NIAC Pluto mission talk now available online

On Tuesday, August 23rd I had the privilege of giving my talk on our Fusion-Enabled Pluto Orbiter and Lander at the 2016 NIAC Symposium. The video of the LiveStream is now archived and available for viewing. My talk starts at 17:30 minutes in, after Michael VanWoerkom’s NIMPH talk.

The talk was well-received and we had some good questions from the audience and the LiveStream. In retrospect I did wish I had added a slide on our overall program plan in terms of the PFRC machine and temperature and field strength, since I got quite a few questions on those specifics at the poster session. PFRC-1 demonstrated heating electrons to 0.3 keV in 3 ms pulses. The goal of the current machine – PFRC 2 – is heating ions to 1 keV with a 1.2 kG field. The next machine I refer to in the talk, PFRC 3, would initially heat ions to 5 keV with a 10 kG field, and towards the end of its life we would push the field to 80 kG, heat ions to 50 keV, and add some helium-3 to get actual fusion events. The final goal would be 100 second-duration plasmas with a fusion gain between 0.1 and 2. A completed reactor would operate in steady-state.

Thank you NIAC for this opportunity!!

Low-jitter Reaction Wheel Prototype for Kestrel Eye

The Army is developing the Kestel Eye imaging microsatellite to provide ground imagery directly to the warfighter.    The goal of the program is to provide tactical grade images to forces on the ground at any time and deliver the images fast enough for use in fast moving ground operations. The satellite will provide battlespace awareness for rapidly evolving tactical situations on the ground, for example: the implanting of Improvised Explosive Devices (IEDs); perimeter security of forward operating locations; or movement of hostile motorized forces.

Princeton Satellite Systems is under contract to develop a control system to  meet the exacting standards of stability, satellite location, and pointing accuracy required to meet the needs of the Kestrel Eye satellite.  The objective of our work at PSS is to improve the pointing accuracy or the ground location accuracy of the Kestrel Eye imagery from 60 meters to 10 meters or less.

The features of the proposed control system that are critical to enabling this superb accuracy are:

• Ultra-precise star image centroiding with custom algorithms
• Miniature precision fiber-optic gyro for attitude base and high bandwidth control
• Low-jitter microsatellite reaction wheels utilizing Halbach array motors
• Nonlinear attitude filters incorporating star camera and nontraditional measurements • Composite structure to eliminate thermal distortion
• GPS orbit determination enhanced with two-way ranging

Recently, PSS has completed the design and fabrication of the first prototype reaction wheel.  The wheel is driven by a low-jitter axial flux brushless DC motor, the design of which is currently under patent review.   An important enabling technology is the Halbach array of magnets.  A Halbach array is sequence of permanent magnet segments, each with its magnetic axis rotated from the axis of its neighbor.  The resulting assembly concentrates almost all of the magnetic field on one side, with an almost negligible field on the other side.  This arrangement favors an axial flux motor with a single stationary stator holding coil windings sandwiched between two permanent magnet rotors, each of which has its Halbach field directed toward the stator.  The sketch shows the arrangement.  The stator is green, and the two rotors are red.

rwa_cutaway

We’ve gone through a number design iterations,  settled on a first prototype design, and fabricated it.  We also purchased a simple general-purpose motor driver in order to explore the operation of the motor before moving on to developing custom driver electronics.

We’re very pleased that our first iteration works.  Here’s a video showing the device in action.

We’re already at work on the second-generation wheel incorporating lessons learned in the first prototype.

NEA Scout Toolbox

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

NEAScoutCAD

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.

RWATorque

This GUI shows the current command and allows you to control the simulation.

CommandGUI

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.

figui

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.

Telemetry

This figure shows solar sail pointing during simulations.

SailPlot

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.

NEAScoutCADWithSail

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.

NIAC Orientation

I had a great time at the NIAC orientation in Washington DC last week, where I got “mugged” with program manager Jason Derleth:

Stephanie Thomas and Jason Derleth posing with a NIAC mug

Stephanie receiving her NIAC mug from Jason

The meeting was at the Museum of the American Indian, which was a great venue with so much beautiful art to see, and a cafe featuring unusual native foods from across America (elderberry sauce on the salmon). I had the opportunity to meet the other NIAC Fellows, and put names and faces to the other creative projects selected, as well as meet the illustrious NIAC external council. These experienced folks provide advice and encouragement throughout the NIAC process from their experience as physicists, engineers, biologists, science hackers, and even science fiction authors.

I have to say, my poster on the fusion rocket engine was popular, and everyone wanted to know how it works, why it hasn’t been funded already, and how soon the engine can be ready. Of course, we have yet to actually demonstrate fusion using Dr. Cohen’s heating method, but that is why we need the NIAC study – to flesh out the science and engineering of the rocket application to help bring in funding for building the next generation machine. And yes, let’s get to Pluto in only 4 years the next time! I’m really looking forward to working on the project in the next few months and presenting it at the NIAC symposium in August!

 

PSS NASA project on SciShow

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.

NASA Innovative Advanced Concepts (NIAC) Selection

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.

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PPPL’s Young Women’s Conference

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.

STEM_Image

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

Rutgers Engineering Honors Council Keynote Speaker Event

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.
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A photo of Mike with the officers.

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Lunar Orbit Insertion Maneuver

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.

LunarMnvr2

The same maneuver looking down on the orbit plane. The green arrows are the force vectors.

LunarMnvr1

The following figure shows a two maneuver sequence. The first puts the spacecraft into an elliptical orbit. The second circularizes the orbit.

Lunar3

Lunar Cube Module for 2016.1

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
  • Thrusters
  • 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.

LunarTrajectory

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.

LunarEncounter

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.

Test21

The next shows the lunar hyperbolic orbit. In this case the transfer is into a high inclination lunar orbit.

Test22

Contact us for more information!