Propulsion Concepts Research Articles

The Jet Age, Continued

The Jet Age, Continued

Theoretical components of the VASIMR plasma propulsion concept

The ongoing development of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) involves basic physics analysis of its three major components: helicon plasma source, ion cyclotron-resonance heating module, and magnetic nozzle. This paper presents an overview of recent theoretical efforts associated with the project. It includes (1) a first-principle model for helicon plasma source, (2) a nonlinear theory for the deposition of rf-power at the ion cyclotron frequency into plasma flow, and (3) a discussion of the plasma detachment mechanism relevant to VASIMR.

Biefeld-Brown Effect: Misinterpretation of Corona Wind Phenomena

With its theoretical origins dating back to the early 1920s, the Biefeld‐Brown effect was believed to be responsible for the generation of thrust in capacitor configurations exposed to high voltage. This thrust was claimed to be unrelated to corona wind phenomena and to exist in vacuum. These claims, although only published in patents, survived until recent publications for very advanced propulsion concepts. Brown’s and similar work, as well as credible theoretical and experimental studies relating to the Biefeld‐Brown effect, are reviewed. Moreover, an experiment was carried out to investigate any thrust not related to corona discharges. No thrust was detected within the accuracy of the experimental setup. This puts new boundaries on any anomalous Biefeld‐Brown force. Measurements indicate that such anomalous force must be at least five orders of magnitude below corona wind phenomena and must have at least a two orders of magnitude higher power-to-thrust ratio compared to traditional electric propulsion thrusters. Hence, even if the effect exists, it would not be attractive for space propulsion. The obtained results suggest that corona wind effects were misinterpreted as a connection between gravity and electromagnetism.

A realistic interstellar explorer

For more than 20 years, an “Interstellar Precursor Mission” has been discussed as a high-priority mission for multiple scientific objectives. The chief difficulty with actually carrying out such a mission is the need for reaching significant penetration into the interstellar medium (∼1000 Astronomical Units (AU)) within the working lifetime of the initiators (<50 years). While there has been much speculation on various aspects of such a mission, we have systematically considered all of the components required, using realistic extrapolations of current and near-current technology. To provide a first-order cut at many of the engineering realities associated with such a mission, we consider a probe that can be launched with available vehicles and infrastructure. To implement the mission, we have revisited an old idea: the probe and a perihelion carrier are launched initially to Jupiter as a combined package and then fall to the Sun where a large propulsive maneuver propels the package on a high-energy, ballistic escape trajectory from the solar system. Outbound in deep space, the two separate, and the probe takes data with its onboard instruments and autonomously downlinks the data to Earth at regular intervals. The implementation requires a low-mass, highly-integrated spacecraft. Engineering issues separate into (1) the systems constraints imposed on the perihelion package by the combination of the propulsion system, carrying the needed propellant into perihelion, and the associated thermal and mechanical constraints, and (2) the requirements of power, autonomous operations, and data downlink from the probe itself. System trades define the minimum mass and power required for such a probe. We find that many of the requirements for a low-mass probe that operates autonomously for this mission are common for either this propulsion concept or more advanced low-thrust concepts, e.g., solar sails and ion propulsion. We describe an implementation, including science instrumentation and measurement goals, structure and thermal system, communications, avionics, propulsion, guidance and control, power, and architecture that could make such a mission into reality. We also describe some of the technology thrusts and developments that are required in order to begin such a mission in the next twenty-five years.

Development of Carbon Materials and Plasma Facing Components for ITER

A significant R&D effort was carried out in EU to develop suitable CFC materials with a three-directional fibre structure. The main goal was to obtain a high thermal conductivity, which is required to remove the expected heat load with a sacrificial thickness of at least 15–20 mm, with a proper balance of the mechanical properties. Two CFC materials have been developed and are both suitable for the ITER divertor construction, namely NB31 by the French company Snecma Propulsion Solide and Concept 2 by the British company Dunlop Aerospace. The main R&D effort is now focussed in developing cheaper grades and optimising the manufacturing process.The development of suitable technologies for the manufacturing of carbon armoured high heat flux components resulted in the construction of a medium-scale divertor prototype, which was successfully tested well above the ITER design requirements. This component was followed by the manufacturing of a full-scale prototype, which is now being high heat flux tested. In parallel to the technology development, suitable non-destructive methods have been developed to inspect the delicate CFC/Cu joint. These techniques include: infrared examinations, lock-in thermography and ultrasonic examinations.An important topic that will be addressed in the near future is the definition of suitable acceptance criteria for carbon armoured components in view of the series production for ITER.

Proposal for a Solar-Laser-Driven Vehicle

We propose an automobile engine driven by water-laser coupling without fuel. The automobile can load a solar- pumped fiber laser or can be driven by ground-based lasers. The vehicle will be useful on other planets because the piston is in a closed system and the water will not be exhausted into a vacuum. In the preliminary experiment, we succeeded in driving a cylindrical piston of 0.2 g on top of water placed inside an acrylic pipe of 8 mm in inner The possible use of laser propulsion for launching a rocket has been intensively studied for last two decades (1). With the advent of new lasers, the use of laser propulsion is not necessarily limited to such expensive applications. As suggested by one of the authors, a micro-airplane driven by a relatively small laser can be used for various atmospheric and volcanic observations. In such a system, the metal target is covered with water which is transparent to a YAG laser. We have previously demonstrated that a very high thrust can be produced by means of this overlay structure (2,3). In this paper, we propose a new concept for driving vehicles by using similar mechanism. About forty years ago, the possibility of pumping a laser by means of solar energy was discussed and a one-watt cw (continuous wave) laser was constructed (4). The theoretical estimation (5) of such an experiment predicted that 30% of the received solar energy can be converted into a cw laser, with this having been confirmed by recent experiments. In the near future, a pulse laser of 20% or more efficiency will be possible. Therefore, a laser producing a few kW from 10 m 2 solar energy could be installed in the car. If we combine this laser with laser propulsion concept, we can realize an engine that uses only water and solar energy. Since a laser can be made of fiber, its weight is

Advanced Space Propulsion for the 21st Century

HE overriding goal of advanced space propulsion is to reduce the costs of doing space missions, and to enable totally new types of missions that basically could not be performed (even at essentially unlimited cost) with existing technology. For example, with Earth-launch costs on the order of $10,000 per kilogram (comparable to the current cost of gold!) of delivered payload, one important application of advanced propulsion is to reduce thecostofaccessto space(andtransportation oncein space), both in the initial Earth-launch vehicle and then in the in-space vehicles, by reducing the total mass (most of which is propellant) that must be launched from Earth. This can be achieved by either developing more efe cient, higher-performance (i.e., higher specie c impulse Isp/ propulsion technologies, or by reducing the propellant requirements by reducing dry mass, mission velocity 1V, and so on. (Note however that launch cost is strongly driven by launch frequency; 1 thus, some advanced propulsion concepts attempt to both improve performance and increase launch rate.) A second goal of advanced propulsion is the ability to perform previously “ impossible” missions. An example of an impossible mission is attempting an interstellar mission using chemical propulsion. No matter how large the rocket, no matter how many stages it has, you simply cannot achieve the speeds (typically at least 10%of the speed of light) required for a practical interstellar mission using a chemical propulsion system. More generally, it is not practical to performaspace mission wherethe mission 1V isgreater than afew (e.g., two to three) times the propulsion system’ s exhaust velocity Vexhaust or, equivalently, Isp. Ultimately,theperformanceofanyrocketislimitedbytheRocket

Mission to Mars using integrated propulsion concepts: considerations, opportunities, and strategies

The aim of this paper is to evaluate the feasibility of a mission to Mars using the Integrated Propulsion Systems (IPS) which means to couple Nuclear-MPD-ISPU propulsion systems. In particular both mission analysis and propulsion aspects are analyzed together with technological aspects. Identifying possible mission scenarios will lead to the study of possible strategies for Mars Exploration and also of methods for reducing cost. As regard to IPS, the coupling between Nuclear Propulsion (Rubbia's engine) and Superconductive MPD propulsion is considered for the Earth–Mars trajectories: major emphasis is given to the advantages of such a system. The In Situ Resource Utilization (ISRU) concerns on-Mars operations; In Situ Propellant Utilization (ISPU) is foreseen particularly for LOX-CH4 engines for Mars Ascent Vehicles and this possibility is analyzed from a technological point of view. Tether Systems are also considered during interplanetary trajectories and as space elevators on Mars orbit. Finally strategic considerations associated to this mission are considered also.

Laser-driven vehicles – from inner-space to outer-space

Laser-supported propulsion of a micro-airplane with a water-covered ablator is demonstrated. The repetitive use of an overlay structure is experimentally demonstrated with a specially designed water supply. Various transparent overlays are investigated by the CIP-based hydrodynamic code and by experiments using a pendulum and using a semi-conductor load cell. A momentum-coupling efficiency of ∼104 N s/MJ is achieved by water–exotic-target experiments, in agreement with the simulation code, which predicts a maximum efficiency of ∼105 N s/MJ. The concept of laser-supported propulsion can also be used for driving a Mach 5 airplane in the stratosphere, a micro-ship inside the human body, and a robot in a nuclear power reactor accident, during which large numbers of neutrons make electronic devices useless.

Microairplane propelled by laser driven exotic target

We propose a propulsion concept to drive a microairplane by laser that can be used for observation of climate and volcanic eruption. Since it does not have to develop thrust for vertical takeoff, and it has no engine in the normal sense, the microairplane can be very light, with its payload consisting only of observation and communication equipment. In order to demonstrate the concept, we succeeded in flying a paper microairplane driven by a 590 mJ, 5 ns pulse yttrium–aluminum–garnet laser that impinges on a double-layer “exotic target.” The coupling efficiency agrees well with simulations and with experiments.

Micropropulsion for Space — A Survey of MEMS-based Micro Thrusters and their Solid Propellant Technology

In the last two decades, advances in microsystems technology have made micro mechanics mature enough to envisage miniaturization in the space industry. The motivation behind this development is the reductions in mass, satellite costs and launch costs in parallel with an increase in the reliability and flexibility of satellites. A cluster of many small satellites, commanded from a mothership, or totally independent, will, without any doubt, reduce the risk of mission failure and increase mission flexibility. This revolution in the space industry will rely on propulsion system development to ensure the maneuvering and fine positioning of micro and nano satellites (defined as satellites with mass between 20—100 kg and under 20 kg, respectively). This paper is provides a state-of-the-art review of micro thruster technologies for space applications. the intention is to overview the different technical solutions under investigation in the micropropulsion field, to assess their merits and disadvantages and to try to identify the promising ones in relation to future missions needs. First, the principles of propulsion and basic concepts and equations useful in describing and comparing propulsion systems are described. Then, a review micropropulsion needs for space is made and the options and technologies available for propulsion are presented. An outline is given of the technological efforts made in miniaturizing propulsion systems through examples from current research programs and the different micropropulsion technologies are compared. After illustrating the assets of microsystem technology in the micropropulsion field by the detailed presentation of one particular micropropulsion option investigated at LAAS-CNRS, namely solid propellant micro thruster arrays, a short discussion is given of the capability of microsystem technology to serve micropropulsion needs.

Nitrous oxide as a rocket propellant

Nitrous oxide is introduced as a multi-purpose propellant for spacecraft. Potential space applications of this propellant are given. Based on comparison to conventional systems, a multi-mode nitrous oxide propulsion concept is expected to deliver higher performance. Main features of a self-pressurising, nitrous oxide storage system are described. A nitrous oxide catalytic decomposition technique is suggested for restartable spacecraft propulsion. Up-to-date experimental results are presented. A conclusion describes the long-term feasibility of novel nitrous oxide propulsion option concepts.

Pulsed detonation engine. Numerical study

A renewal of interest to study the possibilities of using the gas detonation as a thrust - producing mechanism has been observed during the last ten years. This interest can be motivated by the wide simplicity of the design, the low cost of exploitation and the acceptable performance, so that the PDE can give to this propulsion concept a place as a serious competitor device. The aim of this paper consists on an analysis of the performance of a Hydrogen-Air mixture PDE, computed by the PLEXUS code, using an accurate CFD numerical scheme, for many geometric and operating configurations. The main characteristic of this approach is the possibility of using a geometry that could be structured or unstructured with the associated properties. In particular, the modeling of the detonation propagation can make into account the hydrodynamic effects and combustion one. The interaction of the gas jet, stemming from the combustion chamber, with the surrounded air is also examined and discussed. This may lead to study the PDE in flight configuration in particular with atmosphere configuration.

A study of plasma propulsion system with RF heating

Some experiments and computer simulations to develop a plasma propulsion system by using electron and ion cyclotron resonance (EICR) plasma are reported. The EICR thruster is an advanced space propulsion concept that has possible uses in satellite station keeping and interplanetary travel. An experimental apparatus to generate EICR plasma was constructed in 1999. It consists of a cylindrical vacuum chamber (inner diameter of 21 cm and axial length of 150 cm), RF power supply, and eight electromagnets. It is run at a pressure in the 10 −2 Pa range with Ar or He gas as propellant. This experiment aims to generate plasma (without electrode) by ECR and to accelerate ions (without grid) by ICR under a proper magnetic field configuration. We also plan to develop a compact ECR plasma source that uses hot electron ring for ion acceleration.

Mini‐Magnetospheric Plasma Propulsion: Tapping the energy of the solar wind for spacecraft propulsion

Mini‐Magnetospheric Plasma Propulsion is a potentially revolutionary plasma propulsion concept that could enable spacecraft to travel out of the solar system at unprecedented speeds of 50 to 80 km s−1 or could enable travel between the planets for low power requirements of ∼l kW per 100 kg of payload and ∼0.5 kg fuel consumption per day for acceleration periods of several days to a few weeks. The high efficiency and specific impulse attained by the system are due to its utilization of ambient energy, in this case the energy of the solar wind, to provide the enhanced thrust. Coupling to the solar wind is produced through a large‐scale magnetic bubble or mini‐magnetosphere generated by the injection of plasma into the magnetic field supported by solenoid coils on the spacecraft. This inflation is driven by electromagnetic processes, so that the material and deployment problems associated with mechanical sails are eliminated.

Antimatter Requirements and Energy Costs for Near-Term Propulsion Applications

The superior energy density of antimatter annihilation has often been pointed to as the ultimate source of energy for propulsion. However, the limited capacity and very low efficiency of present-day antiproton production methods suggest that antimatter may be too costly to consider for near-term propulsion applications. We address this issue by assessing the antimatter requirements for six different types of propulsion concepts, including two in which antiprotons are used to drive energy release from combined fission/fusion. These requirements are compared against the capacity of both the current antimatter production infrastructure and the improved capabilities that could exist within the early part of next century. Results show that although it may be impractical to consider systems that rely on antimatter as the sole source of propulsive energy, the requirements for propulsion based on antimatter-assisted fission/fusion do fall within projected near-term production capabilities. In fact, a new facility designed solely for antiproton production but based on existing technology could feasibly support interstellar precursor missions and omniplanetary spaceflight with antimatter costs ranging up to $6.4 million per mission.

The Zeus Mission Study — An application of automated collaborative design

The purpose of the Zeus Mission Study was threefold. As an element of a graduate course in spacecraft system engineering, its purpose was primarily educational — to allow the students to apply their knowledge in a real mission study. The second purpose was to investigate the feasibility of applying advanced technology (the power antenna and solar electric propulsion concepts) to a challenging mission. Finally, the study allowed evaluation of the benefits of using quality-oriented techniques (Quality Function Deployment (QFD) and Taguchi Methods) for a mission study. To encourage innovation, several constraints were placed on the study from the onset. While the primary goal was to place at least one lander on Europa, the additional constraint of no nuclear power sources posed an additional challenge, particularly when coupled with the mass constraints imposed by using a Delta II class launch vehicle. In spite of these limitations, the team was able to develop a mission and spacecraft design capable of carrying three simple, lightweight, yet capable landers. The science return will more than adequately meet the science goals established QFD was used to determine the optimal choice of instrumentation. The lander design was selected from several competing lander concepts, including rovers. The carrier design was largely dictated by the needs of the propulsion system required to support the mission, although the development of a Project Trades Model (PTM) in software allowed for rapid recalculation of key system parameters as changes were made. Finally, Taguchi Methods (Design of Experiments) were used in conjunction with the PTM allowing for some limited optimization of design features.

Single crystal mo solar thermal thruster for microsatellites

One potentially attractive propulsion concept offering significant payload gains for orbit transfer from LEO to higher orbits, station keeping and attitude control of spacecraft is thermal propulsion using light gas (typically hydrogen) as propellant and various kinds of heat energy. Solar Thermal Propulsion (STP) is a typical thermal propulsion with high Isp (500 – 1,000 s) in an appropriate thrust magnitude range and provides possibly much less space pollution than conventional chemical propulsion. This paper presents the test results of a 30 mm dia. (medium-sized) windowless type of single crystal Mo thruster for orbit transfer of 50 kg class microsatellites. The cavity dia. is 20 mm, double the size of the previous model, and can apply to a primary solar reflector of up to 3.5 m dia., which is the maximum size containable in the H-II rocket fairing without segmentation. The performed mission analyses indicate that this size of STP is suitable to orbit transfer of 50 kg class microsatellites, such as LEO to GEO, or only multiple apogee kicks from GTO to GEO or deep space missions.

Experimental characterization of plasma effects on energetic materials for electrothermal-chemical launch applications

Energetic electrical plasmas play a fundamental role in the electrothermal-chemical (ETC) propulsion concept, where they are used to provide energy conversion from an electrical power source to the combustion chamber of an ETC launcher. Recent research in the areas of large-caliber ETC gun experiments as well as small-scale plasma experiments have demonstrated the ability to alter the propellant combustion process and the chemical or physical properties of propellant samples exposed to energetic electrical plasmas. Such results have warranted continued investigations into the underlying processes involved in propellant and plasma interactions, specifically in the behavior of exposed propellant samples to plasmas operating at varying degrees of electrical power. Experimental characterization has been performed with various samples of energetic materials including JA2, CL20, RDX, M9, M30, M43, KELP, and BAMO-AMMO (BA), which were allowed to interact with plasmas having different electrical power levels. The plasma power level ranged from 60 MW to a maximum of 264 MW, and total energy transferred to the plasma capillary ranged from 17 to 70 kJ. Propellant samples were analyzed using a Fourier transform infrared spectroscopy (FTIR) technique, which was used to determine the effects of plasma exposure on the energetic materials. Preliminary results from the experiments indicate that some propellant formulations are easily altered (either chemically or physically) or ignited by a plasma while others are less sensitive to the plasma exposure. In addition, the effects of the plasma are found to be minimized with the introduction of protective films even for plasmas of high power and energy levels.

アジポッド推進システム―商船への搭載実績―

The Azipod (Azimuthing Electric Propulsion Drive) propulsion system has been developed jointly by ABB and Kvaerner Masa Yards. The Azipod concept is a main propulsion system based on the ac-ac electric propulsion concept. Development work and references of ABB Azipod Oy are described. Also vessels ordered with the Azipod propulsion system are described.As an example of the concept the propulsion machinery of the earlier Fantasy-class vessels and the seventh vessel of the series, the M/S Elation, are compared. Practical experience of the system is presented in a description of the sea trial experiences.