A small experimental electric thruster, in which power is supplied via Electron-Cyclotron Resonance (ECR) absorption of microwaves by the propellant gas, has been tested at the NASA Marshall Space Flight Center (MSFC). The plasma generated is confined radially by an axial dc magnetic field applied through a series of watercooled coils around the resonance chamber. The B-field is maintained at about the strength required for ECR in the central part of the chamber (the ECR zone), with stronger magnetic fields acting as magnetic Gas Dynamic Mirrors (GDM) at the ends. The plasma is ejected into the vacuum chamber through the downstream magnetic mirror, which acts as a magnetic nozzle. Of the magnetic field configurations tested, the one most similar to the GDM device proposed by Kammash produced the most significant results. The Radio Frequency (RF) waves, or microwaves, that power the thruster, are launched axially into the resonance chamber and couple very strongly with the Argon plasma. Electron densities of 10^11 to 10^13 per cm^3 have been measured in the plume downstream of the magnetic nozzle. Bimodal velocity profiles have been measured in the .plume via Laser Induced Fluorescence (LIF).
An experimental electric thruster has been built for testing at the NASA Marshall Space Flight Center (MSFC). The plasma is formed by Electron-Cyclotron Resonance (ECR) absorption of microwaves at 10.1 GHz frequency. The plasma is confined radially (theta pinch) by an applied axial dc magnetic field, with a strength of 0.36 tesla (3600 gauss) for ECR. The field is shaped by a strong magnetic mirror on the upstream end and a magnetic nozzle on the downstream end. Argon is used as the test propellant, although a variety of gases may be utilized.
The concept of the Gasdynamic Mirror (GDM) device for fusion propulsion was proposed by and Lee (1995) over a decade ago and several theoretical papers has supported the feasibility of the concept. A new ECR plasma source has been built to supply power to the GDM experimental thruster previously tested at the Marshall Space Flight Center (MSFC). The new plasma generator, powered by microwaves at 2.45 or 10 GHz. is currently being tested. This ECR plasma source operates in a number of distinct plasma modes, depending upon the strength and shape of the local magnetic field. Of particular interest is the compact plasma jet issuing form the plasma generator when operated in a mirror configuration. The measured velocity profile in the jet plume is bimodal, possibly as a result of the GDM effect in the ECR chamber of the thruster
A thruster has a chamber defined within a tube. The tube has a longitudinal axis which defines an axis of thrust; an injector injects ionizable gas within the tube, at one end of the chamber. A magnetic field generator with two coils generates a magnetic field parallel to the axis; the magnetic field has two maxima along the axis; an electromagnetic field generator has a first resonant cavity between the two coils generating a microwave ionizing field at the electron cyclotron resonance in the chamber, between the two maxima of the magnetic field. The electromagnetic field generator has a second resonant cavity on the other side of the second coil. The second resonant cavity generates a ponderomotive accelerating field accelerating the ionized gas. The thruster ionizes the gas by electron cyclotron resonance, and subsequently accelerates both electrons and ions by the magnetized ponderomotive force.
The thruster of relies on electron cyclotron resonance for producing a plasma, and on magnetized ponderomotive force for accelerating this plasma for producing thrust.
Improving the performances of the Electrodeless Plasma Thruster at higher
power level requires gaining a deeper understanding of the microwave-plasma energy
coupling. In order to investigate in details the dynamic of this coupling and its variations under diverse operational conditions, the Elwing Company has developed specific, highly versatile, components that can be fitted on the current 8-12 kW model of the electrodeless plasma thruster. This article fully exposes the development process of these components, which involves finite elements modeling, along with the design characteristics and operational capabilities of the microwave applicator and the magnetic structure.
New concepts for electrostatic confinement and control of reactions between fusionable fuels offer the prospect of clean, nonhazardous nuclear fusion propulsion systems of very high performance. These can use either direct-electric heating by relativistic electron beams, or propellant dilution of fusion products. If feasible, QED rocket engine systems may give F = (4000-10,000)/Isp, for 1500 < Isp < 1E6 s; two to three orders of magnitude higher than from any other conventional nuclear or electric space propulsion system concept. All of the systems offer payloads of 14.4%-20.6%, with transit times to Mars’ orbit of 33 to 54 days, over a flight distance of about 90 million km. The mean angle of the flight vector to the tangent to the planetary orbit path is about 40 degrees: this is true “point-and-go” navigation! All vehicle force accelerations are well above the solar gravity field throughout their flight, thus all flights are highthrust in character. This eliminates the need for added vehicle characteristic velocity required to lift propellant mass out through the solar field, as is the case for low-thrust systems a
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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