WO2000005133A2 - High regression rate hybrid rocket propellants - Google Patents
High regression rate hybrid rocket propellants Download PDFInfo
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- WO2000005133A2 WO2000005133A2 PCT/US1999/016556 US9916556W WO0005133A2 WO 2000005133 A2 WO2000005133 A2 WO 2000005133A2 US 9916556 W US9916556 W US 9916556W WO 0005133 A2 WO0005133 A2 WO 0005133A2
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- propellant
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- entrainment
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06D—MEANS FOR GENERATING SMOKE OR MIST; GAS-ATTACK COMPOSITIONS; GENERATION OF GAS FOR BLASTING OR PROPULSION (CHEMICAL PART)
- C06D5/00—Generation of pressure gas, e.g. for blasting cartridges, starting cartridges, rockets
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B47/00—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase
- C06B47/02—Compositions in which the components are separately stored until the moment of burning or explosion, e.g. "Sprengel"-type explosives; Suspensions of solid component in a normally non-explosive liquid phase, including a thickened aqueous phase the components comprising a binary propellant
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02K—JET-PROPULSION PLANTS
- F02K9/00—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof
- F02K9/72—Rocket-engine plants, i.e. plants carrying both fuel and oxidant therefor; Control thereof using liquid and solid propellants, i.e. hybrid rocket-engine plants
Definitions
- the present invention relates generally to the field of propellants suitable for use in hybrid rockets, and more particularly to propellants and a method of selecting propellants that exhibit high regression rates.
- liquid systems and solid propellant systems Two basic types of chemical rocket propulsion systems are widely used in the rocket industry; namely, liquid systems and solid propellant systems.
- liquid oxi- dizer and liquid fuel are fed at high pressure to a combustion chamber where th£y mix and react producing high temperature, high pressure gases which exhaust through a converging- diverging nozzle producing thrust.
- the mixing of reactants requires a high performance pres- surization system for the fuel and oxidizer which must often operate in a cryogenic environment at extreme pressures and mass flow rates.
- the injection system and combustion chamber require exotic materials, complex systems for cooling, and very high precision manufacturing techniques. All of these factors contribute to a high cost.
- Solid propellant systems do not require the complex and expensive machinery of liquid systems. Nevertheless, solid systems are complicated, and are subject to the difficulties of producing crack-free, repeatable, fuel grains, and by the need to transport and handle explosive materials. In a manufacturing process that requires extreme safety precautions, solid fuel and oxidizer are intimately mixed and allowed to cure inside the rocket case producing an explosive fuel with roughly the consistency of plastic or hard rubber. Fuel grains which contain cracks present a risk of explosive failure of the vehicle and must be rejected, driving up the cost of manufacture. Upon ignition the solid fuel burns uninterrupted until all the fuel is exhausted.
- hybrid propulsion system An alternative chemical rocket which has been known since the 1930's is the hybrid propulsion system.
- one propellant is stored in the solid phase while the other is stored in the liquid phase.
- the hybrid lies somewhere between the two basic chemical rocket designs just described.
- the solid is the fuel and the liquid is the oxidizer.
- Reverse hybrids with the fuel in the liquid phase and oxidizer in the solid phase are also feasible and the present invention described below can be applied equally well to both types of hybrid systems.
- Typical oxidizers that are frequently used in hybrid rockets are liquid oxygen, hydrogen peroxide, nitrogen tetroxide, nitrous oxide and occasionally fluorine.
- the fuel combinations used for hybrids are similar in their chemical properties and energy densities to the fuels used in hydrocarbon fueled liquid rocket systems.
- the hybrid system is a closer relative to a liquid system than to a solid system. Solid rockets tend to use lower energy oxidizers and consequently they produce lower specific impulse.
- the main advantages of the hybrid over the liquid rocket include: Lower development and operating costs (life cycle costs), • Lower fire and explosion hazards,
- the hybrid allows the addition of energetic solid components, such as aluminum or beryllium to the fuel.
- FIG. 1 A schematic of a typical hybrid propulsion system 10 with a pressurized oxidizer feed system is shown in Figure 1.
- the feed system is comprised of a pressurization tank 12 that holds an inert gas at high pressure (such as Helium, Argon or Nitrogen), a valve (not shown) to pressurize the oxidizer tank 14, a main valve 16 to turn on the flow of oxidizer and an injection system 18.
- the gas pressurization system can be replaced with a turbopump.
- the other major components are the combustion chamber 20 which contains the solid fuel 22 and the nozzle assembly 24.
- the single port combustion chamber 30 generally includes a pre-combustion chamber region 31 at the front end, a post-combustion chamber region 32 at the opposite end, and an elongated single port 33 extending between the ends.
- the oxidizer in the liquid phase is injected into the combustion chamber at pre-combustion chamber region 31.
- the injected oxidizer is gasified and flows axially along the port 33, forming a boundary layer 34 over the solid fuel 22.
- the boundary layer 34 is usually turbulent in nature over a large portion of the length of the port. Within the boundary layer 34 there exists a turbulent diffusion flame 36 which extends over the entire length of the fuel.
- the thickness of the flame is generally very small compared to the boundary layer thickness.
- the heat generated in the flame which is located approximately 20-30% of the boundary layer thickness above the fuel surface, is transferred to the wall mainly by convection. Some heat is also transferred by radiation but this is usually relatively small compared to the convective heat transfer.
- the wall heat flux evaporates the (generally polymeric) solid fuel and the fuel vapor is transported to the flame where it reacts with the oxidizer which is transported from the free stream by turbulent diffusion mechanisms.
- the unburned fuel that travels beneath the flame, the unburned oxidizer in the free stream, and the flame combustion products mix and further react in the post combustion chamber 32.
- the degree to which fuel and oxidizer are able to fully mix and react before exhausting through the nozzle 24 determines the combustion efficiency of the motor.
- the hot gases expand through a convergent-divergent nozzle 24 to deliver the required thrust.
- the burning rate is limited by the heat transfer from the relatively remote flame to the burning surface of the fuel.
- One of the physical phenomena that limits the burning rate in a hybrid motor is the so-called blocking effect that is caused by the high velocity injection of the vaporizing fuel into the gas stream. This difference in the combustion scheme of a hybrid motor significantly alters the burning rate characteristics compared to a solid rocket. Blocking can be explained as follows. Increasing the heat transfer to the fuel causes the evaporative mass transfer from the liquid-gas interface to increase. But the increased blowing from the surface reduces the temperature and velocity gradient at the surface thus reducing the convective heat transfer.
- the blowing also thickens the boundary layer and displaces the flame sheet further from the fuel surface leading to a further reduction in convective heat transfer.
- the position of the flame sheet and the shape of the thermal and velocity boundary layer is the result of a complex chemical and fluid mechanical balance between the oxidizer flow entering the port, the fuel flow produced by evaporation and the flow of combustion products.
- the burning rate is limited in a fundamental way which is difficult to overcome by either increasing heat transfer to the fuel or by a reduction in the fuel heat of gasification.
- radiative heat transfer from the flame does not suffer from the blocking effect it is usually small compared to the convective heat transfer.
- the upshot of all this is that the regression rate, defined as the recession speed of the solid surface of a conventional hybrid fuel is typically one-tenth or less than that of a solid rocket fuel.
- the thrust generated by a rocket is approximately proportional to the mass flow rate.
- the fuel mass flow generation rate is a product of the fuel density times the regression rate, multiplied by the burning surface area.
- the fuel density is determined by the type of fuels.
- high thrust levels are required for a launch vehicle.
- high thrust can only be achieved by increasing the burning surface area.
- the high burning area requirements, and various other design constraints (such as the maximum grain length to port diameter ratio), leads to complicated multi-port configurations.
- One commonly used multi-port configuration is the wagon wheel geometry as shown in Figure 3, and has been implemented in several hybrid motor designs.
- hybrid rocket propellants that exhibit a high regression rate, or more specifically, that will burn several times faster than conventional propellants at the same operating conditions of port mean mass flux and chamber pressure while retaining the basic advantages of hybrids; throttlability, safety and low cost.
- the propellant have the following characteristics: self-decomposing materials are not involved;
- the port design can be structurally simple; the propellant is safe, easy to handle and easy to process; the propellant burns smoothly; and
- the liquid layer at the melt surface can be hydrodynamically unstable under the mass flux, pressure and temperature conditions which occur in a hybrid rocket combustion chamber.
- This shear-driven instability leads to wave formation on the liquid-gas interface and as the waves develop nonlinearly, the displaced liquid-gas interface exposed to the high speed flow of gas can breakup, leading to the formation of concentrated pockets of high density fuel and/or fuel droplets which are entrained into the gas stream.
- the mechanism of liquid layer instability and entrainment can substantially increase the rate of mass transfer from the fuel surface. This situation is illustrated schematically in Figure 5.
- the present invention provides for a fuel composition suitable for use in hybrid rockets having a fuel component and an oxidizing component.
- One of the components flows past the other, and under the heat of combustion (heat transfer from the flame) one of the components forms an unstable melt layer with viscosity and surface tension such that droplets from the melt layer are entrained in the other component thereby increasing the burning rate.
- the present invention can also be used in formulating a fast burning fuel for solid fuel ramjet applications.
- a propulsion system in another aspect of the present invention, includes a vehicle structure, terminating in a nozzle and having a fuel component within the structure.
- One or more combustion chambers are formed within, or alternatively contain, the fuel component.
- an oxidant vessel within the vehicle structure for flowing the oxidant in contact with the one or more combustion chambers to react with the fuel.
- the fuel is selected such that under the heat transfer from the flame, the fuel forms an unstable melt layer with viscosity and surface tension such that droplets of the melted fuel are entrained in the flowing oxidant thereby increasing the burning rate.
- a combustible hybrid fuel having a solid fuel component and a flowing oxidizer component flowing through one or more ports.
- the solid fuel forms a liquid layer at the interface between the oxidizer and fuel, and the liquid layer exhibits entrainment of liquid droplets in the flowing oxidizer at an entrainment rate of C j P * r ent , oc ⁇ ⁇ ⁇ ' ⁇
- Figure 1 is a schematic diagram of a hybrid rocket which may be employed with the present invention.
- Figure 2 is a schematic diagram of the combustion configuration in a single port hybrid rocket motor.
- Figure 3 is a schematic diagram of a wagon wheel port hybrid rocket motor.
- Figure 4 is a schematic diagram illustrating velocity and temperature profiles in a liquefying hybrid rocket.
- Figure 5 is a schematic diagram showing entrainment of the melt layer during combustion according to the present invention.
- Figure 6 is a graph illustrating melting, vaporization and average melt layer temperature of n-paraffins as a function of molecular weight and according to one embodiment of the present invention.
- Figure 7 is a graph depicting viscosity as a function of the molecular weight for various n-paraffins (normal paraffins) and two highly crystalline polyethylene waxes.
- Figure 8 shows the viscosity and surface tension of the melt layer as a function of the molecular weight for various n-paraffins according to one embodiment of the present invention.
- Figure 9 illustrates the presence of entrainment for various n-paraffins as a function of their molecular weight.
- Figure 10 is a graph showing regression rates as a function of oxidizer mass flux for paraffins A and B according to one embodiment of the present invention.
- Figure 1 la is a photograph showing the plume from a conventional PMMA/GOX hybrid rocket systems.
- Figurel lb is a photograph showing the plume from a paraffin wax (grade B)/GOX hybrid rocket system of the present invention.
- Figures 12a and 12b are schematic cross sectional end views of a double D port, and circular single port, hybrid rocket motor configurations, respectively, according to two embodiments of the present invention.
- Figure 13 is a graph showing the regression rate for paraffin wax B according to the present invention, in comparison to the estimated classical regression rate of the prior art.
- n-alkane normal alkane
- C n H 2n + 2 which are solid at room temperature and having a mean carbon number of n ⁇ 15 , more preferably n is in the range of 15 to 80, with a range of 18 to 40 being most preferred, have low surface tension and viscosity at the melt layer conditions typical of hybrid rockets.
- these fuels are predicted to have high regression rates at oxidizer mass fluxes covering a wide range of hybrid rocket applications.
- some isomers of the alkane series will also satisfy the entrainment criterion found by the inventors.
- the selection procedure is generally as follows.
- the entrainment onset criterion ( ⁇ * 0 niethine set ) is used to estimate the combination of port mass flux given by:
- a high regression rate propellant is one that will entrain for the range of mass fluxes that are expected to occur in the given application.
- a number of fuels including the paraffin waxes, polyethylene waxes, solid organic acids and alkylnapthalenes fall into this category.
- a low regression rate propellant is one that, by this criterion, would only entrain for mass fluxes in excess of those produced in the given application. In other words, at the port mass flux the rocket is designed for, entrainment would not occur.
- HDPE high density polyethylene
- the thickness of the liquid layer is determined by the energy transfer relations both in the solid and also in the liquid.
- the regression rate of the liquid-gas interface and the solid-liquid interface are assumed to be equal and constant. This, of course, implies that the thickness of the melt layer is also constant.
- the thermophysical properties of the material both in the liquid phase and also in the solid phase are uniform. The effect of convection in the liquid layer was also ignored. This assumption can be justified for small melt layer thicknesses for which the Reynolds numbers are relatively small (a few hundred) and the temperature gradients are fairly large.
- the possibility of the penetration of thermal radiation into the slab is considered.
- the radiative flux field is assumed to be one dimensional.
- the absorbing character of both the liquid and the solid material is assumed to behave like a gray body; namely the absorption coefficient is independent of the frequency of the radiation.
- Kcl s T 2 + L m + C/ ⁇ 7 + L V (7)
- the heat of gasification is the total heat required to transform the fuel from the solid state at its ambient temperature, T a , to the gas state at the average liquid-gas interface temperature, T inter e .
- the factor (r v /r) appearing in equation (6) accounts for the fact that a given parcel of fuel mass can reach the free stream through two routes; one route being vaporization and involving the usual four steps of solid heating, melting, liquid heating and evaporation; and the other route being entrainment and involving the first three steps but not requiring evaporation.
- the droplets do eventually evaporate as they convect along the port and interact with the flame but this process does not contribute to the heat or mass balance at the liquid-gas interface.
- T inter f ace The average temperature at the liquid-gas interface, T inter f ace , must be estimated.
- Q r / Q c is the ratio of radiative to convective heat transfer to the liquid-gas interface and must be estimated. A reasonable range, valid over the conditions found in hybrid rockets is Q r /Q c ⁇ 0.2 . Fortunately, as long as Q r /Q c is small, the calculated value of the liquid layer thickness is not sensitive to errors in the quantities which appear in the logarithm. But notice that there is a critical value of Q r /Q c when the denominator in the logarithm in (4) becomes zero. This corresponds to a condition where there is no steady state solution to the melting problem and the thickness of the liquid layer continues to grow toward a state where the entire block of fuel is being heated to the melting point by radiation.
- the port mean pressure may exceed the critical pressure of the liquid.
- Thermodynamic equilibrium theory indicates that above the critical pressure the surface distinguishing liquid and gas is not precisely defined and the density varies continuously from the melt layer to the gas.
- the melt layer in a hybrid rocket may not be in an equilibrium state and the detailed physics of the liquid-gas interface is not well understood.
- the word "droplet” has a generalized meaning referring to any parcel of propellant at or close to the density of the melt layer and the phrase "liquid-gas interface” refers to a transition layer from liquid to gas that may not have a distinct surface although the surface of maximum density gradient is often used as a reference.
- the friction coefficient at the liquid-gas interface is approximately __ interface ⁇ f ⁇ t .-0.2 /n ,
- ⁇ inter f ace is the shear stress at the gas-liquid interface.
- the Reynolds number based on the distance, z, along the port is
- Equation (12) is a local relationship which depends weakly on the axial position in the port.
- the instability of the melt layer needs to be related to the entrainment of liquid droplets into the gas stream.
- the inventors have determined some important factors regarding entrainment mass transfer as follows: • if the mass flux in the port is less than a critical value there is no entrainment mass transfer from the film; and the general empirical expression for the entrainment rate of liquid droplets (the entrainment regression rate) in terms of the relevant properties of the hybrid motor can be written as:
- ⁇ is approximately 1.5, ⁇ is approximately 2.0 and ⁇ and ⁇ are approximately
- a useful criterion for the onset of entrainment must account for two basic effects. First, at a given mass flux a thick liquid layer is more unstable and therefore more likely to entrain than a thin layer. Second, for a given liquid layer thickness a higher free stream gas mass flux is more likely to entrain than a lower mass flux. Following reference [5] the fundamental criterion for the onset of entrainment is
- a nrt . ot The quantity, a nrt . ot , is computed for a given fuel. If the computed value Of Ben, is below a critical range, then the fuel is likely to entrain.
- a Qmet is selected such that Q et has a value that promotes entrainment of droplets from the melt layer.
- a onse( is equal to or less than approximately 0.9, and more preferably a Qnset is equal to or less than 0.4.
- the units of a are kg ' / ⁇ m - sec ' ) .
- the factor, p t ' is fairly close to one over a wide range of liquid densities.
- the coefficient, C ⁇ l is between approximately 0.2 and 0.4.
- the port mean temperature varies rel- ⁇ atively little over the range of applications so the main sensitivity is to the port mean I 3 pressure although the effect is not as strong as P since as the pressure increases the tem- perature of the liquid-gas interface increases also, tending to partially mitigate the increase in a t due to pressure.
- the factor, ⁇ ' , in a Q et indicates the important role of the surface tension and the viscosity, especially the viscosity, in determining whether a propellant will entrain.
- the surface tension is in the range of 5 to 30 milHN/m .
- the viscosity varies widely.
- the viscosity of high density polyethylene (HDPE) is a factor
- the port mass flux required to cause the onset of entrainment for a given fuel is estimated as
- Compounds suitable according to the present invention include the n- alkane class of hydrocarbons of the formula C n H 2n+2 which are solid at room temperature and have a mean carbon number of n ⁇ 15 , more preferably n is in the range of about 15- 80, with a range of about 18 to 40 being most preferred and isomers of said alkane class of hydrocarbons.
- melt viscosity As discussed previously the most important parameters of the melt layer that determine the entrainment (and thus the total burning rate of a prospective fuel) are the melt viscosity at an average temperature between the melting temperature and the liquid-gas interface temperature, and the surface tension at the liquid-gas interface temperature.
- Figure 7 shows a linear variation of viscosity with the molecular weight as expected in this low molecular weight regime.
- Two additional data points for two highly crystalline polyethylene waxes (4040/R7 and 4040/R9 of Marcus Oil & Chemical Corporation) are also included in the plot. This specific polyethylene wax 2b
- melt layer surface tension actually decreases with increasing molecular weight as shown in Figure 8. This effect, which can only be realized for relatively small molecular weights, is also due to the increased melt layer surface temperatures with increasing molecular weight.
- melt viscosity and surface tension indicate that moderate molecular weight, normal alkanes (i.e. paraffin waxes) will generate entrainment rates that are several times the regression rates of classical polymeric hybrid fuels.
- the combined effect of the increase in viscosity and decrease in surface tension is to modestly increase entrainment with increasing molecular weight in this range.
- high density polyethylene (HDPE) polymer is also a member of this linear molecule family in the very high molecular weight extreme (-200,000 kg/kmole).
- the melt viscosity of the high density polyethylene is estimated at an average temperature between the melting point (735 C) and the pyrolysis temperature ⁇ 405 C) with use of a technique presented in reference [6]. Note that a simple extrapolation cannot be used to determine the melt viscosity of these liquids with large molecules since above a critical value of the molecular weight, the linear variation of viscosity with molecular weight does not hold.
- the estimated viscosity value for HDPE is 20 Pascal-sec which is 4 orders of magnitude larger than the melt viscosity of paraffin wax or the viscosity of liquid pentane. This explains the low regression rates (i.e. no entrainment mass transfer) observed for melting polymeric fuels such as high density polyethylene.
- Figure 9 illustrates a qualitative schematic of the overall picture for n-paraffins ranging from the smallest molecular mass (methane) to HDPE polymer. Note that materials at both ends of the spectrum have been tried as hybrid fuels. Both extremes have significant deficiencies, namely the high molecular weight HDPE polymer burns slowly and the fast burning low molecular weight compounds are solid only under cryogenic conditions, reference [10]. It is remarkable that the non-cryogenic materials in the intermediate molecular mass region (potentially optimum for hybrid applications) such as paraffin and PE waxes have not previously been tried as hybrid rocket fuels.
- paraffin grades A and B Preliminary laboratory tests with Plexiglas (PMMA), high density polyethylene, HDPE a high molecular weight PE wax and two grades of paraffin wax with melting points of 61 C and 67 C , hereafter referred to as paraffin grades A and B respectively were made.
- the wax was melted in a melt pot under a controlled pot temperature of 90 C and mixed with carbon black ( ⁇ 1 % mass fraction) with an average particle size of 18 nm.
- the mixture was molded in the motor case at room temperature and atmospheric pressure.
- the PE wax grains were machined with the appropriate port diameter to fit the motor case.
- Table 1 The conditions and results for these preliminary experiments are shown in Table 1 below.
- the regression rate values shown in Table 1 are calculated both by geometrical measurement of the change in the port dimensions and also by measuring the weight reduction in the grain during the experiment. Both methods yield similar values for the regression rate.
- a partial list of suggested additives that could be used in a practical fuel formulation based on the paraffin wax would include Carbon Black (0.2-1% by weight), some PE wax (or other kinds of high molecular weight synthetic waxes) to provide desired mechanical properties and thermal stability and possibly some density increasing agents such as Escorez.
- Carbon Black or an alternative material with high optical absorptivity
- the role of carbon black is to improve the radiative absorptivity of the fuel to insure that most of the radiation from the flame is absorbed at the fuel surface. This is important since paraffin wax alone may be heated in bulk by the penetration of radiation from the flame zone resulting in uncontrolled burning and possible sloughing of the fuel. Additionally, reinforcing or stiffening agents may be added to provide mechanical rigidity.
- the grade of paraffin and the concentration of additives can be adjusted to obtain the combination of burning rate and mechanical properties that suits the mission under consideration. For example, for missions requiring low mass flow generation rates and high mechanical loading conditions, a high molecular weight paraffin could be selected and/or a significant concentration of PE wax could be added.
- the fuel formulation can be varied spatially in the fuel grain in order to passively control the fuel mass flow generation rate as a function of time. This technique would allow one to design hybrid rockets with a desired thrust history and with little or no compromise in the specific impulse.
- alkhylnaphthalenes including straight naphthalene
- anthracene and certain organic acids.
- the organic acids finding use in the present invention include organic acids having the general formula where n is in the range of 8 to 25, and mixtures thereof.
- Naphthalene CJ Q H 8 which is a crystalline material with a melting point of 354 K, is determined to possess melt layer properties that would allow for reasonable entrainment.
- Some of the other organic compounds that belong to the family of Alkhylnaphthalenes with lower melting points and slightly higher viscosity compared to Naphthalene are 2,6 Methylnaphthalene, 1-Phenylnaphthalene, 2,6-Diethyl- naphthalene and 2,6 Diisopropylnaphthalene [7]. All of these materials have high solid
- the other group of materials is the organic acids.
- n 9 (n-nonanoic acid) the melting temperature is 286 K
- n 20 (n-eicosanic acid) melting occurs at 348 K.
- the melt viscosity and surface tension levels are moderate and the expected entrainment rates would be moderate compared to the level predicted and observed for paraffin waxes.
- This series may be useful as additives to higher entrainment rate fuel materials described previously.
- Another acid which is not a member of the normal acid family is Glutaric acid C 5 H 8 0
- ticular acid has a melting point at 407 K and a solid density of 1427 kg/m . It possesses a moderate to low melt viscosity and surface tension.
- the above listed chemicals is not exhaustive, and is not an attempt to give a complete list of compounds that would be used as high burning rate fuel materials in hybrid rockets. The few examples discussed above is only a small fraction of the set of possible fast-burning fuel materials which would satisfy the teaching and criteria of the present invention.
- a hybrid utilizing a fast burning fuel according to the present invention is economically superior to a conventional hybrid or, for that matter, to a conventional liquid or solid system.
- the fast burning hybrid should be able to provide performance which is comparable to or better than a conventional solid or liquid system.
- oxidizer injection in the post-combustion chamber yields marginal advantages for conventional hybrids which operate in a multi-port configuration with a relatively thin web, it promises a greater benefit for the fast burning hybrid.
- Aft-end injection makes a partially controllable system (thrust or Isp, not both) a fully controllable one. Any given thrust and Isp schedule can be obtained by setting the main and aft-end oxidizer injection schedules. This makes the fast burning hybrid propulsion system comparable to liquid systems in terms of controllability.
- the method of selecting a high regression rate fuel is provided in stepwise fashion as follows: 1) Specify the length of the fuel grain, L jfJ and port geometry.
- thermochemical properties of the candidate material including the melting temperature, T m , the normal boiling temperature, T b , latent heat of fusion,
- T b is the normal boiling temperature of the candidate material.
- the use of normal boiling point to evaluate the surface temperature implicitly assumes a surface vapor partial pressure of approximately 1 atm.
- the surface temperature is reduced from its vaporization value using equation (8) to account for the effect of entrainment which decreases the effective surface temperature.
- the gas density is calculated from the ideal gas law.
- the units of a Qnset are kg ' / ⁇ m ' - sec ' ) .
- the entrainment onset mass flux at the port mean pressure of the given application is determined from
- the classical regression rate curve is plotted in figure 13 for comparison with the data. Over the range of mass fluxes studied, the regression rate measured for paraffin is approximately 3.4 times the rate predicted from classical theory.
- the present invention provides a high regression rate propellant and a method for identifying such propellants that produce high burning rates in hybrid rockets and other applications such as solid fuel ramjets.
- the propellant can be either a fuel or an oxidizer.
- the propellants are materials which form an unstable melt layer at the burning surface. Under the right conditions of port mass flux, liquid layer surface tension, and viscosity, droplets may be entrained from the liquid layer into the high temperature gas flow in the port. The process is based on a criterion by which one can determine whether entrainment will occur for a given material.
- n-alkanes n-alkanes
- Other hydrocarbon-compounds have also been identified that satisfy the required criterion. These include the alkhylnaphthalenes (including straight naphthalene), anthracene, and certain organic acids. These relatively dense materials can also be used as additives to paraffin based fuels. Mixtures of materials can also be used.
- paraffin wax can be easily mixed with polyethylene (PE) wax as well as carbon black and/or other common additives such as Stearic acid.
- PE polyethylene
- carbon black and/or other common additives such as Stearic acid.
- the performance of a hybrid system can be optimized for a given mission profile by mixing high and low molecular weight alkanes together to achieve the required regression rate.
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Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
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JP2000561101A JP2003523909A (en) | 1998-07-22 | 1999-07-21 | High reversal speed hybrid rocket propellant |
CA002338213A CA2338213A1 (en) | 1998-07-22 | 1999-07-21 | High regression rate hybrid rocket propellants |
IL14092199A IL140921A0 (en) | 1998-07-22 | 1999-07-21 | High regression rate hybrid rocket propellants |
EP99963120A EP1104390A2 (en) | 1998-07-22 | 1999-07-21 | High regression rate hybrid rocket propellants and method of selecting |
AU11963/00A AU1196300A (en) | 1998-07-22 | 1999-07-21 | High regression rate hybrid rocket propellants and method of selecting |
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US9369698P | 1998-07-22 | 1998-07-22 | |
US60/093,696 | 1998-07-22 |
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WO2008082677A2 (en) * | 2006-02-17 | 2008-07-10 | Syntroleum Corporation | Hybrid rocket fuel |
WO2013019876A3 (en) * | 2011-08-02 | 2013-04-18 | The Aerospace Corporation | Systems and methods for fabricating hybrid rocket motor fuel grains |
ITRM20110628A1 (en) * | 2011-11-28 | 2013-05-29 | Hypotheses S R L | STRUCTURED PROPELLANTS REINFORCED PROPELLANTS |
US8601790B2 (en) | 2008-02-28 | 2013-12-10 | The Aerospace Corporation | Buried radial flow rapid prototyping rocket motors |
US8707676B2 (en) | 2008-02-28 | 2014-04-29 | The Aerospace Corporation | Radial flow rapid prototyping rocket motors |
US8844133B2 (en) | 2008-02-28 | 2014-09-30 | The Aerospace Corporation | Stereolithographic rocket motor manufacturing method |
US9038368B2 (en) | 2011-08-01 | 2015-05-26 | The Aerospace Corporation | Systems, methods, and apparatus for providing a multi-fuel hybrid rocket motor |
RU2561427C1 (en) * | 2014-03-12 | 2015-08-27 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Омский государственный технический университет" | Method of gasification process simulation for residual liquid rocket fuel and device for method implementation |
US9429104B2 (en) | 2011-08-01 | 2016-08-30 | The Aerospace Corporation | Systems and methods for casting hybrid rocket motor fuel grains |
CN111718226A (en) * | 2020-05-25 | 2020-09-29 | 西北工业大学 | Paraffin-containing fuel formula and preparation method |
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FR2875293B1 (en) * | 2004-09-14 | 2009-01-16 | Pyroalliance Sa | HYBRID ACTUATOR WITH CHARGE COMPRISING A DISSOCATED OXIDANT AND REDUCER |
JP5484796B2 (en) * | 2009-06-19 | 2014-05-07 | 三菱重工業株式会社 | Hybrid rocket engine |
JP5666105B2 (en) * | 2009-07-15 | 2015-02-12 | 株式会社Ihiエアロスペース | Hybrid rocket solid fuel |
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- 1999-07-21 JP JP2000561101A patent/JP2003523909A/en active Pending
- 1999-07-21 EP EP99963120A patent/EP1104390A2/en not_active Withdrawn
- 1999-07-21 WO PCT/US1999/016556 patent/WO2000005133A2/en not_active Application Discontinuation
- 1999-07-21 IL IL14092199A patent/IL140921A0/en unknown
- 1999-07-21 CA CA002338213A patent/CA2338213A1/en not_active Abandoned
- 1999-07-21 AU AU11963/00A patent/AU1196300A/en not_active Abandoned
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Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2008082677A2 (en) * | 2006-02-17 | 2008-07-10 | Syntroleum Corporation | Hybrid rocket fuel |
WO2008082677A3 (en) * | 2006-02-17 | 2009-01-22 | Syntroleum Corp | Hybrid rocket fuel |
US8601790B2 (en) | 2008-02-28 | 2013-12-10 | The Aerospace Corporation | Buried radial flow rapid prototyping rocket motors |
US8707676B2 (en) | 2008-02-28 | 2014-04-29 | The Aerospace Corporation | Radial flow rapid prototyping rocket motors |
US8844133B2 (en) | 2008-02-28 | 2014-09-30 | The Aerospace Corporation | Stereolithographic rocket motor manufacturing method |
US9038368B2 (en) | 2011-08-01 | 2015-05-26 | The Aerospace Corporation | Systems, methods, and apparatus for providing a multi-fuel hybrid rocket motor |
US9429104B2 (en) | 2011-08-01 | 2016-08-30 | The Aerospace Corporation | Systems and methods for casting hybrid rocket motor fuel grains |
WO2013019876A3 (en) * | 2011-08-02 | 2013-04-18 | The Aerospace Corporation | Systems and methods for fabricating hybrid rocket motor fuel grains |
ITRM20110628A1 (en) * | 2011-11-28 | 2013-05-29 | Hypotheses S R L | STRUCTURED PROPELLANTS REINFORCED PROPELLANTS |
RU2561427C1 (en) * | 2014-03-12 | 2015-08-27 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Омский государственный технический университет" | Method of gasification process simulation for residual liquid rocket fuel and device for method implementation |
CN111718226A (en) * | 2020-05-25 | 2020-09-29 | 西北工业大学 | Paraffin-containing fuel formula and preparation method |
CN111718226B (en) * | 2020-05-25 | 2021-12-28 | 西北工业大学 | Paraffin-containing fuel and preparation method thereof |
Also Published As
Publication number | Publication date |
---|---|
CA2338213A1 (en) | 2000-02-03 |
WO2000005133A3 (en) | 2000-04-20 |
EP1104390A2 (en) | 2001-06-06 |
IL140921A0 (en) | 2002-02-10 |
AU1196300A (en) | 2000-02-14 |
WO2000005133A9 (en) | 2000-07-27 |
JP2003523909A (en) | 2003-08-12 |
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