Electric Plasma Propulsion
Here is a list of all of the projects that I've documented from various websites. Watch for updates and improved designs.
MAGNETOPLASMADYNAMIC ARC THRUSTER:
This is the project that started it all, and attempts to find a reasonable thruster package that can provide high levels of thrust at high specific impulse levels on a budget. It uses electromagnetic forces to accelerate an electrically conductive, or ionized, propellant gas out of a nozzle, and attempts to sidestep the limitations of chemical rockets by eliminating the dependency on thermal expansion of the propellant.. This description also includes brief introductions to the various subsystems that were built to support this design. The other components used in this project are more thoroughly described in the sections below.
If high energy experiments are to be performed on a reasonable budget then chances are you're going to need to operate your device in a pulsed mode - i.e. at very high power levels for very short periods of time. This approach strongly suggests using a carefully designed capacitor bank. Both the electrical and mechanical design issues are explored, including the reduction of parasitic inductances and the mechanical requirements of high current conductors. Here's my design for a 28kJ electrolytic capacitor bank capable of delivering 200 Megawatts or more.
How do you accurately and reliably trigger a high current discharge across a spark gap, such as the nozzle of a MPD or arcjet thruster? This problem is deceptively difficult, especially on a student's budget. We can take some advice from the design of Tesla Coils and arc welding equipment and develop a relatively robust solution using common components to create a high voltage, high frequency ignition circuit.
GAS INJECTION Gas Injection System
The delivery of a propellant gas into a thruster nozzle is another critical aspect of the design, as the propellant gas not only provides thrust, but can also provides cooling to the nozzle, charge carriers to the plasma stream, and prevents the discharge from consuming the electrodes.
This device operates continuously at a power level of about 11 kW, and therefore replaces the capacitor bank from the pulsed MPD thruster with a switching power supply operating from AC mains. This has the advantage of being much more controllable, and the lower power level increases the useful life of the electrodes enormously. A detailed switching power supply design is presented along with design documentation, simulations, spreadsheets, and manufacturing files.
Higher operating pressures required the design and manufacture of several custom components, particularly the high pressure valve based on a simple ball valve and an electric motor.