Propellant Production Research Articles

Ice-mining lunar rover using Americium-241 radioisotope power systems

Permanently Shadowed Regions (PSRs) of the Moon contain rich deposits of water ice. They are very valuable to the space community as in-situ extracted water can be used for many purposes, such as propellant production and human habitat support. PSR craters never see sunlight, therefore solar power is not available there. They also present a cryogenic environment with regolith as cold as 40 K. These challenges can be overcome by employing a Radioisotope Power System (RPS) to provide both thermal and electrical power to resource extraction systems in the PSRs. The work presented here aims at characterizing an ice-mining lunar rover. The rover will be equipped with an Americium-241 (or 241Am) based RPS. 241Am has a 432-year long half-life and can provide decades of stable power output for the rover operations. The innovation lies in the fact that the RPS will not only provide electrical power to the rover, but that its waste heat will be employed to thermally mine ice from its deposits. The rover is equipped with a sublimation plate irradiating the underlying regolith to sublimate ice contained within, and with a cold trap where extracted volatiles will be deposited. This work studied the rover concept feasibility and developed a model of its Thermal Management System (TMS) to meet sublimation plate and cold trap temperature requirements. The results have been validated by a 3D finite element method thermal simulation for icy regolith conditions of 0–10 vol% water-ice content. The findings of this work suggest that it is possible to perform thermal ice-mining in the lunar PSR environment with an RPS-powered rover, with different degrees of efficiencies depending on the amount of ice in the deposits.

Lunar-Derived Propellants for Fueling Mars-Bound Spacecraft in Cis-Lunar Space

The conventional method to send payloads to Mars is by direct trans-Mars injection (TMI) from LEO. NASA is considering an alternative of fueling large Mars-bound cargo transfer vehicles in cis-lunar space with propellants derived from the Moon by in situ propellant production (ISPP) prior to trans-Mars injection from cis-lunar space. A large team of investigators developed an Evolvable Lunar Campaign (ELC) that defined its strategic objective as follows: "The ELC strategic objective is commercial mining of propellant from lunar poles where it will be transported to lunar orbit to be used by NASA to send humans to Mars." Unfortunately, sending Mars-bound vehicles to cis-lunar space prior to trans-Mars injection saves little mass in LEO, unnecessarily includes lunar ISPP, which is costly, complex, and risky, and at the bottom line, has no benefits. The problem is that the amount of propellant needed to go from LEO to cis-lunar space is roughly comparable to the amount of propellant used for direct TMI from LEO, so the lunar-derived propellants only offset a small amount of propellant used to augment Mars Orbit Insertion and Entry, Descent, and Landing, and the amount of propellant required in LEO is almost the same in both cases. The initial mass in low Earth orbit (IMLEO) is not reduced much by utilizing lunar ISPP. At the bottom line, sending Mars-bound MCTV to cis-lunar space adds complexity, cost, and risk and provides essentially no benefits.

Identification of Isocyanate Number on IPDI and TDI Due to Storage Period and Their Impact on Composite Solid Propellant

Isocyanate compounds serve as a curing agent in the production of composite propellants, playing a crucial role in determining their characteristics. Due to its high reactivity with moisture, it is essential to determine the isocyanate number of stored samples after a specific duration. The investigation identified the isocyanate number of IPDI and TDI that had been held for 84 and 90 months. The FTIR analysis identified the presence of the NCO group at 2240 cm-1 for TDI and 2243 cm-1 for IPDI samples held for 84 and 90 months. The isocyanate number identification decreased by 1-2% after being stored for six months. This reduction in isocyanate quantity undoubtedly impacts the development of propellant compositions. The reduction in isocyanate content will alter the propellant formulation, leading to propellants with different characteristics due to its impact on the curing ratio (NCO/OH). The curing ratio greatly impacts the mechanical properties of composite propellant.

Mars Ascent Propellants and Life Support Resources - Take it or Make it?

Studies of Mars missions over the past thirty years lacked credible cost estimates, so the total mass of materiel delivered to Low-Earth Orbit (LEO) was typically used as a rough measure of relative mission cost because the complexity of the mission was thought to be roughly proportional to the initial mass in LEO (IMLEO). Historically, high launch costs led to large investments in space hardware development which led to high space mission costs. Reducing mass became the central theme of space mission engineering. We are now entering a new era where launch costs no longer have the impact that they would have two decades ago. Launch costs are coming down to the point where we must ask ourselves whether it now makes sense to bring ascent propellants and life support resources from Earth (with higher reliability as a bonus), as opposed to using in situ propellant production and cycling of life support resources. This paper compares various options for bringing ascent propellants and life support resources from Earth vs. developing in situ. In short, it examines the “take it or make it” options for both technologies. For ISPP, the answer is clear: Mars ISPP is not worth the investment when launch costs are low. For life support, the most robust option is to bring life survival resources from Earth, and only use cycling to upgrade the quality of life for the crew.

Research and design of automatic cutting machine for propellant NDSI-2K and FCG-2.B41M

This article introduces the results of research on a new solution in the process of cutting and selecting propellants used for the double-based tubular propellant production line of Factory Z195/General Department of Defense Industry. The traditional method is usually manual, using the foot pedal force of the worker through a mechanical drive system to pull the cutting knife down to cut the propellant. It takes a lot of time, labor and product quality is not high. After cutting it is necessary to lathe the ends of propellant tube to meet technical requirements. With the new solution, the propellant is cut automatically, quickly, safely and accurately and the selection of the propellant is carried out through a weighing conveyor system based on the principle of classification by weight. The entire working process is controlled by a sensor systemand PLC programerthrough a monitoring computer located in the control room. Processing data can be stored and periodically exported for report purposes.

Development of Low-Pressure Die-Cast Al-Zn-Mg-Cu Alloy Propellers-Part Ⅰ: Hot Tearing Simulations for Alloy Optimization.

Recent advances in the leisure boat industry have spurred demand for improved materials for propeller manufacturing, particularly high-strength aluminum alloys. While traditional Al-Si alloys like A356 are commonly used due to their excellent castability, they have limited mechanical properties. In contrast, 7xxx series alloys (Al-Zn-Mg-Cu based) offer superior mechanical characteristics but present significant casting challenges, including hot-tearing susceptibility (HTS). This study investigates the optimization of 7xxx series aluminum alloys for low-pressure die-casting (LPDC) processes to enhance propeller performance and durability. Using a constrained rod-casting (CRC) method and finite element simulations, we evaluated the HTS of various alloy compositions. The results indicate that increasing Zn and Cu contents generally increase HTS, while a sufficient Mg content of 2 wt.% mitigates this effect. Two optimized quaternary Al-Zn-Mg-Cu alloys with relatively low HTS were selected for LPDC propeller production. Simulation and experimental results demonstrated the effectiveness of the proposed alloy compositions, highlighting the need for further process optimization to prevent hot tearing in high Mg and Cu content alloys.

The Moon as an effective propellant source: A comprehensive exergy analysis from extraction to depot

Establishing a permanent lunar base has gained increasing attention since it offers opportunities for international cooperation and the commercialization of space, forming the foundation and testing ground for a human existence independent from Earth. Essential to future missions beyond cislunar space is the exploration and in situ processing of the Moon's resources, especially the sustainable production of energetic resources and propellants. Utilizing in situ generated propellants can dramatically reduce transportation costs by removing the need to source propellants from Earth. Resources on the Moon are limited, and the extraction of available resources are energy-intensive processes demanding advanced techniques and technologies. Consequently, one of the biggest challenges lies in developing process architectures with a positive energy balance, for which comprehensive analyses are still missing. The focus currently lies on the extraction of water ice from lunar regolith and the production of hydrogen and oxygen through water electrolysis. However, alternative fuel and process options may reduce the energy cost while providing equivalent energetic revenue. In the scope of this research, the infrastructure and technologies required for extraction, refining, and storing are assumed to exist in cislunar space; therefore, only the operating cost is considered. Exergy analyses of in situ extraction methods are conducted to investigate whether the required energetic budget allows sustainable implementation. The analysis includes extraction methods and propellant options to reveal the extent to which alternatives to hydrogen are feasible. Exergy analyses determine thermodynamic losses of energy flows giving the ground for process optimization. The exergy destructed represents the margin of improvement within the process architecture and thus reflects the process's thermodynamic and economic value while allowing a more distinct examination of energy use. Assuming the availability of water and carbon dioxide ice in permanently shadowed regions, the analysis shows that choosing methane instead of hydrogen in combination with oxygen as propellants can reduce the required exergy input by up to a third. An example mission allows to directly compare the operating cost of the extraction processes for the different propellant options. The mission entails a spacecraft propelled by a liquid bipropellant engine utilizing the extracted propellant and transporting a payload of the same propellant to a depot located in lunar near-rectilinear halo orbit (NRHO). Although abundant in space, the results suggest that hydrogen may not be the only or even energetically cost-effective resource for developing cislunar and Martian space infrastructures. Likewise, sustainable extraction of propellants suitable for current and future propulsion systems will foster humanity's reach further into the solar system.

Near-Term NASA Mars and Lunar In Situ Propellant Production: Complexity versus Simplicity

Martian in situ propellant production (ISPP) has a fundamental advantage over lunar ISPP because it has much greater leverage. The value of Martian ISPP per liftoff far exceeds that for the lunar ISPP. This study analyzes the challenges and complexity of lunar ISPP versus Mars ISPP and finds that lunar ISPP is so challenging it might not even be feasible, and if it is feasible, the payoff appears to be limited, while the investment is likely to be great. By contrast, Mars ISPP based on atmosphere only is relatively simple with high payoff. NASA is heavily focused on lunar ISPP and seemingly has diminished interest in solid oxide electrolysis of Martian CO 2 to O 2 after an extremely successful demonstration on Mars by MOXIE. This might make sense at first glance, but when the 2 leading candidates for lunar ISPP are analyzed in detail, it is found that they are extremely difficult and challenging to implement, the effort and investment involved in developing and implementing them are high, and the potential payoff is limited. By contrast, Mars ISPP by solid oxide electrolysis cell (SOEC) of CO 2 is comparatively simple and reliable and has high payoff. A SOEC system is basically landed, and a switch is turned on. The only feedstock is the ubiquitous atmosphere. Lunar ISPP involves a seemingly endless number of complex dynamic steps including autonomous traverses of excavator/haulers to unearth (unmoon?) regolith and deliver it to and from a reactor.

Determination of propellant products by time resolved and spatial distribution LIPS combined with high-speed schlieren imaging

The characteristics of time resolution and spatial distribution of propellant products from laser induced micro-detonation are obtained by time correlated laser induced plasma spectroscopy (LIPS) combined with high-speed schlieren imaging.

Impact of Stack Temperature on Solid Oxide Electrolysis System Operation for Lunar Production of Hydrogen and Oxygen Propellants

Solid oxide electrolysis (SOEC) systems have the potential to produce hydrogen and oxygen propellant from lunar ice found in the permanently shadowed cream on the moon. Because SOEC systems electrolyze steam instead of liquid water as in more conventional alkaline and proton-exchange membrane electrolysis systems, they require lower stack voltages for thermal-neutral operation (about 1.29 V/cell vs. 1.48 V/cell for liquid-fed cells) and thus can have lower stack specific energy as defined by stack power requirements per kg of hydrogen produced. However, at a system level, power requirements in a remote lunar setting for vaporizing the steam and flowing it through the stack increase system-level power demands such that the advantages of the SOEC system are reduced due to the balance of plant loads contributing as much as 20 to 25% of the system energy at 800 deg. C. Our team at Mines collaborated with our partners at OxEon Energy to demonstrate an SOEC system with a stack operating temperature of 800 deg. C that demonstrated an overall system-level specific energy just below 50 kWh electric per kg of hydrogen. That study and a supporting model validation study provided a basis for showing the viability for high-temperature SOEC to be scaled-up for lunar production of hydrogen and oxygen propellant for propulsion. The current study builds on that previous work by exploring the impact of SOEC stack temperature on both the stack and balance of plant power requirements. This study explores the trade-offs between reduced balance of plant parasitics and increased stack mass with lower SOEC operating temperatures and explores the advantages of higher conducting mixed-ionic-electronic conducting electrolytes with electron blocking layers to increase current densities at lower temperatures.This study was performed using stack and balance of plant models that have been calibrated in the lab-scale demonstration of an SOEC system with an electrically driven steam generator, a scroll-compressor for driving the steam flow, and cathode and anode exhaust recuperators for heat recovery to the stack inlet steam flow. The system also includes H2 drying from the SOEC cathode exhaust by heat exchange with the incoming water stream. The current study looks updates the previous model by replacing the compressor with a higher pressure steam generator and an expansion valve that allows the operation of the system without the parasitic loads of a compressor. In the current study, three different electrolytes traditional yttrium-stabilized zirconia (YSZ), higher conductivity scandium-stabilized zirconia (ScSZ), and mixed ionic-electronic conducting gadolinium-doped ceria (GDC) with a YSZ blocking layer. The GDC bilayer electrolyte cells have the highest conductivity and allow for reasonable hydrogen production at operating temperatures below 700 deg. C. The results show that the lower operating temperatures enabled by the GDC bilayer electrolyte and by the ScSZ electrolytes not only reduce the system mass with smaller heat exchangers and thermal insulation, but also lower requirements for steam generation by enabling more heat recovery in the steam generator. The impact of stack operating temperatures on the feasibility of scaling up a lunar-deployed SOEC system to produce more than 1 kg/h are presented to further emphasize the feasibility of SOEC systems as part of a lunar propellant production facility.

Study on Rheological Properties and Pouring Process of Hydroxyl-Terminated Polybutadiene (HTPB) Propellants.

The process of solid propellant production, which is the most widely used high-energy material, has garnered significant attention from researchers. However, there have been relatively few studies on its processing, due to the unique nature of the casting process. This paper aims to further analyze the pouring process of the propellant slurry. Initially, we obtained a sample of the propellant slurry and measured its rheological parameters using a rotary rheometer. From the analysis of the experimental results, we derived the viscosity parameters and the yield values of the propellant slurry. Subsequently, we simulated the pouring process, setting the slurry parameters based on the data obtained from the rheological measurement experiment. The simulation results demonstrated that the flower plate significantly impacts upon the cutting and separating effect on the slurry during pouring. Upon leaving the flower plate, the slurry descends onto the core mold platform under the influence of gravity, gradually flowing along the edge of the core mold. Although there may be some small voids in the pouring process, the voids will disappear completely at the end of pouring. A comparison with the actual pouring situation revealed a higher consistency between the simulation results and reality, thus establishing the reliability of the simulation method as a reference for analyzing the pouring process.

Mars mission capabilities enabled by nuclear thermal propulsion

As part of the Artemis era of space exploration, space agencies will be working together with their industry partners to establish systems and infrastructure that enable sustained Lunar missions and develop capabilities for Mars. Lockheed Martin has a longstanding history of designing, building, and operating systems for deep space applications, from Viking to Orion. Lockheed Martin develops concepts, trades, and early system designs for Moon and Mars exploration to enable future missions. In 2016, Lockheed Martin presented a vision for achieving crewed exploration of Mars. Known as Mars Base Camp (MBC), this design reference mission envisioned a crewed vehicle in Martian orbit from which astronauts could perform excursions to Phobos and Deimos and perform telerobotic exploration of the Martian surface, including sample return. This concept served as an “existence proof” for a novel, practical, and affordable path to enable human exploration of the Martian system. In 2017, an update was published that included the production of propellant from water and a single-stage fully reusable Mars lander concept. Then in 2021, Lockheed Martin introduced a nuclear thermal propulsion (NTP) configuration of Mars Base Camp, a technology that will be greatly enabling for crewed missions to Mars. This paper matures the design of the NTP configuration of Mars Base Camp and explores the Mars mission capabilities that the NTP technology will enable. These investigations include optimized trajectories for faster transit to Mars and an analysis of abort scenarios that are made possible by the high thrust and performance of NTP. The results provide insight into the performance and capabilities that are realized when NTP technology is matured and integrated into a Mars transit vehicle. The paper will also describe initial surface infrastructure capabilities that significantly enhance sortie science operations, including mobility and power. The resulting updated Mars Base Camp serves as an example of what is possible with current technologies and technologies under development. The MBC reference mission builds on the capabilities that will be developed and demonstrated through Artemis missions, enabling a viable, sustainable long-term Mars exploration program, with the first crewed Mars mission possible in the 2030s.

Scale Up and Coupling of the MOXIE Solid Oxide Electrolyzer for Both Terrestrial and Space Applications

The Mars Oxygen ISRU Experiment (MOXIE) is a first of its kind demonstration of in-situ resource utilization technology to produce propellant and breathable oxygen from the Mars ambient carbon dioxide. The use of Lunar and Martian resources represents a significant opportunity to reduce the cost of launch from Earth, enabling propellant production for space refueling, and allowing for life support of manned missions to the Lunar and Martian surfaces.Since developing the Solid OXide Electrolysis (SOXE) stacks for the Mars 2020 MOXIE program in 2017, the OxEon team has made significant advancements in scale and capabilities of the SOXE stack technology used in that system. Newer variants have a five-fold larger cell area and a 6.5-fold increase in cells per stack, for a stack scaled 33-times the 0.5% scale of the device in MOXIE. Six of these OxEon mission-scale SOXE stacks will produce 30 tons of propellant oxygen to fuel a Mars Ascent Vehicle (MAV) in the 19-month window between landing an unfueled MAV pre-supply mission and the next launch opportunity for the first crewed Mars Mission, meeting target requirements for a return mission. OxEon has built and demonstrated systems with mission-scale stacks for both Lunar and Martian applications. A system for the production of propellant H2 and O2 from Lunar ice was successfully tested in a cryo-vac chamber at the Colorado School of Mines in 2022. Another mission-scale demonstration system is scheduled to demonstrate production of O2 and methane from Martian H2O and atmospheric CO2 at Jet Propulsion Laboratory in 2022.In addition to SOXE/SOFC systems, the OxEon technology portfolio also consists of a low energy plasma reformer capable of producing sygnas from a variety of hydrocarbons and a modular-scale Fischer-Tropsch reactor for the production of liquid fuels from syngas. These technologies allow OxEon to provide a wide range of terrestrial energy solutions. A DOE Bioenergy Technologies Office (BETO) funded system is currently being fabricated to demonstrate the conversion of both CO2 and CH4 in anaerobic digester gas to liquid transportation fuels. This will be accomplished using an SOEC system to convert steam and CO2 to synthesis gas. OxEon’s plasma reformer will be used to convert methane to synthesis gas, using the plasma to catalyze the reaction of methane with steam and oxygen, supplied in part by the byproduct oxygen from the electrolysis system. The syngas from the plasma reformer and electrolysis systems are then combined to produce liquid fuels in the Fischer-Tropsch (FT) reactor. Figure 1

Benchmarking and Simulation of Solid-Oxide Steam Electrolysis for Propellant Production in a Vacuum Chamber-Simulated Lunar Environment

NASA and other space agencies have prioritized the development of in-situ resource utilization (ISRU) technology for producing critical materials such as propellants in space. Electrolysis to split water found in lunar, asteroid, and Martian environments provides a pathway for liquid H2 and O2 production, but the challenges of deploying such technology in extraterrestrial environments put an extreme emphasis on minimizing specific energy (measured in kWhelec/kgH2) and system specific mass (system kg/(kgH2/h)). High-temperature, solid oxide electrolysis cell (SOEC) systems have the potential to achieve lower specific energy than conventional liquid-phase alkaline and polymer electrolyte membrane (PEM) electrolysis systems, but this requires efficient thermal integration and minimization of balance of plant loads in order to take advantage of the lower electrolysis voltages for steam (vs. liquid H2O). The high operating temperatures of SOECs, however, require significant system mass for steam generators, heat exchangers for recuperation, and insulation of the electrolysis stack, particularly for space applications where ambient temperatures may be extremely low.This NASA-sponsored collaboration between OxEon Energy and Colorado School of Mines explored the feasibility of a lunar-based SOEC system, which was modeled and demonstrated at the lab-scale by operating a breadboard system, consisting of a SOEC stack and associated balance of plant BOP) in a cryogenic vacuum chamber in order to simulate a lunar environment. The combined »2.5-kWelec SOEC stack and BOP achieved a specific energy < 50 kWhelec/kgH2 at an H2 production rate of > 0.075 kgH2/h operating in the cryo-vacuum chamber.This study has benchmarked system-level models of the lab-scale SOEC stack based on doped-zirconia electrolytes fabricated at OxEon and designed to operate near thermoneutral voltage (1.28 V/cell) at 800°C. The stack BOP includes a steam generator, an oil-free scroll compressor, cathode and anode exhaust recuperators, and a H2 dryer, which uses cold incoming liquid water feeds to cool the cathode exhaust and condense most of the excess H2O in the H2 product stream out. Operation of this demonstration system provides a basis for designing scaled-up lunar fuel production systems of 40 kgH2/h. The success of the lab-scale tests in terms of thermal integration and the benchmarked models suggest a pathway to such a full-scale SOEC system that can achieve < 46 kWhelec/kgH2 with much lower specific mass.Both the modeling and the lab-scale demonstration tests revealed that system specific energy was most sensitive to stack steam utilization, and that achieving < 50 kWhelec/kgH2 required stack steam utilization > 75%. In addition, effective thermal integration that limited the electrical heating primarily to steam generation is critical to minimizing the SOEC-system BOP loads. The stack was shown to run reliably at steam utilizations > 90% with a single pass feed. Efforts will be presented on how to simulate such high utilization at larger scales for full lunar deployment. Additional testing of the lab-scale system in larger cryo-vacuum chambers at NASA during 2023 will allow for further confirmation of thermal management strategies to ensure reliable SOEC operation for lunar production of H2/O2 propellants.

Research on the Needle Deformation of Extrusion Mold for 19-hole Propellant

Pore diameter and arc thickness of propellant are decided by the extrusion mold parameters. Mold needles deform during propellant’s forming process because of the propellant material’s high viscosity and needle’s flexibility, which affects the quality of propellant products. Based on fluid-structure interaction, we simulated the extrusion process of 19-hole nitroguanidine propellant and studied the influence law of mold structural parameters on the deformation of needles. The results show that forming section length has the greatest impact on the needles’ deformation, and the effect of compression section height is the second, while contraction angle is the least. The deformation of mold needles increase with forming section length, compression section height, and contraction growing.

Benchmarking and Simulation of Solid-Oxide Steam Electrolysis for Propellant Production in a Vacuum Chamber-Simulated Lunar Environment

Federal space agencies across the globe have prioritized development of in-situ resource utilization (ISRU) technology, such as propellants from lunar ice, to support space activities. High-temperature, solid oxide electrolysis cell (SOEC) systems integrated with an efficient balance-of-plant (BOP) have the potential to produce H2 and O2 at specific energy (kWhelec/kgH2) lower than conventional liquid-phase alkaline and PEM electrolysis systems, due to lower voltages for steam electrolysis (vs. liquid H2O). This NASA-sponsored collaboration explored the feasibility of achieving such low specific energy in a high-temperature SOEC system operating in a cryo-vacuum characteristic of permanently shadowed craters on the lunar surface where H2O ice can be found. A lab-scale »2.5-kWelec SOEC stack and BOP achieved a specific energy < 50 kWhelec/kgH2 at a production rate of > 0.075 kgH2/h operating in a cryo-vacuum chamber. System-level simulation models of the lab-scale SOEC stack were benchmarked with experimental tests and used to explore scaling of a system for lunar deployment. The lab-scale tests and scale-up modeling suggest a pathway to a MW-scale SOEC system that can achieve < 46 kWhelec/kgH2 with relatively low specific mass (kgsystem/(kgH2/h)).

A bayesian network-based safety assessment method for solid propellant granule-casting molding process

The safety of the solid propellant molding process is vital for the stable production of high-quality propellants. Failure events caused by abnormal parameters in the molding process may have catastrophic consequences. In this paper, a Bayesian network (BN) model is proposed to assess the safety of the solid propellant granule-casting molding process. Fault tree analysis (FTA) is developed to construct a causal link between process variables and process failures. Subsequently, expert experience and fuzzy set theory (FST) are used to obtain failure probabilities of the basic events (BEs). Based on the mapping rules, FTA provides BN with reliable prior knowledge and a network structure with interpretability. Finally, when new evidence is obtained, the probability is updated with the diagnostic reasoning capability of BN. The results of the sensitivity analysis and diagnostic inference were combined to identify key parameters in the granule-casting molding process, including curing temperature, vacuum degree, extrusion, calendering roll distance, length setting value, holding time, and polish time. The results of this paper can provide effective supporting information for managers to conduct process safety analysis.

Analysis of Small Modular Nuclear Reactor Construction on the Moon

The current goals of lunar exploration include the return of humans to the Moon for scientific activities and the ability to implement lunar in-situ resource utilization (ISRU) for propellant production and construction. Both goals will consume power and one option to meet these power requirements are small nuclear reactors (Kilopower or Pylon). Launching these might not be beneficial in the future as the lunar infrastructure develops and the power requirements grow. The possibility of lunar independence from Earth in terms of ISRU must be considered. This paper discusses the materials used in each nuclear reactor including the fuel, reflector, working fluid, etc. along with lunar abundancy of each element used in these materials. Since no lunar ore mining or material production concepts were found, a review of Earth-based mining and production methods for each material were described. As a result, furnaces, mills/crushers, and fluidized bed reactors can be utilized for various processes in material production. Other processes including leaching, flotation, etc. will need their own machines. In the future, designing multifunctional furnaces and ball mills or crushers can be considered since this will simplify the lunar infrastructure and can be advantageous in the long run decreasing Earth dependency and cost. Keywords: Lunar Resource Utilization, Fission Surface Power, Material Production

Solvent transport dynamics and its effect on evolution of mechanical properties of nitrocellulose (NC)-based propellants under hot-air drying process

Appropriate drying process with optimized controlling of drying parameters plays a vital role in the improvement of the quality and performance of propellant products. However, few research on solvent transport dynamics within NC-based propellants was reported, and its effect on the evolution of mechanical properties was not interpreted yet. This study is conducted to gain a comprehensive understanding of hot-air drying for NC-based propellants and clarify the effect of temperature on solvent transport behavior and further the change of mechanical properties during drying. The drying kinetic curves show the drying time required is decreased but the steady solvent content is increased and the drying rate is obviously increased with the increase of hot-air temperatures, indicating hot-air temperatures have a significant effect on drying kinetics. A modified drying model was established, and results show it is more appropriate to describe solvent transport behavior within NC-based propellants. Moreover, two linear equations were established to exhibit the relationship between solvent content and its effect on the change of tensile properties, and the decrease of residual solvent content causes an obvious increase of tensile strength and tensile modulus of propellant products, indicating its mechanical properties can be partly improved by adjustment of residual solvent content. The outcomes can be used to clarify solvent transport mechanisms and optimize drying process parameters of double-based gun propellants.

Solid Rocket Propellant Photo-Polymerization with an In-House LED-UV Prototype

Composite solid propellants have used cast molding production technology for many decades, with intrinsic limitations on production flexibility, promptness, and grain geometry, as well as environmental implications on toxicity and global carbon footprint. This traditional method involves the use of toxic chemicals, has a long processing time, requires high temperature, and the products have limited geometries. To overcome those issues, different photo-curable resins have been evaluated as possible matrices. In fact, the UV-curing process is fast and has low energy consumption. The photocuring reaction parameters of six different pristine formulations were evaluated by Fourier transform infrared spectroscopy analysis. After finding the optimal curing parameters, different composites were prepared by adding 75 or 80 wt% ammonium sulfate particles used as an inert replacement for the oxidant. The thermomechanical properties and thermal resistance of the UV-cured composites were characterized via dynamic thermal-mechanical and thermogravimetric analysis. Subsequently, the mechanical properties of the inert propellants were investigated by tensile tests. The most promising resin systems for the production of solid rocket propellants were then 3D printed by an in-house developed illumination system and the obtained object micro-structure was evaluated by X-ray computed tomography.