in thermal communication with these mixtures, will not chill the mixtures down to the exact NBP of LN, these mixtures provide the termini for an alternative range of mixtures of propane and propene that can be used a cryogenically LN compatible rocket propellant. Still further, the combinations of mole fraction of 65% and 35% of each component have a melting point of 78.64K, which is slightly higher than the NBP of LN (77.3K). As discussed above, these mixtures provide the termini for a second alternative range of mixtures of propane and propene that can be used a cryogenically LN compatible rocket propellant. The combinations of mole fraction of 70% and 30% of each component have a melting point of 79.74K, which is also slightly higher than the NBP of LN (77.3K). If efficiency of the thermal communication of the LN is low, these mixtures provide the termini for a third alternative range of mixtures of propane and propene that can be used a cryogenically LN compatible rocket propellant.

Of course, adding pressure to any of these mixtures, can further reduce the melting point of the mixture. Although high pressure in a tank is not the best configuration in a rocket engine while in flight. The tank can be pressurized while the rocket is still on the ground during prelaunch, which can further lower the melting point of any of these mixtures. Moving back to FIG. 3, since both propane and propene have melting points below the NBP of LOX, as illustrated in Table 1 of FIG. 1, any mixture of propane and propene will be in a liquid state at the NBP of LOX. If LOX is used as a coolant, any of pure propane, pure propene, or any mixture thereof, can be used a cryogenically LOX compatible rocket propellant.

Flipping to FIG. 4, a graph illustrates the change in density of propane and propene at a mixture 50:50 in mole fraction over a change in temperature. The graph has density in the units of kg/m3 on the left-hand y-axis and density in the units of lbs/ft3 on the right hand y-axis. A temperature range from 75K to 100K is on the x-axis. From this data, the density of the mixture increases as temperature decreases. At the NBP of LN, the density of the mixture is 761.4 kg/m3. The cryogenic cooling of the mixture to below the NBP of LN increases the fuel density, which increases the performance of this fuel mixture as a rocket propellant. The fuel density of this mixture is greater than RP-1

FIG. 5 is a phase diagram for a mixture of ethane and propene, which has temperature in K on the y-axis and the increasing mole fraction of propene on the x-axis. This phase diagram illustrates that any mixture of ethane and propene has a lower melting point (in degrees K) than the melting point for either pure ethane or pure propene. From an analysis of the phase diagram, the eutectic point is at a mole fraction of 50% ethane and a mole fraction of 50% propene, which has a melting point of 75.2K.

As discussed above, other mixtures of ethane and propane are in a liquid state at the NBP of LN. For example, the combinations of mole fraction of 55% and 45% of each component have a melting point of 76.27K, which is below than the NBP of LN (77.3K). These mixtures provide the termini of a range of mixtures of ethane and propene that can be used a cryogenically LN compatible rocket propellant. In another example, the combinations of mole fraction of 60% and 40% of each component have a melting point of 77.48K, which is slightly higher than the NBP of LN (77.3K). As discussed above, these mixtures provide the termini for an alternative range of mixtures of methane and propene that can be used a cryogenically compatible rocket propellant. In still another example, the combinations of mole fraction of 65% and 35% of each component have a melting point of 78.64K, which is slightly higher than the NBP of LN (77.3K). As discussed above, these mixtures provide the termini for a second alternative range of mixtures of propane and propene that can be used a cryogenically LN compatible rocket propellant.

The mixture of ethane and propene have a larger disparity in the amount of mole fraction for each component. Factors that can contribute to these mixtures being useable, are poor efficiency of thermal communication between the mixture and the LN and/or pressurization of the fuel tank. Of course, there are other factors, which could contribute, which are known to those skilled in the art. Since the both ethane and propene are liquid at the NBP of LOX, if LOX is used as a coolant, any of pure propane, pure propene, or any mixture thereof, can be used a cryogenically LOX compatible rocket propellant.

FIG. 6 is a phase diagram for a mixture of methane and propene, which has temperature in K on the y-axis and the increasing mole fraction of propene on the x-axis. This phase diagram illustrates that any mixture of methane and propene has a lower melting point (in degrees K) than the melting point for either pure methane or pure propene. The eutectic point, as well as, the NBP of LN and LOX are included in this phase diagram. From an analysis of the phase diagram, the eutectic point is at a mole fraction of 67% methane and a mole fraction of 33% propene, which has a melting point of 68.92K.

As discussed above, other mixture of methane and propane are in a liquid state at the NBP of LN. For example, the mixture of mole fraction of 25% of propene and of 75% methane has a melting point of 77.14K, which is below than the NBP of LN (77.3K). The mixture of mole fraction of 55% of propene and of 45% methane has a melting point of 76.57K, which is below than the NBP of LN (77.3K). These mixtures provide the termini of a range of mixtures of methane and propene that can be used a cryogenically compatible rocket propellant. In another example, the mixture of mole fraction of 60% of propene and of 40% methane has a melting point of 78.0K, which is slightly higher than the NBP of LN (77.3K). As discussed above, these mixtures provide the termini for an alternative range of mixtures of methane and propene that can be used a cryogenically LN compatible rocket propellant. In still another example, the mixture of mole fraction of 15% of propene and of 85% methane has a melting point of 80.47K, which is slightly above the NBP of LN (77.3K). As discussed above, these mixtures provide the termini for a second alternative range of mixtures of propane and propene that can be used a cryogenically LN compatible rocket propellant.

The mixture of methane and propene have a larger disparity in the amount of mole fraction for each component. Many factors that can contribute to these mixtures being useable, as discussed above Since the propene and maybe methane are liquid at the boiling point of LOX, if LOX is used as a coolant, any of pure propene, or any mixture methane and propene, can be used a cryogenically LOX compatible rocket propellant.

Flipping to FIG. 7, a graph illustrates the change in density of methane and propene at a mixture 50:50 in mole fraction over a change in temperature. The graph has density in the units of kg/m3 on the left-hand y-axis and density in the units of lbs/ft3 on the right hand y-axis. A temperature range from 75K to 100K is on the x-axis. From this data, the density of the mixture increases as temperature decreases. At the boiling point of LN, the density of the mixture is 678.4 kg/m3. The cryogenic cooling of the mixture to below the boiling point of LN increases the fuel density, which increases the performance of this fuel mixture as a rocket propellant. The fuel density of this mixture is greater than RP-1

FIG. 8 is a bar graph having Impulse in seconds on the y-axis and the 4 propellants on the x-axis. In this bar graph, the specific impulse and the density impulse for each of the propellants are indicated by both bars and the actual number value (in lb/ft3) at the top of the bar. Since RP-1 is the most used rocket propellant, it is on the graph as the current standard. The other propellants on this graph are methane, a eutectic mixture of methane and propene, and a eutectic mixture of propane and propene (Pro/Poly 50). The calculations that were used to generate this graph included the conditions of 1000 psi of chamber pressure, and a nozzle expansion ratio of 100:1.

From analysis of the bar graph, the specific impulse for RP-1 is the lowest of the 4 propellants under these conditions. The specific impulse of the other 3 propellants is very similar ranging from 380 to 385. Moreover, the density impulse for RP-1 is the lowest of the 4 propellants. The density impulse of each of the propellants increases moving from left to right. There is a significant increase of over 5% of the density impulse of the Pro/Poly 50 over the RP-1. According to the data on the graph, both of the eutectic mixtures are superior to RP-1. In addition, Pro/Poly 50 has almost a 2% increase in specific impulse and over a 5% increase in density impulse as compared to RP-1. Further, the eutectic mixture of methane and propene has over a 2% increase in specific impulse and over a 4% increase in density impulse as compared to RP-1.

FIG. 9 is a bar graph having Impulse in seconds on the y-axis and the 5 different propellants on the x-axis. In this bar graph, the specific impulse and the density impulse for each of the propellants are indicated by both bars and the actual number value (in lb/ft3) at the top of each bar. Since RP-1 is the most used rocket propellant, it is on the graph as the current standard. The other propellants on this graph are methane, a eutectic mixture of methane and propene, a eutectic mixture of propane and propene (Pro/Poly 50), and liquid hydrogen. The calculations that were used to generate this graph used the conditions of 1000 psi of chamber pressure, and a nozzle expansion ratio of 20:1.

From analysis of the bar graph, the specific impulse (290) for RP-1 is the lowest of the 5 propellants under these conditions. However, the specific impulse of the methane, the eutectic mixture of methane and propene, the eutectic mixture of propane and propene are similar to the specific impulse for RP-1, ranging from 293 to 299. However, the density impulse (302) for the eutectic mixture of propane and propene is slightly better than the density impulse (297) for RP-1 under these conditions. Although liquid hydrogen has the highest specific impulse (367), the specific density (110) for liquid hydrogen is by far the lowest. According to the data on the graph, Pro/Poly 50 is the best propellant compared to the 4 other propellants. In addition, Pro/Poly 50 has over 3% increase in specific impulse and almost a 5% increase in density impulse as compared to RP-1. Further, the eutectic mixture of methane and propene has over a 3% increase in specific impulse and a 2% increase in density impulse as compared to RP-1.

FIG. 10 is a bar graph having Impulse in seconds on the y-axis and the 5 different propellants on the x-axis. The 5 propellants are the same as on the bar graph of FIG. 9. The calculations that were used to generate this graph used the conditions of 1000 psi of chamber pressure, and a nozzle expansion ratio of 4000:1.

From analysis of the graph, the specific impulse (412) for RP-1 is the lowest of the 5 propellants under these conditions. However, the specific impulse of the methane, the eutectic mixture of methane and propene, the eutectic mixture of propane and propene range from 424 to 426. In addition, the density impulse (439 and 451) for the eutectic mixtures are slightly better than the density impulse (430) for RP-1 under these conditions. Although liquid hydrogen has the highest specific impulse (502), the specific density (195) for liquid hydrogen is by far the lowest. According to the data on the graph, the eutectic mixtures are the best propellants compared to the other propellants. In addition, Pro/Poly 50 is at least 2% better than RP-1 in both specific impulse and density impulse.

Some embodiments provide a rocket propellant comprising a eutectic mixture of a small chain alkane from 1 to 4 carbons and a small chain alkane from 2 to 4 carbons. In some embodiments, the rocket propellant comprises a eutectic mixture of a small chain alkane having 1 carbon and a small chain alkene having 2 or 3 carbons. The mixture of the small chain alkanes is in a proportion that lowers the melting of the mixture below the melting point of each of the small chain alkanes.

FIG. 11 is a phase diagram for a mixture of methane and ethane, which has temperature in K on the y-axis and the increasing mole fraction of ethane on the x-axis. This phase diagram illustrates that any mixture of methane and ethane has a lower melting point (in degrees K) than the melting point for either pure methane or pure ethane. The point at which a mixture has lowest melting (eutectic point) is indicated on the phase diagram. In addition, the NBP of LN and LOX have been added to this phase diagram. From an analysis of the phase diagram, the eutectic point is at a mole fraction of 46% methane and a mole fraction of 54% ethane, which has a melting point of 56.08 K. As illustrated on the phase diagram, the eutectic point is below the NBP of LN and this mixture will remain in a liquid state while in thermal communication with LN. As indicated on the phase diagram, other mixtures of propane and propene have a melting point below the NBP of LN.

Based on the data that generated the phase diagram, at a mole fraction of 80% methane and a mole fraction of 20% ethane, the melting point of this mixture is 77.14K, which is below the NBP of LN (77.3K). Furthermore, at a mole fraction of 25% methane and a mole fraction of 75% ethane, the melting point of this mixture is 73.51K, which is also below the NBP of LN (77.3K). However, at a mole fraction of 20% methane and a mole fraction of 80% ethane, the melting point of this mixture is 78.29, which is just above the NBP of LN (77.3K). These mixtures provide the termini of a range of mixtures of methane and ethane that can be used a cryogenically LN compatible rocket propellant.

In another example, the mixture of a mole fraction of 85% methane and a mole fraction of 15% ethane, the melting point of this mixture is 80.47K, which is slightly higher than the NBP of LN (77.3K). The mixture of a mole fraction of 20% methane and a mole fraction of 80% ethane has a melting point of 78.29K, which is slightly higher than the NBP of LN (77.3K). These mixtures provide the termini for an alternative range of mixtures of methane and propene that can be used a cryogenically compatible rocket propellant.

Turning to FIG. 12, a graph illustrates the change in density of methane and ethane in a eutectic mixture over a change in temperature. The graph has density in the units of kg/m3 on the left-hand y-axis and density in the units of lbs/ft3 on the right-hand y-axis. A temperature range from 75K to 100K is on the x-axis. From this data, the density of the mixture increases as temperature decreases. At the boiling point of LN, the density of the mixture is 575.1 kg/m3. The cryogenic cooling of the mixture to below the boiling point of LN increases the fuel density, which increases the performance of this fuel mixture as a rocket propellant. The fuel density of this mixture is greater than RP-1

FIG. 13 is a is a phase diagram for a mixture of methane and propane, which has temperature in K on the y-axis and the increasing mole fraction of propane on the x-axis. This phase diagram illustrates that any mixture of methane and propane has a lower melting point (in degrees K) than the melting point for either pure methane or pure propane. From an analysis of the phase diagram, the eutectic point is at a mole fraction of 68% methane and a mole fraction of 32% propane, which has a melting point of 69.47K.

Other mixtures of methane and propane are in a liquid state at the boiling point of LN. The mixture of a mole fraction of 80% methane and a mole fraction of 20% propane has a melting point of 77.14K, which is below the NBP of LN (77.3K). The mixture of a mole fraction of 45% methane and a mole fraction of 55% propane has a melting point of 76.24K, which is below the NBP of LN (77.3K). The mixture of a mole fraction of 40% methane and a mole fraction of 60% propane has a melting point of 77.48K, which is almost equivalent to the NBP of LN (77.3K). These mixtures provide the termini of a range of mixtures of ethane and propane that can be used a cryogenically LN compatible rocket propellant.

In another example, the mixture of a mole fraction of 85% methane and a mole fraction of 15% propane has a melting point of 80.47K, which is slightly higher than the NBP of LN (77.3K). The mixture of a mole fraction of 35% methane and a mole fraction of 65% propane has a melting point of 78.64K, which is slightly higher than the NBP of LN (77.3K). As discussed above, these mixtures provide the termini for an alternative range of mixtures of methane and propane that can be used a cryogenically compatible rocket propellant.

Moving to FIG. 14, Table 3 illustrates a comparison of the melting point of various light hydrocarbons and eutectic mixtures thereof. The eutectic mixture of methane and ethane has a melting point of 56.1K, which is far below LN NBP of 77.3K. Furthermore, the melting points of eutectic mixtures of methane and propene (68.9K), ethane and propene (75.0K), as well as, propane and propene (75.0), are below LN NBP of 77.3K. Under the cryogenic conditions of LN, these eutectic mixtures are liquids.

In FIG. 15, Table 4 illustrates a comparison of the ideal specific impulse of various light hydrocarbons and eutectic mixtures thereof using the conditions of 1000 psi of chamber pressure, and a nozzle expansion ratio of 4000:1. The eutectic mixture of methane and ethane has a specific impulse of 425.4, which is has over a 3% increase in specific impulse as compared to RP-1 (412), under the same conditions (See FIG. 10).

In FIG. 16, Table 5 illustrates a comparison of the density (in kg/m3) of various light hydrocarbons and eutectic mixtures thereof at LOX NBP.

FIG. 17 is a bar graph having Impulse in seconds on the y-axis and the 5 different propellants on the x-axis. In this bar graph, the specific impulse and the density impulse for each of the propellants are indicated by both bars and the actual number value (in lb/ft3) at the top of each bar. As discussed herein, RP-1 is the most used rocket propellant, it is on the graph as the current standard. The other propellants on this graph are methane, a eutectic mixture of methane and ethane, a eutectic mixture of propane and propene (Pro/Poly 50), and liquid hydrogen. The calculations that were used to generate this graph used the conditions of 1000 psi of chamber pressure, and a nozzle expansion ratio of 20:1.

From analysis of the bar graph, the specific impulse (290) for RP-1 is the lowest of the 5 propellants under these conditions. However, the specific impulse of the methane, the eutectic mixture of methane and ethane, the eutectic mixture of propane and propene are similar to the specific impulse for RP-1, ranging from 293 to 299. In addition, the density impulse (319 and 304) for the eutectic mixtures are slightly better than the density impulse (297) for RP-1 under these conditions. Although liquid hydrogen has the highest specific impulse (367), the specific density (110) for liquid hydrogen is by far the lowest. According to the data on the graph, the eutectic mixture of methane and ethane is the best propellant compared to the 4 other propellants. In addition, the eutectic mixture of methane and ethane has almost a 3% increase in specific impulse and over 7% increase in density impulse as compared to RP-1.

Finally, in FIG. 18, schematic drawing illustrates a cross-section of an exemplary rocket engine system. Rocket engine 100 comprises at propellant tank assembly 103, which comprises a fuel tank 101 and an oxidizer tank 102. A propellant mixture is a eutectic mixture of a small chain alkane from 1 to 4 carbons and a small chain alkene from 3 to 4 carbons or of a small chain alkane from 1 to 4 carbons and a small chain alkane from 2 to 4 carbons (as described herein). The propellant mixture is stored in the fuel tank 101, which is communication with fuel source or vent via valve 105. The LOX is stored in oxidizer tank 102, which is in communication with LOX source or vent via valve 106. The fuel tank 101 and the oxidizer tank 102 share common wall 109. The propellant tank assembly 103 can be cooled with LN. An oxidizer pump 113 moves the LOX through oxidizer line 112 and the amount of LOX entering into the combustion chamber 116 is controlled by valve 114. A propellant pump 107 moves the propellant mixture through propellant line 107 and the amount of the propellant mixture entering into the combustion chamber 116 is controlled by valve 110. The blend of the oxidizer and the propellant mixture is ignited in the combustion chamber 116 and the thrust is directed through nozzle 120.

Some embodiments provide a reduced-temperature propellant mixture for improving performance of a rocket stage, rockets, and the like, said reduced temperature propellant mixture comprising: propane; and propylene, wherein said propylene and said propane are placed in thermal communication in a rocket stage for reduced cost and a smaller rocket stage.

The reduced-temperature propellant mixture can be a mixture of about 50% propane/50% propylene that exhibits a melting point below that of a melting point of pure propane or pure propene and is compatible with a liquid oxidizer. The reduced-temperature propellant mixture can be any mixture of propylene and propane for freezing point suppression. In some configurations, the reduced-temperature propellant mixture is cooled with liquid nitrogen to between 75 K and 88 K to improve performance.

Some embodiments provide reduced-temperature propellant mixture for improving performance of a rocket stage, rockets, and the like, said reduced-temperature propellant mixture comprising: propane; propylene; and liquid oxidizer, wherein a mixture of said propane and said propylene is maintained in thermal communication with said liquid oxidizer for the purposes of improving a rocket stage.

The mixture of said propane and said propylene is a mixture of about 50% propane/50% propylene, and wherein said mixture of about 50% propane/50% propylene and said liquid oxidizer are cooled below a normal boiling point to improve performance. A eutectic mixture of said propane and polypropylene is cooled to the melting point is the best choice of a propane/propylene fuel combusted with said liquid oxygen subcooled to that same temperature is the superior operating combination for a rocket propellant.

Various embodiments of the present invention, a mixture of propane and propylene makes an improved rocket fuel by lowering the melting point (freezing point) and improving the bulk density of the fuel. In one aspect, the mixture of propane and propylene is a mixture of a mole fraction of about 50% propane and a mole fraction of about 50% propylene. In some embodiments, the rocket fuel is a mixture of a mole fraction of between 40% and 60% propane and a mole fraction of between 60% and 40% propene.

Various embodiments provide a rocket propellant comprising a eutectic mixture of a small chain alkane from 1 to 4 carbons and a small chain alkene from 3 to 4 carbons. In some embodiments, the rocket propellant comprises a eutectic mixture of a small chain alkane from 1 to 3 carbons and a small chain alkene having 3 carbons. The mixture of the small chain alkane and the small chain alkene is in a proportion that lowers the melting of the mixture below the melting point of both the small chain alkane and small chain alkene.

For example, the rocket propellant can be a eutectic mixture of a mole fraction of 67% methane and a mole fraction of 33% propene. In some embodiments, the rocket propellant is a eutectic mixture of a mole fraction of between 75% and 60% methane and a mole fraction of between 25% and 40% propene. In some embodiments, the rocket propellant is a eutectic mixture of a mole fraction of between 40% and 60% ethane and a mole fraction of between 60% and 40% propene.

Various embodiments provide a liquid propellant consisting essentially of: propane; and propylene, wherein said liquid propellant has a melting point less than a melting point of pure propylene and a melting point of pure propane.

In some configurations, the liquid propellant can consist essentially of propane in a mole fraction of about 50% and propylene in a mole fraction of about 50%. In some configurations, the liquid propellant can consist essentially of propane in a mole fraction in a range from 45% to 55% and propene in a mole fraction in a range from 45% to 55%. In some configurations, the liquid propellant can consist essentially of propane in a mole fraction in a range from 40% to 60% and propene in a mole fraction in a range from 40% to 60%. In some configurations, the liquid propellant can consist essentially of propane in a mole fraction in a range from 35% to 65% and propene in a mole fraction in a range from 35% to 65%.

[0099] In some configurations, the liquid propellant is a liquid when cooled with liquid nitrogen to a temperature between 75K and 88K. In some configurations, the melting point of the liquid propellant is less than 84K. In some configurations, the melting point of the liquid propellant is less than 80K. In some configurations, the melting point of the liquid propellant is less than 77K.

In some configurations, the liquid propellant has a bulk density greater than 1000 kg/m³at about 77K. In some configurations, the liquid propellant has a density impulse greater than 400 seconds at about 77K.

Some embodiments provide a rocket propellant comprising a eutectic mixture of a small chain alkane from 1 to 4 carbons and a small chain alkane from 2 to 4 carbons. In some embodiments, the rocket propellant comprises a eutectic mixture of a small chain alkane having 1 carbon and a small chain alkene having 2 or 3 carbons. The mixture of the small chain alkanes is in a proportion that lowers the melting of the mixture below the melting point of each of the small chain alkanes.

For example, the rocket propellant can be a eutectic mixture of a mole fraction of about 46% methane and a mole fraction of about 54% ethane. In some embodiments, the rocket propellant is a mixture of a mole fraction of between 25% and 75% methane and a mole fraction of between 75% and 25% ethane. In some embodiments, the rocket propellant is a mixture of a mole fraction of between 20% and 60% methane and a mole fraction of between 80% and 40% propane.

Various embodiments provide a liquid propellant consisting essentially of: methane; and ethane, wherein the liquid propellant has a melting point less than a melting point of pure methane and a melting point of pure ethane.

In some configurations, the liquid propellant can consist essentially of said methane in a mole fraction of about 46% and said ethane in a mole fraction of about 54%. In some configurations, the liquid propellant can consist essentially of said methane in a mole fraction in a range from 40% to 50% and said ethane in a mole fraction in a range from 60% to 50%. In some configurations, the liquid propellant can consist essentially of said propane in a mole fraction in a range from 25% to 75% and the propene in a mole fraction in a range from 75% to 25%. In some configurations, the liquid propellant can consist essentially of said methane in a mole fraction in a range from 20% to 80% and said ethane in a mole fraction in a range from 80% to 20%.

In some configurations, the liquid propellant is a liquid when cooled with liquid nitrogen to a temperature between 75K and 88K. In some configurations, the melting point of the liquid propellant is less than 84K. In some configurations, the melting point of the liquid propellant is less than 80K. In some configurations, the melting point of the liquid propellant is less than 77K.

Various embodiments provide a rocket engine system comprising: the liquid propellant and a liquid oxidizer. In some configurations, the liquid oxidizer is liquid oxygen at a temperature less than 90K. In some configurations, the liquid propellant and the liquid oxidizer are separated by a common wall. In some configurations, the liquid propellant and the liquid oxidizer are cryogenically cooled to a temperature less than 80 K. The rocket system can comprise liquid nitrogen configured to cryogenically cool the liquid propellant and the liquid oxidizer to the temperature less than 80 K.

As used herein, the phrase “at least one of A, B, and C” can be construed to mean a logical (A or B or C), using a non-exclusive logical “or,” however, can be contrasted to mean (A, B, and C), in addition, can be construed to mean (A and B) or (A and C) or (B and C). As used herein, the phrase “A, B and/or C” should be construed to mean (A, B, and C) or alternatively (A or B or C), using a non-exclusive logical “or.”

The present invention has been described above with reference to various exemplary embodiments and examples, which are not intended to be limiting in describing the full scope of systems and methods of this invention. However, those skilled in the art will recognize that equivalent changes, modifications and variations of the embodiments, materials, systems, and methods may be made within the scope of the present invention, with substantially similar results, and are intended to be included within the scope of the present invention, as set forth in the following claims.

Claims

1. A liquid propellant consisting essentially of: wherein said liquid propellant has a melting point less than a melting point of pure methane and a melting point of pure ethane.

methane; and

ethane,

2. The liquid propellant according to claim 1, wherein said methane in a mole fraction of about 46% and said ethane in a mole fraction of about 54%.

3. The liquid propellant according to claim 1, wherein said liquid propellant is a liquid when cooled with liquid nitrogen to a temperature between 75 Kelvin and 88 Kelvin.

4. The liquid propellant according to claim 1, wherein said methane in a mole fraction in a range from 40% to 50% and said ethane in a mole fraction in a range from 60% to 50%.

5. The liquid propellant according to claim 1, wherein said propane in a mole fraction in a range from 25% to 75% and the propene in a mole fraction in a range from 75% to 25%.

6. The liquid propellant according to claim 1, wherein said methane in a mole fraction in a range from 20% to 80% and said ethane in a mole fraction in a range from 80% to 20%.

7. The liquid propellant according to claim 1, wherein the melting point of the liquid propellant is less than 84 Kelvin.

8. The liquid propellant according to claim 1, wherein the melting point of the liquid propellant is less than 80 Kelvin.

9. The liquid propellant according to claim 1, wherein the melting point of the liquid propellant is less than 77 Kelvin.

10. A rocket engine system comprising: the liquid propellant according to claim 1, and a liquid oxidizer.

11. The rocket engine system according to claim 12, wherein the liquid oxidizer is liquid oxygen at a temperature less than 90 Kelvin.

12. The rocket engine system according to claim 13, wherein the liquid propellant and the liquid oxidizer are separated by a common wall.

13. The rocket engine system according to claim 14, wherein the liquid propellant and the liquid oxidizer are cryogenically cooled to a temperature less than 80 Kelvin.

14. The rocket system according to claim 15, further comprising liquid nitrogen configured to cryogenically cool the liquid propellant and the liquid oxidizer to the temperature less than 80 Kelvin.