Surprisingly, antimatter can be stored for months. They built a 2.5 ton storage box, ultra high vacuum and magnetic trap and a loading mechanism. In a first trial they loaded 70 protons and drove around the campus on a truck.
Impressive that this is even possible. But with 2.56 * 10^-15 Wh/kg still orders of magnitude from current batteries.
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?
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)
This is an open question, and an important one to understanding the early history of the universe. Essentially, as far as everything we have seen in the lab shows, and everything we know about the laws of physics says, certain quantities like charge must be conserved, so matter and antimatter are always generated together. However, this creates a glaring issue- where the Hell is all the antimatter? The universe is, as far as we know, made almost entirely of matter with very little antimatter, and so there must be some kind of asymmetry somewhere that we haven't found yet. Otherwise the universe would be 50/50 matter/antimatter, or would just be constantly forming and destroying matter and antimatter.
From Wikipedia: "The Standard Model of electroweak interactions has all the necessary ingredients for successful baryogenesis, although these interactions have never been observed[11] and may be insufficient to explain the total baryon number of the observed universe if the initial baryon number of the universe at the time of the Big Bang is zero." In other words, there is a process that can in in principle create more matter than antimatter, but it has not been observed experimentally yet.
I think other than this, there are no known ways to even create more antimatter than matter in a process. But it is believed that more processes must exist, in order to explain the predominance of matter over antimatter in our universe.
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)
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.
Their graph with thrust/impulse for various rocket technologies [1] has a huge omission: project Orion [2], a rocket propelled by nuclear bombs. Too bad, this is by far the most promising and technology-ready rocket propulsion idea we have for deep space travel. Antimatter propulsion is pie in the sky, nuclear bomb propulsion is something we can do within a decade if we wanted to.
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.
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.
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.
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. :)
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.
Yup the problem with antimatter propulsion is it’s still subject to the tyranny of the rocket equation. The only way to escape that is to leverage energy external to the vehicle, like laser pushed light sales or relativistic railguns. You just can’t be carrying your own fuel around for an interstellar trip.
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.
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.
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.
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.
I guess many countries on a budget look at this as a "cheap" nuke nowadays, something a few extra steps of physics could make easy reachable, without having to pay for the whole nuclear force "shebang". Thanks russia, thanks china, thanks usa - one world locked in a eternal Mexican standoff it is. Future generations are going to look at the collapse of Assads regime as the last "downfalls" without nail-biting.
No mention of chemical stabilisation that I can see which is what you'd really to do if we were bulk producing antimatter: the idea is you produce a crystal lattice into which an anti-particle can be injected where it stably orbits due to the internal charge configuration.
There's some possible ideas for how to do it out there, but obviously we kind of lack enough antimatter to go experimenting.
Antimatter is the opposite of matter, with the same mass but opposite electric charge. It's considered the rarest, most expensive, and potentially most dangerous substance on Earth. One gram of antimatter costs around $62.5 trillion
Sounds like we won’t be using antimatter for anything practical for a long time.
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.
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.
It is possible to use antimatter directly but it sounds like that only uses the pions with magnetic nozzle.
The main use of antimatter is to heat reaction mass. The advantage over nuclear rocket is that the "temperature" of antimatter is really high so the specific impulse can also be high. One advantage is that can change the amount of reaction mass to get more thrust or better efficiency.
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.
I think we need a complete paradigm shift in the concept of traveling. Instead of traveling mass we need to think about traveling of information, assuming that information traveling is not subject to the same laws of physics that mass is. I hope quantum mechanics will be key here such that some day it will allow an organism that is some combination of mass and information to let the information travel rather than both together. I.e., we need to find solutions to decouple the information from the mass and let the information travel while the mass remains at essentially the „same“ position in space. I think this could allow us instant interstellar traveling, maybe with some overhead of preparation and finalization in the range of minutes or hours, i.e. in the time scale of classic human traveling.
Is my understanding correct that light (electromagnetic radiation, the whole spectrum) arrives instantaneously from the light’s frame of reference? (in a vacuum, etc).
[+] [-] schobi|1 year ago|reply
Surprisingly, antimatter can be stored for months. They built a 2.5 ton storage box, ultra high vacuum and magnetic trap and a loading mechanism. In a first trial they loaded 70 protons and drove around the campus on a truck.
Impressive that this is even possible. But with 2.56 * 10^-15 Wh/kg still orders of magnitude from current batteries.
[+] [-] sampo|1 year ago|reply
The article says 1000 kilograms, that is 1 ton.
[+] [-] JoshTriplett|1 year ago|reply
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?
[+] [-] wiml|1 year ago|reply
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)
[+] [-] markovs_gun|1 year ago|reply
[+] [-] qnleigh|1 year ago|reply
I think other than this, there are no known ways to even create more antimatter than matter in a process. But it is believed that more processes must exist, in order to explain the predominance of matter over antimatter in our universe.
https://en.m.wikipedia.org/wiki/Chiral_anomaly
[+] [-] master_crab|1 year ago|reply
(I’m sure there are other things that would also hinder the 2x outlook you are asking about)
[+] [-] codethief|1 year ago|reply
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.
[+] [-] unknown|1 year ago|reply
[deleted]
[+] [-] credit_guy|1 year ago|reply
[1] https://ars.els-cdn.com/content/image/1-s2.0-S26662027240045...
[2] https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
[+] [-] jmyeet|1 year ago|reply
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.
[+] [-] jp57|1 year ago|reply
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.
[+] [-] thechao|1 year ago|reply
[+] [-] api|1 year ago|reply
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. :)
[+] [-] TOMDM|1 year ago|reply
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.
[+] [-] jmyeet|1 year ago|reply
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.
[+] [-] m463|1 year ago|reply
[+] [-] pdonis|1 year ago|reply
Yes, it's called the relativistic rocket equation.
https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/...
[+] [-] davedx|1 year ago|reply
[+] [-] benlivengood|1 year ago|reply
[+] [-] unknown|1 year ago|reply
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[+] [-] Pingk|1 year ago|reply
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.
[+] [-] int0x29|1 year ago|reply
Is there something I'm missing here? Proxima Centauri is 4+ light-years from us and firmly out of the solar system.
[+] [-] wsintra2022|1 year ago|reply
[+] [-] mmh0000|1 year ago|reply
[+] [-] BurningFrog|1 year ago|reply
[+] [-] weberer|1 year ago|reply
[+] [-] olddustytrail|1 year ago|reply
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[+] [-] asdff|1 year ago|reply
[+] [-] kristianp|1 year ago|reply
https://en.m.wikipedia.org/wiki/Black_hole_starship
[+] [-] ItCouldBeWorse|1 year ago|reply
I wouldnt want to work at the IAA right now.
[+] [-] XorNot|1 year ago|reply
There's some possible ideas for how to do it out there, but obviously we kind of lack enough antimatter to go experimenting.
[+] [-] mmmBacon|1 year ago|reply
Antimatter is the opposite of matter, with the same mass but opposite electric charge. It's considered the rarest, most expensive, and potentially most dangerous substance on Earth. One gram of antimatter costs around $62.5 trillion
Sounds like we won’t be using antimatter for anything practical for a long time.
[+] [-] Animats|1 year ago|reply
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|1 year ago|reply
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.
[+] [-] ianburrell|1 year ago|reply
The main use of antimatter is to heat reaction mass. The advantage over nuclear rocket is that the "temperature" of antimatter is really high so the specific impulse can also be high. One advantage is that can change the amount of reaction mass to get more thrust or better efficiency.
[+] [-] airstrike|1 year ago|reply
[+] [-] Aachen|1 year ago|reply
[+] [-] atulsnj|1 year ago|reply
[+] [-] adrian_b|1 year ago|reply
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.
[+] [-] m463|1 year ago|reply
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"
[+] [-] fnord77|1 year ago|reply
[+] [-] calibas|1 year ago|reply
[+] [-] greesil|1 year ago|reply
[+] [-] calibas|1 year ago|reply
> A general conclusion was drawn that antimatter technology and its development for propulsion is still in its theoretical stages.
[+] [-] twwwt|1 year ago|reply
[+] [-] TheSpiceIsLife|1 year ago|reply
[+] [-] thrw42A8N|1 year ago|reply
[+] [-] unknown|1 year ago|reply
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