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Clearwater, FL 337623840 Copyright ©2007
New Generation Propulsion and Ordnance Technology at SPS:
Developing Environmentally Clean Technologies for both the Military and
Commercial Space Applications
ABSTRACT Serious air, soil and groundwater environmental problems have developed globally form the manufacture, storage and use of current solid rocket propellants and ordnance products. In 1993, the US Government initiated new programs to not only cleanup the current environmental problems, but to reduce the environmental impact and improve the safety of new solid propellants and ordnance products under development.
Current rocket propellants use a chemical called Ammonium Perchlorate (AP). These are the highest energy propellants that are the most stable, so are relatively safe to use (not produce). When these rocket propellants are used, they produce clouds of hydrochloric acid, which are considered a serious pollutant. Serious groundwater and soil contamination has been found for this toxic chemical, and is now considered a serious pollutant. The aerospace industry has been working on a means to use other new, less and non‐toxic (green), chemicals (HZN, ADN, CL‐20, AN) as replacements for AP. Serious problems exist, however, in both processing these new fuels using conventional methods and in the performance of these propellants when used, so none are currently available.
The New Generation SPS MFC™ solid propellant and ordnance product manufacturing technology can readily process these new Green chemicals into rocket fuels (we already demonstrated this with AN (Ammonium Nitrate) at our University of South Florida program). In the MFC™, these chemicals are processed into a suitable form to safely make rocket propellants (first we make spherical particles of these chemicals and then encapsulate them in a highly stable fuel, this forms the core of the MFC™). These MFC™ particles are even easier to process into rocket propellants (as shown by NAWC China Lake during production of test samples) than even current chemicals used in rocket propellants. Other chemicals can also be included in the MFC™ in a safe way to make the final rocket propellants even safer and perform better (tailoring their performance). The MFC™ is a protected environment that can contain highly volatile chemicals that will only be mixed and reacted during the launch of the rocket.
The MFC™ is unique in that nearly ANY combination of chemicals can be made into rocket propellants. All these rocket propellants can be processed easily into final rocket engines in the same way, no matter what chemicals are used, and the performance (how fast it burns and how much push is produced) can be tailored chemically by modifying the properties of the MFC™ particle used to make the propellant. Therefore, Super Propellants, high power Green propellants, and conventional AP propellants currently in use can all be processed in safety and with ease, all exactly in the same way, and made into rocket propellants for use in today's rockets and new future rockets or new ordnance products for commercial or military applications.
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Index
Environmental Concerns: Solid Rocket Propellants and Military Ordnance.....................................................................................1
Hydrochloric acid, a Principal Air Pollutant ............................................................ 1
Soil and Ground Water Contamination from Manufacture and Storage of Ammonium Perchlorate Based Propellants............................................................ 2
Other Contamination Problems – Military Ordnance ............................................ 2
SPS and Green Chemistry in Product Design and Manufacture..................4
Green Chemistry ..................................................................................................... 4
Principles of Green Chemistry ................................................................................ 4
SPS Green Propellants............................................................................................. 6
SPS Green Manufacturing Processes .......................................................... 6
Manufacturing based on Supercritical Fluids ............................................. 6
Prevention of Accidental Releases during Manufacture ........................................ 7
Propellant and Ordnance Safety and Hazards Analysis – Insensitive Propellants and Ordnance .................................................................... 8
Summary ..................................................................................................... 9
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New Generation Propulsion and Ordnance Technology at SPS:
Developing Environmentally Clean Technologies for both the Military and
Commercial Space Applications
Executive Order 12856 of 3 August 1993, paragraph 3‐303 requires each Federal Agency to establish a plan and goals for eliminating or reducing the unnecessary acquisition of products containing extremely hazardous substances or toxic chemicals. Furthermore, DODD 5000.1 paragraph 23 states that “All systems containing energetic material will comply with Insensitive Munitions criteria.”
Environmental Concerns: Solid Rocket Propellants and Military Ordnance Perchlorate is used in fireworks, safety flares, matches and car air bags, but 90 percent of it goes into solid rocket fuel for military missiles and the NASA space shuttle. American Pacific Corp. of Las Vegas and Kerr‐McGee Corp. of Oklahoma City were the sole U.S. producers until 1998, when American Pacific bought out its rival.
Hydrochloric acid, a Principal Air Pollutant
The classic example of environmental impact caused by current solid rocket propellants is in Kazakhstan at the Baikonur launch site, where there are reports of quite serious environmental damage.
For most shuttles, the damage comes from the solid rocket boosters, or SRBs, The SRBs are required at shuttle launch to provide 71.4% of the thrust at lift‐off and elevate the shuttle to an altitude of 45km (28 miles).
As a shuttle launches, a "cloud" becomes visible which contains SRB exhaust products, either dissolved or as particles in the water vapor released by the main engines.
Hydrochloric acid formed in this launch cloud leads to acidic deposits in the surrounding area, a phenomenon which may also be observed some distance away if exhausts are carried on prevailing winds.
John Pike, president of GlobalSecurity.org, and an expert on the US space program says: "The hydrochloric acid can pit the paint on your car if it is too close to the launch site."
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A 1993 NASA technical manual considered environmental effects of space shuttle launches at Kennedy Space Centre, and stated that some cumulative effects of launches in the nearby area are "reduction in the number of plant species present and reduction in total cover".
The manual also pointed out that acid deposit from the launch cloud can also impact nearby water lagoons and their wildlife.
Soil and Ground Water Contamination from Manufacture and Storage of Ammonium Perchlorate Based Propellants
Perchlorate (ClO4‐) is used primarily as an oxidant in solid propellant in rockets,
pyrotechnics, airbag inflators, and highway safety flares. From accidental releases during propellant manufacturing, process waste stream management, and improper disposal practices, ClO4
‐ has become a contaminant in surface and groundwaters. It is highly mobile and, due to its chemical stability, can persist for decades. ClO4
‐ has been found in drinking water in 34 states.
ClO4‐ interferes with thyroid hormone production by blocking iodine (I‐) from entering
the thyroid gland. Thyroid hormones play a crucial role in metabolism throughout life. They are also critical for proper prenatal brain development, making developing fetuses a sensitive subpopulation.
Currently, the National Academy of Sciences is reviewing the health and toxicological studies used by the EPA to help assess the risk posed to humans by ClO4
‐ in the environment and to determine the health endpoint of concern. At the EPA, research continues to better characterize the occurrence of ClO4
‐in the environment, assess human exposure pathways, and to refine treatments to remove ClO4
‐ from drinking water.
Methods for measuring low levels of ClO4‐in drinking waters have improved dramatically
in the past decade. However, the concentration of human health concern maybe lower than the best methods of the past is capable of detecting. Scientists at the U.S. EPA in Cincinnati, Ohio, are working to develop better methods for identifying and quantifying ClO4
‐ in drinking waters.
Other Contamination Problems – Military Ordnance
Other compounds used in missile and military and commercial ordnance have been found to be extremely toxic to most organisms and have become global environmental health hazards. In humans, exposure to RDX and TNT and their degradation products causes symptoms such as anemia and liver damage. These chemicals can be lethal and are suspected carcinogens. Hundreds of tons of these compounds are found in
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sediments at innumerable manufacturing sites and storage sites for unexploded ordnance around the world. Tens of thousands of acres of land and water resources are unsafe because of RDX and TNT contamination.
RDX ‐ Royal Dutch, Royal Demolition or Research Department Explosive is used as part of a composite explosive in military munitions and in explosive demolition charges
HMX ‐ High Melting Explosive is a white crystalline solid used as a part of a composite explosive used in military munitions
TNT ‐ 2,4,6‐Trinitrotoluene is produced at military arsenals and commercial facilities and is used alone, or as part of a composite explosive in military munitions
Acetic acid was found as the a major pollutant from manufacturing processes of the major energetic materials currently used in the U.S., 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), 1,3,5,7‐tetranitro‐1,3,5,7 tetraazacyclooctane (HMX) .
RDX has very low solubility in water and has an extremely low volatility. RDX does not stick to soil very strongly and can move into the groundwater from soil. It can be broken down in air and water in a few hours, but breaks down more slowly in soil.
RDX has become the second‐most‐widely used high explosive in the military, exceeded only by TNT. As with most military explosives, RDX is rarely used alone; it is widely used as a component of plastic explosives, detonators, high explosives in artillery rounds, Claymore mines, and demolition kits. RDX has limited civilian use as a rat poison.
Waste‐water treatment sludges resulting from the manufacture of RDX are classified as hazardous wastes and are subject to EPA regulations. Munitions such as RDX have been disposed of in the past by dumping in deep sea water. By‐products of military explosives such as RDX have also been openly burned in many Army ammunition plants in the past. There are indications that in recent years as much as 80% of waste munitions and propellants have been disposed of by incineration.
RDX in the wastewater from manufacturing and loading operations has also contaminated the environment.
HMX is currently produced at only one facility in the United States, the Holston Army Ammunition Plant in Kingsport, Tennessee. The amount of HMX made and used in the United States at present is not known, but it is believed to be greater than 30 million pounds [15,000 tons] per year between 1969 and 1971.
Wastes from explosive manufacturing processes are classified as hazardous wastes by EPA. Generators of these wastes must conform to EPA regulations for treatment, storage, and disposal. The waste water treatment sludges from processing of explosives are listed as hazardous wastes by EPA based only on reactivity. Although its solubility in
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water is very low, HMX can be present in particulate form in water effluent from manufacturing, munitions and propellant manufacture, and destruction of old, unused, munitions or missiles. Studies in rats, mice, and rabbits indicate that HMX may be harmful to the liver and central nervous system if it is swallowed or contacts the skin.
HMX, TNT and RDX are often found in the soil, groundwater, and surface waters at facilities where they are manufactured as the result of negligent waste stream disposal methods. The toxicity of these compounds and their degradation products has led to concern about their fate in the environment and the potential for human exposure. HMX and RDX do not easily break down in the environment, and hence can cause long‐term problems.
SPS and Green Chemistry in Product Design and Manufacture
Green Chemistry
Green chemistry is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances. Whereas environmental chemistry is the chemistry of the natural environment, and of pollutant chemicals in nature, green chemistry seeks to reduce and prevent pollution at its source. In 1990 the Pollution Prevention Act was passed in the United States. This act helped create a modus operandi for dealing with pollution in an original and innovative way.
As a chemical philosophy, green chemistry derives from organic chemistry, inorganic chemistry, biochemistry, analytical chemistry, even physical chemistry. However, the philosophy of green chemistry tends to focus on industrial applications. The focus is on minimizing the hazard and maximizing the efficiency of any chemical choice. It is distinct from environmental chemistry which focuses on chemical phenomena in the environment.
In 2005 Ryoji Noyori identified three key developments in green chemistry: use of supercritical carbon dioxide as green solvent, aqueous hydrogen peroxide for clean oxidations and the use of hydrogen in asymmetric synthesis. Examples of applied green chemistry are supercritical water oxidation, on water reactions and dry media reactions.
Principles of Green Chemistry
Paul Anastas, then of the EPA, and John C. Warner developed 12 principles of green chemistry, which help to explain what the definition means in practice. The principles cover such concepts as:
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• the design of processes to maximize the amount of raw material that ends up in the product;
• the use of safe, environment‐benign solvents where possible; • the design of energy efficient processes; • the best form of waste disposal, aiming not to create it in the first place.
The 12 principles are:
1. Prevent waste: Design chemical syntheses to prevent waste, leaving no waste to treat or clean up.
2. Design safer chemicals and products: Design chemical products to be fully effective, yet have little or no toxicity.
3. Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to humans and the environment.
4. Use renewable feedstock: Use raw materials and feedstock that are renewable rather than depleting. Renewable feedstock are often made from agricultural products or are the wastes of other processes; depleting feedstock are made from fossil fuels (petroleum, natural gas, or coal) or are mined.
5. Use catalysts, not stoichiometric reagents: Minimize waste by using catalytic reactions. Catalysts are used in small amounts and can carry out a single reaction many times. They are preferable to stoichiometric reagents, which are used in excess and work only once.
6. Avoid chemical derivatives: Avoid using blocking or protecting groups or any temporary modifications if possible. Derivatives use additional reagents and generate waste.
7. Maximize atom economy: Design syntheses so that the final product contains the maximum proportion of the starting materials. There should be few, if any, wasted atoms.
8. Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If these chemicals are necessary, use innocuous chemicals. If a solvent is necessary, water is a good medium as well as certain eco‐friendly solvents that do not contribute to smog formation or destroy the ozone.
9. Increase energy efficiency: Run chemical reactions at ambient temperature and pressure whenever possible.
10. Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.
11. Analyze in real time to prevent pollution: Include in‐process real‐time monitoring and control during syntheses to minimize or eliminate the formation of byproducts.
12. Minimize the potential for accidents: Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.
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SPS Green Propellants
SPS Green Manufacturing Processes
Current rocket propellants use a chemical called Ammonium Perchlorate (AP). These are the highest energy propellants that are the most stable, so are relatively safe to use (not produce). When these rocket propellants are used, they produce clouds of hydrochloric acid, which are considered a serious pollutant. The industry has been working on a way to use other new chemicals (HZN, ADN, CL‐20, AN) as replacements for the AP since when these chemicals are used they are non‐polluting (green). Serious problems exist, however, in both processing these new fuels using conventional methods and in the performance of these propellants when used, so none are currently available.
The SPS MFC™ can readily process these new chemicals into rocket fuels (we already demonstrated this with AN (Ammonium Nitrate) at our University of South Florida program). In the MFC™, these chemicals are processed into a suitable form to safely make rocket propellants (first we make spherical particles of these chemicals and then encapsulate them in a highly stable plastic fuel, this forms the core of the MFC™). These MFC™ particles are even easier to process into rocket propellants (as shown by NAWC China Lake during production of test samples) than even current chemicals used in rocket propellants. Other chemicals can also be included in the MFC™ in a safe way to make the final rocket propellants even safer and perform better (tailoring their performance). The MFC™ is a protected environment that can contain highly volatile chemicals that will only be mixed and reacted during the launch of the rocket.
The MFC™ is unique in that nearly ANY combination of chemicals can be made into rocket propellants. All these rocket propellants can be processed easily into final rocket engines in the same way, no matter what chemicals are used, and the performance (how fast it burns and how much push is produced) can be tailored chemically by modifying the properties of the MFC™ particle used to make the propellant. Therefore, Super Propellants, high power Green propellants, and conventional AP propellants currently in use can all be processed in safety and with ease, all exactly in the same way, and made into rocket propellants for use in today's rockets and new future rockets.
Manufacturing based on Supercritical Fluids
In the last ten years and so, there has been influx of new supercritical fluid aided material processing techniques for encapsulation, nucleation of particles/powders, impregnation of porous matrices, formation of porous materials, coating/spraying of flat surfaces, extrusion, comminution (solids grinding), and drying. The technical and economic drivers for using supercritical techniques are many. These processes usually employ a single material‐processing step. The solvating power and selectivity are tunable, enabling ease in separation of a particular component from a multi‐component mixture and complete solvent recovery with residue levels well below FDA thresholds.
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The gas like mobility of supercritical fluids allow very fast processing times, increasing throughput for a given equipment size. The low surface tension in the processing environment allows smooth coating and drying of surfaces. The popular supercritical solvent carbon dioxide is readily available, inexpensive, non‐toxic, allow near room temperature processing. The carbon dioxide based environment is favorable for particle coating since no chemical interaction between the coating and the substrate may occur. There are several reasons why processing with supercritical fluids are attractive throughout the world. It is not only because they are green processes and are effective on‐site processing of natural resources. The interest is primarily due to controllability and tunability of the processing environment to enable robust synthesis of products with unique characteristics. There is a portfolio of supercritical techniques that can be used for supercritical fluid aided encapsulated nanoparticles.
The supercritical technology permits engineering of flexible plants that can employ different variations and can be tailored for different product slates; is scalable and tunable. Although the capital costs per equipment is about four times higher due to pressure, overall capital investment is usually still less since the production time and number of units (processing steps/equipment) is reduced,. Operating costs are usually less due to the inexpensive carbon dioxide environment and high recovery rates. However, the primary motivation for using supercritical fluids is their ability to enable products/specifications that can not be achieved by any other scalable technology, e.g. polymeric thin films with uniform pore characteristics (pinhole free to highly porous) on flat surfaces or particles.
Prevention of Accidental Releases during Manufacture
An important area for safety in process control that are directly addressed by neural network control systems is the direct measurement of variables key to performance and to safety in operation that are either too expensive to measure accurately, or even impossible to measure fast enough for closed‐loop control,
The aim of these systems is to compare actual process operation with nominal operation given the current control actions. Any deviation is indicative of process malfunction, which can trigger a diagnostic search for the most likely fault, in real‐time. The benefit here is in rapid earlier warning of incipient faults, as well as the potential for providing the control system with a prioritized list of possible hazards. The control system can then take steps to mitigate these potential hazards before they become a serious problem. The difference between using neural networks rather than purely knowledge‐based systems for this application lies in the ability to integrate complex signals at a low level, yielding more complex response than may be possible by representing the activity of individual sensors directly in symbolic form to an operator at a control panel.
Novelty detection is a primary feature of neural‐network logic based control systems. The completeness of the artificial intelligence process model, since it is difficult to argue
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that any conventional (Non‐AI or heuristic) formal model is formally complete, when dealing with real‐world data, is found in the AI’s ability to identify, analyze and control potentially hazardous process variances that have never been previously observed. In this respect, at least with statistical tests the completeness of the model can be assured for the design data, and the novelty of future data can be tested with reference to those same design data, resulting in a well‐posed problem amenable to theoretically satisfactory solutions.
Additional important factors in using neural‐net based control systems (AI) for operation of the MFC™ propellant manufacturing process is in both process economics and assurance of adhering to the principals of Green Chemistry in manufacturing. The close reaction control afforded by this control technology permits operation of the manufacturing system at maximal efficiency, increasing product yields, improving both product reproducibility and conformity to specifications, and reducing the need for waste recycling.
SPS is fully aware of two the potential problems in the use of AI systems in process management and control:
1. Over‐reliance, where even specialist users become complacent about the accuracy of the advisory/control system, reducing their critical awareness of the processes inherent limitations; and,
2. When non‐specialist users rely on the system’s performance to act beyond their normal scope of competence.
SPS will only use highly skilled personnel trained in the oversight of the propellant manufacturing control system, with the ability to appropriately intervene in the manufacturing process, when necessary and as needed. They will act in an auxiliary capacity to the AI system, verifying appropriate measures for process control are being taken by the AI control system to mitigate potential hazards. A benefit for process control to SPS and manufacturing technicians are the short durations of the propellant manufacturing runs, where required attention spans of personnel should not pose any problems.
When combining explicit linear models, neural network AI process control systems provide a process control framework that demonstrates stability and constantly evaluates stability margins, which is lacking in widely used conventional (heuristic) approaches to non‐linear process control.
Propellant and Ordnance Safety and Hazards Analysis – Insensitive Propellants and Ordnance
(Excerpts taken from: Sunol, et. al.; Safety and Hazard Evaluation for MFC Propellant Particle and Propellants Grains; University of South Florida, August, 2005 for Space Propulsion Systems, Inc.)
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The work performed by the University of South Florida has clear demonstrated the significant potential of SPS to develop truly insensitive propellants and ordnance products based upon the unique structure of the MFC™ and MFC™ products derived therefrom, in comparison to current solid propellants. This New Generation SPS technology provides a unique opportunity to combine key fundamental experimental data, such as reaction rates and thermophysical as well as transport properties with well‐accepted mathematical models to analyze both the safety and performance of MFC™s. The goals of this report are therefore two‐fold:
• Evaluate the likelihood of potential hazards, particularly internal to the MFC™ and study their impact on the MFC™ particle, local vicinity, and the 55 gallon storage drum. Mass and energy balances along with simple transport models are used to quantify and analyze the safety issues.
• Articulate the experimental and theoretical studies that are applicable for safety and design/performance related issues
The inherent structure of the MFC™ based technology provides an avenue to accurately predict performance when combined with key experimental data and mathematical models of MFC™s and MFC™ propellant grains.
Summary
The key observations based on approximate models and impact analysis on control volumes of interest, in the MFC™ particle, local vicinity, and fifty‐five gallon storage drum and related recommendations are as follows:
• The reaction happens to be at the fuel/oxidizer interface and whether it continues or ceases depends on competition between the relative rates of heat generation through reaction and heat dissipation through conduction within the MFC™. The analysis further demonstrates that unless there is irradiation from an external source (a source at propellant ignition temperature), like in most self‐propagating reaction issues, you are not likely to have a safety problem.
• Sensitivity analysis was used to demonstrate that for a single MFC™, as the extent of reaction increases, the temperature and off‐gas generation increase. If the extent of reactions is high and the reaction rates are faster the diffusion rates, the integrity of a single MFC™ would be destroyed. Energy balances shows that, even for a complete MFC™ reaction and with no thermal diffusion, the temperatures within adjacent MFC™s are no more than 120 °C, which is well within inner barrier encapsulant performance thresholds for non‐defective MFC™s. In terms of gas liberation and temperature, the effect of a complete MFC reaction in a storage drum or cast within a propellant grain is negligible.
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o Simple mass balance and density calculations show that the volume of gases evolved are within the gas sorption tolerances of the polymeric binders and encapsulant within the neighborhood of the reacting MFC™.
o The heat dissipation issue warrants not only energy balances, but an analysis of heat transfer rate through the single MFC™ as well. Based on calculations, the rate of heat dissipation is much higher than reaction rates possible under those temperatures. Thermal diffusion values for MFC™s are high. Therefore, unless the reaction is very fast, less than one second for complete MFC™ reaction, the rate of heat dissipation exceeds the heat generation rate and the temperatures of adjacent MFC™ will be much less than the 120 °C calculated from the applicable energy balance of the MFC™ in its’ vicinity.
• As expected for the MFC™ fuel/oxidizer geometry, there is not much reaction until you get to very high temperatures (in the range of ignition temperatures for the propellant), after which the reaction proceeds vigorously to completion. This conforms well to known aging properties of explosive and propellant compositions.
• From the heat evolved and the thermal diffusion analysis, it is estimated that a thousand or more MFC™s randomly distributed throughout the storage or propellant mass and reacting simultaneously at maximum possible rate would be required before instability of a mass of MFC™s in either 55‐gal drum storage or cast propellant grain would pose a stability issue.
• It must be noted that if oxidizer/fuel reactions in barrier deficient MFC™s go to completion very rapidly (in less than the 1 second required to exceed thermal diffusion capacity) at or under maximum aging conditions (160 °F (71 °C) and 1 atm), than those reactions would occur DURING the MFC manufacturing process (temperatures to 75 °C and pressure above 1000 psi and times around 15 minutes). Therefore, the survival of barrier deficient MFC™s with high reaction rates is not possible. It should further be noted that if the barrier deficient MFC™s do react during processing due to defective or missing internal barriers, the excellent heat dissipation environments of fluidized beds, plus the relief system, will address any issues relating to manufacturing safety. In other words, the processing environment will eliminate MFC™s that may cause the most severe stability issues in storage or cast propellant grains calculated for MFC™s in this analysis.
The clear conclusion from the analytical work performed and reported here is that safety in storage and/or handling of MFC™ based propellant grains is at least as good, if not better, than those of conventional propellant grains made using significantly less energetic materials. Recommendations for potential hazard abatement and future modeling directions:
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• If you have irradiation from an external source, the MFC™ integrity will be destroyed and you need to worry about the binder design. There are high temperature resistant binders, high thermal conducting polymers...etc to work with resolution in that direction, which in MFC™ propellant grain design geometries can be used to transport thermal energy away from potential hot spots. In the MFC™, you have quite a few choices in selection of material. Based on a Fourier law analysis, combined with possible solid conductivities (you need data for it as well and we used model compound data), you are not likely to have a problem.
• A set of refined distributed models for solid‐gas spherical systems based on mathematical analysis currently developed. These models can be further adapted for MFC™s with proper choice of boundary conditions and, when combined with experimental data, will provide closed form solutions for simultaneous heat mass transfer with reaction. These closed form solution will enable approximate but reliable models for optimization of MFC™s for both safety in manufacturing, storage and handling, as well as the performance modeling of MFC™ propellants and ordnance products.
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