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Solidus curves for ternary mixed carbides of (U, Zr, Nb) C [20].
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![Figure 3. Solidus curves for ternary mixed carbides of (U, Zr, Nb) C [20].](publication/340007325/figure/fig1/AS:870700646682624@1584602619632/Solidus-curves-for-ternary-mixed-carbides-of-U-Zr-Nb-C-20_Q320.jpg)
Nuclear thermal propulsion (NTP) systems have been studied in both the USA and the former Soviet Union since the 1950s for use in space science and exploration missions. NTP uses nuclear fission to heat hydrogen to very high temperatures in a short amount of time so that the hydrogen can provide thrust as it accelerates through an engine nozzle. Be...
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... melting point for singlephase solid solution carbides has been shown to be 100-700 K higher than the melting temperature for carbides that have formed a separate carbon phase (e.g., [U, Zr] C x +C) [20,21]. Figure 3 shows the solidus curves for ternary mixed carbides of (U, Zr, Nb) C from [20]. This study showed higher melting temperatures for ternary mixtures than for binary carbides of ZrC or NbC with an equal amount of UC. ...
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A flight demonstrator (FD) High-assay Low Enriched Uranium (HALEU) Nuclear Thermal Propulsion (NTP) system that can advance the technology for a Mars crew transportation system extensively studied in late 2019 and early 2020. This demonstrator development activity would use a nuclear fuel material that is capable of high temperature (e.g., peak tem...
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... The efficiency though is limited by the maximum temperature possible for a solid core. It is critical to conduct research to increase the reactor core temperature, but it will be difficult to go significantly beyond current capabilities (Burns, 2020). The trick to reaching a high specific impulse is the use of only hydrogen as the propellant. ...
Recent advances in chemical propulsion have brought a revolution in the ability to economically access near-Earth orbit. As the world turns its eye on returning to the Moon and then on to Mars, understanding the factors to overcome from a technical perspective of space propulsion is important. First, readers are provided with motivation for why sustained missions to Mars is not as simple as sending a rocket to the planet (but still a momentous step for humanity). Next, near-term technologies and their capabilities are discussed along merits and limitations. Finally, we are in one of those exciting inflection points of human exploration and some suggestions are provided on how we must continue enabling exploration through the lens of space propulsion technology maturation.
... Additionally, advancements in energy collection, storage, and utilization systems are being explored to enhance the specific impulse and thrust of rocket engines for deep space exploration and other space missions [74]. Ground testing of Nuclear Thermal Propulsion (NTP) engines poses unique challenges due to environmental regulations, necessitating innovative approaches for testing to mitigate health and safety risks [75][76]. ...
... The system typically consists of a reactor containing fissionable material and fuel pebbles, a neutron source for initiating fission reactions, and a fluid for moderating neutrons and transferring heat [77]. Figure 8 shows recession rate of U 0.1 Zr 0.9 C compared to other uranium compounds and refractory carbide materials [75]. The reactor heats the fluid, which is then expelled through a nozzle to produce thrust [73]. ...
... Figure 9 shows nuclear Thermal Propulsion Engine Exhaust Total Containment Concept [76]. However, challenges exist, such as the need to develop extremely high-temperature reactors for space nuclear propulsion [75]. Additionally, the harsh operating conditions of NTP systems present significant design and operational challenges [2]. ...
In recent years, there have been notable breakthroughs in rocket propulsion technology. The desire to improve efficiency, reliability, and versatility in the fields of space exploration and satellite deployment has motivated these advancements. This document provides a comprehensive summary of the latest advancements. Propulsion systems for rocket engines utilize it, emphasizing significant breakthroughs and their impact on space missions. Recent advancements in propulsion systems encompass a wide range of factors, such as propulsion techniques, engine configurations, materials, and control mechanisms. Ion and Hall effect thrusters are examples of electric propulsion systems that have greatly changed long-duration missions by offering better specific impulse and fuel efficiency than traditional chemical propulsion. Satellite station-keeping, orbit transfer, and deep space missions have utilized these systems. Furthermore, the development of sophisticated propellants, combustion technology, and engine designs has led to advancements in conventional chemical propulsion. Technological advancements, including additive manufacturing, have made it possible to produce intricate engine parts with improved accuracy and effectiveness. This has resulted in better performance and lower expenses. Additionally, researchers have focused their efforts on advancing reusable rocket technologies to lower launching costs and increase space availability. Significant progress in engine reusability, thermal protection systems, and landing techniques, as demonstrated by the successful deployment of reusable launch vehicles by many aerospace companies, has enabled the achievement of this aim. Furthermore, progress in propulsion systems has enabled ambitious space exploration missions, such as human-crewed expeditions to Mars, lunar exploration initiatives, and asteroid mining enterprises. Propulsion systems are essential for allowing spacecraft to travel long distances, move in space, and effectively achieve mission objectives. Recent advancements in rocket engine propulsion technologies have expanded the limits of space exploration, providing unparalleled prospects for scientific inquiry, business ventures, and global cooperation. This discipline's ongoing research and innovation have the potential to uncover additional improvements, thereby transforming the future of space exploration and usage.
... In the field of nuclear energy, the Nuclear Thermal Propulsion (NTP) engine systems are attractive options for planetary exploration applications due to their high performance, such as Mars exploration [43][44][45][46] . In order to achieve better performance of NTP systems, the NTP reactors will be utilized at temperatures above 2,500 K and maintaining pressures exceeding 3 MPa. ...
High entropy carbide ceramics have garnered significant interest as a novel class of ultra-high temperature and superhard metallic materials. In the present work, a comparative investigation was conducted for the first time on the stability, mechanical, and thermodynamic properties of two medium entropy carbides (MECs), (TaZrU)C and (YZrU)C, using high-throughput first-principles calculations. Additionally, data from groups IV and V transition metal monocarbides were employed for comparison. The temperature-dependent thermodynamic properties, including bulk modulus (B), constant volume/constant pressure heat capacity (Cv/Cp), Gibbs free energy, volume, entropy, and thermal conductivity, were evaluated using the Debye-Gruneisen model. The results demonstrate that (TaZrU)C and (YZrU)C exhibit similar trends in their thermodynamic properties, with (YZrU)C displaying slightly superior performance as the temperature rises. This work provides valuable insights into the design of innovative high entropy fuels, holding significant implications for the advancement of MEC ceramic fuels in advanced nuclear power systems and nuclear thermal propulsion systems.
... The Rover program consisted of several research and development phases, including laboratory experiments, component testing, and full-scale engine testing. During the laboratory phase, researchers conducted experiments to study the behavior of various materials and components in a nuclear environment, including the heat transfer and cooling systems, the fuel elements, and the reactor core [11]. ...
Nuclear propulsion utilizes nuclear reactions to produce energy, which is then used to propel a vehicle. There are three main forms of nuclear propulsion: naval nuclear propulsion, aero-nuclear propulsion, and space nuclear propulsion. Naval nuclear propulsion involves the use of nuclear reactors to power ships. This propulsion type provides several advantages over traditional propulsion methods, including increased range, speed, and maneuverability. The first nuclear-powered submarine, the USS Nautilus, was commissioned in 1955, and since then, many countries have developed nuclear-powered submarines and ships. Aero-nuclear propulsion involves the use of nuclear reactors to power aircraft or missiles. This concept has been the subject of much research and development. Space nuclear propulsion involves the use of nuclear reactors to power spacecraft. This type of propulsion provides several advantages over traditional propulsion methods, including increased speed and efficiency. The main challenge with space nuclear propulsion is developing extremely high-temperature reactors.
... The uranium carbides fuel (UC and UC2) taken alone does not present good properties: its evaporation rate is very high (over 10 -9 m/s) at 2000 °C and the melting temperature for its dispersion in a graphite matrix is in the order of 2800 °C, too low for the performance required by nuclear thermal propulsion systems. From the Rover program [23], several fuels with different compositions have been proposed to increase the performance given by the carbide fuel particles: from the UC2 particles coated by NbC inside a graphite matrix, passing through the solid solution (U,Zr)C with an extremely high melting temperature of 3600 K, but with the drawbacks associated to the variation of the composition due to the material losses at high temperatures [25,27], finally arriving to the ternary carbides developed by the INSPI High Temperature Material Laboratory [29], which demonstrated to suffer less than 1% of mass loss in four hours of operations in non-nuclear flowing hydrogen test. In most recent years, various companies further improved the performance given by the ternary carbide, with a composition similar to the one developed by the INSPI, by embedding particles of this fuels inside carbide matrix (such as ZrC), forming composite materials CerCer. ...
... The compatibility of carbide containing fuel materials with hydrogen is well documented in the literature [23,27,28]. The main problem in the coupling of this fuel and propellant is the hydrogen corrosion action that produces a mass loss of the fuel surface inducing free carbon realizing in the mid-temperature region (1500-2900 K) [27]. ...
... The compatibility of carbide containing fuel materials with hydrogen is well documented in the literature [23,27,28]. The main problem in the coupling of this fuel and propellant is the hydrogen corrosion action that produces a mass loss of the fuel surface inducing free carbon realizing in the mid-temperature region (1500-2900 K) [27]. This free carbon can react with the flowing hydrogen leading to the formation of hydrocarbons gas species (i.e., methane (CH4) and acetylene (C2H2)). ...
From the late 1950s to date, nuclear thermal propulsion has the purpose of making possible missions impossible to accomplish with chemical propulsion. The use of hydrogen as a propellant and a fuel resistant to very high temperatures guarantees exceptional propulsive performance. Since the NERVA project, a propulsion system with such capabilities has proven to be the most suitable to carry out missions to Mars. Even today, the literature on nuclear thermal propulsion systems appears to be full of Mars mission studies. Little attention is given to other missions potentially made accessible by this type of propulsion. The purpose of this work is to investigate different mission scenarios that could be made accessible by nuclear propulsion and to identify the most efficient configurations of the propulsion system for each scenario. Some mission scenarios are presented, covering both interplanetary and earth orbit missions. The specific requirements that each mission imposes on the propulsion system are determined. Particular attention is given to the analysis of the safety requirements, which constitute the most stringent constraints to be respected for the use of nuclear reactors in space. A literature review identifies the most promising fuels and propellants, with a focus on the recently developed high temperature fuels. A preliminary design determines the mass, size and materials of the components of the propulsion systems satisfying the imposed requirements for the diverse missions. All the proposed configurations have associated different combinations of fuels and propellants among the one chosen from the previous literature reviews. For each mission, a trade-off is made based on the performance offered by the various propulsion systems proposed. Particular attention is given to the parameter of the system specific impulse, which weighs the specific impulse on the mass of the propulsion system. This parameter is very important in systems using nuclear propulsion, where the mass of the engine occupies a large part of the total mass of the system. From this preliminary trade-off, the nuclear thermal propulsion system configurations worth to be studied in detail and optimized emerge for each identified mission. Finally, the possible benefits in terms of system specific impulse derived by the use of the fission reactor also for power generation purposes are discussed.
... The technology was too new and not well understood in the early 1960s, but was being investigated in parallel to the NERVA experiments. CERMET compacts consist of ceramic fuel particles embedded in a refractory metal matrix [19,20]. The choice of matrix and fuel material influences thermal stability, thermal conductivity, structural integrity, and neutronics performance of the CERMET compact. ...
... In a simplistic sense, CERMET fuels are particles of ceramic fuel (i.e., UO 2 or UN) encapsulated in a metal matrix, typically, but not limited to, tungsten, rhenium, or molybdenum. The research conducted by ANL and GE included the development and testing of the CERMET fuel and the design of the ANL-200, ANL-2000 [20,21], and the GE 710 reactors [21,23]. These CERMET programs focused entirely on HEU fuel kernels and fast reactor concepts. ...
... The matrix material of a CERMET usually makes up about 30-60% of the compact volume [23], so its properties are both neutronically and structurally important. The ANL and GE programs focused mostly on natural tungsten as matrix material [20]. Among the available matrix materials, tungsten provides the largest fracture strength and temperature stability [6]. ...
This chapter will cover the fundamentals of nuclear thermal propulsion systems, covering basic principles of operation and why nuclear is a superior option to chemical rockets for interplanetary travel. It will begin with a historical overview from early efforts in the early 1950s up to current interests, with respect to fuel types, core materials, and ongoing testing efforts. An overview will be provided of reactor types and design elements for reactor concepts or testing systems for nuclear thermal propulsion, followed by a discussion of nuclear thermal design concepts. A section on system design and modeling will be presented to discuss modeling and simulation of driving phenomena: neutronics, materials performance, heat transfer, and structural mechanics, solved in a tightly coupled multiphysics system. Finally, it will show the results of a coupled physics model for a conceptual design with simulation of rapid startup transients needed to maximize hydrogen efficiency.
... The biggest challenges in the NTP research field relate to minimizing three things: high-temperature hydrogen corrosion, fracture caused by temperature gradients, and radiation damage that would impede reactor performance during operation. 141 In general, reduced hydrogen ingress into carbon fuel elements, along with reduced property mismatching in the materials, could improve component lifetime and overall performance. Another fuel option being studied for use in NTP systems is W/UO 2 and Mo/UO 2 ceramic metal (CERMET) fuel, which must be able to operate in excess of 2700 K while remaining compatible with the H 2 propellant. ...
Today's competitive world economy is creating an indispensable demand for increased efficiency of engineering components that operate in harsh environments (i.e., very high-temperature, corrosive, or neutron irradiation environments), for applications in the energy, automotive, aerospace, electronics, and power industries. Increased research is being done on thermal barrier coatings (TBCs) for protecting such components, since the versatility of manufacturing techniques and the scale of deployment result in increased life, economics, performance, and durability. This review focuses on the advances that led to using TBCs for component life extension and, more recently, as an integral part of advanced component design for high-temperature and other types of harsh environments, such as those found in nuclear-related applications. Factors that led to state-of-the-art advanced coating-fabrication techniques [e.g., electron-beam physical vapor deposition (EB-PVD), plasma spray deposition, and electrophoretically deposited TBCs, as well as functionally graded material (FGM) manufacturing] have also been emphasized in current coating R&D. This review explores the current state of TBCs, i.e., the latest advances regarding their fabrication and performance, associated challenges, and recommendations for their future use in aerospace, nuclear, high-temperature, or otherwise harsh environments.
