Welcome
to MyElectricEngine.Com! I've created this page to present the work and
research I've done on electrical aerospace propulsion systems such as
magnetoplasmadynamic (MPD) and arcjet thrusters. This work is both my
hobby and the focus of my recently completed Masters
thesis
paper which I completed as a requirement of my Master's program. I
received my Bachelor's degree in Electrical Engineering with high
distinction from the Electrical and Computer Engineering
Department at Worcester Polytechnic Institute
in 2006, and followed that up with a Masters degree in Electrical and
Computer Engineering from Worcester Polytechnic Institute in 2007. If
you'd like to read the complete text of my Masters thesis, you can find
it here.
My
original involvement in electrical propulsion began as a bit of a
dining hall joke, and demonstrates the dangers of keeping too many
engineers in one place. One of my mechanical engineering buddies
remarked over a particularly uninspiring dinner that he had always
wanted to see a magnetoplasmadynamic thruster fire and proceeded to
explain how these devices work. The basic construction is simple
enough, involving only a power supply, some capacitors, and a suitable
spark gap. The first design was soundly within the category of
"kludge", but adequately demonstrated this simple device
which at the time amounted to a large spark machine. More advanced
designs
quickly appeared and were built, culminating in an independent study
and finally a Masters thesis project.
I
am currently
seeking employment as an electrical engineer in power systems,
controls, aerospace, microelectronics, and much more. I
am very flexible and able, so if you're willing to forgive
this
shameless plug please feel free to e-mail me at MyElectricEngine@gmail.com
and take a look at my resume here
or view it as a word document here.
Anyway, on to the good stuff.
Here
is a list of all of the projects that I've documented. Watch for
updates and improved designs.
 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.
 The
previously described
ignition circuit works very nicely, but is very heavy and
generates
a huge amount of EMI that persistently fouled up sensors, interfered
with data collection, and even crashed computers within several tens of
feet. This design uses the same concepts but replaces the bulky and
heavy line frequency neon transformer with a more compact high high
frequency transformer. Similarly, the spark gap is replaced with solid
state switches that can operate at high frequency without the EMI
associated with a spark gap.
 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.
One
of the more
difficult aspects of this project was precisely charging the capacitor
stack to its full voltage of 700V, if both stacks are
connected in
series. This project aims to remove any guess work from charging by
using a switching DC to DC converter to precisely charge the capacitor
stacks.
The
arcjet thruster has more in common with chemical rockets than the MPD
thruster in that it heats a propellant gas to a high temperature and
then expands that gas through a nozzle to convert the thermal energy
into thrust. The big difference here is that the propellant gas is
heated by an arc discharge, allowing for much high temperatures and
specific thrust. This project was selected as a follow-up to
the MPD thruster as it is easily implemented without the use of a
vacuum chamber.
I
spend a lot of
time researching and collecting information on a wide range of
subjects, much of which is dispersed widely and often of an obscure
nature. I've collected those bits of information that I find useful
here, in hopes that other people may find it useful as well.
A large portion of the projects on this site involve plasmas and arc
discharges. This page presents some of the basic features of an arc
discharge, some of the basic equations that govern plasmas,
and
some helpful tips I've picked up along the way.
 Gasses
under high pressure or at high velocities behave in ways that seem
counter-intuitive to our everyday experience, but can greatly influence
how certain flows behave. This page explains some of the basic
differences between incompressible flows and compressible flows, and
how they differ from how we might otherwise expect them to behave.
 If you're ever looking to purchase a valve or gas solenoid, you're probably going to come across this funny parameter called cv.
As an electrical engineer, no one every explained this to me, so I had
to figure it out myself. Here's the important stuff you need to work
with this parameter laid out for you so you can find the flow of a
fluid through a valve.
visitors since September 2007
Questions? Comments? Suggestions? E-Mail me at MyElectricEngine@gmail.com
Copyright 2007 by Matthew Krolak - All Rights Reserved.
Don't copy my stuff without asking first.
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