NIAC Phase II Award: Fusion-Enabled Pluto Orbiter and Lander

Fusion-Enabled Pluto Orbiter and Lander (Credit: Stephanie Thomas)

Fusion-Enabled Pluto Orbiter and Lander

Stephanie Thomas
Princeton Satellite Systems, Inc.
Plainsboro, NJ

Amount: up to $500,000
Length of Study: 2 years

Description

The Direct Fusion Drive (DFD) concept provides game-changing propulsion and power capabilities that would revolutionize interplanetary travel. DFD is based on the Princeton Field-Reversed Configuration (PFRC) fusion reactor under development at the Princeton Plasma Physics Laboratory.

The mission context we are proposing is delivery of a Pluto orbiter with a lander. DFD provides high thrust to allow for reasonable transit times to Pluto while delivering substantial mass to orbit: 1000 kg delivered in 4 years. Since DFD provides power as well as propulsion in one integrated device, it will also provide as much as 1 MW of power to the payloads upon arrival. This enables high-bandwidth communication, powering of the lander from orbit, and radically expanded options for instrument design.

The data acquired by New Horizons’ recent Pluto flyby is just a tiny fraction of the scientific data that could be generated from an orbiter and lander. Engine modeling accomplished during Phase I has shown that we can expect 2.5 to 5 N of thrust per megawatt of fusion power, with an Isp of about 10,000 seconds and 200 kW available as electrical power.

We have evaluated the components of the Pluto trajectory including an Earth departure spiral, constant thrust planar transfer, and Pluto insertion using these thrust and Isp levels, and confirmed the plausibility of the proposed mission. In fact, the mission can depart from LEO with about the mass we originally estimated for an interplanetary insertion, widening the range of available launch vehicles and reducing the cost.

The key objective of the Phase II proposal is to further advance the design and TRL of selected subsystems, such as the superconducting coils, RF heating, and shielding. PPPL will perform experimental work on the existing PFRC-2 testbed using a gas puff valve, to further investigate the dynamics of the thrust augmentation system (additional gaw flowing through the FRC scrape-offlayer).

We will explore the design of a no-thrust mode that captures and reuses the propellant, possibly extracting more power while in orbit around Pluto. Finally, we will develop a model of the synchrotron radiation that is specific to the FRC configuration, as available models are derived from tokamaks.

Direct Fusion Drive is a unique fusion engine concept with a physically feasible approach that would dramatically increase the capability of outer planet missions. The fusion-enabled Pluto mission proposed here is credible, exciting, and the benefits to this and all outer planet missions are difficult to overstate. 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.

Full List of 2017 NIAC Awards

Save

Save

Save

Save

Save

  • Kapitalist

    There are video presentation available for several of these exciting NIAC projects, here about the Pluto fusion thing:
    https://www.youtube.com/watch?v=IlydFJtWeXg

    A fusion rocket should be a bit easier to make than a fusion electric power plant, because the very purpose of an engine is to just spew out hot gas into space. If they can be made as small as suggested in this study, it could become a huge military and commercial success.

  • therealdmt

    Wow, make it so!

    “This enables…powering of the lander from orbit”

    Crazy.

    I wonder what the stumbling blocks are…

  • therealdmt

    Ah, the ol’ superconducting coils hang up…

  • therealdmt

    Hmm, maybe there really is going to be something to all that He3 folderol after all

  • Kapitalist

    Fusion rocketry will happen. Even if it takes a million years, it will happen. All the stars do it naturally. An engineering civilization will figure out how to use this nature one way or another. It scales up from fusion bombs and fusion rockets to fusion electrics.

    Thank God we survived the first stage there!
    That was the easiest and most dangerous step to take. And now it is behind us. Even nuke waging politicians seem to have a limit to their madness, that’s a good sign!

    The power of the Sun, fusion power, is so immense that it deters warriors. Making them look for more useful jobs instead.

  • Paul_Scutts

    Fortunately, therealmt, that’s one area (superconductivity) where the harsh environment of space can become a real plus, as materials at cyrogenic temperatures naturally tend to become superconductive. Regards, Paul.

  • JamesG

    If this propulsion system actually works, it will have a LOT more application than just a short-cut to Pluto. In fact at this TRL I don’t see why its even coupled to a proposed Pluto mission, unless the bucket o’ NIAC money it came out of was the “planetary sciences” one..

  • Paul451

    “Space” isn’t cold. A fusion reactor in space is really not cold.

  • Paul_Scutts

    Thanks for your reply, Paul451. “Space” is a near perfect vacuum, which means that if you “shade” an object it will absorb precious little “energy” from it’s external environment. Cyrogenic temperatures, therefore, require far less “energy” to be expended, to be sustained. Regards, Paul.

  • therealdmt

    I was actually thinking more about the hang ups to get it ready to develop (and get funding for) a ground demonstration so that a precursor [to the notional Pluto orbiter application] could be funded, developed and eventually flown — basically, the TRL stuff that will need to be done here on Earth.

    But it’s an interesting point you make that in some ways this would actually be easier to do in space (well, at least in regard to the superconductor coils involved).

  • Paul451

    That same vacuum makes it much harder to get rid of excess heat. Maintaining cryogenic temperatures in any kind of working vehicle is extremely difficult, even when its systems are only running at a few hundred watts. In practice, we’ve only been able to do it for space-telescopes by having on-board stores of cryo-liquids (in addition to sun shades). Doing so for longer than a few minutes while running a fusion reactor is going to be impossible; barring SF-level technology.

    Oh, and that shade, it’s reflecting your own heat back at you, making your radiators even less efficient. You can’t get cryo-temps from radiators alone. Otherwise we would have already done that for IR telescopes.

    Space is not cold.

  • Michael Vaicaitis

    It’s been quite well known for the last 75 years that net positive fusion energy devices using magnetic confinement are only 30 years away. I fully expect this machine to be in the same category – in a thousand years, it will be only 30 years away. Magnetic confinement of fusion plasma – when will they learn?.

  • Saturn13

    This award should be reported to the US Gov. waste, fraud, abuse website.

  • geostar1024

    A 40 m^2 radiator at 1000K can radiate just over 2 MW. So there’s no physics reason why you can’t cool a 2 MW fusion reactor and keep onboard liquids at cryogenic temperatures with a cryocooler. Probably it’s not done with current IR telescopes because the power requirements, mass, and additional complexity for a cryocooler outweigh the benefits over the duration of the mission.

  • geostar1024

    -demonstrating the heating method for the fusion reactor and achieving breakeven
    -building superconducting magnets with low enough mass
    -system integration of the heat engine and cooling systems
    -design of the laser system

    Of these, the main physics stumbling block is the first point; the rest are much more engineering problems.

  • NASA’s complete disconnection of discernible empirical reality is complete.

    Mo Disney, less NASA.

  • JamesG

    But any of which could make this a $500K exercise in wishful thinking…

  • JamesG

    This is small change compared to the money the USG wastes on a daily basis.

  • Paul451

    How much heat could a 40m^2 radiator get rid of on Earth?

    Convective cooling is at least an order of magnitude more effective, even relying on passive (adiabatic) air flow. Add in a fans and… Here’s one I prepared earlier. 0.7m^2 radiator for 2MW cooling, $200ea.

  • geostar1024

    Yes, convective cooling is great to have when you’re immersed in a fluid with a nontrivial heat capacity. My point was simply that cooling a 2 MW-producing device in space entirely by radiation is not a big deal (incidentally, that 40 m^2 radiator could be just two 2m x 5m carbon-carbon radiators, with a mass of around 100 kg). There are a number of physics and engineering challenges for this mission, but cooling the spacecraft is not one of them.

  • Paul451

    Yes, convective cooling is great to have when you’re immersed in a fluid with a nontrivial heat capacity.

    I was responding to Paul Scutts’ implication that it’s somehow particularly easy to maintain cryogenic temps in “space”. “Fortunately, [] that’s one area (superconductivity) where the harsh environment of space can become a real plus”.

    There are a number of physics and engineering challenges for this mission, but cooling the spacecraft is not one of them.

    The issue wasn’t cooling the spacecraft, it was cooling the superconductors.

  • geostar1024

    The issue wasn’t cooling the spacecraft, it was cooling the superconductors.

    Fair enough; I was mistaken about what point you were arguing. Anyway, we agree: just exposing the superconductors to space isn’t going to get the job done in terms of cooling.

  • Kapitalist

    I think NIAC has a great value for motivating and recruiting the most ambitious people and is seen as a learning opportunity for them. It’s cheaper than a toilette on the Orion anyway.

  • Paul_Scutts

    “Space is not cold” – Do a little research, Paul451 and don’t get cute about semantics. Objects in space shaded from sources of heat, lose their own heat and “get cold” really fast. If you don’t believe me, just ask Jim Lovell or Fred Haise (the only thing that saved them and saves us is the energy provided by our sun).

  • I always thought of NASA NIAC as a writing opportunity, as I have more respect for achievable goals more worthy of public funding rather than space cadet wet dreams.

  • Paul451

    So, things that are cold … stay cold

    And things that produce a lot of heat, stay hot. A fusion reactor produces a lot of heat. The rest of the vehicle will not reach cryo-temps simply by being in space. Superconducting magnets around the fusion reactor will not reach cryotemps by being exposed to space. Being in space not only doesn’t help, it makes things very very difficult.

    You said something stupid, I called you on it. It’s got nothing to do with semantics.

  • Paul_Scutts

    Paul451, don’t “burst into flames” over all this, Paul, the principles of thermodynamics dictate that heat energy flows from a “warm” body to a “cold” body until they reach the same “temperature”. The average temperature of space is 3 degrees Kelvin. Therefore, maintaining cyrogenic temperatures in space is much easier than maintaining them upon Earth where, fortunately, things are much, much warmer. I am not attempting to discuss the engineering required to capitalise upon this principle, just that the principle is there to be capitalised. Or, do you deny this principle (calling it “stupid”)? Paul.

  • JamesG

    Depends on if they can isolate the reactor part from the solenoid part. Superconducting magnets can create very sharp magnetic gradients that might/should prevent conductive heating of the throat. All you have to do is dump the radiative heating overboard. Maybe.

  • JamesG

    “30 years away” is the sweet spot for funding. Close enough that you can keep convincing holders of the purse strings to keep giving you money, far enough away that you don’t actually have to produce any real results. All you have to do is build hardware that looks impressive and spends a lot of money.

  • Paul451

    the principles of thermodynamics dictate that heat energy flows from a “warm” body to a “cold” body until they reach the same “temperature”.

    {sigh} Fine. The rate of radiative cooling depends on the fourth power of the temperature difference between the source and the sink. Okay? If you want to cool a material to cryogenic temperatures in space, you are trying to eliminate built-up heat into a background only a few K cooler than the target temperature. That results in very slow rates of cooling.

    However, the fusion reactor is… hot. Therefore, even ignoring conductive heating of the superconductors, the radiative temperature difference is very high, thousands, perhaps millions of K. Raised to the fourth power, that gives you at least tillions, and perhaps quintillions of times more rapid rates of heating than cooling. Therefore the radiator area would need to be tillions, perhaps quintillions of times larger than the area of superconductor.

    [If there is any material contact between the inner surface of the fusion chamber and the magnets, then no matter how well insulated, thermal conduction will completely dominate the equation.]

    Therefore, maintaining cyrogenic temperatures in space is much easier than maintaining them upon Earth where, fortunately, things are much, much warmer.

    Wildly incorrect. And the reason I made my initial comment. Dumping heat into space is very difficult. It’s one of the major issues in spacecraft design once you start adding serious power.

  • JamesG

    Fiscal death of a thousand cuts. Every government minion with the authority to spend taxpayer’s money says the same thing. “Oh, its only $10 here, or… $19,765 there. No big deal. We’ve got it in the budget. Use it or lose it! An’t my money after all.”

    Until it all adds up to $19 Trillion dollars.

  • Robert G. Oler

    No lets not do this…instead keep on doing the same things we have been doing for the last 50 years and in particular the last 16 building SLS and Orion to go meekly where we once went boldly

    Snark off…I hope this works…it would be amazing

  • DrPlamsa

    Hello! Graduate student here working on the PFRC experiment from which the DFD is based.

    It looks like your biggest question is “What makes this different from other magnetic fusion devices?” Well, I think I can answer:
    1) High “plasma beta.” In a Tokamak or Stellarator, the vast majority of the magnetic field isn’t a confining field, it’s a stabilizing field. The PFRC uses entirely confining field. The result is that, compared to a Tokamak, using the same magnetic field strength the PFRC could contain 20x the plasma pressure or 400x the fusion power density.
    2) Size. Size infects everything. In the 1990s we reached the point at which the next fusion science experiment in the leading magnetic fusion devices would cost >$1B. When your experiment iteration costs $1B, every little aspect of its design is similarly afflicted with cost. The PFRC can’t get that big. It’s method of current drive and heating fails before it gets that big.
    3) Aneutronic. Burning Deuterium and Tritium as your fusion fuel makes a lot of sense on paper. It’s very power-dense and happens at a lower temperature than others. But as soon as your fusor has to withstand 100X the neutron flux of the core of a fission power plant, your reactor becomes mostly shielding. The choice of Helium-3 isn’t arbitrary; it’s a game changer.

    Please don’t think of the magnetic fusion program as a failure. It’s not produced a useful fusion reactor; that’s true. But the 60+ years of experimentation haven’t given us 60+ years of wasted time. We have 60+ years worth of understanding of plasma physics. Our models for how plasma behaves and can be contained are huge leaps and bounds more advanced and accurate than they were in the 1970’s when fusion’s PR heyday was.

  • geostar1024

    Aside: Your radiator calculation assumes maintaining a vehicle temperature of 1000k.

    Well yes, to be perfectly accurate, the 1000K panels would be for the heat engine attached to the reactor. You’d probably need additional smaller panels operating at a lower temperature for the output of the cryocooler.

  • geostar1024

    And how would you classify the hundreds of billions spent each year on military expenditures? At least NIAC money encourages the investigation of interesting solutions to hard scientific/engineering problems, rather than optimizing the killing efficiency of weapons platforms.

  • JamesG

    Ah, but see, from the government, and in particular Congress’s, perspective it s all the same. Its the exercise of power in the form of allocating spending. Be it funding better mousetraps and other killing machines, enlargening the welfare state, to dubious “art”, every cent the government spends is done to some rational or another. Which is more important depends on where your interests are. Scientists, General, Community Organizer, etc. An endless number of mouths constantly calling out to be fed all sure that their program is the most important of all.

  • Vladislaw

    Would be nice to have 100 million to toss at her company just to see where they can take this…

  • geostar1024

    All of the proposed projects had to be presented in the context of a real mission. Using Pluto as the destination highlighted some of the important benefits of fusion propulsion over chemical propulsion while taking advantage of the interest surrounding the New Horizons flyby of Pluto.

  • Michael Vaicaitis

    Thanks for the comprehensive reply – perhaps I should recalibrate my scepticism.

    “…the magnetic field isn’t a confining field, it’s a stabilizing field. The PFRC uses entirely confining field.”
    “…could contain 20x the plasma pressure or 400x the fusion power density.”

    Is not the major confinement issue, ultimately plasma instabilities?. Temperature and density (i.e. pressure) are clearly required for sufficient fuel burn, but somewhere on the road to net energy, instability is bound to occur. If the plasma is net energy positive, then by definition the plasma has more energy than the magnetic confinement. Which in turn means that the magnetic fields of instabilities will be stronger than the confinement fields. In short, I don’t see how artificial confinement is possible – in particular magnetic or electrostatic.
    I am somewhat of an admirer of Focus Fusion, in that, like stars, they use instabilities to generate confinement – I suspect this is the only feasible confinement method for net energy. That said, stars don’t have the materials and engineering challenges that a power plant does. I’m also an advocate of molten salt reactors. Why do we even need fusion, unless they can be cheaper than the alternatives?. Fission can be simple and cheap and we have billions of years of fuel.

  • DrPlamsa

    Hello again. It’s gratifying to see interest in fusion!

    I do want to clarify some things I read in your response, though. The first is the difference between net power out and high plasma energy. While the PFRC does expect to have almost as much stored plasma energy (volume-integral of plasma pressure) as magnetic energy, not all schemes to produce magnetic fusion reactors do. In fact, in a Tokamak, the plasma energy is 20X lower than the magnetic energy and even Tokamaks are plagued by instabilities. What I want to indicate with this example is that while plasma energy vs magnetic energy is one of the important parameters that determines what type of instabilities occur, it is not by any means the final word in the analysis.

    Analysis really is the right word; the past 60+ years of research has given us a much better picture of when instabilities will form and how bad they’ll make confinement. In plasma physics conferences you will hear talk of almost a taxonomy of different instabilities, “kinetic ballooning modes” and “firehose instability” and “drift instabilities” etc., but while this sounds like stamp-collecting, these esoteric names are really backed up with very detailed understanding of how particles and fields collectively oscillate to self-amplify. For the PFRC we’ve identified a collection of parameters which is predicted to be essentially free of global instabilities and have a level of local instabilities much lower than that of a Tokamak. Our experiment, for example, has run for >300ms, 100,000x longer than the characteristic instability growth time for what was predicted to be the most virulent category of instabilities for our configuration.

    Regarding focus fusion, I think you give fusion scientists too little credit. Instabilities are used all over fusion science. In Tokamaks, the phenomenon of “bootstrap current”, which is responsible for driving the confining field, is technically an instability. So, too, is the technique of “helicity injection” which is used to start up some devices.

    As a fun fact, the PFRC produces a magnetic configuration that has the same magnetic topology as the “plasmoid” that’s produced in dense focus fusion! We may be more alike than you realize.

    Also, stars cheat. We can’t use gravity in our fusors.

  • Michael Vaicaitis

    “…the plasma energy is 20X lower than the magnetic energy…”
    Is the plasma transparent to the fusion energy?. How do they plan to get the heat out without energising the plasma further?; and does a similar question apply to PFRC?.

    “…Tokamaks are plagued by instabilities.”
    They do have lots of lovely arcing surfaces.

    “…a much better picture of when instabilities will form and how bad they’ll make confinement.”
    I have read this coming from the tokamak folks (probably with regards to ITER), but I don’t feel inclined to accept their confidence until they prove me a pessimistic naysayer.

  • geostar1024

    For tokamaks that run on D-T, most of the energy comes out in neutrons, which aren’t confined and which deposit their energy in the walls of the reactor. The remaining energy comes out in alpha particles, which are supposed to deposit their energy in the core plasma to keep it hot, sustaining the conditions for fusion reactions to occur. This is known as an ignited plasma. So, in that sense, D-T fusion plasmas are actually mostly transparent to the fusion energy produced.

    The setup in the DFD/PFRC seems to be substantially different. Since they aim to use the aneutronic D-He3 reaction, very little of the energy comes out in neutrons. Charged particles (tritium, helium-3, and protons) carry the energy instead, but don’t deposit much, if any, of that energy in the core because the core is so small. Instead, it’s absorbed by the cool edge plasma surrounding the core, and that heated plasma stream is what is used for thrust in the DFD. Energy could be extracted from that plasma as well. The hot core plasma also emits x-rays which heat the walls of the reactor, and that heat is sent through a heat engine (the presentation mentions a Brayton cycle). So a PFRC-based reactor is even more transparent to fusion energy than a tokamak-based reactor.

    Since the core isn’t being heated by alpha particles, it has to be continuously heated from the outside (using some of the energy from the heat engine and the output plasma stream). So, it’s a driven, rather than ignited, reactor, which means it doesn’t suffer from the large-scale instabilities that can tear apart tokamak plasmas via disruptions. As I was saying in an earlier comment, the main plasma physics challenge is demonstrating that the external heating method produces a fusion plasma, and that it can be made efficient enough to achieve breakeven.

  • Michael Vaicaitis

    Thanks for the explanation – you get today’s wiki award for helpfulness. Seems like I may have unjustifiably tarred PFRC with the same brush as tokamaks – opinion recalibration in process. Thanks again.

  • Stephanie Thomas

    Thanks geostar1024! You’re right, we chose Pluto as our “context mission” for NIAC, but we have previously published papers on going to Alpha Centauri, Mars, Lagrange Points, Jupiter icy moons, or visiting asteroids using this technology – just about any deep space mission would be faster and cheaper using DFD. There are many terrestrial applications as well!