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.
We are very pleased to announce that Ms. Stephanie Thomas of Princeton Satellite Systems has been selected to be a 2016 NIAC Fellow. This Phase I study, entitled “Fusion-Enabled Pluto Orbiter and Lander,” will explore the possibility of using Direct Fusion Drive (DFD) to deliver an orbiter to Pluto complete with a lander. DFD is a fusion propulsion concept built upon a small, clean field-reversed configuration fusion reactor with a naturally linear geometry. The reactor becomes a rocket engine when additional propellant flows through, providing power as well as propulsion in one integrated device. This engine could halve the transit time to Pluto to 5 years from the nearly 10 years needed for New Horizons, while delivering 1000 kg worth of payload into orbit and providing up to 2 MW of power. This will enable remarkable data collection such as high-definition video and drilling into the planet’s surface. The technology provides a path to terrestrial fusion as well as eventual human missions across the entire solar system. The Phase I study will focus on creating higher fidelity models of the engine performance to enable optmization of possible mission trajectories and better quantification of the predicted specific power.
Princeton Satellite Systems had a booth at the PPPL’s Young Women’s Conference at Princeton University. Stephanie Thomas and Gary Pajer talked with students about our work in aerospace and energy.
Our booth featured a CubeSat frame designed by our mechanical engineers, a simulation of a lunar lander which could be controlled via a joystick, a copy of our new textbook MATLAB Recipes, and a Lego model of our Space Rapid Transit space plane.
The girls were divided into three large groups that rotated through the various attractions available to them, so every hour or so the the attendees changed. And every hour or so we had a fresh cohort of faces to meet. Many of the girls were very interested in what we are doing, and asked insightful questions. For example, one girl asked “What happens when a satellite loses track of where it is? Does it just get lost?” Of course, that’s an important issue, one that we at PSS have spent considerable time addressing.
Some girls were very interested to learn about tiny CubeSats (“This isn’t a model, this is the actual size of the satellite!”), and still others were interested in horizontal launch possibilities as shown by the Lego model – i.e. most rockets launch vertically, but this could take off at any airport. Both of these are examples of systems that we regularly model using our commercial software packages.
For more information see the 2016 Young Womens’ Conference
Mike Paluszek gave a talk on the Pluto Orbiter mission to the Rutgers Engineering Honors Council Keynote Speaker Event on March 22, 2016. The talk covered the mission and spacecraft and outlined the design process. Mike also discussed engineering careers and how to make the most of one’s own career.
From a member of the audience, “Just wanted to thank you once more for the wonderful talk you gave last Tuesday evening!”
This is a photo of the group.
A photo of Mike with the officers.
New functions in the Lunar Cube module in 2016.1 allow you to easily plan lunar insertion and orbit change maneuvers. In the following pictures you can see a lunar orbit insertion from a hyperbolic orbit. In all figures the lunar terrain is exaggerated by a factor of 10.
The same maneuver looking down on the orbit plane. The green arrows are the force vectors.
The following figure shows a two maneuver sequence. The first puts the spacecraft into an elliptical orbit. The second circularizes the orbit.
We are adding the Lunar Cube Module in 2016.1 to our CubeSat Toolbox for MATLAB! It allows users to analyze and simulateCubeSats in lunar transfer and lunar orbit. It includes a new dynamical model for CubeSats that includes:
- Earth, Moon and Sun gravity based on the JPL ephemerides
- Spherical harmonic lunar gravity model
- Reaction wheels
- Power generation from solar panels
- Battery energy storage
- Variable mass due to fuel consumption
- Solar pressure disturbances
- Lunar topographic model
- New graphics functions for lunar orbit operations
- Lunar targeting function
- Lunar mission control function for attitude control and orbit control
The module includes a script with a simulation of a 6U Cubesat leaving Earth orbit and reaching the moon. The following figure shows the Earth to Moon trajectory.
This figure shows the transfer orbit near the moon. The lunar topography is exaggerated by a factor of 10 to make it visible. It is based on Clementine measurements.
Here are results from the new LunarTargeting function. It finds optimal transfers to lunar orbits. The first shows the transfer path to the Moon’s sphere of influence.
The next shows the lunar hyperbolic orbit. In this case the transfer is into a high inclination lunar orbit.
Contact us for more information!
Stofiel Aerospace LLC had a display at the Consumer Electronics Show. They invited Princeton Satellite Systems to display its products on their table. The booth is shown in the following picture. You can see Stofiel’s rockets.
Here is a closeup showing our 3U CubeSat with a camera mounted in one of the bays.
Members of the Stofiel team:
More members of the Stofiel team:
Stofiel Aerospace LLC is an aerospace solutions company created by five U.S. military veterans from Cleveland, Ohio. Stofiel Aerospace LLC is currently developing a portable micro/nano-satellite launch system. Their revolutionary system drastically reduces the wait time for small payloads to reach low Earth orbit to days, not years. By utilizing solid rocket motors and Hydrogen-filled balloons, their system finally offers CubeSat manufacturers and clients the opportunity to be considered a “primary payload” for orbital missions. Currently, they are partnered with the Ohio Aerospace Institute in Cleveland, Ohio and working for further funding to continue development of this industry-changing technology. For inquiries, please contact Jason Beeman, CFO at (440) 994-9035.
The following image shows SunStation in operation on a bright October day! The load for the day was 12.4 kWh. This includes charging a Nissan Leaf and a Toyota Prius Plugin-in. The total power generated was 40.3 kWh and 21.4 kWh was sold to the grid. As you can see, the installation is much more than carbon neutral with regard to electrical power. It has a gas heating system so is not completely carbon neutral.
The orange line is the state of charge for the batteries. The 14.4 kWh of batteries is enough to keep the home running, charge the Prius fully and the Leaf partially, when the grid is down. The system automatically disconnects itself from the grid when there is an outage.
The house itself is fairly energy efficient with mostly LED lights and a few CFLs. The heating system is high efficiency with a 60 W fan that operates most of the time. The house is air-tight and has a whole house air exchange system that operates continuously. The refrigerator is 10 years old and the washer and dryer are less than 10 years old. As you can see, the typical load is 500 W except when the cars are charging. The efficiency could be further improved by installing a state-of-the-art central air system and replacing the refrigerator.
The Nissan Leaf is 100% electric. On a normal day the Prius operates on battery stored energy about 80% of the time. It visits the gas station once every 3 weeks or so.
Besides saving money on power, the system produces 7 Solar Renewable Energy Credits (SRECs) yearly. At current SREC prices, that is about $1500 a year in revenue. The homeowners own the system so all the revenue goes directly to them.