Plasma Jet Electric Thrusters for Spacecraft
Demonstrate a prototype electric pulsed plasma jet thruster which can enable highly reliable, high performance, low cost interplanetary space transportation.
Our vision is to design, build, and experimentally demonstrate a prototype pulsed plasma jet thruster targeted for orbital maneuvering, asteroid/comet rendezvous, orbital debris cleanup and interplanetary transportation. Our company, HyperV Technologies Corp., has extensive experience designing, building, operating, and deploying extremely high performance single-shot plasma accelerators of many different shapes, sizes, and power levels. These plasma jet accelerators have been developed for applications in fusion energy and high energy density plasma physics research [www.hyperv.com].
We believe this same basic pulsed plasma jet technology can be adapted to increase the robustness and decrease the cost of spacecraft electric propulsion, thus opening the door to many new exciting robotic and manned space missions. Our first step with this project is to successfully demonstrate repetitive operation as a thruster.
We invite you, the citizens of Earth, to join with us as we design, construct, test, and execute this demonstration. The culmination of this project will be an all-up, laboratory demonstration of our prototype thruster. You will be updated via our Kickstarter Blog, Facebook, Twitter and uploaded video of the firing posted to our website.
Our technical objectives for this thruster development project are to meet or exceed the following thruster performance goals:
- Design and construct a high density gas fed plasma thruster operated at an average continuous input power level of about 1.0 kW
- Achieve a specific impulse (Isp) of 2000 sec (which means an average exhaust velocity of about 20,000 m/s)
- Operate at 5 pulses per second (5 Hz) for a minimum duration of one minute
A Plasma Jet What?:
A plasma accelerator is a device which forms a slug of hot, ionized particles, or plasma, and launches these plasma pulses at high velocity. Our plasma accelerators, one of which is shown in Figure 1, consist of two parts: A formation section and an acceleration section. The formation section forms and ionizes a plasma armature or slug from a source material and injects it into the next section. The acceleration section consists of a pair of straight parallel metallic electrodes separated by a pair of ceramic insulators. A large current is then driven through the electrodes and plasma armature, accelerating the plasma slug using the resultant self-generated magnetic Lorentz force. The performance of our existing single shot plasma accelerator designs has already been demonstrated [poster presentations from the 2009, 2010, and 2011 American Physical Society Division of Plasma Physics annual meetings www.hyperv.com/papers.html ]. We must now adapt this existing low cost, scalable technology to transform it into a repetitively pulsed, continuously operable, compact plasma thruster.
Why are plasma thrusters important for space travel?:
Spacecraft electric propulsion is extremely fuel efficient and dramatically reduces the amount of propellent mass and volume that a spacecraft needs to travel to and/or return from its destination in space. Because a spacecraft's size and weight are reduced, the overall cost of launching that spacecraft into orbit or onto an interplanetary trajectory is significantly reduced. Since the 1960's there have been nearly a dozen different types of electric propulsion thrusters which have been developed, some of which have already flown in space. Yet while many of today's modern communications satellites employ a variety of electric thrusters to maintain their precise orbits above earth, to date, only four robotic science spacecraft have flown missions using electric propulsion as the primary means to propel the spacecraft through deep space. Because of its great potential, NASA, which was the first to launch a deep space mission using electric propulsion, is using and continues to study electric propulsion for greatly expanded space missions in the future. For many future missions, electric propulsion is the only viable option. It is therefore imperative that we investigate all useful forms of electric propulsion, including pulsed plasma jet thrusters.
For fun here is a fascinating Walt Disney clip from around 1957 of a massive manned mission to Mars using electric propulsion as envisioned by Wernher von Braun: http://www.youtube.com/watch?v=3wIXZsbjIxA. Today we could also use solar panels instead of nuclear to generate the electrical power. Yes indeed, spacecraft electric propulsion has the potential to bring back the magic of the early years of space exploration!
So why bother to develop Plasma Jet Thrusters if there are other types of electric propulsion systems that have already flown in space?:
Because, quite simply, we think ours will be better! We believe our thruster technology has the potential to be just as efficient as existing electric thrusters (such as ion and Hall effect thrusters) and with similar specific impulse. But our advantages will be derived from a thruster that is less complex (and much more robust), which can use a variety of propellants including gases, inert plastics, and propellants derived from asteroids, Mars, the Moon, etc., It will also be far cheaper to build, and can be more readily scaled to larger sizes and very high power levels than current electric propulsion systems. Our plasma thruster technology should be scalable from a few kilowatts all the way up to megawatts of average power. The electricity which is needed to power electric thrusters would most likely come from new high performance solar panels, but could also utilize other compact energy sources. From a practical viewpoint for satellite design, our thruster will have much higher thrust per unit area than ion or Hall thrusters, thus taking up less room on the rear of the spacecraft.
Due to the efforts of a number of private space companies, there is significant potential for the cost to reach orbit to be significantly reduced, but even these lower launch prices will still be expensive. This means that once a spacecraft reaches Earth orbit, there is still a need for more cost effective methods of in-space transportation. That's where we come in. With our plasma thruster project we want to work on reducing the cost of space transportation further by cutting the mass and volume needed for spacecraft fuel, while increasing the transportation capabilities of the spacecraft. Cheaper robust spacecraft thrusters will serve as an enabler for daring low-cost robotic and ultimately new manned space missions. These missions could return samples from near-Earth asteroids, or support a more ambitious effort to return samples from Mars and beyond.
Plus, since our technology stems from our already scalable single-shot pulsed plasma accelerators, our plasma thruster design also promises to be scalable, including up to sizes large enough to support future large interplanetary manned space missions. We believe our thruster technology will be best suited for spacecraft with minimum masses of 100 kg (about 220 lbs) and larger.
Why you should be involved:
You should be involved because not only are we offering to let you help us lay the cornerstone for a new type of robust spacecraft electric propulsion which is well suited for use in heavy robotic and manned interplanetary space missions, but also because we are offering to take you behind the scenes for the prototype development process. We will be providing progress reports and status updates to the Kickstarter blog, and on Twitter, and the latest test results and preliminary analysis will be available to our friends on Facebook, including post-experimental summaries. You should also know that in addition to our limited ticketed main firing event, we will be hosting tours where you can stop by and see our facility. See our laboratory! See our plasma accelerators! We are offering you a chance to see plasma physics in action. Plus we are going to take some really cool high speed photos of plasma which will also be available to our backers.
So who are we?
We are a team of three scientists, Dr. Doug Witherspoon, Dr. Andrew Case, Dr. Sam Brockington, and an energy & space entrepreneur, Chris Faranetta who quite frankly build the world's best plasma jets for nuclear fusion and plasma physics research. But did we mention that we really, really like space too and we would like to see the cost and complexity of deep space exploration come down so that lots more cool manned and un-manned missions can happen? Our company is called HyperV Technologies Corp. The HyperV part stands for HyperVelocity - we are all about moving plasma fast, really fast, I mean hyperfast! Check out our website at www.hyperv.com where we talk about the cool stuff we've done in plasma physics research funded through competitive government research grants.
HyperV Technologies Corp is based in Chantilly, Virginia USA. We have a machine shop from which our existing accelerator designs and high power switches have already been produced. Our 9000 square foot facility contains not one, but two fully functional very high voltage/high vacuum laboratories, complete with high voltage charge/dump control systems and high vacuum ( 1 microTorr) chambers, and other experimental support. We have over 80 channels of 1-2 Gigasample per second state-of-the-art, computer-controlled, data acquisition, and multiple high voltage charging supplies already installed and operating. We also maintain an extensive suite of plasma and pulsed power diagnostics, including ICCD fast-framing cameras for high speed (nano second gate) photography, digital cameras for long exposure color photography, photodiode arrays for real-time streak photography, batteries of magnetic probes, collimated optical and interferometric density diagnostics, as well as apparatus for survey and high-resolution spectroscopic measurements and other diagnostics for high-voltage high-current measurements.
How far along are you?
HyperV has already designed, constructed, and operated multiple single-shot, linear plasma accelerator configurations of several bore lengths and bore cross-sections ranging from 3mm square to 50mm square and up to 30cm long. HyperV has working designs for both gas fed and ablative capillary fed plasma accelerators. Adaptations of the gas fed designs would be used for the thruster, but ablative concepts using simple plastic as the “propellant” are also being explored.
Existing HyperV accelerators are already very compact. For example, the main body structure of our 1 x 30 cm accelerator weighs in at about 2.5 kg (5 lbs), and our existing 0.5x10 cm accelerators can be as little as 0.25 kg(0.5 lbs). And since none of these devices was especially designed for low mass, we can probably reduce them another factor of two lower!
The principal focus of this new project would be on adapting one of our existing minirail accelerator designs to a 5 Hz repetitively pulsed system capable of producing 2000 sec specific impulse. We have a plan for the first round of testing, including an initial design concept for the driver circuit, an initial concept for the plasma thruster, and estimates for diagnostic requirements, and the modifications necessary to support burst mode operation and data acquisition.
The next step is to finalize the first experiment plans, construct the device, prepare the diagnostics necessary for the first test, and perform the tests.
Our initial target funding goal is $69,000. At this level of support we will be able to achieve the following:
1) We will design, build and test a prototype plasma jet thruster that can operate repetitively. This will be a proof-of-principle demonstration that our plasma jet accelerators can indeed be transformed into a working plasma thruster.
2) We will demonstrate basic repetitive operation of the thruster at 5 Hz, i.e. 5 pulses per second. A space qualified thruster would ultimately operate at many hundreds of pulses per second, even as much as 1000 pulses per second, in order to provide an average steady thrust with high Isp. Our present plasma accelerators can fire once every few minutes, but operate at extremely high performance, i.e. about 8000 micrograms of argon at 50 km/s. The repetitive thruster will operate at perhaps only 10 micrograms of argon (or xenon) at 20 km/s. We will accomplish this by reducing the size of the accelerator and reducing the pulsed drive current from 600,000 amps, down to only about 10,000 amps. This will allow us to operate at high rep rates.
3) We will make basic measurements of thrust using a ballistic pendulum. This is accomplished by directing the plasma slug onto a pendulum where the impact causes the pendulum to recoil. Measuring the amount of recoil tells us how much momentum was in the jet. By using other optical techniques to measure the velocity we can then infer the mass of the plasma jet. Once we know the mass and velocity, we can calculate things like the specific impulse and average thrust.
4) We will make additional basic plasma diagnostic measurements so we know what's going on in the thruster. These will include things like measuring the density of the plasma using a laser interferometer, and measuring its temperature using spectroscopic techniques. Using very fast framing cameras in which the shutter can open and close in 50 billionths of a second allows us to get snapshots of the plasma plume. We'll also use open shutter photography with a DSLR camera to observe the plume evolution exiting from the thruster nozzle. This is going to make some really cool high speed pictures of plasma blasting out from the thruster.
5) Using all these diagnostic measurements will allow us to make calculations of the overall thruster efficiency, Isp, and thrust/power ratio – parameters critically important to the success of the thruster.
That's going to be a lot of work for our basic goal of $69,000, but we are confident of success. This will provide the basic demonstration and data we need to confirm that our plasma jet units can indeed function successfully as a high performance thruster. Our hope, of course, is that we will receive more than that from you our supporters. If that occurs we have a plan for advancing the thruster development process even further. We intend to go all the way with this thruster and we'd love to see you come along with us!
If we exceed the initial funding goal, we will be able to
achieve even more!
For example, at the $100,000 level, we will also be able to:
Build a simple thrust stand to make direct continuous thrust
measurements, to compare with the ballistic pendulum measurements. This
will be important for definitively measuring the thrust as opposed to
calculating it from other parameters. We will also be able to build and
test a breadboard energy recovery circuit. This circuit is crucial for
maximizing the long term overall efficiency of the thruster. At the end
of each thruster pulse, there is some remaining energy stored in the
magnetic field of the current pulse just as the plasma blob exits the
nozzle. We need to recover this energy and reuse it on the next pulse
to maximize the overall efficiency of the thruster. We plan to design a
circuit that stores this energy capacitively so that the voltage for
the next pulse only needs to be “topped-off” instead of charged all the
way from zero. We'll also be able to increase test run time and thus
gather more data for future design modifications to the thruster.
At the $150,000 level, in addition to the above accomplishments, we
will also be able to: Add additional pumping and cooling features to
allow even longer run times. Like all electric thrusters, our thruster
will ultimately need to incorporate some heat management features to
ensure it does not overheat when operating for months at a time. We
would also be able to add a functional energy recovery circuit (not
just a breadboarded circuit) to the thruster and operate them together
to demonstrate an high efficiency system. Our goal is an efficiency of
about 50%, meaning the kinetic energy of the thruster exhaust is 50% of
the amount of electrical energy delivered by the power supply.
At funding levels above $150,000, we would be able to accomplish
further tasks such as: 1) Perform more extensive lifetime testing of
the thruster components, 2) Build an improved thrust stand with
improved fidelity, 3) Perform test runs with xenon gas (which is more
expensive than using argon gas), and 4) Test the thruster entirely in
vacuum, which provides a better thermal test of the hardware in an
actual simulated working space environment. This will be important for
learning how best to incorporate cooling features.
Risks and challenges
The risks and challenges are mainly technical, but the technical risks are low for achieving the stated project demo goals of 5 Hz, 1 kW, 2,000 sec specific impulse operation. The specific impulse goal of 2,000 sec is pretty straightforward, since we have already achieved over four times that number in our previous work. The main risk is actually getting a repetitive pulsed thruster working smoothly and dissipating the heat generated from the drive current. For the 5 Hz burst mode planned for the project demo, heating should not be a problem as long as we limit the run time to a few minutes. If it survives that, we'll try running it for longer duration times to learn more about its thermal characteristics. The external drive circuitry will need to be modified so that the capacitors are charged and discharged in a quasi-continuous manner, but again, this is relatively straightforward. We feel the parameters set forth in this project are sufficient to prove the thruster is worthy of further development. We plan to build an energy recovery circuit to recycle the stored magnetic field energy at the end of the pulse that would otherwise be wasted, but that effort is beyond the resources of our initial funding goal. Such a circuit would be able to increase the overall efficiency of the thruster to a level that is attractive for a space qualified system. None of the technical issues really affect whether we can pull off the project demonstration, but only affect what specific parameters we might achieve for that demo. We plan to aggressively push the parameters as far as we can during the project.Learn about accountability on Kickstarter
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