Upgrade underway of Princeton Field Reversed Configuration-2


The Princeton Field Reversed Configuration-2 (PFRC-2) upgrade in field and frequency is underway. We are currently installing new coils around the experiment to increase the magnetic fields and new capacitors to help lower the RF operating frequency – all to reach our target milestones of measuring ion heating! This is an essential next step in our development of Direct Fusion Drive.

The power supplies are stacked in their rack, ready to supply power to the belt coils. The supplies must be programmed to energize for each pulse as they are not cooled and the coils would otherwise overheat. The belt coil holder component on the right was 3D printed at PPPL.

The new 2 nF capacitors, shown above (left image), must be enclosed in a custom copper box that will be part of the tank circuit of PFRC-2. Each component must be carefully designed, including the lengths of the connecting cables, for us to get the right frequency without exceeding voltage limits of the materials.

The above image is of the cable that will connect the tank circuit and the PFRC-2. These cables are very robust, and stiff so that the layout must be carefully planned. We will continue to post updates as we work towards that 2 MHz frequency milestone!

PFRC-2 has been funded by ARPA-E OPEN 2018, NASA NIAC and DOE Fusion Energy Sciences grants.

A Third Planet Discovered Orbiting Proxima Centauri


A third planet, as large as 26% of the mass of Earth, has been discovered orbiting our nearest stellar neighbor, Proxima Centauri .Astronomer João Faria and his collaborators detected Proxima Centauri d using the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations.

It would be exciting to send a spacecraft to enter the Alpha-Centauri system and orbit this planet. At Princeton Satellite System we’ve looked at interstellar flight using the Direct Fusion Drive nuclear fusion propulsion system.

Interstellar Fusion Propulsion

At the 2021 Breakthrough Energy Conference we presented findings for both flyby and orbital missions. Flyby missions are easier, but orbit entry would allow detailed study of the planet. A flyby gets your spacecraft close, but it is moving really fast!

The following charts give an outline of our talk. The first shows the optimal exhaust velocity based on sigma, the ratio of power to mass. Our designs have a sigma from 0.75 to 2 kW/kg. With 2 kW/kg, the optimal exhaust velocity is 4000 km/s. The mission would take about 800 years. Our current designs can’t get exhaust velocities higher than 200 km/s. We’d need another method to produce thrust.

Mission Analysis

The next plot shows a point mission that reaches Alpha Centauri in 500 years. This requires a sigma of about 20. The spacecraft accelerates and decelerates continuously. The mission could be improved by staging, much like on a rocket that launches from the Earth into orbit.

Selected Mission

The next figure shows how the starship would enter the Alpha Centauri system.

Alpha Centauri System Insertion

The final plot shows the orbital maneuvers that lower the orbit and rendezvous with the planet.

Lowering the orbit to rendezvous with the planet.

Even 500 years is a long time! This is over ten times the lifetime of Voyager, but much less than some engineering marvels built on the Earth.

We hope to someday be able to build fusion powered spacecraft that will head into interstellar space!

Nuclear Fusion Power

Nuclear fusion power research started in earnest in the 1950’s. Initially, researchers thought that the work needed to produce a fusion power plant would be comparable to that needed to produce the first fission plants. That turned out to be unrealistic as the physics was not well understood and plasma confinement was much more difficult than expected. Many of the first machines were Stellarators. One of the first was Lyman Spitzer’s Stellarator at the Princeton Plasma Physics Laboratory (PPPL).

Many machine geometries were tried such as mirrors and pinches. In the 1960’s the Soviets disclosed success with the Tokamak (тороидальная камера с аксиальным магнитным полем). Unlike the Stellarators, Tokamaks have a circulating current that helps confine the plasma. Since then Tokamaks have been the focus of fusion power research. The Princeton Plasma Physics Laboratory produced 10.7 MW of fusion power in 1994 in the Tokamak Fusion Test Reactor (TFTR). The Joint European Torus (JET) produced 22 MW of fusion power in 1997. In 1998 the Japanese JT-60 produced an equivalent power gain of 1.25, that is 1.25 MW of fusion power for 1 MW of input power. The next step in Tokamaks is the International Thermonuclear Experimental Reactor (ITER).

ITER is a large-scale scientific experiment to demonstrate that it is possible to produce commercial energy from fusion. Its goal is to produce a fusion power gain of 10 at a power level of 500 MW and to generate this power for 500 seconds. Operation with tritium is scheduled to begin in 2027. The next step after ITER is DEMO which will be a prototype of a practical fusion power plant. Demo will produce between 2 and 4 GW of thermal power and have a power gain of 25. After DEMO the next machine will be PROTO which will be a fully commercial power plant. PROTO is expected to built after 2050.

In parallel with ITER many other magnetic confinement devices are under test. These include the U.S. National Spherical Tokamak (NSTX) and the Princeton Field Reversed Configuration (on which DFD is based) both at PPPL. Many new Stellarators are under test including the Wendelstein 7-X in Germany, the Helically Symmetric eXperiment (HSX) in the U.S. and the Large Helical Device in Japan. These devices may result in more economical fusion machines than Tokamaks. The field of fusion researchis very vibrant and work around the world is serving to improve our knowledge of plasma physics and the help solve the engineering problems. For example, recently a new method for reducing instabilities was developed at JET.

The first commercial reactors will likely use deuterium and lithium as fuels. The reaction (used in TFTR, JET and ITER) is deuterium and tritium but in a commercial plant the tritium would be produced from the neutron bombardment of lithium as the D-T reaction produces most of its energy in energetic neutrons. Advanced fuels like deuterium helium 3 and boron proton that produce fewer neutrons are also under investigation. Deuterium and helium 3 would power the DFD. The boron-proton reaction would power TriAlpha’s reactor.

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!

PSS at Princeton Plasma Physics Lab Open House

On Saturday April 1, PSS participated in the Princeton Plasma Physics Lab Open House to show case our Direct Fusion Drive and our conceptual nine-month manned space mission to Mars in 2024! Our new fusion engine enables shorter transfer times and total mission durations, critical for interplanetary manned space flight. We had great interest in our human mission and many budding astronauts were ready to sign up for the trip.


Please see our educational page for some fun DFD material for your space enthusiast:


More information on this exciting project is available on our Fusion webpage:


Our SunStation products for Home Back-Up and EV Charging were also on display at the PPPL Open House. SunStation is a green way to provide emergency power to critical loads in your home during an electrical service interruption or to charge your electric vehicle without using any grid power!


Get to Mars Quickly with the Direct Fusion Drive

Do you really want to spend the next 501 days locked in a tiny room with your spouse, hurtling toward the Red Planet just to take a few snap shots from 100 miles away? What about competing with 10,000  people to build the first Martian colony on a “Big Brother”-style reality TV series?

What if you could just go for a few months to do some research?  What if you could not only get there quickly but without any of the radiation dangers from fission or even from burning deuterium-tritium fuels?

The Direct Fusion Drive (DFD) is a novel system that we have been developing with the Princeton Plasma Physics Lab, and two weeks ago we filed a thrust-augmentation patent for the DFD.  Propellant gasses such as deuterium and helium can be pumped into a gas box and weakly ionized. These flow out along the magnetic field lines of the scrape off layer and pass around the closed-field region of the field-reversed configuration.  Fusion products fly out into the scrape off layer at 25 millions meters a second and collide with the propellant, heating it up (and therefore speeding it up), and then everything gets ejected through the magnetic nozzle.

If propellant wasn’t added, then the fusion products would give the spacecraft a velocity of around 25 million meters per second but would provide only a fraction of a Newton.  By adding propellant, the exhaust velocity drops directly proportional to the thrust.  An exhaust velocity of a few dozen km per second is sufficient for many missions and therefore tens and even hundreds of newtons of thrust can be achieved.