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!

AIAA Space Forum paper on Pluto mission is live

Sadly, the AIAA Space Forum in Orlando, FL was canceled due to hurricane Irma. So, we didn’t get to present our paper on our DFD mission to Pluto. AIAA has, however, published all the forum papers and is providing free access for a few months in lieu of the actual conference. This means anyone can download it!

Fusion-Enabled Pluto Orbiter and Lander paper:
https://arc.aiaa.org/doi/abs/10.2514/6.2017-5276

Open access to the AIAA Space Forum technical program:
https://arc.aiaa.org/doi/book/10.2514/MSPACE17

Enjoy!

WHYY Radio Story Featuring DFD

WHYY reporter Alan Yu has done a radio show featuring our work for The Pulse, which presents stories of health, science, and innovation. You can read the article and listen to a podcast of the show segment, which features Stephanie, Mike, Sam, and members of the NASA NIAC program including director Jason Derleth, external council member Ariel Waldman, and NIAC fellow Phil Lubin.

http://www.newsworks.org/index.php/thepulse/item/105669-inside-the-nasa-program-that-makes-science-fiction-technology-real-

The headline for the show is, aptly, “Inside the NASA program that makes science fiction technology real.” Reporter Alan Yu visited the lab to see the PFRC in action during development of the show. The show played on the radio today, July 21, at 9 am and will repeat on Sunday at noon. Enjoy!

Foundations of Interstellar Studies Workshop

Dr. Sam Cohen and I had a good time at the Foundations of Interstellar Studies Workshop this week in NY! While we were only able to stay for the first day on “Energetic Reaction Engines”, there were many thoughtful discussions on applying fusion technology to interstellar travel. Here I am in the group photo from the welcome event Monday night, held at the Harvard Club with an interesting and wide-ranging display of interstellar art! (I’m in the first row on the far right).

Group photo

Group photo from Foundations of Interstellar Studies workshop

The workshop was almost a mini-NIAC reunion, as NIAC fellows Phil Lubin and Ray Sedwick were there, and Heidi Fern was due to present her Mach Effect thruster on Thursday. Also NIAC External Council member Lou Friedman of the Planetary Society was in attendance (very back of the photo).

Our presentation for this conference focused on how the PFRC addresses the key parameters needed for a “net positive” fusion reactor: energy confinement, current drive, plasma heating, and plasma stability. We are often asked “why fusion will work this time”, and this paper does a good job of explaining why the PFRC is different enough from other approaches to work! The workshop is going to submit all of the papers to the Journal of the British Interplanetary Society, which is the oldest astronautical journal in the world (1934).

We also discussed the parameters the propulsion system will need to achieve to reach Alpha Centauri in various time scales, as well as a more near-term mission deliver a gravitational lens telescope to 550 AU. Reaching Alpha Centauri in anything close to a human lifetime remains a significant challenge, but PFRC could be part of an architecture to reach the star in 300 to 500 years, and slow down enough to go into orbit around the potentially Earth-like planets there! The 550 AU telescope mission, however, could be achieved in as little as 12 years with just one small PFRC and is an exciting new mission possibility.

Our next interstellar appearance will be at the Tennessee Valley Interstellar Workshop in October in Huntsville, AL!

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!!