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Interstellar Implications of the Electric Sail

Not long ago we looked at Greg Matloff’s paper on von Neumann probes, which made the case that even if self-reproducing probes were sent out only once every half million years (when a close stellar encounter occurs), there would be close to 70 billion systems occupied by such probes within a scant 18 million years. Matloff now considers interstellar migration in a different direction in a new paper addressing how M-dwarf civilizations might expand, and why electric sails could be their method.

It’s an intriguing notion because M-dwarfs are by far the most numerous stars in the galaxy, and if we learn that they can support life, they might house vast numbers of civilizations with the capability of sending out interstellar craft. They’re also crippled in terms of electromagnetic flux when it comes to conventional solar sails, which is why the electric sail comes into play as a possible alternative, here analyzed in terms of feasibility and performance and its prospects for enabling interstellar migration.

The term ‘sail’ has to be qualified. By convention, I’ve used ‘solar sail,’ for example, to describe sails that use the momentum imparted by stellar photons – Matloff often calls these ‘photon sails,’ which is also descriptive, though to my mind, a ‘photon sail’ might describe both a beam-driven as well as a stellar photon-driven sail. Thus I prefer ‘lightsail’ for the beamed sail concept. In any case, we have to distinguish all these concepts from the electric sail, which operates on fundamentally different principles.

In our Solar System, a sail made of absorptive graphene deployed from 0.1 AU could achieve a Solar System escape velocity of 1000 kilometers per second, and perhaps better if the mission were entirely robotic and not dealing with fragile human crews. The figure seems high, but Matloff gave the calculations in a 2012 JBIS paper. The solar photon sail wins on acceleration, and we can use the sail material to provide extra cosmic ray shielding enroute. These are powerful advantages near our own Sun.

But the electric sail has advantages of its own. Rather than drawing on the momentum imparted by solar photons (or beamed energy), an electric sail rides the stellar wind emanating from a star. This stream of charged particles has been measured in our system (by the WIND spacecraft in 1995) as moving in the range of 300 to 800 kilometers per second at 1 AU, a powerful though extremely turbulent and variable force that can be applied to a spacecraft. Because an interstellar craft entering a destination system would also encounter a stellar wind, an electric sail can be deployed for deceleration, something both forms of sail have in common.

How to harness a stellar wind? Matloff first references a 2008 paper from Pekka Janhunen (Finnish Meteorological Institute) and team that described long tethers (perhaps reaching 20 kilometers in length) extended from the spacecraft, each maintaining a steady electric potential with the help of a solar-powered electron gun aboard the vehicle. As many as a hundred tethers — these are thinner than a human hair — could be deployed to achieve maximum effect. While the solar wind is far weaker than solar photon pressure, an electric sail of this configuration with tethers in place can create an effective solar wind sail area of several square kilometers.

We need to maintain the electric potential of the tethers because it would otherwise be compromised by solar wind electrons. The protons in the solar wind – again, note that we’re talking about protons, not photons – reflect off the tethers to drive us forward.

Image: Image of an electric sail, which consists of a number (50-100) of long (e.g., 20 km), thin (e.g., 25 microns) conducting tethers (wires). The spacecraft contains a solar-powered electron gun (typical power a few hundred watts) which is used to keep the spacecraft and the wires in a high (typically 20 kV) positive potential. The electric field of the wires extends a few tens of meters into the surrounding solar wind plasma. Therefore the solar wind ions “see” the wires as rather thick, about 100 m wide obstacles. A technical concept exists for deploying (opening) the wires in a relatively simple way and guiding or “flying” the resulting spacecraft electrically. Credit: Artwork by Alexandre Szames. Caption via Pekka Janhunen/Kumpula Space Center.

For interstellar purposes, we look at much larger spacecraft, bearing in mind that once in deep space, we have to turn off the electron gun, because the interstellar medium can itself decelerate the sail. Operating from a Sun-like star, the electric sail generation ship Matloff considers is assumed to have a mass of 107 kg, assuming a constant solar wind within the heliosphere of 600 kilometers per second. The variability of the solar wind is acknowledged, but the approximations are used to simplify the kinematics. The paper then goes on to compare performance near the Sun with that near an M-dwarf star.

We wind up with some interesting conclusions. First of all, an interstellar mission from a G-class star like our own would be better off using a different method. We can probably reach an interstellar velocity of as high as 70 percent of this assumed constant solar wind velocity (Matloff’s calculations), but graphene solar sails can achieve better numbers. And if we add in the variability of the solar wind, we have to be ready to constantly alter the enormous radius of the electric field to maintain a constant acceleration. If we’re going to send generation ships from the Sun, we’re most likely to use solar sails or beamed lightsails.

But things get different when we swing the discussion around to red dwarf stars. In The Electric Sail and Its Uses, I described a paper from Avi Loeb and Manasvi Lingam in 2019 that studied electric sails using the stellar winds of M-dwarfs, with repeated encounters with other such stars to achieve progressively higher speeds. Matloff agrees that electric sails best photon sails in the red dwarf environment, but adds useful context.

Let’s think about generation ships departing from an M-dwarf. Whereas the electromagnetic flux from these stars is far below that of the Sun, the stellar wind has interesting properties. We learn that it most likely has a higher mass density (in terms of rate per unit area) than the Sun, and the average stellar wind velocity is 500 kilometers per second. Presumably a variable electric field aboard the craft could adjust to maintain acceleration as the vehicle moves outward from the star, although the paper doesn’t get into this. The author’s calculations show an acceleration, for a low-mass spacecraft about 1 AU from the Sun, of 7.6 × 10−3 m/s2 , or about 7.6 × 10−4 g. Matloff considers this a reasonable acceleration for a worldship.

So while low electromagnetic pressure makes photon sails far less effective at M-dwarfs as opposed to larger stars, electric sails remain in the mix for civilizations willing to contemplate generation ships that take thousands of years to reach their goal. In an earlier paper, the author considered close stellar encounters, pointing out that 70,000 years ago, the binary known as Scholz’s Star (it has a brown dwarf companion) passed within 52,000 AU of the Sun. We can expect another close pass (Gliese 710) in about 1.35 million years, this one closing to a perihelion of 13,365 AU. From the paper:

Bailer‐Jones et al. have used a sample of 7.2 million stars in the second Gaia data release to further investigate the frequency of close stellar encounters. The results of this analysis indicate that seven stars in this sample are expected to approach within 0.5 parsecs of the Sun during the next 15 million years. Accounting for sample incompleteness, these authors estimate that about 20 stars per million years approach our solar system to within 1 parsec. It is, therefore, inferred that about 2.5 encounters within 0.5 parsecs will occur every million years. On average, 400,000 years will elapse between close stellar encounters, assuming the same star density as in the solar neighborhood.

If interstellar missions were only attempted during such close encounters, we still have a mechanism for a civilization to use worldships to expand into numerous nearby stellar systems. It would take no more than a few star-faring civilizations around the vast number of M-dwarfs to occupy a substantial fraction of the Milky Way, even without the benefits of von Neumann style self-reproduction. With the number of planetary systems occupied doubling every 500,000 years, and assuming a civilization only sends out a worldship during close stellar encounters, we get impressive results. In the clip below, n = the multiple of 500,000 years. The number of systems occupied is P:

At the start, n = 0 and P = 1. When 500,000 years have elapsed, the hypothetical spacefaring civilization makes the first transfer, n = 1 and P = 2. After one million years (n = 2), both the original and occupied stellar systems experience a close stellar encounter, migration occurs and P = 4. After a total elapsed time of 1.5 million years, n = 3 and they occupy eight planetary systems. When n = 5, 10 and 20 the hypothetical civilization has respectively occupied 32, 1024 and 1,048,576 planetary systems.

With M-dwarfs being such a common category of star, learning more about their systems’ potential habitability will have implications for the possible spread of technological societies, even assuming propulsion technologies conceivable to us today. What faster modes may eventually become available we cannot know.

The paper is Matloff, “The Solar‐Electric Sail: Application to Interstellar Migration and Consequences for SETI,” Universe 8(5) (19 April 2022), 252 (full text). The Lingam and Loeb paper is “Electric sails are potentially more effective than light sails near most stars,” Acta Astronautica Volume 168 (March 2020), 146-154 (abstract).

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{ 46 comments… add one }
  • Alex Tolley April 26, 2022, 11:13

    I recently saw this meme and its rebuttal:
    “The dinosaurs went extinct because they didn’t have a space program”
    “The dinosaurs lasted 100 million years because they didn’t have a space program.”

    The point of mentioning this is that I think Matloff muddies the value of generation ship flight by assuming that they will only happen during close stellar encounters (and much greater distances than the world-ending encounter in “When Worlds Collide”). Civilizations may well not last the lengths of time between encountours. Modern humans have only be around since the cultural explosion for perhaps 80,000 years. Are we to wait some indefinite time, averaging 500,000 years before we make any attempt at reaching another star? For context, our interstellar snail-paced Voyager 2 will pass by Ross 248 in just 40,000 years. We have just talked about craft reaching much higher velocities to reach 1000 AU in 50 years, and even chemical rockets to reach 1000 AU in approximately 150 years. We don’t need to wait 100’s of thousands of years before launching generation ships. More than likely, humans 1.0 won’t even be around, and maybe not even technological humans x.0.

    If electric ships can slow boat to other stars, then launch them whenever the technology and desire to do so emerges.

    Now I have to say that if the 10^7 kg electric sail ship is the reference, this is just 10,000 tonnes, a very small volume in which to house a viable colony population in a generation ship. It might be better to have a seed ship with robots to make a shorter, faster journey, or perhaps a small population to provide the needed crew, with the last crew nurturing the incubated fertilized ova to adulthood. Of course, this assumes terrestrial vertebrate biology. A civilization that has biology more like insects that can lay eggs that stay dormant, might find this technologically easier. And lastly, generation ships assume terrestrial biology crews. Far more likely is that artificial entities, whether robots or other ways to house intelligence, will be the starfarers. They will simply switch off or slow their time perception and arrive at their destination after a relatively short perceived trip time. No stable, complex ecosystem and life support need be supplied, just an energy supply, probably fusion or antimatter, given the long journey times.

    Bottom line, I don’t think mixing the value of a particular interstellar propulsion method with a particular model of colony diffusion is a good idea. They should be kept separate.

    • Robin Datta April 27, 2022, 17:32

      A xenobioogic technological species might be expected to have a substantial brain-equivalent, with steady, abundant fuel components supply and waste removal, akin to vertebrate (tetrapod) respiratory + circulatory systems and to hemoglobin in corpuscles avoiding viscosity issues. Binocular vision (overlapping fields) could provide perception and conceptualization of depth-of-field at a distance; prehensile hands with a strong pinch would permit manipulation of small objects close-up promating perception and conceptualization in stereoscopic vision. Three axis movement at a prehensile appendage would permit reaching for and throwing objects in many directions. Some form of advanced speech-oquivalent communication to transmit complex ideas would be needed.

      The historical precedents that permitted the evolution of all these components in the right order in humans were remarkably complex; if indeed there are enormous numbers of planets with evolving biota, then perhaps the series of events may be replicated elsewhere by “the luck of the draw”.

      • Alex Tolley April 28, 2022, 0:28

        Just this evening I was watching a webinar from Foothill College Astronomy Society by Charles Lineweaver from Australia on the subject of Cosmobiology. He made what I thought was an almost extraordinary claim – that organisms with heads are so unlikely as to be almost zero elsewhere. (I actually challenged him on that.) Almost paradoxically, he supports SETI even though he doesn’t seem to believe intelligence elsewhere is likely. I agree that life is more likely to be common and intelligence rare, although there is a meritorious argument that intelligent life can spread across the galaxy and therefore may be more common than life. We just don’t have the data.

        I think you and I agree that evolution is highly contingent, and Lineweaver thinks so too. What he doesn’t seem to accept is any sort of convergent evolution or any possibility that some features, like bilateral body plans, have an evolutionary advantage. (He also gets confused about biological hierarchies with only mentions of species, rather than phyla, genera, etc. in a context that didn’t make a lot of sense to me.)

        It was, however, an interesting talk and he presented data in a way I hadn’t seen before that was very informative, IMO.

        • Spaceman April 28, 2022, 9:06

          Alex:

          What leads you to suspect that life is common elsewhere in the Universe?

          • Alex Tolley April 29, 2022, 9:55

            I didn’t say that, although I admit I should have phrased my sentence better. What I meant was that while we usually think of planets with intelligent technological life as a subset of planets with life, the possibility of interstellar travel may reverse that relationship – more so if ETI is artificial. What the actual occurrence of living planets is, IDK, but the rapid appearance of life on Earth suggests it is common, whether from abiogenesis or possibly, panspermia.

        • Robin Datta April 28, 2022, 20:37

          A motile organism without a preferred direction of movement, such as an amoeba, will not concentrate sensory organelles and a mouth in one area to form a head. Even microbes that have a preferred direction of movement in relation (opposite to) a large flagellum concentrate sensory organelles such as eye spots and a “mouth” towards the direction of motion. Thereafter symmetrirally duplicating the body plan is the parsimony of the Bilateria

          • Alex Tolley April 29, 2022, 9:51

            That is a great point!. I wish I had thought of that as an argument to Lineweavers’ assertion.

    • Tiens van Greuning April 30, 2022, 19:59

      Alex, while I concur with the whole of your sentiment here above, there’s just one small detail that caught my eye.

      Technically, our snailcraft Voyager 2, which NASA tells everybody is going to pass within a lightyear from Ross248 in 40000, will really only be a bit more than a lightyear from us at that point.

      More accurately it is Ross248 which will be passing by us at quite a clip 40000 years from now, with Voyager 2 having covered just a bit more than half the distance to Ross248’s closest point to us.

      It’s just a better-sounding soundbyte to say it’s Voyager 2 which will be doing the passing…

      • Alex Tolley April 30, 2022, 23:16

        Thanks. I didn’t realize that.

        • Tiens van Greuning May 2, 2022, 15:39

          Just out of curiosity, Ross 248 is currently 10.3 lightyears away, and appears to be approaching us at a radial velocity of around 77km/s.

          Gliese 445 is currently approaching us at around 112km/s and should pass 1.7ly from Voyager 1 in around 40000 years.

          Compare to Voyager 1’s current speed of 16.948km/s, which is steadily decreasing due to the Sun’s gravity.

  • Michael Fidler April 26, 2022, 11:15

    Red dwarfs also have magnetic reconnections when flaring and have the potential for much higher velocities. The solar wind is mild when compared to the typhoon winds from flares. As we are seeing now the the sunspot cycle is revving up the particle are slamming earth with huge amounts of fast moving protons.
    ” Solar protons accelerated to nearly light speed by the explosion reached the Earth-moon system minutes after the flare; it was the beginning of a days-long “proton storm.”

    https://www.space.com/solar-x-class-flare-april-2022

    Sickening Solar Flares.
    https://www.nasa.gov/mission_pages/stereo/news/stereo_astronauts.html

    https://www.centauri-dreams.org/2019/11/18/the-electric-sail-and-its-uses/#comment-199253

    So just how fast could the Electric Sail go if it caught the nearly light speed protons created by the explosion of a large solar flare???

    All those flaring red dwarfs out there, maybe ‘Oumuamua was an advanced electric sail Generation Ship.

    • Alex Tolley April 26, 2022, 17:52

      So just how fast could the Electric Sail go if it caught the nearly light speed protons created by the explosion of a large solar flare???

      From the Nasa article, there is this:

      From Earth we see a flash of light and X-rays. This is the “solar flare,” and it’s the first sign that an explosion has occurred. Light from the flare reaches Earth in only 8 minutes. High energy protons can follow in another ten to twenty minutes, although sometimes they take longer.

      [emphasis mine]

      So the protons are arriving at 1 AU at about 1/2-1/4 light speed. But, as they continue, they plow into the much slower solar wind, creating a shockwave and must slow down.

      So the ship must ride the CMe at an early stage of acceleration, and then turn off the sail at some point to prevent it being decelerated again by the solar wind in front of the sail. There is presumably some nice calculations to be made based on CME density and velocity, and presumably some measurement of the ship’s acceleration. When a => 0, turn off the sail and coast. As the acceleration distance is likely relatively short, perhaps 1 AU, give or take, this has to be compared to using the gentler, more constant, and isotropic solar wind or solar radiation. An electric sail riding the solar wind cannot exceed the upper range of the wind speed using a sail, so perhaps 800 km/s. For a solar sail riding the photons at c, the upper limit is dependant on the overall aerial density of the sail and ship combined.

      For space sailors, catching and riding the CME would be a far more interesting and difficult task than that for captains of solar sails or electric sails riding the solar wind. It would have made a good sequel to Clarke’s “The Wind From the Sun”. The ship would start inside the orbit of Mercury, either “hovering” in statite mode, or possibly having made a sundiver maneuver, and then like a surfer, deploy the sail just before the CME protons arrive, manage the sail in the turbulence of the CME and its interaction with the solar wind, looking for various local velocity advantages, and finally cruising past Earth, probably coasting, and using other means to decelerate and dock the ship with stowed sail in orbit in Earth’s shadow.

      • Michael Fidler April 26, 2022, 22:00

        Actually, according to your figures, that would be 40 to 80 percent the speed of light. CMEs are produced by flares, but flares can also be by themselves. The flare is where magnetic reconnections take place and have extreme energy output that may trigger a CME.

        The Flare/CME Connection
        https://ntrs.nasa.gov/citations/20090014766

        Let’s call this the proton sail, to avoid confusion, and the best option is to get as close to the sunspot that has a flare as possible. They are very short lived but being over a flaring sunspot may be enough to catch the near lightspeed blast of protons when they do happen. That close to the sun should give the most velocity to the Proton Sail from the flare. Just how much speed can be achieved when the flare lets loose is a quention best left to the mathematicians.

        Biggest Solar Flare on Record.
        https://earthobservatory.nasa.gov/images/1331/biggest-solar-flare-on-record

        This would be similar to the laser arrays or particle beams (ion beam) used for Breakthrough Starshot but without the outlay of money and time to build an array!

        https://images.fineartamerica.com/images-medium-large-5/solar-flare-claus-lunauscience-photo-library.jpg

      • Robin Datta April 26, 2022, 22:50

        Dictionary entries for isotropic

      • Michael Fidler April 27, 2022, 7:04

        You’re right 1/2 to 1/4 speed of light, forgot to add the 8 minutes in…

    • Michael Fidler April 26, 2022, 22:24
    • Project Studio April 27, 2022, 19:05

      Riding the re-connection event would require the ability to predict these events and adapt to rapidly to changing conditions. Good candidate for an AI pilot. Wondering how are the electrostatic tethers are kept taut under such high acceleration?

  • VIY April 26, 2022, 15:21

    Great idea! One possible extension could be to focus the reflected protons in a point focus by making the electrically charged wires in
    a parabolic shape, and then use additional strong magnetic field to accelerate them backwards for additional trust, using them as a reaction mass. The needed energy could be from photovoltaic cells or a nuclear powerplant. If the protons could be accelerated from 600 m/s to say 6000 m/s backwards, that will add 10 times higher acceleration. The parabolic shape could be achieved by an additional net of wires behind the reflecting ones and controlling the charges of the two nets, accordingly.

    A possible critic to this whole idea is that the electromagnetic field, created by the reflected protons needs to be accounted for as it interacts with the incoming protons and likely dispersing them away. Has this been calculated in the analysis?

  • Jeff Greason April 26, 2022, 15:56

    The concern over the variability of the solar wind as a drawback to magnetic or electric solar wind sails is wildly overstated. Modulating the drag of such sails is done at electronic speeds (much faster than furling or unfurling a physical sail), so adjusting for the wind variation is an interesting navigational challenge but hardly a barrier to using the solar wind.

  • Mike Serfas April 26, 2022, 17:04

    The speed limit of the electric sail somewhat reminds me of this pleasant physics demonstration: https://hackaday.com/2021/07/02/10-000-physics-wager-settles-the-debate-on-sailing-downwind-faster-than-the-wind/

    Of course, there is no “ground” for the ship to use in this case… but are all the particles striking it moving at the same velocity? If the ship can harvest the energy of particles moving in different directions (whether at once or over time due to turbulence) – then even if some are moving more slowly, it might tap into their relative kinetic energy to move much more quickly by using that energy to push the other particles backward as exhaust. I think… (after all, even on Earth this is the sort of topic even real physics professors lose thousands-dollar bets on)

  • Geoffrey Hillend April 26, 2022, 17:32

    The concepts of how the propulsion in he Electric sail concept in this paper is vague so I can’t see how it works. There is no propulsion physics. First an electron gun is too inefficient since it has to boil off electrons from a cathode like those old CRT (cathode ray tube TV sets). The temperature is (1,470–1,830 °F). The temperature of an ion thruster is only 572 F. Why would we need an electron gun to keep the positive potential of the wires? Why is an electron gun needed to be connected to the wires? When the electrons are boiled off from the cathode of a CRT, they are accelerated by a positive magnetic field grid. Just putting a battery onto a wire makes a current through it which makes a magnetic field. Now what? Tethers with electric current moving through them will not create any kind of propulsion when interacting with the solar wind. It certainly will cause an electric current through the tethers, but I don’t see how these can lead to any kind of useful thrust. The velocity of electrons in a CRT are faster than ion thrusters, but much they are more power and current hungry. I don’t see any civilizations traveling the stars on electron guns, not even cell phones.

    • Alex Tolley April 26, 2022, 20:34

      The electric sail works by creating a positive charge on the wires (and a field) between the wires that reflects the protons and transfers their momentum. But the electrons in the solar wind are attracted to those +ve charged wires and reduce their charge. The electron gun is used to maintain the +ve charge by removing the -ve electrons.

    • Adam April 27, 2022, 0:23

      Geoffrey Hillend, the e-sail is pushed by the solar wind – that’s the propulsion. To make a sail it must have an electrostatic charge and that is maintained by the electron gun spraying off excess charge into space.

      • Paul Gilster April 27, 2022, 7:18

        Yes, as discussed in The Electric Sail and Its Uses, amongst other articles here:

        https://www.centauri-dreams.org/2019/11/18/the-electric-sail-and-its-uses/

        • Jeff Wright April 28, 2022, 4:15

          Now, I saw on phys.org thin film speakers-that might have an unimagined tuning use…maybe in a Powell airship at Venus if nowhere else.

      • Geoffrey Hillend April 27, 2022, 15:23

        I’ll admit I am not the expert on solar sail propulsion, but I assume that solar sails use the whole surface area of the sail to get the angular momentum of the protons and electrons. The electric sail does not have much surface area and a magnetic field generated by those tethers would be strong enough to deflect the solar wind and that would require a lot of power. Furthermore, for an efficient magnetic field, the wire has to be wrapped in a circle like around like a nail in an electromagnetic to generate a strong, magnetic field since charged particles have to move in circles to create a strong magnetic field. This has not been addressed in the tether design. In other words, the magnetic field can’t be efficient enough to equal the efficiency of an ordinary solar sail the same size or beamed propulsion and I doubt even with a magnetic field, this tether design could match that efficiency.

        I will admit that I am biased against the idea that any civilization would use any type of solar sails for interstellar travels since the specific impulse is too slow because the solar wind is too slow. An electron gun would have a higher specific impulse than the solar wind, but the thrust is too low and one could not have a large payload and it would still be too slow unless one considers world ships which would not be dependent on electron guns for thrust and specific impulse which sound more to me like an emergency thrust if the ship’s engines have a break down.

      • Geoffrey Hillend April 27, 2022, 15:32

        Without the circling of charged particles, the tethers would not have a strong enough magnetic field. Even with this, the surface area of the tethers is still much less that a solar sail. Also an electron gun is very power inefficient since it has to get very hot to boil of the electrons. One needs plug socket voltage 120 volts at 120 amps for the journey of the whole trip. Solar cells are useless between stars. When the Sunlight becomes two dim, there will be no voltage from the solar cells sufficient to work the electron gun and no strong solar wind for working propulsion.

        • Alex Tolley April 28, 2022, 0:15

          I think you are getting confused with magsails. Electric sails, as Adam stated above, use static +ve charge on the wires to repel the protons, not magnetic fields. IIRC, the charged field expands between the wires depending on the proton density of the solar wind, so that as it moves into deep space away from the sun, the solar wind proton density declines, the field widens, and the acceleration stays nearly constant.

          • Geoffrey Hillend April 28, 2022, 15:44

            Static electricity has a magnetic field since electricity and magnetism are part of the same force, the electromagnetic force. The force carrier of the electromagnetic field is a boson called the photon which has no charge. Charged particles attract and repel each other through the exchange virtual photons without charge You are right Alex Tolley. I stand corrected. I did not look at the design carefully enough. The problem with that idea is the electrons or protons with the same charge have to collide or get quite near the tethers to repel or push the spacecraft which is less surface area than an ordinary solar sail. There is no significant solar wind pressure between stars and no sunlight, but only star light, insufficient to make any solar panel electricity. There is no free power in interstellar space, so one has to take it with one.

    • Michael Fidler April 28, 2022, 9:17

      Here is a larger image of the electric sail and you can see the positive charge of the protons being repelled by the negative electric charge on the tethers;
      https://3.bp.blogspot.com/-NSOPLCwqoCg/VwH3I5YMMWI/AAAAAAABH6Y/AUayC0rEn8MMMIY7JpCrsULrXp7_YQ_8w/s1600/electricsail.jpg

  • Michael April 27, 2022, 3:54

    I would think a sundiver trick with a solar or laser sail drive and then openning it up near the sun would Boost it quite a bit. Graphene can handle very high temperatures near the sun, and I believe the solar wind from the poles is nearer a 1000 km/s. Perhaps solar light or UV enduced charging would help ie. the photons kick off electrons from the structures charging it to positive.

  • Spaceman April 27, 2022, 17:36

    @Alex Tolley:

    I love the quote about the dinosaurs. It speaks directly to the notion that our intelligence does NOT automatically make us less like to avoid extinction and this clever quip calls into question the oft-held assumption many make to the contrary. Our intelligence may make us less likely to last anywhere near as long as the dinosaurs did on this planet!! The dinosaurs had a long run on Earth. Love it :-)

  • Michael Fidler April 28, 2022, 4:43

    Something I’ve been giving some thought to is how exterrestrial civilizations would put to use the huge amount of energy released by flares. The largest amount of energy released in a short period of minutes to hours in a very small area in the solar system. A KARDASHEV SCALE Type II civilization would be using the energy of their sun and would have a thorough understanding of solar flares. Could they figure out how to control and direct the electrons and protons being ejected from the flare at near light speed? The use of electric and magnetic fields to beam these particles where needed and to propel starships would be a high value asset. Different configuration of rings, disc and other forms of magnetic/electric fields generated by the objects powered by the energy of the particles passing through and around them. Immersed in these huge fields would give the device the ability manipulate the protons/electrons in a beamed direction. This could be used to send signals over interstellar distances via a solar flare mechanism that would dwarf anything man has produced. A giant flare
    particle accelerator generator on a solar system scale!

    This would have little if any effect on the star or planets over the long term and give a healthy star its normal lifespan, meaning sustainable!
    This should be what we are looking for in tecno signatures since that would be closest to us technically and yet have the highest power level to communicate at interstellar distances. Maybe cosmic ray telescopes would be the cosmic way to communicate…

    Just a thought…

    • Alex Tolley April 28, 2022, 9:27

      What about propelling the star? In the context of the post’s idea of only migrating a colony at close encounters between stars, what if the CMEs could be used to improve the closeness of the encounter rather than leaving it purely to chance?

      • Geoffrey Hillend April 28, 2022, 20:22

        If you could repel a star you could repel a planet which requires gravity and a space warp or gravity control. You could also make FTL propulsion. The electromagnetic force only is strong at a short distance, but not a long distance because there are always an equal number positive and negative changes in a large body like a star and a planet, so they cancel out.

      • Geoffrey Hillend April 28, 2022, 20:36

        The CME’s are not very fast and caused by breaks in the helical magnetic fields. They don’t give the Sun enough of a push thankfully for us.

      • Michael Fidler April 28, 2022, 21:01

        Yes, all those old red dwarfs speeding through the plane of the milky way are trying to stay away from all the young hoodlum civilizations, like us, in the galactic arms! ;-}

    • Michael Fidler April 29, 2022, 7:39

      The CME are not the power to drive anything fast, but the flares is where all the power is at and they are expelling matter (protons, heavier nuclei and electrons) at near light speed so they are just like a rocket.

      • Alex Tolley April 29, 2022, 9:59

        Assuming CME protons have a velocity of c, rather than the more usual 100s km/s, and the size and frequency of CMEs on M Dwarfs, can you calculate a possible upper bound on the delta v of a star if all the material ejected was in the form of a unidirectional beam? Most importantly, can it reduce the period of close encounters between stars?

      • Geoffrey Hillend April 29, 2022, 15:32

        True. If we were only the size of protons and electrons we could travel the stars at high velocity and leave the galaxy from the powerful magnetic fields of galactic central black holes.

  • Brett Bellmore April 28, 2022, 6:19

    I myself have been wondering about the feasibility of using a giant current loop to focus the solar wind. I suppose not, it’s supersonic, so squeezing it together would just slow it down.

    You might be able to enhance the density quite a bit for higher acceleration, though.

  • Michael April 28, 2022, 8:45

    Perhaps mass could be saved by not having long feelers but a rolled up grid structure as the inner feelers of the orginal design would not have such a great effect due to their closeness at the centre.

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