Mike Paluszek gave a talk on Saturday, June 3, 2017
Direct Fusion Drive – A Small Nuclear Fusion Rocket Engine for In-Space Propulsion
at Columbia University as part of the conference Dawn of Private Space Science 2017.
You can see the talk on Facebook Live.
A key feature of the NIAC program is making the project results available to the public. In that spirit, we are making our complete Phase I final report, “Fusion-Enabled Pluto Orbiter and Lander”, available on our website!
NIAC Phase I Final Report [PDF]
I’ve copied the executive summary below:
The Pluto orbiter mission proposed here is credible and exciting. The benefits to this and all outer-planet and interstellar-probe missions are difficult to overstate. The enabling technology, Direct Fusion Drive, is a unique fusion engine concept based on the Princeton Field-Reversed Configuration (PFRC) fusion reactor under development at the Princeton Plasma Physics Laboratory. The truly game-changing levels of thrust and power in a modestly sized package could integrate with our current launch infrastructure while radically expanding the science capability of these missions.
During this Phase I effort, we made great strides in modeling the engine efficiency, thrust, and specific impulse and analyzing feasible trajectories. Based on 2D fluid modeling of the fusion reactor’s outer stratum, its scrape-off-layer (SOL), we estimate achieving 2.5 to 5 N of thrust for each megawatt of fusion power, reaching a specific impulse, Isp, of about 10,000 s. Supporting this model are particle-in-cell calculations of energy transfer from the fusion products to the SOL electrons. Subsequently, this energy is transferred to the ions as they expand through the magnetic nozzle and beyond.
Our point solution for the Pluto mission now delivers 1000 kg of payload to Pluto orbit in 3.75 years using 7.5 N constant thrust. This could potentially be achieved with a single engine. The departure spiral from Earth orbit and insertion spiral to Pluto orbit require only a small portion of the total delta-V. Departing from low Earth orbit reduces mission cost while increasing available mission mass. The payload includes a lander, which utilizes a standard green propellant engine for the landing sequence. The lander has about 4 square meters of solar panels mounted on a gimbal that allows it to track the orbiter, which beams 30 to 50 kW of power using a 1080 nm laser. Optical communication provides dramatically high data rates back to Earth.
Our mass modeling investigations revealed that if current high-temperature superconductors are utilized at liquid nitrogen temperatures, they drive the mass of the engine, partly because of the shielding required to maintain their critical temperature. Second generation materials are thinner but the superconductor is a very thin layer deposited on a substrate with additional layers of metallic classing. Tremendous research is being performed on a variety of these superconducting materials, and new irradiation data is now available. This raises the possibility of operating near- future “high-temperature” superconductors at a moderately low temperature to dramatically reduce the amount of shielding required. At the same time, a first-generation space engine may require low-temperature superconductors, which are higher TRL and have been designed for space coils before (AMS-02 experiment for the ISS).
We performed detailed analysis of the startup system and thermal conversion system components. The ideal working fluid was determined to be a blend of Helium and Xenon. No significant problems were identified with these subsystems. For the RF system, we conceived of a new, more efficient design using state-of-the-art switch amplifiers, which have the potential for 100% efficiency.
This report presents details of our engine and trajectory analyses, mass modeling efforts, and updated vehicle designs.
We are looking for an energetic, results-oriented person able to combine the responsibilities of financial manager and coordinator of back office operations, working part time (16-20 hours/week).
Responsibilities include but are not limited to:
- financial planning and budgeting;
- accounting and bookkeeping;
- customer invoicing and cash management;
- HR record keeping and benefits management;
- coordinating payroll working with an external service provider;
- managing office facilities.
A candidate must have financial education and a proven record of at least 3 years independently performing on a job with similar responsibilities, possession of skills in QuickBooks or a similar financial package along with MS Office. Excellent communication skills are anticipated.
Please send resumes to email@example.com! Also see our post on LinkedIn.
Apress just published our new book, “MATLAB Machine Learning”
written by Michael Paluszek and Stephanie Thomas. The book covers a wide variety of topics related to machine learning including neural nets and decision trees. It also includes topics from automatic control including Kalman Filters and adaptive control. The book has many examples including autonomous driving, number identification and adaptive control of aircraft. Here is a view of a neural net tool included with the book.
Full source code is available. For more information go to MATLAB Machine Learning.
Princeton Satellite Systems was awarded its first patent in Japan, “Method to produce high specific impulse and moderate thrust from a fusion-powered rocket engine”. This technology was licensed from Princeton University’s Princeton Plasma Physics Laboratory. It is for a compact, low-neutron, nuclear fusion reactor that can be used as a rocket engine or as a power generator. The reactor can be built in sizes from 1 to 10 MW. A typical robotic spacecraft would use two engines. A human mission to Mars or the outer planet might use six 5 MW engines.
Here is the Japanese patent certificate.
Mike Paluszek of Princeton Systems, Sam Cohen of the Princeton Plasma Physics Laboratory and Charles Swanson also of PPPL attended the US – Japan Compact Toroid 2016 meeting in Irvine California this past August.
We presented papers related to Sam’s Princeton Field Reversed Configuration nuclear fusion reactor research program. Charles presented, “Extracting electron energy distributions from PFRC X-ray spectra,” Sam presented “Long pulse operation of the PFRC-2 device” and Mike presented, “Fusion-enabled Pluto orbiter and lander”.
Here are the workshop attendees.
It was fascinating to listen to all of the papers at the workshop! John Santarius, who has done cutting edge work on space propulsion and small fusion reactors presented his talk, “Aspects of Advanced Fuel FRC Fusion Reactors.” He gave a very informative overview of small fusion reactors and advanced fusion fuel technology. Thomas McGuire discussed the Lockheed Martin research on small reactors. There were several presentations by Tri-Alpha Energy scientists on their beam heated FRC.
We look forward to the next Compact Toroid Workshop!
Michael Paluszek and Gary Pajer of Princeton Satellite Systems attended the Celebrate Princeton Invention (CPI) 2016 reception in the Chancellor Green Rotunda on the university campus.
Our research on small nuclear fusion reactors is part of a team effort with the Princeton Plasma Physics Laboratory (PPPL) so our display was part of the PPPL booth.
The poster describes our project to design a nuclear fusion propelled robotic spacecraft to go into orbit around Pluto. It would get there in about 3 years and deploy a lander. While in orbit it would return HDTV quality images and massive amounts of data through its high power communications links. The short duration of the trip would save almost $300M in operations costs. It would be launched from Low Earth Orbit, saving even more money!
The propulsion system could also be used for a Neptune Orbiter, missions to Jupiter’s icy moons, an Enceladus lander, asteroid deflection and human exploration of Mars. More down-to-earth applications include powering bases in Antarctica and driving the propulsion systems for unmanned underwater vehicles.
Our reactor uses helium-3 as a fuel. As the supplies of helium-3 grow, possibly from Canada’s CANDU reactors, helium gas from natural gas extraction or mining the moon, the reactor could be used to generate power everywhere. It is the ideal supplement to wind and solar power.
Gary Pajer and I talked with many attendees at CPI. Here is Gary talking with a visitor to our booth.
Visitors to our booth included researchers from Schlumberger, ExxonMobil and from around the campus. It was great fun talking to everyone and seeing all the interesting research done at Princeton University!
My name is Matthew Daigger and I’m a mechanical and aerospace engineering major at Princeton University going into my senior year. I was given the opportunity to intern and learn at Princeton Satellite Systems this summer. Through this internship, I got a lot of valuable experience in 3-D modelling, research and design. I was able to work with the fantastic engineers at Princeton Satellite Systems as well as Princeton Plasma Physics Lab, who helped whenever questions in their areas of expertise arose.
DFD CAD model generation by Matt Daigger
The Direct Fusion Drive (DFD) is an innovative and exciting new technology being designed by Princeton Satellite Systems. This Rocket engine utilizes the Princeton Reverse Field Cycle fusion reactor setup in order to create both thrust and power for a satellite. The vehicle it is currently being designed for is an exploratory satellite being sent to Pluto. What makes the DFD unique is that it can potentially halve the flight time to Pluto, from ten years to five, as well as have enough fuel left to put the satellite into orbit. Along with this, the craft should have enough extra power to deploy a rover to the surface of Pluto and power a drill. This technology could also open other exciting doors, such as manned missions to Mars, given its capability to cut travel times so drastically.
The first task I worked on this summer was looking into how to incorporate a Brayton cooling cycle into the design of the DFD. This Brayton cycle had a dual purpose. The first is to help cool the reactor and prevent too much heat and radiation from escaping and potentially damaging other parts of the satellite. The second function is to re-use this waste heat and convert it back into usable energy. Two simple brayton cycles running in parallel were chosen in order to maximize heat absorption from the reactor and power developed. The working fluid, its flow rate and the diameter of piping, as well as approximate dimensions of the turbine and compressor were also determined. Another important design factor is the ability for the satellite to withstand launch loads. Preliminary launch load calculations were also done in order to get a better idea for the stresses involved with launch using a Delta IV Heavy launch vehicle.
All of this information helped to conceptualize the physical design, which was drawn up in Inventor. The shielding and incorporation of the Brayton cycle flowing through the shielding were ideas which were confirmed by members at PSS and PPPL. The length of the reactor is a key factor in determining how high energy it will be. The length was chosen so to produce a 1 MW engine. The superconducting coils were also a main topic of research. These are active superconductors which are used to shape the plasma. This is still an ongoing process, as using active coils hasn’t been done before, and our engine has unique weight and size limitations which other similar lab reactors don’t. The debate as to whether to use high temperature or low temperature superconducting coils comes down to total size and weight, including that of a cryo-cooling system in the case of the low temperature coils. High temperature superconducting coils are the more massive option, which generally makes them less desirable for space application. The support structure was designed to keep the size compact while being able to handle the stresses calculated earlier. All information about the RMF heating coils, which are used to actually excite and drive the plasma, was received and confirmed by colleagues at Princeton Plasma Physics Lab. The separation coils at the tail-end of the thruster are power variable, and allow the expelled products to be manipulated, giving the engine high precision control in space travel.
Overall, this was an incredibly interesting and educational experience. The work that the Engineers are doing at PSS is innovative and exciting. The big ideas that are being developed here today are what lead to the next big step in space travel tomorrow. I am very thankful for the opportunity to spend my summer here and learn from some of the best engineers in the industry.
Near-Earth Asteroid Scout, or NEA Scout is a exciting new NASA mission to map an asteroid and achieve several technological firsts, including being the first CubeSat to reach an asteroid and demonstrate CubeSat technologies in deep space. http://www.nasa.gov/content/nea-scout
NEA Scout will perform a survey of an asteroid using a CubeSat and solar sail propulsion and gather a wide range of scientific data. NEA Scout will be launched on the first Space Launch System (SLS) launch.
NASA asked Princeton Satellite Systems to develop custom MATLAB software based on the Princeton Satellite Systems Spacecraft Control Toolbox and Solar Sail Module to assist with this mission. We just delivered our first software release to NASA!
The NEA Scout module provides MATLAB scripts that simulate the spacecraft. One, TrajectorySimulation, simulates just the trajectory. It includes a solar sail force model and uses the JPL Ephemerides to compute the gravitational forces on the sail. In addition it can use a 150 x 150 Lunar Gravity model during lunar flybys. It also simulates the orbit dynamics of the target asteroid.
AttitudeSimulation expands on this script. It adds attitude, power and thermal dynamics to the model. A full Attitude Control System (ACS) is included. This ACS uses reaction wheels and optionally cold gas thrusters for control. Momentum unloading can be done with the thrusters our using NASA’s Active Mass Translation (AMT) system that moves one part of the CubeSat relative to the other to adjust the center-of-mass so that it aligns with the system center-of-pressure or adds a slight offset to unload momentum. The control system reads command lists that allows the ACS to perform attitude maneuvers, do orbit changes with thrusters and for the user to change parameters during simulations. It adds the rotational dynamics of the asteroid.
The dynamics of the AMT can be modeled either with a lag on the position or a full multi-body model. Dynamics of the reaction wheels, including a friction model, are included in the simulation. The following are a few figures from a typical simulation.
The first figure shows reaction wheel torques during attitude maneuvers. The ACS uses quaternions as its attitude reference. You can mix reaction wheels and thrusters or use either by themselves for attitude control.
This GUI shows the current command and allows you to control the simulation.
The Figure GUI lists all figures generated by the simulation. It makes it easy to find plots when you have many, as you do in the attitude simulation.
The Telemetry GUI gives you telemetry from the ACS system. You can easily add more data to the telemetry GUI which can have multiple pages.
This figure shows solar sail pointing during simulations.
The following figure shows the spacecraft with its solar sail deployed. This is built in the CAD script using the Spacecraft Control Toolbox CAD functions. The sail is 83 meters square.
The sail is huge but the core spacecraft would sit comfortably on your desk.
If you want more information about our products or our customization services you can email us directly by clicking Mission Simulation Tools.
We just discovered that our NASA NIAC project on the DFD mission to Pluto was covered in a SciShow episode from June 14, 2016.
Hank Green does a great job talking about our project, and I love that he called it a “Pluto Explorer”, which rolls of the tongue better than “Pluto Orbiter and Lander”. However, he did get our fuel wrong: we are using deuterium and Helium-3, a reaction which produces no damaging neutrons. Hank cited “two types of heavy hydrogen”, which would imply deuterium-tritium fusion; this produces most of its every in very damaging neutrons, and is a reaction we go to great lengths to avoid in our machine. There will always be some tritium produced from the side reactions of deuterium with itself, but our machine is designed to exhaust it before it can fuse.
The comments from the viewers were interesting, including several along the lines of, “wait, did I miss fusion becoming a working technology?” Of course the fusion rocket is still theoretical, but it’s based on a real plasma heating experiment going on now at Princeton Plasma Physics Lab! And its true that many people don’t realize that fusion itself has been achieved in many machines, just not break-even fusion. Our machine is very different from the large tokamaks most people are familiar with.