[HN Gopher] Antimatter Production, Storage, Control, Annihilatio...
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Antimatter Production, Storage, Control, Annihilation Applications
in Propulsion
Author : belter
Score : 83 points
Date : 2024-12-14 17:21 UTC (5 hours ago)
(HTM) web link (www.sciencedirect.com)
(TXT) w3m dump (www.sciencedirect.com)
| jp57 wrote:
| I don't have references in front of me, (EDIT: I do!) but IIRC it
| takes about a kilogram of mass-energy to accelerate a kilogram
| mass to about 0.85c. But that kilogram would have to be carrying
| another kilogram of matter/anti-matter fuel to decelerate again.
| So there is a kind of relativistic Tsiolkovsky equation for mass-
| energy propulsion vehicles that carry their own fuel.
|
| Zipping around the galaxy at 0.95c, stopping at destinations and
| then zipping off again will require carrying a lot of antimatter
| with you.
|
| EDIT: Thanks to Wolfram Alpha I was able to see that it the
| kinetic energy of 1 kg at 0.87c is very close to the mass energy
| of 1kg of matter.
| m463 wrote:
| If you could avoid accelerating so much and go a little slower,
| you could get better lypkg.
| jp57 wrote:
| Sure, and if you want to go at non-relativistic speeds you
| hardly need to carry much fuel at all.
| api wrote:
| This is why there's ideas like the Bussard ramjet, which may
| not work but try to work around this problem by using in situ
| mass-energy.
|
| Now I have read that it may be possible to use a powerful
| magnetic field to assist with slowing down by braking against
| the interstellar medium, which helps.
|
| The Avatar films have (in spite of very derivative plots)
| fairly realistic (at least physics wise) interstellar ships.
| They accelerate using beamed laser propulsion from the Sun and
| use antimatter rockets to decelerate, then repeat this in
| reverse to come home. One assumes they somehow recharge at
| their destination but this is not shown. Too bad all that cool
| tech is in service to humans who decided to be the bad guys
| from War of the Worlds.
|
| Still traveling that close to c brings up tons of other
| problems. Collision with a micrometeorite would be like an
| atomic explosion, and blue shifting of incident and cosmic
| background radiation would blast you in the head with x-rays
| and gamma rays. Those problems would demand more mass for
| active or passive shielding, and you're already mass
| constrained.
|
| All things considered it's way more practical to go slower --
| which could still be insanely fast e.g. 0.25c -- and figure out
| how to cryosleep or become an AI that can just turn yourself
| off for the trip. Cryosleep for humans is a brutally hard
| biomedical problem but way easier than trying to approach the
| speed of light. There are other multicellular animals that can
| do it, albeit much simpler ones, so it's probably possible.
|
| 0.25c allowing for acceleration and deceleration gets you to
| Centauri in around 25 years and to further star systems with
| promising exoplanets in hundreds of years.
|
| Then there's generation ships, but that's the kind of thing
| Mormons would do. :)
| PaulHoule wrote:
| I'd imagine interstellar travelers who have mastered D+D
| fusion could break the journey down into hops of maybe 10,000
| or 100,000 AU looking for large comets or plutoid objects
| which they could use to replenish their supplies.
|
| I'd imagine it would take them 10,000 years or so to make it
| to the next star system but they might not care if they can
| live a comfortable lifestyle in the great dark.
| api wrote:
| Something I didn't think about: there is debate over how
| empty the space between stars is or whether there are a lot
| of rogue planets, comets, asteroids, maybe even exotic
| objects like asteroid or planet mass primordial black holes
| (these are a dark matter candidate). If the space between
| stars is not as empty as we imagine it opens other
| possibilities like flybys and refueling.
| giantrobot wrote:
| Interstellar space can be filled with junk yet still be
| effectively empty because it's so mind bogglingly large.
| Comets and rogue planets also aren't helpful unless 1)
| you can see/chart them ahead of time and 2) they're on
| the way to your destination.
|
| The first problem is a big challenge as they're cold,
| dark, and small. Just finding them to begin with is a
| giant problem. Accurately charting them is another order
| of magnitude increase in difficulty. Even tiny error bars
| in the measure of their proper motion means your
| spaceship can miss them by millions of miles. Even
| missing them by a dozen miles is the difference between
| life and death.
|
| Even with a huge catalog of extremely accurate
| interstellar fuel-capable objects they don't do you any
| good if they're not on the way to where you want to go. A
| meandering route to a destination in order to visit
| refueling stops adds tons of extra complexity and points
| of failure.
| thechao wrote:
| Even at .99c, everything interesting is years, decades,
| centuries, and millennia apart. All interstellar solutions
| include maintenance over millennia. Once you're doing that,
| relativistic velocity is just a hazard, not a boon. If we do
| conquer interstellar travel it'll probably be at 1% c. The
| factor of 10-20x scale won't matter to such long lived
| civilizations.
| weberer wrote:
| From the perspective of someone on the ground, yes. But due
| to time dilation, it could be just a few days for the people
| on the ship.
| Sanzig wrote:
| At .99c, the Lorentz factor is only about 7, so 1 year of
| ship time for 7 years of earth time.
| brandall10 wrote:
| .99c only dilates time by a factor of 7, so one year of
| time passed on a vehicle would yield ~7 light years.
|
| Heck, you have to get better than 5 nines to even compress
| a year into a day, .9999963c, which would take a freakish
| amount of energy to accelerate a KG to (3.3 x 10^19 J).
| Retric wrote:
| On top of this at 1g it takes ~1 year accelerating to
| that speed and another year decelerating. So even the
| nearest star is going to be a multi year subjective
| journey or a really unpleasant trip.
| thrance wrote:
| With a ship that accelerates at a constant 1G, you can go
| pretty much anywhere in the universe in less than 50
| (subjective) years [1]. And when I say anywhere, I mean
| _anywhere_.
|
| [1] https://www.reddit.com/r/dataisbeautiful/comments/s4tbry/
| oc_...
| diggan wrote:
| Maybe I'm mistaken, but that graph would be for _passing
| by_ places, as it doesn 't include the time it would take
| to slow down from that constant acceleration, if you want
| to actually visit any other places than your zipping
| spaceship.
| creato wrote:
| The title of the graph says it is for accelerating half
| way, then decelerating the other half
| aardvark179 wrote:
| This comes up every time this sort of thing is discussed on
| HN. Sustained 1 g acceleration takes a staggering amount of
| fuel, and carrying enough to slow down again makes it even
| worse.
| thrance wrote:
| It's definitely sci-fi for now, but we can always imagine
| some far out way to store energy much more densely than
| antimatter. A huge amount of photons orbiting a micro
| black hole on its Schwarzschild radius, would only weigh
| as much as the black hole and let you store a potentially
| infinite amount of energy.
| dehrmann wrote:
| So it's only worthwhile to do big excursions if participants
| self-fund it or we missed something about relativity and
| faster-than-light travel. Funding it would be like the Roman
| empire telling us a small boat will land in Genoa in 2025
| that spent the last two millennia traveling the world and
| collecting data with the best tools of the first century.
| jmyeet wrote:
| The energy budget for any kind of interstellar travel is large,
| almost incomprehensibly large. Like many orders of magnitude
| greater than what our entire planet produces and consumes. The
| numbers you're quoting seem reasonably accurate but they also
| assume perfect mass-to-energy conversion, which we'd never get.
|
| It's why some kind of generation ship, that is basically a
| colony, is really the only conceivable method of traveling
| between stars.
|
| Also remember that whatever energy is produced by antimatter,
| you need _more_ than that to produce the antimatter to begin
| with. Where are you getting that energy? I believe it 's from
| solar power from a Dyson Swarm.
| benlivengood wrote:
| Hopefully Von Neumann probes will be much lighter than a Kg and
| we can construct receiving stations on the other end and
| transport the information we care about back and forth directly
| at light speed.
| TOMDM wrote:
| Which is to say nothing of the mass of whatever containment
| equipment would be necessary.
|
| For stop and go; we'd be looking at something that could deploy
| a dyson swarm, generate and contain its own antimatter and then
| go again right?
|
| I should play universal paperclips again.
| atulsnj wrote:
| I am just thinking out loud and stupid but this could be
| something like the Cold Fusion/LENR or be actually something
| useful.
| m463 wrote:
| If you could figure out production and storage of antimatter,
| space travel would be very different.
|
| I remember reading a Robert L Forward book where he described
| all this in great detail.
|
| EDIT: I think the book was "Indistinguishable from Magic" which
| was interesting science-wise but not compelling as a science
| fiction book.
|
| He also seems to have written about antimatter directly:
| "Mirror Matter: Pioneering Antimatter Physics"
| ClumsyPilot wrote:
| You can start by getting nuclear rockets to work
|
| And imattwr is at the end of a tech tree that we have not
| started
| adrian_b wrote:
| While it may be fun to write a paper that attempts to analyze
| the feasibility of using antimatter for energy storage, in real
| life this does not have any chances to be done, except in a
| very distant future, like at least a century or more likely
| several centuries from now.
|
| The energetic efficiency of producing antimatter in order to
| store energy in it is well approximated by zero.
|
| Storing antimatter requires a huge volume and mass per the
| energy stored and it also requires a continuous power
| consumption, so long term storage would degrade the energetic
| efficiency even more.
|
| There are methods of producing energy that nobody knows how
| they could be done, like nuclear fusion without producing
| neutrons (aneutronic fusion), but which nonetheless have a
| chance to be realized that is much, much greater than
| discovering a method of producing antimatter with high
| efficiency and also solving the problems of long term storage
| and of harnessing the energy produced by annihilation as
| intense destructive radiation.
|
| For now, the only realistic research target for improving space
| propulsion in the next few decades is the use of nuclear
| fission reactors, which could allow travel inside the Solar
| System with much more acceptable durations.
| wsintra2022 wrote:
| Why would carbon emissions be an issue in space propulsion?
| BurningFrog wrote:
| It could only be an issue for the launch.
| mmh0000 wrote:
| And where is the carbon in space supposed to go? It'll just
| stay there forever contaminating the space whales. We, as a
| responsible and intelligent species, must develop clean and
| sustainable fuels to protect the space whales and our future
| generations.
| weberer wrote:
| I guess its just a keyword they have to put in for
| grants/funding purposes.
| int0x29 wrote:
| > Spacecrafts can traverse the Solar System to reach nearby stars
| in span of days to weeks
|
| Is there something I'm missing here? Proxima Centauri is 4+
| light-years from us and firmly out of the solar system.
| sedatk wrote:
| Relativity?
| prox wrote:
| At the actual speed of light, that's still 4 lightyears. If
| you mean how much time will pass for the traveler, that might
| be it yeah.
| sedatk wrote:
| Yes, that's what I mean.
| bboygravity wrote:
| Traverse the solar system to reach the nearby star (the sun)
| maybe?
| m463 wrote:
| That is just sort of an ambiguous sentence.
|
| How about this one though:
|
| _At a constant acceleration of 1 g, a rocket could travel the
| diameter of our galaxy in about 12 years ship time, and about
| 113,000 years planetary time. If the last half of the trip
| involves deceleration at 1 g, the trip would take about 24
| years. If the trip is merely to the nearest star, with
| deceleration the last half of the way, it would take 3.6
| years._
|
| https://en.wikipedia.org/wiki/Space_travel_under_constant_ac...
| sethev wrote:
| From the perspective of someone on the spaceship, this is
| absolutely possible by the laws of physics. It's a common
| misunderstanding that the speed of light is like a highway
| speed limit that's enforced by the universe. In reality, it
| means that light always travels at the speed of light and that
| you can never observe an object traveling faster than that.
|
| However, a key part of relativity is that the laws of physics
| are the same in every reference frame. If you're on a ship with
| sufficient fuel, you can keep accelerating forever and cover
| vast distances. You'll never reach a point where the universe
| prevents you from accelerating. If it were otherwise, then
| relativity wouldn't be true - because there would be special
| rules that apply to people traveling at a certain speed. That's
| the whole point of relativity is there can't be such laws
| because there isn't a preferred reference frame in the
| universe!
|
| However, the more you accelerate away from the earth the longer
| time will have passed on earth if you turn around and come
| back.
|
| Here's a calculator you can play with:
| https://spacetravel.simhub.online
|
| As an example, if you could accelerate at 9.8 m/s (same as
| gravity - so you could walk around the 'back' of the ship as if
| in earth gravity), then you could travel 50 light years in 7.7
| 'ship years'. However, if you turned around and went back to
| earth 102 years would have passed there, even though you would
| only be ~15 years older.
| api wrote:
| There's a classic sci fi novel called Tau Zero about a
| Bussard ramjet breaking so they can't turn it off, so they
| keep asymptotically accelerating toward c and experiencing
| more and more time dilation. Won't spoil the rest.
| thrance wrote:
| Everything you said is true, but I think reaching Proxima
| Centauri in a matter of days would require an acceleration
| that would crush the most well trained of astronauts into a
| thin meat pancake. I do think the article meant _planets_
| instead of _stars_.
| airstrike wrote:
| Helpful "high-res" graphical abstract: https://ars.els-
| cdn.com/content/image/1-s2.0-S26662027240045...
| Aachen wrote:
| I can't read the smallest text, not sure I'd call it high res
| (unless the quotes are for sarcasm maybe?)
| airstrike wrote:
| I thought the same, but they called it high-res, so I had to
| put it in quotes...
| JoshTriplett wrote:
| Is there any fundamental law of physics that says if you want to
| turn mc^2 energy into mass, that you _have_ to create particle
| /antiparticle pairs together? Or could you, theoretically, create
| exclusively antimatter, and we just don't have a known method of
| doing so?
|
| In theory, could you use mc^2 energy to create a mass m of
| antimatter, combine it with m matter (which is rather more
| readily available), get 2mc^2 energy back out, and repeat,
| effectively consuming matter to make energy?
| master_crab wrote:
| IANAP (physicist, just an Engineer) but any sort of reaction
| like this is probably pretty hard to control so you won't get
| twice the energy. Just like with combustion engines, you're
| probably looking at some significant percentage loss (~50%?) in
| efficiency from various things.
|
| (I'm sure there are other things that would also hinder the 2x
| outlook you are asking about)
| JoshTriplett wrote:
| Yeah, as the article here notes, the energy released is
| effectively an explosion, and harnessing that energy into
| something more useful is a substantial challenge. As is the
| concept of turning energy into _specific_ (anti-)matter,
| which we have no idea how to do at the moment.
|
| This is more a theoretical question of whether any law of
| physics makes this _impossible_ (e.g. you _can 't_ create
| unpaired particles), or whether this is _theoretically_
| possible but it 's difficult to get enough efficiency to make
| it net positive.
|
| (We currently haven't even gotten _fusion_ to be reliably net
| positive; practicality is as always a set of concerns all its
| own.)
| api wrote:
| Project Orion style pusher plate nuclear pulse designs can
| handle turning big boom boom into space propulsion but as
| the parent said you are not 100% efficient.
| JoshTriplett wrote:
| More interested in electrical power than propulsion, in
| this case.
| ben_w wrote:
| > This is more a theoretical question of whether any law of
| physics makes this impossible (e.g. you can't create
| unpaired particles), or whether this is theoretically
| possible but it's difficult to get enough efficiency to
| make it net positive.
|
| It's theoretically impossible, with the slight problem that
| there seems to be more matter than antimatter in the
| universe today and nobody really knows why.
|
| Either the theory is wrong (and it being a conservation
| rule, then by Noether's theorem there's an equivalent
| symmetry* you'd have to violate if the conservation doesn't
| hold), or the initial value that's getting conserved wasn't
| ever zero.
|
| * the wikipedia page says this is specific to continuous
| symmetry; but integers aren't continuous, so has this been
| generalised, or is it just assumed?
| EA-3167 wrote:
| You have a solid intuition, in addition to the usual
| efficiency losses, a large amount (20%-50% would be usual, up
| to 80% in some cases) of the energy released during
| annihilation is in the form of... neutrinos. I don't foresee
| a realistic means of harnessing that energy any time soon,
| even where "soon" indicates quite a stretch of time.
| wiml wrote:
| Charge is conserved, so if your energy input is in the form of
| (say) a photon, you'll have to produce equal numbers of
| positive and negative charged particles.
|
| Baryon and lepton number are _almost_ conserved, which would
| require you to produce (or consume) equal numbers of particles
| and antiparticles, unless you can figure out a way to make
| nonconservation happen outside of a black hole or whatever.
|
| (Feeding matter to a black hole and using the Hawking radiation
| as an energy source would probably do what you describe, but
| there are practical difficulties)
| api wrote:
| AFAIK a black hole could be a near perfect mass energy
| converter, and I think the evaporation rate (Hawking
| temperature) can be regulated by adjusting black hole spin.
|
| There's just the wee problem of getting or making a black
| hole and then grabbing it and controlling its spin.
| ben_w wrote:
| There's the second problem that the temperature and power
| are directly related, so if you want the temperature low
| enough to not photo-ionise stuff much (6eV/70,000 K) then
| be power output is 114 microwatts.
|
| https://benwheatley.github.io/blog/2022/05/14-17.06.59.html
| JoshTriplett wrote:
| > Charge is conserved, so if your energy input is in the form
| of (say) a photon, you'll have to produce equal numbers of
| positive and negative charged particles.
|
| Charge alone doesn't seem like it'd be a fundamental
| limitation here, considering that (for instance) antineutrons
| exist.
|
| > Baryon and lepton number are almost conserved
|
| Is the "almost" here something other than the Hawking
| radiation "one half falls in a black hole and the other half
| doesn't"?
| PaulHoule wrote:
| In the _Forge of God_ universe there is a way to convert
| chunks of matter (like you and your spaceship) to antimatter,
| for instance it 's a violation of the conservation rules that
| actually get conserved to turn hydrogen -> antihydrogen.
| codethief wrote:
| One obstacle is momentum conservation: You can't just turn a
| single massless particle (a photon, say) into a massive one or
| vice versa because that would violate conservation of
| 4-momentum. The way out is to involve more than one massless
| particle in that interaction, e.g. convert two massless
| particles into one or more massive ones, or vice versa. (If a
| single massive particle is produced, the 3-momentum of the two
| massless particles cancels out in the center-of-mass frame,
| while their energy / p_0 adds up to the rest mass of the
| particle that's produced.)
|
| Which interactions exactly are possible depends on the
| particles & forces involved, and further conservation laws for
| quantum numbers (e.g. charge) that the force obeys.
|
| TL;DR Turning a single massless particle into a single massive
| one is not possible, you always need at least two.
| asdff wrote:
| It seems there's some hard physical limits with regard to taking
| matter and moving it somewhere via propulsion. However, I wonder
| if we could get to a point where rather than spending energy to
| move something someplace, we consider the energy to reform a
| given structure identically somewhere else. I assume at some
| distance there is a tipping point where you now save energy
| building that structure in situ vs the energy spent to move a
| structure elsewhere. And there are probably environments where it
| is cheaper still to create this structure vs others. I'm not sure
| how to establish a distant build site without actually reaching
| it in some way though, but maybe such a thing is resolved in
| time.
| refulgentis wrote:
| The problem I have with teleportation is that it seems we're
| closer to being reference types than value types, so I'm not
| sure a rebuilding in situ would work for the cases we care
| about.
|
| For static objects, I'm not sure how you'd get past the
| constraint that at some point you want mass somewhere else, and
| it needs to be moved.
| thrance wrote:
| You could totally (at least in theory) make a super-precise MRI
| scan of your brain at nanometer scale, send this data to
| wherever you want to go as a coherent beam of light (laser) and
| have the guy on the other hand rebuild your brain atom by atom.
| To the brain that would awake on the other side, the trip would
| have been instantaneous. Wether it's still you or someone else,
| ask philosophers.
| jmyeet wrote:
| One should view antimatter propulsion or energy as the ultimate
| battery. Why? Because antimatter needs to be manufactured.
| There's no natural source to mine. So whatever energy you get
| out, you had to spend _at least_ that (because of thermodynamics,
| it 's really more) to make the antimatter in the first place.
|
| So where do you get that energy in the first place? Everything
| leads back to solar power. In this case, since we're talking
| about far-future tech, we return to what I consider the most
| likely path for humanity: the Dyson Swarm. This is the sort of
| thing you can do with a truly mind-bogglingly large energy
| budget.
|
| And this matters because the energy budget, regardless of the
| energy source, for interstellar travel, is so ridiculously large.
| greesil wrote:
| Is this reputable journal?
| Pingk wrote:
| To make 1 gram of antimatter, from E=mc^2, would take about 90
| Terajoules. For reference, the atomic bomb that dropped on
| Hiroshima released about 60 Terajoules of energy.
|
| So you would need at least (and with the efficiency loss of
| production, much more than) 1.5 Little Boy atomic bombs worth of
| energy to make a single gram of antimatter.
| micw wrote:
| Or vice versa you can store the energy of 1.5 little boy atomic
| bombs into a handy gram of antimatter ...
| fnord77 wrote:
| They need a proof-reader. There's several grammar problems in
| that paper that seem like common ESL errors.
| Animats wrote:
| The paper doesn't seem to go into the reaction mass issue much.
| What are they using for reaction mass? And how do you aim the
| exhaust?
|
| With fission nuclear propulsion you run out of reaction mass long
| before you're out of energy. It's a few times better than
| chemical fuels, but not 10x better.
| peterburkimsher wrote:
| The antimatter exhaust could be aimed by putting matter behind
| it, but it would erode the matter. Better to have it in an
| electromagnetic field (torus + magnetic monopole) so it doesn't
| touch the matter.
|
| Those electromagnets would need power too, so I guess a battery
| or RNG (nuclear) solution could be used.
|
| What concerns me most is the radiation risk of travelling close
| to light speed. Surely we'd pass by some ionising radiation, or
| weakly-interacting neutrinos.
|
| I suppose the only way to be sure is to build a prototype and
| try it.
| kristianp wrote:
| This is only slightly less practical than a black hole starship.
|
| https://en.m.wikipedia.org/wiki/Black_hole_starship
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