MIT Externs at Princeton Satellite Systems

Every year during MIT’s Independent Activities Period in January MIT students can apply for externships at alumni’s places of business. Externships last from one to four weeks. Over 300 undergraduate and graduate students participate each year. As part of the program, MIT also helps students find housing with alumni who live near the businesses sponsoring the externship. Externships are a great opportunity to learn about different types of career opportunities. Students apply in September and go through a competitive selection process run by the MIT Externship office.

This year Princeton Satellite Systems had two externs, Tingxao (Charlotte) Sun, a sophomore in Aeronautics and Astronautics and Eric Hinterman, a first year graduate student in Aeronautics and Astronautics. Eric started January 9th and Charlotte on the 16th after spending time on the west coast visiting aerospace companies as part of an MIT Aeronautics and Astronautics trip. Eric took a break during the externship to attend a meeting at JPL on an MIT project.

Both externs worked on our Direct Fusion Drive research program to develop a space nuclear fusion propulsion system. An artist’s conception is shown below.

Second Unit-render-1d

This project is currently funded by NASA under a NIAC grant. Eric worked primarily on the Brayton cycle heat recovery system that turns waste energy from bremsstrahlung radiation, synchrotron radiation and heat from the plasma into power that drives the rotating magnetic field (RMF) heating system. He produced a complete design and sized the system. He also wrote several MATLAB functions to analyze the system. Charlotte worked on the design of the superconducting coil support structure making good use of her Unified Engineering course skills! Here is a picture of Charlotte and Eric in front of the Princeton Field Reversed Configuration Model 2 test machine (PFRC-2) at the Princeton Plasma Physics Laboratory. Dr. Samuel Cohen, inventor of PFRC, is showing them the machine.


Both Charlotte and Eric made important contributions to our project! We enjoyed having them at Princeton Satellite Systems and wish them the best of luck in their future endeavors!

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!!

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.

Continue reading

DFD for Europa Exploration


The Galileo moons of the Jovian system are of great interest for future space exploration due to the belief that three of the four of the largest moons (Europa, Ganymede, and Callisto) contain water (in liquid and/or ice form). So far the eight spacecraft that have visited the vicinity of Jupiter are Pioneer 10 and 11, Voyager 1 and 2, Ulysses, Galileo, Cassini, and most recently New Horizons. NASA has ambitions to send another probe to further study Europa.

At Princeton Satellite Systems, in collaboration with Dr. Samuel Cohen at the Princeton Plasma Physics Laboratory, we’ve been working on the Direct Fusion Drive (DFD) engine, an advanced technology for space propulsion and power generation. Using the DFD, we have simulated two potential missions to Europa, an orbiter mission and a lander mission. The simulations were completed in MATLAB using functions contained within our Spacecraft Control Toolbox.

Continue reading

Direct Fusion Drive Mars Mission – Deep Space Habitat

Check out our new banner! We modified our spacecraft to use NASA’s Deep Space Habitat:







Image Source: NASASpaceFlight

The habitat has a 500 day configuration, with more than enough room for all of the astronauts and their supplies!

We will use the Orion spacecraft for transfer from Earth’s surface to Earth orbit, where it will dock with the DFD powered spacecraft.  That is what the banner image is portraying! Once the astronauts are aboard the DFD powered spacecraft, they will travel to Mars and back in roughly 10 months, including a 1 month stay at Mars.  After they have returned to Earth orbit, the spacecraft will dock with the Orion capsule. The crew can then safely return to Earth’s surface aboard the Orion!

Twenty-Four People

That is the number of people in the entire history of human civilization who have left Low Earth Orbit (LEO).  You heard me right, only 24 people (all Apollo astronauts) have left the protection of Earth’s magnetic field.  The prospects of journeying past LEO is a daunting one.  There is dangerous radiation in deep space that the magnetic field protects us from.

There are two types of radiation that pose a risk to astronauts: those that originate outside the solar system, the Galactic Cosmic Rays (GCR), and those that come from the sun, called Solar Proton Events (SPE).  The GCR consist mainly of heavy atomic nuclei, while the SPE, as the name suggests, consists mostly of protons.  Both of these types of radiation are high energy, so if they hit an unshielded astronaut they could cause damage to DNA, cell replication, and even lead to cell death.

The SPE, released during solar flares and coronal mass ejections, are especially dangerous as they emit so much radiation that it could be fatal to an unprotected astronaut.  Luckily SPEs are rare and none occurred during the Apollo missions.  Most of the damage from radiation is from prolonged exposure to it, which increases an astronaut’s risk of developing problems such as cancer and cataracts.

Radiation is not the only danger to astronauts on a deep space mission, though.  On a long mission, such as our proposed 308 day DFD powered mission to Mars, the extended period in weightlessness can cause issues as well.  Bones and muscles that normally have to deal with gravity suddenly do not have any load on them.  For this reason astronaut’s bones and muscles (including the heart!) begin to atrophy and lose mass.  The ones most affected are those that fight with gravity: the bones and muscles in the lower back and legs.

Astronaut Ken Bowersox runs on a treadmill using a loading harness.

Image Source: NASA 

Astronauts will need to exercise daily to minimize these losses, but even that will not be 100% effective.  Similarly there will be radiation shielding on the spacecraft and a storm shelter for the SPE, but nothing is perfect.  These are just some of the risks associated with a voyage to Mars.  Despite the risks, I do not think we will have any problems finding volunteers to be number 25!

Human Missions To Mars

You may have noticed that we have a new banner image of our Direct Fusion Drive (DFD) transfer vehicle with the Orion spacecraft.

This is because we have been able to shrink the spacecraft so that it fits on top of a single NASA Space Launch System (SLS)

Evolved Configuration launcher which can launch up to 130 metric tons into low earth orbit! The first mission would be to orbit Mars for a few days and then return to Earth. The vehicle would remain in orbit around the Earth. The next SLS launch would bring up a second transfer stage with the lander. A third launch would bring up another Orion and the crew for the landing mission.

The DFD transfer vehicles stay in low-earth orbit where they can be used for a variety of missions, such as deflecting asteroids or lunar missions.

We are currently working on the mission design along with conceptual designs of the transfer vehicle and Mars lander. A key consideration in the mission plan is keeping the astronauts healthy so astronaut physiology is a key part of our research.

Our colleagues at the Princeton Plasma Physics Laboratory

are running two experiments that support DFD. One is PFRC-2, Princeton Field Reversed Configuration 2, which is testing the reactor core. Here you see the experiment in action!


and MNX which is studying magnetic nozzles. We have two more test reactors planned, PFRC-3 and PFRC-4. The last will burn deuterium and helium-3 to produce fusion power. After that we will be ready to build a space version of the fusion propulsion system.

Of course, this reactor could be used for terrestrial power generation. In future posts we’ll talk about sources of helium-3 and alternative fuels that could power this reactor.