Propulsion Concepts Research Articles

Multi-disciplinary design investigation of propulsive fuselage aircraft concepts

Purpose Motivated by the potential of gaining noticeable improvements in vehicular efficiency, this paper aims to investigate the benefits attainable from introducing a more synergistic propulsion/airframe integration. In previous work, the concept of a boundary layer ingesting propulsor encircling the aft section of an axisymmetric fuselage was identified to be particularly promising for the realisation of aircraft wake filling, and hence, a significant reduction of the propulsive power required. Design/methodology/approach After reviewing the theoretical principles of the propulsive fuselage concept, a book-keeping and model matching procedure is introduced, which is subsequently used to incorporate the numerically computed aerodynamic characteristics of a propulsive fuselage aircraft configuration into a propulsion system (PPS) sizing and performance model. As part of this, design heuristics for important characteristics intrinsic to propulsive fuselage power plants are derived. Thereafter, parametric study results of the PPS are discussed, and the obtained characteristics are compared to those of a conventionally installed power plant. Finally, the impact of the investigated PPS on the integrated performance of a propulsive fuselage aircraft concept is studied, and the results are compared and contrasted to previously conducted analyses based on semi-empirical characteristics. Findings It was found that the aircraft-level benefit originally predicted based on semi-empirical methods could be confirmed using the numerically derived PPS design heuristics, specifically an improvement in vehicular efficiency of 10.4 per cent over an advanced conventional reference aircraft. Practical implications The approach presented in the paper may serve as a guideline when incorporating the results of high-fidelity aerodynamic methods into a PPS sizing and performance model suitable for aircraft-integrated assessment of a propulsive fuselage concept. The vehicular efficiency potentials offered through the synergistic PPS integration approach are highlighted. Originality/value The paper contributes to a deeper understanding of the characteristics of a boundary layer ingesting fuselage fan (FF) power plant relative to a conventionally installed PPS. In addition, a set of PPS design correlations are presented allowing for the integrated sizing of a FF power plant.

Trajectory tracking control of electric sail with input uncertainty and saturation constraint

The electric sail (ES) is a novel propellantless propulsion concept, which extracts the solar wind momentum by repelling the positively charged ions. Due to the difficulty of attitude adjustment by the large flexible structure and the uncertainty of ion density, velocity and electron temperature by solar wind, there exist thrust input uncertainty and saturation with time-varying bounds for ES. The trajectory tracking problem for ES in three-dimensional (3-D) space is studied, and the composite sliding mode control scheme with corresponding guidance strategy is proposed for the single-input–multiple-output (SIMO) non-linear system. The hierarchical sliding surfaces are constructed with an auxiliary design system to analyse the effect of input saturation constraints and decouple the SIMO non-linear system to reduce the control complexity. Also, the disturbance estimation based on a super-twisting algorithm is employed to decrease the switch chattering and improve the system robustness. It is proved that all the sliding mode surfaces are asymptotically stable, and all the signals of the closed-loop system are bounded with input saturation constraints. Furthermore, all the signals are converging to zero and the closed-loop system is asymptotically stable without saturation. Finally, the simulation demonstrates the proposed composite sliding mode control is fit for ES 3-D trajectory tracking.

Validation of laser‐induced thermal acoustics for chemically reacting H2/air free jets

The scramjet engine is a promising propulsion concept for future space transportation systems. To enhance the engine efficiency, a strong understanding of combustion mechanisms is essential. Laser‐induced thermal acoustics (LITA) – a seedless, non‐intrusive measurement technique – is an auspicious technique for the investigation of supersonic combustion. Here, we present two validation cases and first LITA measurements in a chemically reacting hydrogen/air free jet. The first validation case is the investigation of premixed methane/air and hydrogen/air flames, produced with a commercially available flat flame burner. The comparison with coherent anti‐Stokes Raman spectroscopy measurements resulted in a deviation between the two measurement techniques smaller than the uncertainty of the techniques. The second validation case is the investigation of hot, supersonic air/air free jets at total temperatures of Tt = 1050 K and Tt = 1300 K. The comparison with computational fluid dynamics predictions shows a reasonable agreement with a maximum deviation of 13.9% for the free jet with a temperature of Tt = 1300 K and a good agreement with a maximum deviation of 4.4% for the free jet with a temperature of Tt = 1050 K. The LITA measurements in a chemically reacting hydrogen/air free jet showed a good reproduction of the flame position determined from an OH∗ image. For the presented investigations, we used a homodyne, resonant LITA setup with a pulsed interrogation beam. Copyright © 2016 John Wiley & Sons, Ltd.

Electric vehicle dynamics control during electrical system faults

This paper focuses on a propulsion concept for electric vehicles (EVs). The considered actuators consisting of permanent magnet synchronous machines and the conventional hydraulic braking system are mounted on the rear axle of the vehicle and offer new degrees of freedom in vehicle motion control. The proposed control structure consists of cascaded feedback loops for wheel slip, yaw rate and sideslip angle and accesses these actuators concurrently. The focus of the present work is on possible machine/inverter faults. Two characteristic electrical system faults are described, and their impacts on vehicle stability are investigated. It is shown how the proposed vehicle motion controller can preserve driving safety even in the presence of electric system faults. The consequences on vehicle motion are discussed in detail.

Robust model of a transient wind tunnel for off-design aerothermal testing of turbomachinery

Short duration wind tunnels offer an economical approach to study the aero-thermal operation of propulsion components, while reproducing temperature ratios, Reynolds and Mach numbers of the actual engine conditions. The present paper aims at modeling with high fidelity the von Karman Institute compression tube facility. This wind tunnel was simulated using the EcosimPro suite to characterize the behavior of each subcomponent during the whole test envelope, including the turbine map at off-design. The numerical predictions were then assessed through the comparison with experimental data. The model was proven to be an effective tool to accurately evaluate all the operating regimes that a research turbine experienced during the experimental sequence. Consequently, the present model allows exploiting the complete test run duration to obtain unique experimental data from the turbomachinery operating at far off-design conditions. The capability to experimentally test components at off-design is fundamental to understand the flow physics of any gas turbine engine operating at extreme conditions and to characterize the transient performances of fluid-machinery in high-speed propulsion concepts. However, technical dissemination on these aspects is scarce.

Drag and propulsive forces in electric sails with negative polarity

An electric solar sail (E-sail) is a recent propellantless propulsion concept for a direct exploration of the Solar System. An E-sail consists of a set of bare, conductive tethers at high positive/negative bias, prone to extract solar wind momentum by Coulomb deflection of protons. Additionally, a negatively biased E-sail has been proposed as a concept for de-orbiting space debris with drag forces produced in Low Earth Orbit (LEO). The present work focuses on the negative-bias case with a sheath that must be correctly modeled for a flowing plasma ambient. Ion scattering within the sheath and the resulting force are determined for several plasma conditions. Since the plasma flow does reduce the effective range for the ion scattering within the sheath, the resulting force is then reduced. Tethers at very high negative bias should be required for extremely high plasma flow.

Nanoengineered thrusters for the next giant leap in space exploration

Abstract

Propulsive Force in an Electric Solar Sail for Outer Planet Missions

An electric solar sail (E-sail) is a recent propellantless propulsion concept for a direct exploration of the solar system. An E-sail consists of an array of bare, conductive tethers at very high positive/negative bias, prone to extract solar-wind momentum by Coulomb deflection of protons. This paper focuses on the positive-bias case with a thick sheath that must be correctly modeled. Ion scattering within the sheath and the resulting thrust are determined. Use of E-sail for outer planet missions would reduce the time of flight; a 2-ton spacecraft might reach Jupiter in less than two years.

Platinum Catalysts Development for 98% Hydrogen Peroxide Decomposition in Pulsed Monopropellant Thrusters

A number of platinum catalysts for the decomposition of 98% hydrogen peroxide, based on different substrates, geometries, and sizes, have been prepared using different procedures. The catalysts have undergone a set of dedicated tests for screening their catalytic activity and their thermomechanical resistance in order to identify the most efficient and suitable catalyst to be used for a pulsed monopropellant propulsion system. An experimental test campaign on a 20 N monopropellant thruster prototype has been carried out with the aim of assessing the capability of the finally selected new catalysts of effectively decomposing 98% hydrogen peroxide and the attainable propulsive performance in steady-state conditions for the future assessment of the propulsive performance of the intrinsically unsteady new propulsion concept. The catalysts have been able to decompose up to 1 liter of 98% with very good efficiencies ( and ) and without any pellet breakage or catalytic degradation. The thrust profile has been particularly smooth and the experimental specific impulse measured at sea level with the matched conical nozzle has been 130 s, which corresponds to an extrapolated vacuum specific impulse for a high-expansion-area-ratio bell-contoured nozzle higher than 185 s.

Wrecker: an unreeling mechanism for a thin electrically conductive space tether

This paper presents the development of a deployment mechanism for the first demonstration mission of the Electrical Sail (Esail) propulsion concept. The mechanism will fly on Estonia’s first satellite, the EstCube-1 picosatellite. The major goals of this mission are the deployment of a 10-m tether by the WRECKER mechanism and the positive charging of the tether to interact with Earth’s ionosphere. The force acting on the tether will be measured to demonstrate the functionality of the Esail concept. The WRECKER mechanism can be further established as a standard tether deployment mechanism for deorbiting picosatellites.

Thermonuclear Operation Space Lift

The “Project Orion” small fission bomb propulsion concept proposed the one-stage launching of large payloads into low Earth orbit, but it was abandoned because of the radioactive fallout into Earth’s atmosphere. The idea is here revived by the replacement of the small fission bombs with pure deuterium–tritium fusion bombs, and the pusher plate of Project Orion with a large magnetic mirror. The ignition of the thermonuclear fusion reaction is done by the transient formation of keV super-explosives under the high pressure of a convergent shock wave launched into liquid hydrogen propellant by a conventional high explosive.

Research on the Influence of Reflected Shock Wave on Continuously Rotating Detonation Engine

The Continuously Rotating Detonation Engine (CRDE) is a new concept of aerospace propulsion. The detonation wave propagatescircumferentiallyaround the annular combustor with only one ignition. Compared with conventional engines with deflagration or other detonation engines, CRDEs are simpler, more powerful and more stable. The experimentsof this study are carried out with hydrogen/oxygen.Influences of reflected shock wave reduced by the groove on the wall of combustor and by obstacles downstream are discussed. Experimental results show that small groove or indentations on the combustor wall does not affect detonation waves a lot. But downstream obstacles may result in strong reflected shock wave and kills the detonation waves.

Methods for simulation and analysis of hybrid electric propulsion systems

Today, research performed for new aircraft propulsion concepts is driven by the requirement of achieving significant emission reductions to meet the environmental objectives of future air traffic. A current trend visible in the aviation industry shows the attempt to reduce inflight emissions as well as overall energy consumption of conventional combustion engines through electrification via electrical energy sources. With the growing interest in novel hybrid electric propulsion concepts, in the same way, a demand for conceptual design and performance simulation methods in combination with analysis capabilities rises. Based on primarily introduced and discussed hybrid electric propulsion systems, this paper presents a set of aircraft propulsion system simulation (APSS) methods which allow for an integrated simulation and consistent analysis. Particularly, methods for the modelling of electric motor and battery systems as implemented in APSS are described in detail.

Turboelectric distributed propulsion benefits on the N3-X vehicle

Purpose – The purpose of this article is to present a summary of recent study results on a turboelectric distributed propulsion vehicle concept named N3-X. Design/methodology/approach – The turboelectric distributed propulsion system uses multiple electric motor-driven propulsors that are distributed on an aircraft. The power to drive these electric propulsors is generated by separately located gas turbine-driven electric generators on the airframe. To estimate the benefits associated with this new propulsion concept, a system analysis was performed on a hybrid-wing-body transport configuration to determine fuel burn (or energy usage), community noise and emissions reductions. Findings – N3-X would be able to reduce energy consumption by 70-72 per cent compared to a reference vehicle, a Boeing 777-200LR, flying the same mission. Predictions for landing and take-off NOX are estimated to be 85 per cent less than the Tier 6-CAEP/6 standard. Two variants of the N3-X vehicle were examined for certification noi...

Parametric design studies for propulsive fuselage aircraft concepts

Breaking with the classical separation of airframe and power plant system, new synergy effects may be rooted in close design coupling and the approach of distributing the production of thrust along the main components of the airframe. Beside greater configurational flexibility, airframe structural relief, improved noise shielding, and, the potential for control power augmentation, distributed propulsion is particularly interesting due to the reduced propulsive power demands expected from the notion of aircraft wake filling. In previous work, the concept of a propulsor encircling the aft fuselage with intent to entrain the fuselage boundary layer was identified to be one of the most promising concepts for aircraft wake filling. In this paper, the analytical basis for the quantification of efficiency benefits connected to the propulsive fuselage concept is discussed. Appropriate control volume and consistent efficiency chain definitions are introduced. A simplified boundary layer model is derived from axisymmetric fuselage CFD simulation and used to determine the momentum deficit ingested by the fuselage propulsor. Based on a novel figure of merit for vehicular efficiency, the energy-specific air range, ESAR, the dependency of aircraft cruise efficiency on basic propulsion system and aircraft design changes is parametrically investigated. Specifically, the sensitivities of vehicular efficiency w.r.t. wing aspect ratio and flow transition characteristics, propulsor size, and aircraft design cruise Mach number are studied.

Fast E-sail Uranus entry probe mission

The electric solar wind sail is a novel propellantless space propulsion concept. According to numerical estimates, the electric solar wind sail can produce a large total impulse per propulsion system mass. Here we consider using a 0.5N electric solar wind sail for boosting a 550kg spacecraft to Uranus in less than 6years. The spacecraft is a stack consisting of the electric solar wind sail module which is jettisoned roughly at Saturn distance, a carrier module and a probe for Uranus atmospheric entry. The carrier module has a chemical propulsion ability for orbital corrections and it uses its antenna for picking up the probe׳s data transmission and later relaying it to Earth. The scientific output of the mission is similar to what the Galileo Probe did at Jupiter. Measurements of the chemical and isotope composition of the Uranian atmosphere can give key constraints to different formation theories of the Solar System. A similar method could also be applied to other giant planets and Titan by using a fleet of more or less identical probes.

Complex composition and exquisite architecture of bacterial flagellar propellers

Flagellum-propelled swimming is one of the most efficient means of locomotion used by bacteria to search for optimal concentrations of nutrients. The archetype of a flagellum comprises structures called the basal body, hook, and filament. The assembly of flagellar propeller is a temporally and spatially controlled process that involves the products of approximately 50 genes. Our knowledge of the structures of flagella and their propulsive mechanisms comes from research on a limited number of bacterial species. Recent studies of marine magnetotactic bacteria reveal an unprecedented compositional complexity and highly exquisite architecture of their flagellar apparatus. Twelve filament subunits (flagellins), presenting in more than 20 glycosylated isoforms, assemble into 7 flagella, which together with 24 fibrils, are arranged into 7 intertwined hexagonal arrays enveloped by a sheath. This flagellar architecture, which is known only for magnetotactic cocci dwelling in marine sediments, might have evolved during ecological differentiation. Further, this exquisite structure challenges the current concept of the flagellar assembly and propulsion and offers an inspirational challenge to our efforts to gain a better understanding of the assembly and evolution of bacterial surface appendages.

Propulsive Force in an Electric Solar Sail

AbstractAn electric solar sail (e‐sail) is a promising propellantless propulsion concept for the exploration of the Solar System. An e‐sail consists of an array of bare conductive tethers at very high positive/negative bias, capable of extracting solar‐wind momentum by Coulomb deflection of protons. The present work focuses on the positivebias case with a potential profile that must be correctly modeled. Ion scattering does occur at some point of the profile and the resulting thrust is determined; that thrust scales slower with distance to the Sun, than it was previously suggested in the literature. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

MAAT – Promising innovative design and green propulsive concept for future airship's transport

Airships were the first air vehicles, which had the ability to generate lift without the use of aerodynamic flow around wings, also to enable controlled, powered flight, providing long endurance at low energy consumption. They were widely used before the 1940s, but their use decreased as their capabilities were exceeded by those of the airplanes. Their decline continued with a series of several accidents, including the burning of the hydrogen-filled Hindenburg, and the destruction of the USS Akron.Nowadays, airships are used in certain applications: cargo transportation, tourism, aerial observations and many others, where the ability to hover in one place for an extended period of time is important.In Europe the reborn of airships is being supported by the European Union, recently providing financing for Project MAAT – Multibody Advanced Airship for Transportation, supported by 7 FP Program. This project, comprises twelve research institutions, introduces the concept of feeder–cruiser airship for transportation of people and goods. The main idea is to use a cruiser (PTAH)–feeder (ATEH) concept to allow transport of people and goods [9,10,47]. For this novel airship concept a new envelope and propulsion concept design is envisaged.The present study deals with the methodology and results for numerical modeling and research on airship with an innovative shape and implementation of its unconventional propulsion system.Attention has been paid to the logical sequence and obtained results for modeling and research of an airship with innovative shapes.The innovative design concept is analyzed and comprised with classic airship shape in point of aerodynamic and energetic needs. It was found that the classic airship shape provokes many problems, which are mainly referred to as high bending moments, in case of given buoyancy volume and optimal fineness ratio. The newly proposed shape needs an extensive research, which cannot rely on classic approach for drag coefficient calculations.Furthermore, based on the research results and conclusions for the airship shape, aerodynamic features at given altitudes and the propulsion needs, a feasible and innovative propulsion concept air-jets, is analyzed. Attention was focused on the performance of the air-jets working with high mass flow rates and low jet flow speeds.The outcome of the research highlights the opportunities for future developments of the propulsion concepts for airships with innovative shape as it is a very important and promising area in nowadays air-vehicles technology.

Relativistic rocket: Dream and reality

The dream of interstellar flights persists since the first pioneers in astronautics and has never died. Many concepts of thruster capable to propel a rocket to the stars have been proposed and the most suitable among them are thought to be photon propulsion and propulsion by the products of proton–antiproton annihilation in magnetic nozzle. This article addresses both concepts allowing for cross-section of annihilation among other issues in order to show their vulnerability and to indicate the problems. The concept of relativistic matter propulsion is substantiated and discussed. The latter is argued to be the most straightforward way to build-up a relativistic rocket firstly because it is based on the existing technology of ion generators and accelerators and secondly because it can be stepped up in efflux power starting from interplanetary spacecrafts powered by nuclear reactors to interstellar starships powered by annihilation reactors. The problems imposed by thermodynamics and heat disposal are accentuated.