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Mars Space

Could This Powerful New Fusion Rocket Thruster Propel Us Beyond Mars? (sky.com) 88

Long-time Slashdot reader schwit1 shared this article from Sky.com: Dr. Fatima Ebrahimi "has invented a new fusion rocket thruster concept which could power humans to Mars and beyond," writes Sky.com

Long-time Slashdot reader schwit1 shared their report: The physicist who works for the U.S. Department of Energy's Princeton Plasma Physics Laboratory designed the rocket which will use magnetic fields to shoot plasma particles — electrically charged gas — into the vacuum of space. According to Newton's second and third laws of motion, the conservation of momentum would mean the rocket was propelled forwards — and at speeds 10 times faster than comparable devices.

While current space-proven plasma propulsion engines use electric fields to propel the particles, the new rocket design would accelerate them using magnetic reconnection... Dr. Ebrahimi's new concept performs much better than existing plasma thrusters in computer simulations — generating exhaust with velocities of hundreds of kilometres per second, 10 times faster than those of other thrusters.

That faster velocity at the beginning of a spacecraft's journey could bring the outer planets within reach of astronauts, the physicist said.... "The next step is building a prototype!"

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Could This Powerful New Fusion Rocket Thruster Propel Us Beyond Mars?

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  • Isn't this basically putting the rocket cart before the fusion horse?
    • The power required necessary to generate the magnetic fields makes it not feasible. Laser wake field accelerators would be way more efficient [aps.org].
      • That is an accelerator technology proposal - nothing to do with fusion power.

        • Not really, in the article they say that there are anomalies in plasma containment that could be used as a variable thrust mechanism

          That is interesting because tokamaks are entering operational phases and could become net energy positive and much smaller in the not to distant future

          I would add that the Wendelstein 7-X (another fusion technology) is currently installing heat shielding around their plasma exit ports, where 100 million degree plasma leaves the containment area, which seems to me another poten

          • megawatts of power

            Just curious, how often do you use the phrase "meters of length"? Or "kilograms of mass"? Or "liters of volume"?

            • by mlyle ( 148697 )

              The former is rare in common usage.. But "kilograms of mass" and "liters of volume" are very common phrases. Perhaps redundant, though not exactly (both kg-mass and kg-force are in common usage)

            • You should ask yourself whether or not you are actually adding to the conversation... I think not

              However, I did find that the 39-day transit to Mars is projected to require a 200 MW reactor

              Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram"
              https://www.spaceflightinsider... [spaceflightinsider.com]

              Uninterestingly enough "meters

        • That is an accelerator technology proposal - nothing to do with fusion power.

          No shit Sherlock. Nobody claimed it was. The facts are to use particle acceleration via magnetic reconnection is an incredibly power hungry method. Laser Wakefield acceleration uses a lot less power and produces higher energy particles ie more thrust.

          • The facts are to use particle acceleration via magnetic reconnection is an incredibly power hungry method

            Not at all, in fact it’s the reverse. Using particle acceleration via magnetic reconnection is quite simple, feasible, and cheap. Solar sails work grea... what’s that? You mean make and use them for thrust that way?!? Wtf no.

          • The very headline of TFA claimed that it was.
    • Have you read the actual article?

  • by Geoffrey.landis ( 926948 ) on Saturday January 30, 2021 @04:56PM (#61010124) Homepage

    I like it, but the headline seems wrong-- this isn't a fusion device.

    • That is what I thought until I read the linked to article and it appears that she wants to use a Tokamak to generate the power and I think the magnetic fields use to accelerate the plasma.
      • by ShanghaiBill ( 739463 ) on Saturday January 30, 2021 @05:31PM (#61010200)

        Several problems with her proposal:

        1. Tokamaks don't actually work yet.

        2. Tokamaks produce plenty of waste heat. Heat is difficult to shed in a vacuum.

        If what she is saying is actually true, then instead of using it to build rockets, we could use it for power stations on earth. She says the velocity of the particles is 10 times higher. Energy is velocity squared. So that means 100 times the energy.

        I am extremely skeptical. So far, this is all based on computer simulations. Plenty of stuff works great in simulations but not at all in reality.

        • So far, this is all based on computer simulations. Plenty of stuff works great in simulations but not at all in reality.
          You are mixing up: "working not at all in reality" - as opposed to simulations - with: difficult to built.

          It is extremely rare in our times that a simulation is not accurately simulating reality. Perhaps not in the same time and space resolution, but most certainly pretty accurate.

          • by mlyle ( 148697 )

            > It is extremely rare in our times that a simulation is not accurately simulating reality. Perhaps not in the same time and space resolution, but most certainly pretty accurate.

            Hahaha! I can tell you've never worked in numerical methods. We have to find lots of simplifying assumptions to make any problem tractable to simulate, and those simplifying assumptions bite us all the time.

            Not to mention all the ways that meshing, numerical artifacts, etc, bite us.

            The sheer amount of time I've had to spend to

            • Hahaha! I can tell you've never worked in numerical methods.
              Actually
              I did.
              We have to find lots of simplifying assumptions to make any problem tractable to simulate, and those simplifying assumptions bite us all the time.
              Both has nothing to do with "simulation" as the parent and I meant it.

              • by mlyle ( 148697 )

                "It is extremely rare in our times that a simulation is not accurately simulating reality. "

                Never are we using a complete model of reality--- almost never are we even using something close (and these are generally things that take days of supercomputing time to simulate a couple atom system). And almost never can we take success in a simulation in whatever domain -- CFD, electromagnetics, or even simpler mechanical codes -- as an indication that something unprecedented is achievable in reality.

                Simulations

        • by Antique Geekmeister ( 740220 ) on Saturday January 30, 2021 @06:02PM (#61010264)

          I'm afraid that fusion power plants are much like Marxist governments. None have fulfilled their promise of providing safe power.

          • i dont get it, all i see after quick rtfa is "plasmic fart in cosmic setting" e.g. in space you can fart yourself to mars, beavis. but im sure its a bit more complicated and ms. Fatima seems to be above my braingrade, id be more than happy to be enlightened during some after hours pillowtalk ? Perfect time for learning how to spacetravel
        • Basically, what we have here is another system that looks great on paper but in really will probably never work.

          What I don't understand is why we are not pressing forward with a engine system that we know will work. Mainly a Nerva fission engine. We know it will work. The design was extensively tested in the '60s.

          • 1. The Minerva Fission Engine violates international law.

            2. There would be enormous political opposition, especially by those downwind of the launch site.

            3. It may have be more economically viable than a Saturn V, but much less so compared to a SpaceX StarShip.

            4. You can't use it in earth orbit without much of the radioactive exhaust falling back to the earth. If you only use it in deep space, then it is pointless because the hardest part of the journey (getting to deep space) is already behind you.

            • by mlyle ( 148697 )

              > You can't use it in earth orbit without much of the radioactive exhaust falling back to the earth. If you only use it in deep space, then it is pointless because the hardest part of the journey (getting to deep space) is already behind you.

              Rocket equation, anyone? Having a last stage with incredibly high impulse massively improves your capabilities. Not to mention that when we talk about many missions, it'd be nice to be able to do the long part of the journey quicker than the minimum energy ITN tra

            • by spitzak ( 4019 )

              Although there certainly are problems with even launching this, and it obviously won't be used until the spacecraft is in space, I think the exhaust will exceed Earth's escape velocity and if directed correctly will not end up in the atmosphere.

        • 1. Tokamaks don't actually work yet.

          Depends on your definition of "work". "Doesn't work" usually implies "...at all." Have they been demonstrated to work in principle? Most certainly.

          Do they currently provide a usable sustained energy output for indefinite periods of time? No.

      • by sjames ( 1099 )

        No. She got the idea from observing plasma behavior in a tokamak but doesn't necessarily want to actually use a tokamak for the thruster, just a particular behavior of the magnetic containment.

    • by fermion ( 181285 )
      The headline and the article is misleading. This is an EM drive that will use technology from fusion reactors to accelerate the particles. What will power the particle accelerator is unclear.

      The other inaccuracy has to do with thrust. The nice thing about a EM drive is that is can provide continuous acceleration, if given a small mass and lots of energy. This is different form a conventional rocket engine that provide a short period of thrust by burning great quantities of mass. For instance, about 75%

    • They should've just used the headline that was submitted on the firehose instead of this clickbaity Betteridge-affirming bullshit
    • To throw mass out thebakc you eithe rhave to bring the mass along to start with, which won't work in the long run, or you have to scoop it up as you fly along and accelerate it.
      But then there probably has to be a terminal velocity where the average speed of particles entering can't be increased. SO there can't be a fixed exit velocity or you have terminal velociyt that isn't high enough to be useful. You need to get to a speed larger than C (calculated from your iniertial frame's intergated impulses, not

      • To throw mass out thebakc you eithe rhave to bring the mass along to start with, which won't work in the long run, or you have to scoop it up as you fly along and accelerate it.

        The faster you can expel the mass, the more momentum you gain per unit mass, so the less mass you need to achieve the same impulse. Of course, this also requires more energy, roughly to the square of the velocity increase. You need to carry that with you also. In the long run, it could work if you optimize the amount of expelled mass and the energy-density of your fuel so that it is sufficient for the trip.

        But then there probably has to be a terminal velocity where the average speed of particles entering can't be increased. SO there can't be a fixed exit velocity or you have terminal velociyt that isn't high enough to be useful. You need to get to a speed larger than C (calculated from your iniertial frame's intergated impulses, not some observer's point of view.) otherwise it take 100 years to go 100 light years and you are dead.

        This makes no sense. Your speed in your inertial frame is always zero. A nonzero speed must be relativ

        • No you can easily exceed C if you define C by the distance you traveled divided by the time it took in your own frame. If you think that's wrong it's because you don't understand what relativity really says,.

          • by ceoyoyo ( 59147 )

            The irony.

          • No, you cannot divide a distance measured in one reference-frame by a time measured in another, and call it a velocity. Relativity does not work that way.

            And if you think that's wrong, let me say that one of us has a PhD in physics. Guess who?

            • No, you cannot divide a distance measured in one reference-frame by a time measured in another, and call it a velocity. Relativity does not work that way.

              And if you think that's wrong, let me say that one of us has a PhD in physics. Guess who?

              Yes you can.
              1. before your journey starts see how far away the destingation is. Say it's 2 light years

              2. you travel there and find it takes you 1 year of your lifetime.

              How fast did you go from your point of view? an average of 2C.
              It's that simple. It's not a violation of relativity because from the point of view of any outside observer either it 1) took longer or 2) the distance was shorter (one or the other or both) But from your point of view you will find that 1. your mass did not increase 2, the

              • Let's use your example of a trip of 2 light-years that takes 1 year from the traveler's perspective. According to time-dilation, this means the traveler's speed v relative to the observer is given by solving 1/sqrt(1-v^2/c^2) = 2, or v = 0.866 c approximately. But the apparent speed of the observer relative to the traveler is -v, the same, but in the opposite direction.

                How can the traveler see the observer go away from him with the same speed, yet take half the time to reach the destination? The answer is l

                • Sorry, my explanation is a bit untidy. There is no need to use lorentz cancellations to show that the observer and the traveler see the same relative speed 0.866c with respect to each other. That fact arises from the inverse of the lorentz transforms between the two frames.

                  The observer sees the traveler's clock run half as fast. The traveler sees the distance as half as long. The two views are consistent with the relative speed of each person being the same.

                  Again, in no reference-frame are you going to see

                  • As long as were talking here let me describe a point I'm not really clear on and see if you can help me with it.

                    let's consider two rockets, one without any windows to look out of, and one with windows. Were heading to a planet near a star 2 light years away.
                    with no windows:
                    1. star is 2 light years away
                    2. you accelerate steadily by burst of impulses P out the back.
                    3. So after feeling N impulses, you would assume you have changed your momentum by N*P
                    4. Since in between each impulse you are in an inertial fra

                    • Thank you sincerely for your interest. Relativity is weird and counter-intuitive, because its consequences lie outside our usual everyday experiences. Most physics students struggle with it before getting a grasp on it. (I certainly did.)

                      Also, I have to point out that your thought-experiment includes reference-frames that are being accelerated, not just traveling at constant velocity with respect to each other. That puts the problem in the realm of general relativity, not just special relativity. The former

      • You can carry a lot of water, and split off the hydrogen as fuel for the fusion reactor (and oxygen to breath as a side effect)

        water is also an effective shielding against cosmic rays

        In all ways, it is better than chemical rockets, and the NASA Helical Engine [nasa.gov] may be as much smoke and mirrors as the EM Drive.

        just sayin'

        • google "rocket equation". you can't carry enough mass.

          • I hope that you realize that the rocket equation [wikipedia.org]applies to getting off of the Earth and into orbit, not the interplanetary application that the article is about where providing a relatively small amount of thrust continually for half of the trip results in a fairly high velocity and much shorter transit time.

            The VASIMR article talks about trimming 30-60 days off the travel time wit the use of a 52 megawatt fission reactor.

            In the case of either VASIMR or the proposed fusion design, there needs to be a sourc

            • The rocket equation defines how much velocity you can gain from your energy source and reaction mass. Nothing else. For leaving a gravity well, very very roughly you need to calculate the escape velocity separately, the rocket equation will then help tell you if your rocket can provide enough velocity change to overcome it.

              • I would reply, BULLSHIT, there is a consideration for Standard Gravity of 1G in the fucking equation: g_{0} is standard gravity, which is not involved (at least not at 1G level) in interplanetary travel, so there is no 1G to overcome

                Or if you were to read any further into the article that I linked, you would see that the tyranny of the rocket equation applies to getting off and on to a planet, not travelling between them:
                As such, when using it to calculate the propellant requirement for launch from (or powe

  • Maybe somebody has described a fantasy, bit the human race has not mastered fusion at this time. There is steady progress in that direction, but it is slow.

    • According to the article, his is not a fusion reactor, it is a way to use the plasma for propulsion. Details are scant.

  • Even if this pans out (which is a complete uncertainty) it's not going to get us far. At best this could provide better intrastellar travel but if you want to reach another star then you are going to need something on par with Matter-Antimatter engine. That said, all advancements in rocket propulsion are welcome one and I very much hope it works out like they expect.

    • by ceoyoyo ( 59147 )

      Anything would be better than our current intrastellar travel. So far we can't even get close to, never mind inside a star.

  • OK, so the basis of this idea is that you use a magnetic field to compress a plasma stream until the density is high enough for fusion to occur. Then allow the energetic particles to interact with the magnetic field and thereby propel a spacecraft forwards.

    So, the first hurdle is to accelerate the particles, presumably deuterons and tritons (no, not the mythical creatures!!), to the point where fusion is possible. This means we need an onboard energy source able to accelerate these particles to a few MeV a

    • If you read the article, the starting point is a Tokamak fusion reactor, the plasma bubbles are a side effect of running a Tokamak reactor that they have some control over.

      To quote the article, quoting the scientist:
      "During its operation, this tokamak produces magnetic bubbles called plasmoids that move at around 20 kilometres per second, which seemed to me a lot like thrust,"

      Reading _is_ fundamental

  • by clovis ( 4684 ) on Saturday January 30, 2021 @07:07PM (#61010426)

    https://www.cambridge.org/core... [cambridge.org]

    from the abstract:
    A new concept for the generation of thrust for space propulsion is introduced. Energetic thrust is generated in the form of plasmoids (confined plasma in closed magnetic loops) when magnetic helicity (linked magnetic field lines) is injected into an annular channel. Using a novel configuration of static electric and magnetic fields, the concept utilizes a current-sheet instability to spontaneously and continuously create plasmoids via magnetic reconnection. The generated low-temperature plasma is simulated in a global annular geometry using the extended magnetohydrodynamic model. Because the system-size plasmoid is an Alfvenic outflow from the reconnection site, its thrust is proportional to the square of the magnetic field strength and does not ideally depend on the mass of the ion species of the plasma. Exhaust velocities in the range of 20 to 500 km s1, controllable by the coil currents, are observed in the simulations.

    • by clovis ( 4684 ) on Saturday January 30, 2021 @07:59PM (#61010590)

      Found a non-paywalled link
      https://arxiv.org/pdf/2011.041... [arxiv.org]

    • Yes. Its a plasma thruster, just happens to be similar in some aspects to fusion research machines. Then non-technical articles got it all confused. Lots of details might or might not make this superior to other electric drive designs. High exhaust velocity is not by itself interesting - one of the problems with electric drives is that their exhaust velocity is so high that the power required is enormous (the higher the exhaust velocity, the more power (but less propellant mass) needed for the same vel
    • Exhaust velocities in the range of 20 to 500 km s1

      That "s1" should read "s^-1" or "/s".

  • This isn't a fusion rocket. It's a plasma rocket. It gets very high exhaust velocities, which are good for specific impulse, but it gets terrible thrust.You'd still need a power source with a specific power better than 1kg/kW to make it more attractive than something like a solar moth.
    • RTFA

  • Would the rate of acceleration required to get anywhere produce high enough Gs to squish you flat?

  • Just because the propulsion promises high specific impulse does not mean that it can produce high trust. Classic ion engines have high specific impulse but also very low thrust so can't be used to get anywhere quickly (only cheaper). I think both technologies share the same limitation - it's difficult to produce enough electrical energy in space with very low mass equipment.

  • If she had invented a fusion reactor, it would also solve our energy and environmental problems on earth, which I thought would have been a bigger headline. The problem is of course that she didn't. But if _someone else_ invents a fusion reactor, it will (apart from saving the environment and solving our energy problems) also provide this neat way to travel through space faster.

  • Looks really neat. Apparently can use a variety of gases not depending on atomic weight so can use those mined from asteroids. I have a question. The speed of plasmoids from the thruster is from 25km/s to 500km/s. The speed of a coronal mass ejection from the Sun is 250km/s to 3000km/s.
    1. Is it possible that the thrust on takeoff could have the effect of a solar storm on that hemisphere? And at landing...
    2. Thrust is apparently 1/10 to tens of newtons / kg. How many Gs would this be for crew?
    3. What kind of

  • All questions posed in a headline have the same answer: "No."

  • Just make sure there is an easy to reach off switch [youtube.com].

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