Chemical Rocket Research Articles

A Comprehensive Review on Nuclear Thermal Propulsion System: Solid Core Design

Nuclear thermal propulsion (NTP), and more so the solid core type of it, is considered a quite notable example of advancement in space propulsion technology. NTP systems as opposed to normal chemical rockets use nuclear fission to heat hydrogen or other propellants, thus achieving much better efficiency and specific impulse than chemical rockets do, making NTP systems suitable for long duration space missions. This paper presents a detailed investigation of solid core NTP systems, including their engineering such as nuclear reactor core, propellant flow and nozzle for the propellant exhaust. It addresses the significant engineering problems of the design of the NTP system such as materials of high temperature capable of operating within the reactor, radiation shielding, hydrogen storage, along with some of the methods that can be used to solve each problem. It also includes the disadvantages of NTP systems and counterarguments, such as the time of transit and the capacity of the payload, especially in case of missions for deposition of large masses on Mars, in the deep spaces and in the outer space. Lastly, the paper explores the existing efforts and objectives of further research, focusing on the developments of materials, hybrid propulsion systems and the ability to work with other countries in order raise the pace of the NTP propulsion progress and eventually use it in the future space exploration.

Design and Fabrication of TRISO Based ZrC Fuel for Nuclear Thermal Propulsion

Nuclear thermal propulsion is a higher specific impulse option for in-space propulsion compared with chemical rockets, offering reduced transit times, higher payload, and reduced launch costs. Ultra Safe Nuclear (USNC) has designed a demonstration reactor and developed the manufacturing capabilities to produce the nuclear fuel in-house. The fuel consists of ceramic uranium fuel kernels coated with layers of low-density and high-density carbon along with zirconium carbide (ZrC). These particles are suspended in a printed ZrC matrix so that the particles are immediately adjacent to the hydrogen flow path. An additional ZrC chemical vapor deposition (CVD) coating is applied to act as an ablation layer and an additional protection for the fuel. All of these processes have been demonstrated. Preliminary testing was conducted on the printed ZrC matrix and ZrC CVD coatings in flowing hydrogen up to 2600 K.

Numerical Studies of Solid Rocket Propellant PMMA-PBAN-ALF3-Nitrocellulose-Difluoramine

Abstract The aim of the new investigation is the evaluation of solid rocket Propellant. In which performing numerical analysis of solid rocket propellant and calculating the constraints involved as derived from thrust i.e. velocity involved in the solid rocket propulsion motor usage. This paper aims to show the viability of solid rocket propellant for modern and future applications. Solid rocket motors are simple in design and fabricating. The need for a propellant that produces the same specific impulse as another chemical rocket engine. So it is needed to have a solid rocket motor with an enhanced combustion characteristic at a reasonable O/F ratio. For a healthy ecology, an economically reliable, highly effective, and environmentally concerned propellant is constantly suitable. As a superior alternative among the already used propellants in the sector, the paper suggested fuel PolyMethyl MethAcrylate (PMMA), PolyButadiene AcryloNitrile (PBAN) CoPolymer, and Aluminum hydride (AlH3), and oxidizers such as Nitrocellulose and Difluoramine. The desired O/F ratio for the technical criteria was found to result in a high combustion characteristic. With the features discovered through numerical and analytical research, we have suggested a design for the SRM that includes post-combustion, which enhances the reaction and creates the innovative elements of the existing SRM.

Effect on the performance of a hybrid rocket using AP in the PVC and HTPB-based hybrid fuel

Hybrid rocket is a type of chemical rocket propulsion system where the fuel and the oxidizer are stored separated and in different state of aggregation. Typically, the fuel is in the solid state and the oxidizer is either in the liquid or gaseous state. It offers various advantages over other type of chemical rockets such as throattability, controllability and reduced complexity. It also has some drawbacks such as low regression rate, poor combustion efficiency, higher sliver losses, etc. Various methods have been adopted to overcome these drawbacks and improve the performance of hybrid rocket. The present study focus on the improvement of regression rate with the addition of oxidizer particles in fuel content. Ammonium Perchlorate is used as an additive in Hydroxyl Terminated Polybutadiene (HTPB) and Poly Vinyl Chloride (PVC) based fuel grain. From the experimentations, it was observed that the thrust, pressure and regression rate of the HTPB fuel grain with additive have higher improvement than with the PVC based fuel grain. The sliver losses are also reduced due to uniform burning after addition of oxidizer in fuel grain. The overall study strongly suggests that addition of oxidizer in limited quantity can be used to overcome the drawbacks of hybrid propellant rocket.

Numerical Study of Porous Cylindrical Containment for the Fuel Element of a Centrifugal Nuclear Thermal Rocket

For deep-space propulsion and interplanetary exploration, the centrifugal nuclear thermal rocket (CNTR) has the ability to achieve a very high specific impulse (Isp) metric beyond that of conventional chemical rockets or solid-core nuclear thermal propulsion systems. The high Isp allows the rocket to use less propellant or achieve a higher velocity for shorter transit times. However, the cylindrical containment structure of a CNTR fuel element encounters extreme conditions, as it houses molten uranium at temperatures exceeding 1408 K, leading to challenges such as dissolution, chemical reactions, and thermal stresses that conventional materials struggle to withstand. This study aims to address this issue by analyzing appropriate materials for constructing the cylindrical containment component. The operating conditions of the annular porous medium that confines the liquid uranium in the centrifugal fuel element are simulated by conducting a comprehensive one-dimensional numerical analysis using a range of candidate porous materials, including Mo, W, zirconium carbide, and silicon carbide. The porous structure facilitates the flow of the hydrogen propellant into the internal molten uranium section, where it gains significant thermal energy while simultaneously cooling the cylinder. The containment cylinder has an internal temperature of 1478.1 K, exceeding the melting point of uranium, while the external gas temperature of the hydrogen propellant is much lower. This temperature difference induces significant thermal stresses in the cylinder. The porous containment cylinder made from molybdenum was able to maintain elastic deformation throughout the thickness of the cylinder, showcasing its ability to handle these extreme thermal stress conditions. Tungsten, on the other hand, experienced plastic deformation at the cylinder’s edges and elastic deformation through the middle radial locations. In contrast, the stresses experienced by the ceramic materials far exceeded their failure stress values, leading to brittle failure. These findings will help with the refinement of the CNTR design, edging it closer to practical implementation.

Beyond the Rocket: A Review of Propellantless Propulsion Technologies and Concepts

For decades, the dream of unfettered space travel, free from the constraints of traditional chemical rockets, has captivated humanity's imagination. The realization of an interstellar faring civilization hinges on breakthroughs in space propulsion that transcend the limitations imposed by current chemical rocket technology. Scientists explore the intriguing realm of propellantless propulsion, a futuristic vision for space exploration that transcends the limitations of conventional propulsion. The article explores the historical roots of this field, including controversial concepts like the EmDrive and the Biefeld-Brown effect. It further examines theoretical frameworks encompassing asymmetric electrostatic pressure generation and even spacetime warping. However, the quest for reactionless motion faces a fundamental hurdle – the law of conservation of momentum. Efforts to circumvent this law involve manipulating the enigmatic quantum vacuum or creating asymmetric thrust generation within the spacecraft itself. While challenges like precise microthrust measurement, immense energy demands and material limitations persist, the potential rewards are truly transformative. Interplanetary voyages completed in significantly shorter timeframes and drastically reduced launch costs could be attained. Propellantless drives hold the potential to overcome numerous obstacles that current chemical propulsion cannot. This article underscores the critical need for continued exploration through rigorous experimental verification, the development of robust theoretical frameworks and collaborative efforts between physicists, engineers and materials scientists. This continued exploration necessitates the exploitation of existing high-efficiency solar collection technologies. Furthermore, investigations into innovative approaches, such as those utilizing metamaterials, could be pivotal in unlocking the transformative potential of propellantless propulsion systems.

Dynamics of the plasma induced by laser on a cryogenically cooled aluminum target for application in space propulsion

In this work, we investigate the properties of the plasma induced by focusing a high-power laser beam on an aluminum target that was cooled by a helium refrigerator from room temperature down to 20 K. Fast, streak photographs of the plasma were taken at different temperatures and laser energies. From the images obtained, position-vs-time plots were made for each experiment, and from them, the speed was calculated. Additionally, narrowband interference filters were employed to image the dynamics of ions and neutrals separately. It was found that the plasma plume has two distinct speeds: that of its center and that of the outer edge. For unfiltered images, the former has values within the interval 6.2 to 9.1 km/s, while the latter can reach speeds of the order of hundreds of km/s. It was found that the plume of a target cooled to 20 K has a length that is 8%–12% less than the corresponding size at room temperature. Chilling the target did not seem to affect significantly either the plume's speed of expansion or the size of the crater produced. Lower bounds were estimated for the momentum imparted to the ejecta and the specific impulse. The latter can reach a 920-s level, nearly twice as much the amount obtained with chemical rocket fuel.

Nature-Inspired Concepts for High-Power Electric Propulsion Systems

The development of new space missions and the growing interest in space exploration have created an urgent need to develop high-thrust propulsion systems capable of propelling spacecraft far beyond the Earth and the solar system for long periods. Electric propulsion can potentially enable space missions to reach speeds thousands of times greater than conventional high-thrust chemical rockets. However, high speed comes at the cost of low power-to-thrust efficiency when considering propulsion systems as a whole, including the power generation system, transmission lines, and thrusters, which prevents high thrust from being achieved with any conceivable power system, resulting in long acceleration times. In addition, modern electric propulsion systems rely on external power sources that suffer significant power transfer losses at the high power levels required for high thrust levels. In addition, modern electric propulsion systems suffer from a number of critical physical and engineering problems that affect thrust levels and longevity. In addition, modern electric propulsion systems do not follow the principles of generation and acceleration of plasma flow that can be observed in space and potentially borrowed for artificial applications. This paper discusses several promising electrodeless plasma thruster concepts for high-power, high-thrust electric propulsion systems based on a combined power source/power converter/thruster architecture. These concepts have the potential to overcome modern limitations of high-power electric propulsion systems and enable new outer space missions that would not be possible with conventional thrusters.

The Horizon of Future Intergalactic Travel

I show that non-relativistic objects traveling in intergalactic space at an initial peculiar velocity v will traverse in the future of the LCDM cosmological model a maximum comoving distance of ∼(v/1.7H 0), irrespective of travel time, where H 0 is the Hubble constant. This follows from the future exponential growth of the scale factor. Hypervelocity stars escaping the halo of the Milky Way galaxy will not go beyond a few tens of comoving Mpc, even over the trillions of years that represent the lifetime of low-mass stars. To reach beyond the Virgo cluster of galaxies, requires an initial peculiar speed ≳3 × 103 km s−1, a hundred times faster than the chemical rockets launched to space so far.

Analysis on the working mode of electric propulsion system

At present, the electromagnetic propulsion technology and the electrostatic propulsion technology are more mature than before. With the increase of available power on the spacecraft, the performance can be better improved. This paper mainly reviews the electric propulsion technology for long-term space travel. It can be concluded that, compared to traditional chemical rocket systems, electric propulsion systems are more suitable for long-term space missions and have the ability to transport relatively heavy objects in space.

Launching Earth radiation monitoring satellites using the combined thrust

The paper considers the problem of launching satellites into the orbits for Earth radiation monitoring using the upper stage previously inserted into a reference circular orbit and equipped with a combined propulsion system, i.e. chemical rocket engines and electric rocket propulsion system (ERPS). The combined launch scheme implies formation of the intermediate orbit using the chemical rocket engines and further successive satellites insertion into the target orbits using the electric rocket propulsion system. Calculation of the satellite group launch trajectory parameters is provided, single accompanying and two more in cluster formation, to the given elliptical orbits. The spacecraft flight is approximated at the chemical rocket engines operation phase by a pulse action using the double-pulse apsidal maneuvers; and the spacecraft flight trajectory in the ERPS phase is calculated under the condition of minimizing the flight time with the Pontryagin maximum principle. The results obtained demonstrate technical feasibility of the task of launching satellites into specified orbits using the combined thrust, as well as advantages of a combined scheme for launching a payload in order to reduce flight duration compared to using the ERPS throughout the entire flight.

The second fusion of laser and aerospace—an inspiration for high energy lasers

Since the first laser was invented, the pursuit of high-energy lasers (HELs) has always been enthusiastic. The first revolution of HELs was pushed by the fusion of laser and aerospace in the 1960s, with the chemical rocket engines giving fresh impetus to the birth of gas flow and chemical lasers, which finally turned megawatt lasers from dream into reality. Nowadays, the development of HELs has entered the age of electricity as well as the rocket engines. The properties of current electric rocket engines are highly consistent with HELs’ goals, including electrical driving, effective heat dissipation, little medium consumption and extremely light weight and size, which inspired a second fusion of laser and aerospace and motivated the exploration for potential HELs. As an exploratory attempt, a new configuration of diode pumped metastable rare gas laser was demonstrated, with the gain generator resembling an electric rocket-engine for improved power scaling ability.

The use of diffusion chambers in embryotoxic research

Introduction. Currently, there are no standard methodological approaches that allow assessing the danger to human and animal reproduction of poorly soluble chemicals (industrial waste, products of destruction of organic substances, polymer materials), including substances that form complex poorly soluble systems with environmental objects. It may be impossible or ineffective to use standard routes of administration of such substances and complexes to assess their reproductive hazard. An attempt to find an experimental model for conducting toxicological and embryotoxicological studies that allow assessing the danger of prolonged interaction of poorly soluble compounds directly with tissue fluids was the main aim of the work. The study aims to investigate the possibility of using diffusion chambers to assess the reproductive hazard of poorly soluble chemicals. Material and methods. In experiments with chemicals, the researchers placed samples of dry preparations in the inner cavity of one of the rings. Experts sealed the ring on both sides with millipore membranes. The diffusion chambers obtained in this way were implanted into the abdominal cavity or under the skin in the cervical region of female rats during the most sensitive days of pregnancy to pathogenic effects. Results. When implanting diffusion chambers to animals, the possibility of assessing the embryotoxic properties of poorly soluble chemicals, such as bitumen-salt masses, polymer materials and coatings, etc., as well as soil contamination with substances potentially dangerous to the reproductive function of humans and animals is shown. With the help of diffusion chambers, experts assessed the embryotoxic activity of known dysmorphogens, cyclophosphamide, cadmium sulfate, as well as a number of polymer materials (di-paraxilylene film, acrylic acid copolymer, silloxane rubber), Scientists assessed soil contamination with a known insecticide and acaricide - endosulfan. Limitations. In the work, the experts used diffusion chambers with a volume of 400, 900 or 3000 m3. Conclusion. As a result of the experiments conducted, scientists determined that the presented method can be used to assess the reproductive hazard of poorly soluble chemicals (products of destruction of organic matter, polymer and endoprosthesis materials), when assessing the risk of prolonged presence of foreign bodies in tissues, when assessing soil contamination in places of chemical accidents, rocket crashes, storage and destruction of chemical weapons. Ethics. The study was carried out in compliance with the rules of bioethics approved by the European Convention for the Protection of Vertebrates Used for Experimental and Other Purposes (Protocol No. 4 of 8.11. 2022).

Hydrogen as a Nuclear Thermal Rocket Propellant

Nuclear Thermal Propulsion (NTP) is a successfully developed technology, though it hasn’t been officially used in the propulsion system of an astronautical mission. It is the technology most likely to make long distance journeys in space possible. It is considerably more efficient than the traditional chemical rocket engines, regarding propellant consumption for each unit of thrust generated. The reason for that is the greater number of choices regarding the propellant composition. Therefore, in this work, Hydrogen has been chosen as propellant due to its low molecular mass compared to other possible substances. The main aim is to explain how the propellant molecular mass impacts a rocket performance, and to show, by Computational Fluid Dynamics (CFD) simulations that, indeed, hydrogen seems to be the best choice available among possible nuclear thermal rocket propellants.

Theory of radiation pressure on a diffractive solar sail

Solar sails propelled by radiation pressure enable space missions that cannot be achieved using chemical rockets alone. Significant in-space propulsion for missions such as a solar polar orbiter may be achieved with a sail that deviates sunlight at a large average angular direction. The momentum transfer efficiency of sunlight diffracted from a Sun-facing diffractive sail comprising periodic right prism elements is examined here. The spectrally averaged efficiency, integrated across the solar blackbody spectrum, is found to approach that of a monolithic prism when the grating period is much longer than the peak of the solar spectrum. This idealized diffraction analysis predicts a greater transverse radiation pressure force compared to an idealized reflective sail. With modern optical design and fabrication techniques, optimized diffractive solar sails may one day replace reflective sails.

THRUST GENERATION BY ION PROPULSION TECHNOLOGY

Electric propulsion system proven to be a suitable and efficient alternative for conventional propulsion systems .Ion thrusters is one of the electric propulsion systems. It has very high specific impulse generation (Isp) and consumes very low amount of fuel. Ion thrusters can easily compete with chemical rockets propulsion, even if the thrust produce is very low compares to chemical propulsion. Ion propulsion system can be used for various space missions like orbit station keeping for geostationary satellite, orbit and altitude controlling, multi-goal missions. Ion thrusters are more compatible for deep space missions as they are tested for endurance test where as chemical proportion is highly unsuitable for deep space mission.

Hybrid material performance assessment for rocket propulsion

Abstract Fuel based on hybrid green material is of paramount importance for various military and civilian purposes. This work presents a novel expert-based multi-criteria hierarchy and decision-making model to evaluate various chemical rocket propulsion technologies with different fuel material types under an uncertain environment. This helps select the most appropriate fuel material types according to the performance requirements considering various evaluation criteria toward achieving better performance economic benefits of the sustainable hybrid green material-based fuel for various applications. Here, the analytical hierarchy process model was utilized to enhance more informative decisions from both numerical and linguistics information regarding the performance of the fuel based on hybrid green material under an uncertain environment. The model considers various simultaneous evaluations and conflicting criteria to practically demonstrate economic, technical, and sustainable issues for the decision makers in this field. Results demonstrate that cost and size criteria are the most important in the evaluation process from experts’ points of view for the rocket propulsion technology. The fuel based on hybrid green material has the highest priority regarding the whole evaluation criteria. The sensitivity analysis illustrates the robustness of the model as well as the reliability of the drawn decisions.

Steady-State Irradiation of Characterized Instruments for Nuclear Thermal Rockets Using In-Pile Experiment Apparatus

The development of nuclear rocket technology is critical for further exploration of extra-terrestrial bodies. Nuclear rockets can provide various advantages over current chemical rockets. However, the harsh environment provides several challenges regarding instrument performance. Temperature extremes, radiation (reactor and space), and the inability to conduct traditional maintenance activities can lead to severe degradation in instrument performance. To better understand the effects of radiation on instrumentation, an irradiation campaign has been designed to test a set of instruments provided by a collaborator in the aerospace industry. Details concerning instrument performance before and after irradiation are provided to allow for an analysis of the tested instruments. Additionally, the design of the irradiation test is described in detail.

Editorial

Editorial

Hybrid rocket propulsion technology for space transportation revisited - propellant solutions and challenges

This paper presents the status of developments worldwide regarding use of hybrid rocket motors for space transportation. Historical roots are presented and reasons for revisiting hybrid technology after a few decades of limited interest are examined. Modern developments in sounding rockets, reusable suborbital systems and launch vehicles are discussed with particular focus on propellant technology. Various propellant combinations include use of liquid oxygen, hydrogen peroxide, nitrous oxide and nitrous oxide-oxygen mixtures as oxidizers. Different fuels are considered, taking into account performance, as well as inter alia obtainable regression rates. Results of preliminary calculations for vehicles using different propellant combinations are presented and analysed. This is compared with proposed configurations of hybrid rockets worldwide. Unresolved problems and several unknowns are pointed out, including hybrid rocket motor scalability issues, large motor combustion instabilities, combustion efficiency of metalized fuels, propellant volumetric performance and mass of fuel residuals in case of wagon wheel grain geometry. It is discussed whether new-space hybrid launch vehicles, while typically with limited stage reusability, may be cost-competitive in regard to other chemical rocket propulsion system developments. The paper is summarized with a list of potential future advances and technical opportunities. The main purpose of the conducted research is to provide a comparison between different hybrid propulsion technologies available, or currently under development, worldwide.