Propulsion Schemes Research Articles

Research on an optimization design method for a TBCC propulsion scheme

Abstract An optimization methodology for a TBCC propulsion schemes was established for hypersonic vehicles, focusing on the integration of aircraft and engine performance. Altitude-velocity characteristics of TBCC propulsion were obtained through engine performance calculations. By analyzing mission requirements, lift-drag characteristics, and flight constraints, the take-off thrust-weight ratio and wing load of the vehicle were optimized to meet the flight conditions. In addition, the fuel ratio was calculated. To determine the vehicle’s gross take-off weight and the engine’s take-off thrust, a model considering the weight of the vehicle and the turbine engine were used. The optimization process selects four thermodynamic cycle parameters for the turbine engine as the independent variables. An improved particle swarm optimization-back propagation neural network was used to establish the relationship between the four parameters and the gross take-off weight, aiming to minimize the vehicle’s weight. The results of the optimization process show that the total take-off weight of the optimized vehicle has decreased from 112363.41 kg to 102218.98 kg. The required uninstalled take-off thrust of TBCC has also been reduced from 162.86 kN to 147.49 kN, resulting in a decrease in mass flow from 156.50 kg/s to 133.30 kg/s.

Promising methods for improving the radio-frequency ion thruster performance

Improving the reliability and efficiency of available electric propulsion schemes is one of the priority areas of space technology development. In particular, this should be done for ensuring the guaranteed removal of spacecraft to a disposal orbit at the end of their active life, which, in turn, will slow down the growth in the number of space debris objects in the most exploited regions of near-Earth space. The paper considers ways to improve the power and mass efficiency of one of the modern electric propulsion types - a radio-frequency ion thruster with an inductive radio-frequency discharge. Using an engineering physico-mathematical model, computational studies were performed to optimize the shape of the radio-frequency ion thruster main components, namely the discharge chamber and the grids of ion-extraction system. The thrust of the thruster was used as the optimization criterion; it was determined from the calculated ion density distributions in the radio-frequency discharge plasma. Such an approach to refine the performance improvement methods has not previously been applied to radio-frequency ion thruster. The ion density distributions, as well as the thruster integral characteristics determined from them, such as the thrust, total ion current from the thruster, propellant utilization factor, ionization cost and a number of others, were calculated for two actual standard sizes of radio-frequency ion thruster with the beam diameters of 80 mm and 160 mm, which can be used to solve the problems listed above. Besides, for the defined optimal configurations of thruster with two standard sizes the calculations were made to assess the possibility for increasing the thruster integral characteristics by applying an additional magnetostatic field in the radio-frequency discharge region. The study revealed the possibility of noticeable performance improvement compared to the basic radio-frequency ion thruster design with hemispherical discharge chamber and flat grids of the ion-extraction system.

Multi-Objective, Multi-Disciplinary Design Optimization and Multi-Attribute Evaluation of Hybrid Rocket Motors Used for Manned Lunar Lander

This paper proposed a multi-objective, multi-disciplinary design optimization and multi-attribute evaluation method for the manned lunar lander descent stage. A system design model is established considering multiple disciplines such as propulsion, structure, trajectory and cost. With the goal of minimizing mass, minimizing cost and maximizing velocity increment, the overall scheme for hybrid rocket motors was optimized by altering various grain shapes and feed systems, acting as an alternative propulsion scheme for the manned lunar lander. Under the same design conditions, the optimal scheme of hybrid rocket motors considering continuous and discrete attributes was studied and compared with that of liquid rocket engines to elucidate the characteristics of the hybrid rocket motors for deep space exploration. The results showed that the evaluation results obtained by considering only continuous attributes were different from those by considering both continuous and discrete attributes. The liquid propulsion scheme with liquid oxygen/kerosene is superior to the hybrid propulsion schemes due to its excellent cost and specific impulse performance when only continuous attributes are considered. However, hybrid rocket motors have shown good performance in terms of operability, manufacturability, safety and environmental protection. So, after introducing discrete attributes, the hybrid propulsion schemes show greater potential. In brief, based on the multi-attribute evaluation method considering comprehensive attributes, the hybrid rocket motor provided with tube grain and gas pressure feed system was considered as the optimal propulsion system for the lunar lander. Furthermore, the parametric analysis showed that the fuel grain outside diameter, the initial design thrust and the initial oxygen-to-fuel ratio had a significant influence on the performance of the hybrid rocket motor for the lunar lander, and in particular, the effect of the fuel grain outside diameter was more than 50%.

Закономірності зміни оптимальних складу і параметрів силових установок з прямоточними контурами від швидкості надзвукового крейсерського польоту

There are two aircraft concepts for transoceanic flights at supersonic speed. The first is the aircraft with moderate supersonic cruising speed M = 1.7...2.2, and the second is the aircraft with cruising speed M ≥ 3. Propulsion with a ramjet engine (ramjet) is preferable for high supersonic speeds. However, a ramjet has no starting thrust and is uneconomical at subsonic flight speeds. Combined propulsion with a turbojet duct for takeoff and a ramjet duct for supersonic cruise flight are used to overcome this contradiction. There are known propulsion with turboramjet engines, as well as various propulsion schemes with turbofan engines (afterburning and duct-burning ones), in which the outer contour together with the afterburner and nozzle can be considered the ramjet duct. When the turbojet duct is turned off, the operating process of such turbofan engines is practically the same as the ramjet, which allows using the advantages of a ramjet in supersonic cruise flight. Because flight at supersonic cruising speed can be provided by different propulsion compositions, the choosing problem of the composition and parameters of the propulsion for an aircraft with supersonic cruising speed is relevant. A calculation-analytical method was used to select the composition and parameters of the propulsion, which is based on the maximum relative mass of the payload criterion. Using the aircraft mass balance equation this criterion can be represented as a minimum conditions for the relative mass of the fuel and propulsion. Using this method, for an aircraft with a given mass, aerodynamic characteristics and a given flight profile, for the indicated propulsion compositions, the change patterns of the minimum relative mass of fuel and propulsion in the range of M = 2.5...4 are established. The established patterns allow choosing the propulsion composition and parameters depending on the speed of the supersonic cruising flight or choosing the flight speed of the aircraft at a given propulsion composition. The dependance of the propulsion working process optimal parameters for takeoff and cruising mode on the speed of supersonic cruising flight according to the criterion minimum of relative mass of fuel and propulsion were obtained.

Comparison of Electrified Aircraft Propulsion Drive Systems with Different Electric Motor Topologies

Electric aircraft propulsion is a growing research area that looks into achieving propulsion through fully electric or hybrid electric systems while achieving low emissions. The system-level benefit gained by different electric and hybrid-electric propulsion schemes depends heavily on the performance of system-level components in the electric drive-train, including the electric motor, gear box, motor drive, protection systems, as well as the thermal management system. When comparing motor topologies, it is important to understand performance measures such as efficiency and specific power on a drive system level. Many different motor types have been qualitatively compared and can be found in the literature. To guide appropriate component selection, this paper presents details of a quantitative study for a given electric propulsion drive system. A Pareto optimal front for a notional drive system of a 1.5 MW electrical propulsor with different motor types is generated and compared. An optimization algorithm coupled with an electromagnetic finite element analysis software tool was used to optimize the induction motor, switched reluctance motor, wound rotor synchronous motor, permanent magnet synchronous motor (PMSM), slotless PMSM, permanent-magnet-assisted synchronous reluctance motor, brushless DC motor, and brushless doubly fed reluctance motor types for efficiency and specific power. Overall advantages considering system-level efficiency, specific power, and a few other key metrics such as origin of losses, cooling complexity, manufacturing tolerance, and fault tolerance are discussed. This gives an indication of the relative performance of different motor types and confirms the overall advantage of PM motor topologies in aircraft propulsion.

Hardware-in-the-Loop Validation of Different Power Train Topologies’ Models in Electric Vehicles: A Plug-and-Play Capability

This study presents a novel modelling methodology for electric vehicle power train. This covers both Front Wheel and all-wheel drives. The simulation is built in PSIM and verified in Typhoon's hardware in the loop (HIL) solution. HIL technology is used for real time verification. The approach is highly attractive due to characteristics of rapid prototyping which allows quick and easy adjustment in simulation in real time. Thus, avoiding the high costs associated with physical prototypes. The paper presents results (dynamic responses of various vehicle components) and the effects of adjusting various vehicle parameters. The results obtained from simulation is successfully verified in the HIL platform. The result from this study proves the robustness of the simulation and HIL model and control algorithms. This methodology saves costs and lead time to build and design a physical hardware. Additionally, the results from the modeled vehicles agree with data provided by the manufacturer. Finally, the design is simulated in a modular way such that they can be used for various propulsion setups and schemes

Energy management of a fuel cell hybrid ultra-energy efficient vehicle

This paper focuses on energy management in an ultra-energy efficient vehicle powered by a hydrogen fuel cell with rated power of 1 kW. The vehicle is especially developed for the student competition Shell Eco-marathon in the Urban Concept category. In order to minimize the driving energy consumption a simulation model of the vehicle and the electric propulsion is developed. The model is based on vehicle dynamics and real motor efficiency as constant DC/DC, motor controllers and transmission efficiency were considered. Based on that model five propulsion schemes and driving strategies were evaluated. The fuel cell output parameters were experimentally determined. Then, the driving energy demand and hydrogen consumption was estimated for each of the propulsion schemes. Finally, an experimental study on fuel cell output power and hydrogen consumption was conducted for two propulsion schemes in case of hybrid and non-hybrid power source. In the hybrid propulsion scheme, supercapacitors were used as energy storage as they were charged from the fuel cell with constant current of 10 A.

Project Lyra: Catching 1I/‘Oumuamua–Using Nuclear Thermal Rockets

The first definite interstellar object observed in our solar system was discovered in October of 2017 and was subsequently designated 1I/‘Oumuamua. In addition to its extrasolar origin, observations and analysis of this object indicate some unusual features which can only be explained by in-situ exploration. For this purpose, various spacecraft intercept missions have been proposed. Their propulsion schemes have been chemical, exploiting a Jupiter and Solar Oberth Maneuver (mission duration of 22 years) and also using Earth-based lasers to propel laser sails (1–2 years), both with launch dates in 2030. For the former, mission durations are quite prolonged and for the latter, the necessary laser infrastructure may not be in place by 2030. In this study Nuclear Thermal Propulsion (NTP) is examined for chasing interstellar objects after they have left the inner solar system, taking 1I/‘Oumuamua as an example. NTP has yet to materialise as far as real missions are concerned, but due to its research and development in the US government sponsored Rover/NERVA programs, actually has a higher Technology Readiness Level (TRL) than laser propulsion. Various solid reactor core options are studied, using either engines directly derived from these programs, or more advanced options, like a proposed particle bed nuclear thermal rocket (NTR). With specific impulses at least twice those of chemical rockets, NTP opens the opportunity for much higher ΔV budgets, allowing simpler and more direct, time-saving trajectories to be exploited. For example a spacecraft with an upgraded NERVA/Pewee-class NTR travelling along an Earth-Jupiter-1I trajectory, would reach 1I/‘Oumuamua within 14 years of a launch in 2031. The payload mass to 1I/’Oumuamua would be around 2.5 tonnes, but even larger masses and shorter mission durations can be achieved with some of the more advanced NTR options studied. In all 4 different proposed NTRs and 5 different trajectory scenarios are examined. It is concluded that NTP has the potential to increase payload size by an order of magnitude and trip durations reduced to < 15 years compared to > 20 years for chemical propulsion.

Reconfigurable microbots folded from simple colloidal chains

To overcome the reversible nature of low-Reynolds-number flow, a variety of biomimetic microrobotic propulsion schemes and devices capable of rapid transport have been developed. However, these approaches have been typically optimized for a specific function or environment and do not have the flexibility that many real organisms exhibit to thrive in complex microenvironments. Here, inspired by adaptable microbes and using a combination of experiment and simulation, we demonstrate that one-dimensional colloidal chains can fold into geometrically complex morphologies, including helices, plectonemes, lassos, and coils, and translate via multiple mechanisms that can be varied with applied magnetic field. With chains of multiblock asymmetry, the propulsion mode can be switched from bulk to surface-enabled, mimicking the swimming of microorganisms such as flagella-rotating bacteria and tail-whipping sperm and the surface-enabled motion of arching and stretching inchworms and sidewinding snakes. We also demonstrate that reconfigurability enables navigation through three-dimensional and narrow channels simulating capillary blood vessels. Our results show that flexible microdevices based on simple chains can transform both shape and motility under varying magnetic fields, a capability we expect will be particularly beneficial in complex in vivo microenvironments.

Extremely small-diameter, high-density, radio frequency, plasma sources and central gas feeding for next-generation electrodeless plasma thrusters.

Radio frequency (RF) waves including helicon waves can readily produce high-electron-density (ne up to 1013 cm-3) plasmas with a broad range of external operating parameters. Various featured RF and helicon sources in a wide range of scales are suitable for plasma propulsion schemes. Electrodeless RF plasmas have no direct contact between electrodes and antennas, which enables long-life operation. However, one of the crucial problems is to reduce the plasma size for future applications in nano- and pico-satellites. Diagnostics of the plasma parameters in a small area should also be improved. Furthermore, to increase plasma performance, it is important to consider the radial electron density (ne) profile with an increasing upper limit, observed in high-density helicon sources due to the depletion of neutrals. This problem may be controlled by the location of neutral gas feeding and knowledge of the gas pressure distribution. Here, production of RF plasmas, with extremely small diameters from 3-mm down to 0.5-mm including 1-mm, was demonstrated, and characterization of ne and the electron temperature was performed with a collisional radiative model. Finally, to improve plasma performance such as ne and the thrust force, internal gas feeding was demonstrated using a developed Pirani gauge to measure neutral density.

Hybrid colloidal microswimmers through sequential capillary assembly.

Active colloids, also known as artificial microswimmers, are self-propelled micro- and nanoparticles that convert uniform sources of fuel (e.g. chemical) or uniform external driving fields (e.g. magnetic or electric) into directed motion by virtue of asymmetry in their shape or composition. These materials are currently attracting enormous scientific attention as models for out-of-equilibrium systems and with the promise to be used as micro- and nanoscale devices. However, current fabrication of active colloids is limited in the choice of available materials, geometries, and modes of motion. Here, we use sequential capillarity-assisted particle assembly (sCAPA) to link microspheres of different materials into hybrid clusters of prescribed shapes ("colloidal molecules") that can actively translate, circulate and rotate powered by asymmetric electro-hydrodynamic flows. We characterize the active motion of the clusters and highlight the range of parameters (composition and shape) that can be used to tune their trajectories. Further engineering provides active colloids that switch motion under external triggers or perform simple pick-up and transport tasks. By linking their design, realization and characterization, our findings enable and inspire both physicists and engineers to create customized active colloids to explore novel fundamental phenomena in active matter and to investigate materials and propulsion schemes that are compatible with future applications.

Surface-enabled propulsion and control of colloidal microwheels.

Propulsion at the microscale requires unique strategies such as the undulating or rotating filaments that microorganisms have evolved to swim. These features however can be difficult to artificially replicate and control, limiting the ability to actuate and direct engineered microdevices to targeted locations within practical timeframes. An alternative propulsion strategy to swimming is rolling. Here we report that low-strength magnetic fields can reversibly assemble wheel-shaped devices in situ from individual colloidal building blocks and also drive, rotate and direct them along surfaces at velocities faster than most other microscale propulsion schemes. By varying spin frequency and angle relative to the surface, we demonstrate that microwheels can be directed rapidly and precisely along user-defined paths. Such in situ assembly of readily modified colloidal devices capable of targeted movements provides a practical transport and delivery tool for microscale applications, especially those in complex or tortuous geometries.

A Force to Be Reckoned With: A Review of Synthetic Microswimmers Powered by Ultrasound.

Synthetic microswimmers are a class of artificial nano- or microscale particle capable of converting external energy into motion. They are similar to natural microswimmers such as bacteria in behavior and are, therefore, of great interest to the study of active matter. Additionally, microswimmers show promise in applications ranging from bioanalytics and environmental monitoring to particle separation and drug delivery. However, since their sizes are on the nano-/microscale and their speeds are in the μm s(-1) range, they fall into a low Reynolds number regime where viscosity dominates. Therefore, new propulsion schemes are needed for these microswimmers to be able to efficiently move. Furthermore, many of the hotly pursued applications call for innovations in the next phase of development of biocompatible microswimmers. In this review, the latest developments of microswimmers powered by ultrasound are presented. Ultrasound, especially at MHz frequencies, does little harm to biological samples and provides an advantageous and well-controlled means to efficiently power microswimmers. By critically reviewing the recent progress in this research field, an introduction of how ultrasound propels colloidal particles into autonomous motion is presented, as well as how this propulsion can be used to achieve preliminary but promising applications.

Consequences of Unusual Behaviour in Einstein's Field Equations for Advanced Propulsion Schemes

The notion of faster than light travel, passing through parallel universes, or even going back and forth in time is an interesting scientific issue. These activities are examined within Einstein's field equations from an engineering perspective to potentially create a suitable propulsion system. The evaluation revealed a set of circumstances that may lead to an anomalous gravitational distortion in what is normally referred to as the “vacuum field equation.” This can occur in a near flat space-time continuum without any electric, magnetic or torsion fields when the stressenergy tensor vanishes. The distortion, possibly created by a gravitational vortex, is driven purely by the gravitational tensor. The field equations also imply that unusual consequences may follow if one includes nonlinearities; off-diagonal terms in the gravitational or space-continuum tensors; more detailed boundary condition specifications or by creating systems that enjoy over-unity performance. Depending upon definition of the curvature tensor, this may lead to conditions for travel in a parallel universe, faster than light travel and past/future time travel. The problem is to include such conditions within a suitable propulsor design to explore unknowns within the cosmos.

Review: Laser-Ablation Propulsion

LASER ablation propulsion (LAP) is a major new electric propulsion concept with a 35-year history. In LAP, an intense laser beam [pulsed or continuous wave (CW)] strikes a condensedmatter surface (solid or liquid) and produces a jet of vapor or plasma. Just as in a chemical rocket, thrust is produced by the resulting reaction force on the surface. Spacecraft and other objects can be propelled in this way. In some circumstances, there are advantages for this technique compared with other chemical and electric propulsion schemes. It is difficult to make a performance metric for LAP, because only a few of its applications are beyond the research phase and because it can be applied in widely different circumstances that would require entirely different metrics. These applications range from milliwatt-average-power satellite attitude-correction thrusters through kilowatt-average-power systems for reentering near-Earth space debris and megawatt-to-gigawatt systems for direct launch to lowEarth orbit (LEO). We assume an electric laser rather than a gas-dynamic or chemical laser driving the ablation, to emphasize the performance as an electric thruster. How is it possible for moderate laser electrical efficiency to givevery high electrical efficiency? Because laser energy can be used to drive an exothermic reaction in the target material controlled by the laser input, and electrical efficiency only measures the ratio of exhaust power to electrical power. This distinction may seem artificial, but electrical efficiency is a key parameter for space applications, in which electrical power is at a premium. The laser system involved in LAP may be remote from the propelled object (on another spacecraft or planet-based), for example, in laser-induced space-debris reentry or payload launch to low planetary orbit. In other applications (e.g., the laser–plasma microthruster that we will describe), a lightweight laser is part of the propulsion engine onboard the spacecraft.

Basic Research on Heat Exchange Laser Propulsion

A scheme of laser propulsion using a heat exchange principle has been proposed. The scheme uses pressure of vaporized water (condensing steam nuclei) or other safe propellants and significantly reduces the complexity and technical hurdles of both engine structure and laser system compared to other laser propulsion schemes such as one utilizing laser ablation. In the proposed scheme, laser power is used for vaporization and overheating water molecule. To realize the scheme, CW-CO2 laser is adopted as a power source. This pap>Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, er describes the experimental characterization of laser radiation interaction with water vapor on which our thruster model design is based.

ARRADCOM/DARPA compact homopolar generator

If electromagnetic (EM) rail guns are to be used to propel substantial projectiles, large amounts of energy must be delivered in a fast, high-current pulse. Homopolar generators (HPGs) store megajoules (MJ) of energy in the inertia of a flywheel and then electromagnetically convert this energy into megampere (MA) current pulses that typically have a duration between a thousandth of a second and a second. These machines appear to be the most likely power supply for military rail guns, space launchers, and other large EM propulsion schemes. It is concluded that inertial energy storage with homopolar conversion provides the most suitable primary energy store for driving large EM rail guns. An assessment of the state-of-the-art of the various technologies relevant to pulsed HPG design, especially those limiting energy or power density was made. This evaluation concluded that HPG energy and power densities could be substantially improved by eliminating the back iron, which contributes to the mass of the machine but not the stored energy. 5 refs.

Performance Potential of the Colloid Core Reactor Concept in Near-Earth Applications

An Air Force research program has produced performance estimates for the colloid core nuclear reactor rocket engine concept. These values are parametrically varied to determine their individual influence on an advanced nuclear upper stage to the Space Transportation System. Pessimistic and optimistic performance of the concept is estimated. The concept is compared with other propulsion schemes on the basis of velocity capability (as an indication of performance) and the mass which must be initially boosted into orbit (as an indication of cost). Based upon the analysis, it is concluded that the concept warrants further consideration for development as a future operational system. (10 references) (auth)

COMBINED DIESEL‐GAS TURBINE POWER PLANTS IN COAST GUARD VESSELS

SUMMARYAs was pointed out in the beginning of this paper, the gas turbine as a means of marine propulsion, is making inroads into a field once dominated by steam turbines and diesel engines. More important, it is being realized to a greater extent, that the gas turbine when used in conjunction with other prime movers illustrates definite advantages to be realized. Most important of these is the high horsepower to weight ratio, even realizing at the same time the turbine's additional specific fuel consumption and added weight due to larger inlet and exhaust ducts.The two applications discussed previously are both of the CODAG variety with minor variations. CODAG was selected in both instances due to the fuel requirement for Coast Guard vessels of long range with good top speed characteristics. In both cases, the vessel can operate for most of its normal duties on the diesel engines, realizing the low specific fuel consumption of the diesel and hence the relatively long range produced. For top speed, the turbines are employed; in the 210 footer as a boost power plant, and in the 350 footer as the sole means of propulsion. In this manner it is felt that the most optimum plant was selected in each case to meet the various and many faceted duties of the Coast Guard.A conclusion to this paper cannot really be written. Only after successful vessel trials and successful operating experience can a purely objective conclusion be reached. It is the author's opinion, however, that more combined plants will be used for marine propulsion in the future, whether they be CODAG, COSAG, or COGAG. As the frequency of successful applications grow, the natural reluctance many feel toward these types of propulsion schemes will most certainly diminish, until someday gas turbines combined with other modes of propulsion will be as common as the presently out‐moded Scotch marine boiler and triple expansion engine.

The use of electrets in electrostatic generators for space

Electric propulsion schemes for space travel will be competitive only to the extent that electric power generation systems can be made extremely lightweight, efficient, and reliable. Electrostatic generators employing electrets have been designed and tested, with promising results. It is believed that further research in this area, particularly on new materials, will prove to be rewarding