Propulsion Options Research Articles

Overview of Clean Automotive Thermal Propulsion Options for India to 2030

This paper presents the evaluation of near-future advanced internal combustion engine technologies to reach near zero-emission in vehicles with in the Indian market. Extensive research was carried out to propose the rationalise the most promising, new ICE technologies which can be implemented in the vehicles to reduce CO2 emissions until the year 2030. A total of six technologies were considered that could be implemented in the Indian market. An initial market survey was carried out on the Indian automotive industry and electric vehicles in India, followed by an in-depth analysis and understanding of each technology through literature review. The main aim of the paper was to construct methods for a successful implementation of clean ICE technologies in the near future and to, also, predict a percentage reduction of CO2 tailpipe emissions from the vehicles. To do this, different objectives were laid out with a view to reducing the tailpipe CO2 emissions. Especially with the recent and legitimate focus on climate change in the world, this study aims to provide practical solutions pathway for India. Widespread research was carried out on all six technologies proposed within the automotive market in India and a set of main graphs represent CO2 emission reduction starting from 2020 until 2030. A significant reduction of CO2 was observed in the graph plot at the end of the paper and the technologies were successfully implemented for the Indian market to curb tailpipe CO2 emissions. A methodology based on calculating the vehicle fuel consumption was implemented and a graph was plotted showing the reduction of CO2 emissions until 2030. The starting point of the graph is 2020, when BS-VI comes into effect in India (April 2020). The CO2 limit taken into consideration here has been defined by the Government at 113 CO2 g/km. The paper fulfilled the aim of predicting the effects of implementing the technologies and the subsequent reductions of CO2 emissions for India.

Event-Driven Network Model for Space Mission Optimization with High-Thrust and Low-Thrust Spacecraft

Numerous high-thrust and low-thrust space propulsion technologies have been developed in the recent years with the goal of expanding space exploration capabilities; however, designing and optimizing a multimission campaign with both high-thrust and low-thrust propulsion options are challenging due to the coupling between logistics mission design and trajectory evaluation. Specifically, this computational burden arises because the deliverable mass fraction (i.e., final-to-initial mass ratio) and time of flight for low-thrust trajectories can vary with the payload mass; thus, these trajectory metrics cannot be evaluated separately from the campaign-level mission design. To tackle this challenge, this paper develops a novel event-driven space logistics network optimization approach using mixed-integer linear programming for space campaign design. An example case of optimally designing a cislunar propellant supply chain to support multiple lunar surface access missions is used to demonstrate this new space logistics framework. The results are compared with an existing stochastic combinatorial formulation developed for incorporating low-thrust propulsion into space logistics design; this new approach provides superior results in terms of cost as well as utilization of the vehicle fleet. The event-driven space logistics network optimization method developed in this paper can trade off cost, time, and technology in an automated manner to optimally design space mission campaigns.

LEU NTP Engine System Trades and Mission Options

The future of human exploration missions to Mars is dependent on solutions to the technology challenges being worked on by the National Aeronautics and Space Administration (NASA) and industry. One of the key architecture technologies involves propulsion that can transport the human crew from Earth orbit to other planets and back to Earth with the lowest risk to crew and the mission. Nuclear thermal propulsion (NTP) is a proven technology that provides the performance required to enable benefits in greater payload mass, shorter transit time, wider launch windows, and rapid mission aborts due to its high specific impulse and high thrust. Aerojet Rocketdyne (AR) has stayed engaged for several decades in working NTP engine systems and has worked with NASA recently to perform an extensive study on using low-enriched uranium NTP engine systems for a Mars campaign involving crewed missions from the 2030s through the 2050s. Aerojet Rocketdyne has used a consistent set of NASA ground rules and they are constantly updated as NASA adjusts its sights on obtaining a path to Mars, now via the Lunar Operations Platform-Gateway. Building on NASA’s work, AR has assessed NTP as the high-thrust propulsion option to transport the crew by looking at how it can provide more mission capability than chemical or other propulsion systems. The impacts of the NTP engine system on the Mars transfer vehicle configuration have been assessed via several trade studies since 2016, including thrust size, number of engine systems, liquid hydrogen stage size, reaction control system sizing, propellant losses, NASA Space Launch System (SLS) payload fairing size impact, and aggregation orbit. An AR study activity in 2018 included examining NTP stages derived from Mars crew mission elements to deliver extremely large cargo via multiple launches or directly off the NASA SLS. This paper provides an update on the results of the ongoing engine system and mission trade studies.

Plasma plume diagnostics of a LaB6 hollow cathode with triple Langmuir probes

High-power Hall Effect thrusters (HETs) represent an attractive propulsion option for the next-generation manned and robotic missions. The main challenging feature of these missions is a lifetime in the order of 104 hours required to the propulsion system. One of the most critical components of a HET is the cathode, used to emit electrons to sustain the discharge and to neutralize the ion beam. The main life-limiting factor of hollow cathodes designed for HETs is the material wear due to ion bombardment by the discharge plasma. The aim of this paper is to present the characterization of the electrical parameters and plasma plume properties of a hollow cathode. The effect of the cathode orifice geometry was also investigated, in terms of different length-to-diameter aspect-ratio (AR). Two ARs were analyzed to assess the effect of the orifice geometry on the plasma parameters and onset of unstable modes. The cathode analyzed, named HC20, is a hollow cathode developed for a mid-range power HET under development at SITAEL. The cathode was designed to provide discharge currents between 5 and 30 A, already characterized during previous experimental campaigns. The measurements in the plasma plume of the cathode were performed with triple Langmuir probes, one of which capable of scanning the plume along the cathode axis. The results show that a larger orifice AR can shift the transition to an unstable mode of operation of the cathode, named plume mode, at lower mass flow rate, increasing the cathode operative range.

Autoindustrie — auf dem richtigen Weg?

The German automotive industry is facing serious problems: After a long period of growth in production and exports, it threatens to lose its dominant position as a result of international trade disputes. But the requirements of the European climate protection targets also call for far-reaching change. However, this change does not only apply to the production of cars but also to the increasing demand for mobility services. Car-Sharing and better links between public and private transport will make it easier to achieve these goals. This is probably not possible simply by using new energy and propulsion options. Nevertheless, these drastic changes also mean drastic changes in the production and distribution system.

An analytical model for characterizing the thrust performance of a Low-Pressure Micro-Resistojet

There is a clear trend towards the developments of micro-propulsion system to enhance the capabilities of nano- and pico-satellites. A promising propulsion option to meet the strict requirements of these small satellites is the Low-Pressure Micro-Resistojet (LPM) which works under rarefied gas dynamic regime. To simplify the engineering design of this propulsion system an analytical model has been developed using the fundamental physical models. This analytical model is based on the Kinetic theory of gases and the Maxwell-Boltzmann distribution of molecular velocities to describe the macroscopic flow parameters such as mass flow rate, velocity and pressure, and then to estimate the thruster performance. The equations are well known, but they are applied in this case using a particular approach in order to describe the physics behind this micro-propulsion system. Comparisons between numerical simulations using the Direct Simulation Monte Carlo method and the results of the analytical model, as well as experimental results, have been carried out. The analytical model using an accurate estimation of the transmission coefficient compared to the numerical simulation presents a maximum difference of 3%.

High-pressure thermo-chemical recuperation – a way toward sustainable propulsion systems

To meet GHG emission targets and to decrease oil dependency, overall energy consumption of road vehicles must be substantially reduced. Various types of propulsion technologies are under consideration, like internal combustion engine (ICE), hybrid electric (HE), plug-in hybrid electric (PHE), range extended electric (REE), electric battery, fuel cell, etc. The article provides a comparison of various propulsion technologies and arrives to the conclusion that internal combustion engines (ICEs) will be a major propulsion option in the foreseen future with massive penetration of hybrid vehicles to global markets. Utilization of more energy-efficient ICEs together with low-carbon-intensity fuels is, therefore, of great importance on a way toward development of sustainable propulsion systems. About one-third of fuel energy introduced to ICE is wasted with engine exhaust gases. A promising way of engine’s waste heat recovery is by using the energy of the exhaust gases to sustain endothermic reactions of fuel reforming. This approach is called Thermo-Chemical Recuperation (TCR).We go beyond the previous studies in this field by applying direct injection of the reformate gas together with the high-pressure steam-reforming process. We aim at developing a high-pressure TCR-ICE set as a part of a series hybrid propulsion system, thus alleviating the acute problems of the reformer’s startup and transient behavior. The obtained experimental results showed that engine energy efficiency is improved by 18%-39% (higher values at lower loads) and pollutant emissions are reduced by 73-94%, 90-96%, 85-97%, 10-25% for NOx, CO, HC and CO2 emissions, respectively, compared with gasoline in a wide power range, without any need in exhaust gas aftertreatment.

Electrostatic/magnetic ion acceleration through a slowly diverging magnetic nozzle between a ring anode and an on-axis hollow cathode

Ion acceleration through a slowly diverging magnetic nozzle between a ring anode and a hollow cathode set on the axis of symmetry has been realized. Xenon was supplied as the propellant gas from an annular slit along the inner surface of the ring anode so that it was ionized near the anode, and the applied electric potential was efficiently transformed to an ion kinetic energy. As an electrostatic thruster, within the examined operation conditions, the thrust, F, almost scaled with the propellant mass flow rate; the discharge current, Jd, increased with the discharge voltage, Vd. An important characteristic was that the thrust also exhibited electromagnetic acceleration performance, i.e., the so-called “swirl acceleration,” in which F≅JdBRa ∕2, where B and Ra were a magnetic field and an anode inner radius, respectively. Such a unique thruster performance combining both electrostatic and electromagnetic accelerations is expected to be useful as another option for in-space electric propulsion in its broad functional diversity.

시스템 구성에 따른 정지궤도 발사체의 임무성능 비교

시스템 구성에 따른 정지궤도 발사체의 임무성능 비교

Plume Characterization of Electric Solid Propellant Pulsed Microthrusters

Electric solid propellants are an attractive option for propulsion because they are ignited only by an applied electric current. This leads to capabilities such as on-demand throttling and reignition in chemical combustion operation, and it lends itself to application in electric propulsion. In this work, the plasma plume created by electric solid propellant pulsed microthrusters is investigated using a nude Faraday probe, a triple Langmuir probe, and residual gas analysis. The thrusters are tested at a vacuum level of . Results indicate an average plume electron temperature of 1.7 eV and a density of to . A time-of-flight analysis indicates an exhaust velocity of on the centerline. Additionally, ionization fraction is estimated to be 0.3% for an ablation mass bit of on average. Thermal equilibrium and adiabatic expansion calculations suggest a nonequilibrium gas with high-temperature electrons and lower-temperature neutral and ion species. Results indicate the pulsed microthruster operates similar to a coaxial pulsed plasma thruster, which is dominated by electrothermal effects.

Propulsion options for very low Earth orbit microsatellites

The growing competitiveness in the commercial space market has raised the interest in operating small spacecraft at very low altitudes. To make this feasible, the space industry has started developing propulsion options tailored specifically to these platforms. This paper presents a review of emerging micropropulsion technologies and evaluates their applicability to microsatellite missions in the altitude range 250–500km. The results of the proposed analysis are demonstrated on two different remote sensing applications.

A Novel Gas Generator Concept for Jet Engines Using a Rotating Combustion Chamber

A gas generator—consisting of a single-stage shrouded mixed-flow compressor without a diffusor, a rotating combustion chamber, and a vaneless single-stage shrouded centripetal turbine—is presented and analyzed here. All components comprise a coherent rotating device, which avoids most of the problems usually associated with small gas generators. In other words, the concept avoids all radial clearances; it is vaneless, shortens the combustion chamber, minimizes the wetted area, and enables ceramic materials to be used, due to compressive blade stresses. However, the concept faces severe structural, thermal, and chemical reaction challenges and is associated with a large Rayleigh-type total pressure loss. All these features and their implications are discussed and their benefits and drawbacks for several jet engines are quantified, mainly by means of thermodynamic cycle calculations. As a result, it has been demonstrated that the concept offers a thrust-to-weight ratio which is higher than the standard when incorporated into small unmanned aerial vehicles (UAV)-type jet engines. It also enables an attractive multistage and dual-flow, but fully vaneless design option. However, the concept leads to a decrease in thermal efficiency if these were to be accomplished in the (small) core of turbofans with highest overall pressure ratios (OPRs) and high bypass ratios. In summary, the paper presents a gas generator approach, which may be considered by designers of small jet engines with high power density requirements, like those used in UAV applications. But this has been proven not to be an option for high-efficiency propulsion.

What does the future bring? A look at technologies for commercial aircraft in the years 2035–2050

Demographics and economics in the next 20 years are being examined. They reflect a significant GDP growth and with this a strong demand for commercial aircraft not only in the US and Europe but across Asia and the Middle East. The demand will focus on more fuel efficient and more environmentally friendly vehicles.Significant progress is being made with the new regionals, narrow-body, and wide-body aircraft between now and the year 2020. Looking beyond, the world will examine new airplane architectures, new changes in propulsion systems, and higher thermal and propulsion efficiencies. Distributed propulsion options will come into play. With them, higher operating pressure gas generators will be developed and great attention will have to be given to highly integrated propulsion/airplane systems. Energy transfer requirements will lead to bigger gear systems as well as new hybrid systems. The new machines are forecasted to offer improvements in fuel efficiencies of over 40%.There are many technical challenges to make all these things happen. The aerospace engineers and scientists of today and tomorrow face unlimited opportunities to make a difference for what looks like a very exciting future.

Solar Electric Propulsion for Discovery-Class Missions

This paper offers a user-centric consolidation and comparison of the full range of government and commercial solar electric propulsion options available in the near term for primary propulsion on deep-space science missions of the class commonly proposed to NASA’s Discovery program. Unlike previous papers, this work does not emphasize feasibility from a mission-analysis perspective. Rather, it emphasizes requirements uniquely imposed by competitively reviewed cost-capped mission proposals, for which system-level flight heritage and cost credibility can trump sheer performance and mission capture. It describes criteria that mission architects and review boards can use to select and evaluate electric propulsion systems, provides descriptions of viable government and commercial electric propulsion system options, describes the modifications needed to adapt commercial electric propulsion systems to deep space, and discusses appropriate methods for costing commercial-based electric propulsion systems. It concludes that the solar electric propulsion systems best suited for Discovery missions have a solid system flight heritage that can meet the requirements for deep space with minimal modifications. Commercially developed electric propulsion systems offer significant heritage potential and, in many cases, the required changes for deep-space application introduce comparatively low technical and cost risk.

Overview of alternative fuels with emphasis on the potential of liquefied natural gas as future marine fuel

Economic and population growths are the most important drivers of growing global energy demand. They led to a rapid development of international seaborne trade and an increase in the number of global vessels. Air pollution from these ships is of great concerns and regulations are currently enforced since May 2005 by the International Maritime Organization to limit such pollution. In this study, we will first review the current global energy demand and its driving forces over next decades, second evaluate the existing alternative fuels that can be used as a bunker fuel to reach sustainability with relatively small changes in the existing marine propulsion options and finally focus on near-term solution, which has the potential for large-scale use. The different alternative fuels were compared in terms of several parameters such as availability, renewability, safety, cost, performance, economy and compliance with emission regulations. This comparison revealed that liquefied natural gas could be considered as the future replacement to the current marine bunker fuel. This conclusion has been further verified by comparing diesel engine with different powers when using both heavy fuel oil and liquefied natural gas. The engines were compared against fuel consumption, cost saving as well as emissions. Liquefied natural gas has proved to be better than heavy fuel oil due to fuel cost reduction by about 31% per year and decrease in emissions of SOx, NOx, CO2 and particulate matter by about 98%, 86%, 11% and 96%, respectively. The resulted emissions from using liquefied natural gas were found to comply with the current International Maritime Organization regulations. Moreover, this article highlights the latest rules and regulations that govern the use of liquefied natural gas as marine fuel onboard ships.

GTOC5: Results from the European Space Agency and University of Florence

This paper describes the methodologies used to tackle the problem of the 5th Global Trajectory Optimization Competition within the team composed by the Advanced Concepts Team of the European Space Agency and theGlobal Optimization Laboratory of the University of Florence. The method pursued is powered by two innovative approaches: a linearized model of the ‘self fly-by’ aiding a first broad tree search of chemical propulsion options and the use of global optimization techniques (Monotonic Basin Hopping, in this case) applied directly to the low-thrust trajectory model.

Investigation of propulsion system for large LNG ships

Requirements to move away from coal for power generation has made LNG as the most sought after fuel source, raising steep demands on its supply and production. Added to this scenario is the gradual depletion of the offshore oil and gas fields which is pushing future explorations and production activities far away into the hostile environment of deep sea. Production of gas in such environment has great technical and commercial impacts on gas business. For instance, laying gas pipes from deep sea to distant receiving terminals will be technically and economically challenging. Alternative to laying gas pipes will require installing re-liquefaction unit on board FPSOs to convert gas into liquid for transportation by sea. But, then because of increased distance between gas source and receiving terminals the current medium size LNG ships will no longer remain economical to operate. Recognizing this business scenario shipowners are making huge investments in the acquisition of large LNG ships. As power need of large LNG ships is very different from the current small ones, a variety of propulsion derivatives such as UST, DFDE, 2-Stroke DRL and Combined cycle GT have been proposed by leading engine manufacturers. Since, propulsion system constitutes major element of the ship's capital and life cycle cost, which of these options is most suited for large LNG ships is currently a major concern of the shipping industry and must be thoroughly assessed. In this paper the authors investigate relative merits of these propulsion options against the benchmark performance criteria of BOG disposal, fuel consumption, gas emissions, plant availability and overall life cycle cost.

The future of natural gas as a fuel in marine gas turbine for LNG carriers

This paper discusses the suitability of using natural gas as a fuel for marine gas turbine electric propulsion (DFGE), utilizing natural boil-off gas and forced boil-off gas, as well as investigating its economical and environmental benefits over other propulsion options. The benchmark ship chosen for this study has a capacity of 150,000 m3 and is powered by conventional steam propulsion. For this purpose a spreadsheet model was developed to determine the liquefied natural gas carrier operating costs for different propulsion options. This is in addition to a sensitivity analysis to study the effect of varying range, heavy fuel oil (HFO) and natural gas prices on ship operating cost. Recently, about 40% of the new orders shifted to slow speed diesel engines with re-liquefaction plant and dual fuel diesel electric propulsion. To date, marine gas turbines are not used in liquefied natural gas carriers. It was found that using natural gas as a fuel with the proposed marine gas turbine cycle at current HFO and natural gas prices provides the highest cost saving for a distance less than 4000 nautical miles (NM). With the expected changes in fuel prices, the proposed cycle achieves cost saving of 3% per round trip, and this saving is directly proportional to increasing fuel prices, compared to other options.

Application of electrical propulsion for an active debris removal system: a system engineering approach

One of the main challenge in the design of an active removal system for space debris is the high ΔV required both to approach space debris lying in different orbits and to de-orbit/re-orbit them. Indeed if the system does not target a number of objects during its lifetime the cost of the removal will be far too high to be considered as the basis of an economically viable business case. Using a classical chemical propulsion (CP) system, the ΔV is limited by the mass of propellant that the system can carry. This limitation is greatly reduced if electrical propulsion is considered. Electrical propulsion (EP) systems are indeed characterized by low propellant mass requirements, however this comes at the cost of higher electrical power and, typically, higher complexity and mass of the power supply system. Because of this, the use of EP systems has been, therefore, primarily limited to station keeping maneuvers. However in the recent past, the success of missions using EP as primary propulsion (e.g. GOCE, SMART-1, Artemis, Deep Spcae1, Hayabusa) makes this technology a suitable candidate for providing propulsion for an active debris removal system. This study case will provide the analysis of the possible application of electrical propulsion systems in such a context, presenting a number of possible mission profiles. This paper will start with the description of possible mission concepts and the assessment of the EP technology, comparing near-term propulsion options, that best fits the mission. A more detailed analysis follows with the relevant trade-off to define the characteristics of the final system and its size in terms of mass and power required. A survey of available space qualified EP systems will be performed with the selection of the best candidates to be used and/or developed for an active debris removal system. The results of a similar analysis performed for a classical CP system are then presented and the two options are compared in terms of total cost of the mission.The output of this study case shows that the EP is a suitable solution in a very demanding ΔV system such as active debris removal satellites and that the current technology is sufficiently mature to be used in the very near future.

Single-Channel Hollow Cathodes in 5–20-eV Argon Discharge for Spacecraft Thruster Applications

High-power magnetoplasmadynamic (MPD) thrusters are an attractive option for providing primary propulsion on flagship-class spaceflight missions beyond the Low Earth Orbit (LEO), such as piloted Mars and Mars cargo, and more near-term cargo missions supporting a crewed lunar outpost due to their unique ability to process large amounts of power in a relatively small footprint size. This results in significant savings in system mass and volume over competing propulsion options such as ion or Hall-effect thrusters. This paper presents a partial summary of data from recent research at the University of Southern California, in collaboration with NASA's Jet Propulsion Laboratory, investigating several concerns of the mechanisms influencing the performance and lifetime of high-current single-channel hollow cathodes (SCHCs), the central electrode, and the primary life-limiting component in MPD thrusters. The overall objective of such research is to extend the operational lifetime of the cathode to mission-enabling lengths, generally considered to be in the range of 5-10 000 h. Specifically covered are the trends seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), the cathode exit plume plasma density and energy, and the plasma property distributions of the internal plasma column of an SCHC.