About Stephanie Thomas

Ms. Thomas is vice president of Princeton Satellite Systems. She is the Principal Investigator for the NASA NIAC grant supporting Direct Fusion Drive. Ms. Thomas has been with PSS since her first internship as an MIT undergraduate in 1996!

Princeton Satellite Systems Selected for Two NASA STTRs

We have been selected for two NASA STTRs on their new topic, T2.01-9960, Advanced Nuclear Propulsion! Our research institution partner is Princeton Plasma Physics Laboratory. Our proposals were featured in NASA’s official press release! Here is a quote:

High temperature superconducting coils for a future fusion reaction space engine. These coils are needed for the magnetic field that allows the engine to operate safely. Nuclear fusion reactions are what power our sun and other stars, and an engine based on this technology would revolutionize space flight.

You can read our project abstracts as posted on NASA’s SBIR website:

These Phase I STTRs of $125,000 each will run for one year, at which point we have the opportunity to propose Phase II work up to $750,000. If successful, they will go a long way towards demonstrating critical subsystem technology needed for DFD and other high-tech space propulsion technologies!

 

NIAC Phase I Final Report

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.

Enjoy!

DFD paper accepted for Workshop of Interstellar Flight

Our paper “Direct Fusion Drive for Interstellar Exploration” has been accepted for the Workshop of Interstellar Flight that will be held at CUNY City Tech, 13-15 June 2017! The workshop is organized by the Institute for Interstellar Studies and City Tech’s Physics Department and Center for Theoretical Physics.

We will present the latest results from our NASA NIAC work on DFD design as well as applications to interstellar missions, including:

  • A mission to 550 AU to perform gravitational lensing imaging of exoplanets;
  • Flyby missions to the nearest star;
  • A mission to go into orbit about a planet orbiting either Alpha-Centauri A or Alpha-Centauri B.

NASA NIAC Phase II selected!

We received notice today, March 31, 2017, that our NASA NIAC Phase II proposal was selected for award! We will be able to continue working on the Direct Fusion Drive with PPPL for two more years. Hooray! Dr. Joseph Minervini of MIT will be joining our team to help advance our understanding of the trade space for the superconducting coils, using the very latest data from high-temp superconductor manufacturers. It’s going to be exciting research!

Here’s a link to NASA’s official project summary.

Opening for a part-time bookkeeper/administrator

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;
  • procurement;
  • 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 info@psatellite.com! Also see our post on LinkedIn.

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!!

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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