Antimatter production, storage, control, annihilation applications in propulsion(sciencedirect.com)
sciencedirect.com
Antimatter production, storage, control, annihilation applications in propulsion
https://www.sciencedirect.com/science/article/pii/S2666202724004518
168 comments
> They built a 2.5 ton storage box
The article says 1000 kilograms, that is 1 ton.
The article says 1000 kilograms, that is 1 ton.
1 tonne
Yeah, which works out to 2200 lbs, give or take.
Sounds like someone (LLM) then treated lbs like KG to turn that into tonnes again?
Dumb. Easy to do if not paying attention.
Sounds like someone (LLM) then treated lbs like KG to turn that into tonnes again?
Dumb. Easy to do if not paying attention.
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?
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)
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)
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.
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.
There’s just the wee problem of getting or making a black hole and then grabbing it and controlling its spin.
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
https://benwheatley.github.io/blog/2022/05/14-17.06.59.html
I love the “practical difficulties”
> 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"?
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"?
The neutrons and the antineutrons are made of multiple electrically charged particles whose electric charges sum to zero, exactly like the electric charges of all particles that compose a neutral atom or neutral anti-atom sum to zero.
Therefore there is no path to generate antineutrons in which you do not have pairs of electrically charged particles with opposite charges that are generated or annihilated.
The annihilation and pair generation reactions are electromagnetic interactions between electrically charged particles and antiparticles with opposite electric charges, which are otherwise identical, in order to satisfy all conservation laws.
Only the neutrinos do not have electric charge and about them it has not been proved beyond reasonable doubt that the antineutrinos are different from the neutrinos (in other ways except opposite spin). Neutrinos do not participate in annihilation and pair generation reactions.
Neutrinos may appear and disappear in similar reactions that are mediated by weak interactions (i.e. by the heavy bosons), like the inter-conversions between protons and neutrons (actually between u and d quarks), but in these weak-force based reactions the energy that is produced is much less than in annihilation reactions and frequently much of it is lost by being carried away by neutrinos. It is possible to make electric generators with beta-radioactive isotopes, where this kind of reactions happen, but the only advantage of those is the extremely long lifetime, because otherwise the power density and energy density are low.
So when talking about using antimatter for energy storage purposes, that refers exclusively to generating electrically-charged particle-antiparticle pairs, separating and storing the antiparticles, then annihilating the antiparticles with their corresponding particles, resulting in extremely intense gamma radiation, which carries the reaction energy.
When the annihilation is done inside matter, which includes annihilation between nucleons (where there may be multiple annihilation events between the component quarks) the gamma photons interact with the surrounding matter or sub-nucleon components, producing a cascade of various accelerated particles, including many new particle-antiparticle pairs, which will cause later other annihilations. So from a single initial annihilation a great number of accelerated particles and gamma photons may result, but the first stage is always the generation of a pair of gamma photons.
Therefore there is no path to generate antineutrons in which you do not have pairs of electrically charged particles with opposite charges that are generated or annihilated.
The annihilation and pair generation reactions are electromagnetic interactions between electrically charged particles and antiparticles with opposite electric charges, which are otherwise identical, in order to satisfy all conservation laws.
Only the neutrinos do not have electric charge and about them it has not been proved beyond reasonable doubt that the antineutrinos are different from the neutrinos (in other ways except opposite spin). Neutrinos do not participate in annihilation and pair generation reactions.
Neutrinos may appear and disappear in similar reactions that are mediated by weak interactions (i.e. by the heavy bosons), like the inter-conversions between protons and neutrons (actually between u and d quarks), but in these weak-force based reactions the energy that is produced is much less than in annihilation reactions and frequently much of it is lost by being carried away by neutrinos. It is possible to make electric generators with beta-radioactive isotopes, where this kind of reactions happen, but the only advantage of those is the extremely long lifetime, because otherwise the power density and energy density are low.
So when talking about using antimatter for energy storage purposes, that refers exclusively to generating electrically-charged particle-antiparticle pairs, separating and storing the antiparticles, then annihilating the antiparticles with their corresponding particles, resulting in extremely intense gamma radiation, which carries the reaction energy.
When the annihilation is done inside matter, which includes annihilation between nucleons (where there may be multiple annihilation events between the component quarks) the gamma photons interact with the surrounding matter or sub-nucleon components, producing a cascade of various accelerated particles, including many new particle-antiparticle pairs, which will cause later other annihilations. So from a single initial annihilation a great number of accelerated particles and gamma photons may result, but the first stage is always the generation of a pair of gamma photons.
>The neutrons and the antineutrons are made of multiple electrically charged particles whose electric charges sum to zero, exactly like the electric charges of all particles that compose a neutral atom or neutral anti-atom sum to zero.
Does this mean neutrons are (or can be) polarized like a water molecule (but much weaker)?
Does this mean neutrons are (or can be) polarized like a water molecule (but much weaker)?
Maybe but I don't think anyone has seen it.
https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_mome...
https://en.m.wikipedia.org/wiki/Neutron_electric_dipole_mome...
Charge here is just one thing that has to be conserved. Baryon number is a property of quarks and must also be conserved, and this prevents a neutron turning into an anti neutron as that would have opposite baryon number.
There are others such as isospin, lepton number…
These types of conservation laws are what limits the possible particle interactions.
There are others such as isospin, lepton number…
These types of conservation laws are what limits the possible particle interactions.
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.
https://en.m.wikipedia.org/wiki/Chiral_anomaly
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
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)
(I’m sure there are other things that would also hinder the 2x outlook you are asking about)
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.
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.)
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.)
> 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?
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?
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.
More interested in electrical power than propulsion, in this case.
The classic stand-in of boiling a bunch of water, then spinning turbines is likely our best bet.
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.
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.
Could two particles be: anti proton and anti electron?
(What conservation law would it violate?)
(What conservation law would it violate?)
Lepton and baryon number.
Thanks for the explanation!
[deleted]
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.
[1] https://ars.els-cdn.com/content/image/1-s2.0-S26662027240045...
[2] https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
[1] https://ars.els-cdn.com/content/image/1-s2.0-S26662027240045...
[2] https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
If you like Project Orion, you might like to read about the Medusa Drive, which is a related, but probably more promising concept using a sail instead of a giant pusher plate.
https://www.centauri-dreams.org/2012/07/20/medusa-nuclear-pu...
https://m.youtube.com/watch?v=DYuBt2nFG98
https://www.centauri-dreams.org/2012/07/20/medusa-nuclear-pu...
https://m.youtube.com/watch?v=DYuBt2nFG98
Medusa Drive is interesting, and so are lots of other space propulsion idea, like the nuclear light bulb [1], the direct fusion drive [2], the fission fragment rocket [3] or the pulse nuclear thermal rocket [4]. The difference is that Project Orion was actually funded, and some of the smartest nuclear scientists worked on it for a few years. Of course, they never built the actual rocket, but they carried out a tremendous amount of theoretical and experimental work. All other designs were only done on paper. For Project Orion, they put actual spheres coated in graphite next to nuclear bombs to see if they withstand the explosion, while being inside the fireball. They did, and Scott Manley covered this in one of his youtube videos [5] (see 9:30 where he mentions the Orion project). They got a little island from the Navy where they could carry explosive tests. They built a conventionally powered version of the rocket. They found out by accident that adding a bit of oil on the pusher plate reduces the ablation significantly. They did a lot of testing to see if the pusher plate can withstand the various stresses. When someone comes up with a new idea for interstellar travel, they spend a few days thinking of a few aspect of the design, and then they publish a paper or write a novel. For Project Orion, they hired Ted Taylor, one of the greatest minds in nuclear weapons design, and they also hired Freeman Dyson, one of the greatest minds in the world in general.
[1] https://en.wikipedia.org/wiki/Nuclear_lightbulb
[2] https://en.wikipedia.org/wiki/Direct_Fusion_Drive
[3] https://en.wikipedia.org/wiki/Fission-fragment_rocket
[4] https://en.wikipedia.org/wiki/Pulsed_nuclear_thermal_rocket
[5] https://www.youtube.com/watch?v=by1xpy8ob8E
[1] https://en.wikipedia.org/wiki/Nuclear_lightbulb
[2] https://en.wikipedia.org/wiki/Direct_Fusion_Drive
[3] https://en.wikipedia.org/wiki/Fission-fragment_rocket
[4] https://en.wikipedia.org/wiki/Pulsed_nuclear_thermal_rocket
[5] https://www.youtube.com/watch?v=by1xpy8ob8E
Nuclear Salt Water Rocket is a fun one too: https://en.m.wikipedia.org/wiki/Nuclear_salt-water_rocket
Thanks for sending me down a rabbit hole :-)
A fun collection of articles!
A fun collection of articles!
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.
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.
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.
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.
.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 × 10^19 J).
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 × 10^19 J).
Damn, c is too big for traveling with compressed enough time for cheap, yet too small to make communication within the earth be pretty much instantaneous (like getting 1ms roundtrip latency everywhere).
Right? I’ve often thought this. Light is both frustratingly fast and frustratingly slow at the same time.
It’s not that light is too fast it’s that space is too big.
The problem is that we don't live long enough. We're fireflies.
Idk, given how things are going I'll take 45yrs over 10^6yrs
Isn't this a pointless goal anyways since any spaceship we'd have capable of getting to any meaningful percentage of c would get destroyed by any small amounts of matter or gas it bumps into on the way.
That's why we usually end up starting with projectiles instead of ships. Once the drive is ready, someone will take it from you for a few decades to shoot at things.
Impact seems to have a timelined meaning, starting with destruction, then following up with conquering, and exploration coming somewhere before constructive applications at the far end.
As apes we just can't keep holding back till we can build houses or something with it, when we also could just throw that stone at something. Especially before someone else does :)
Impact seems to have a timelined meaning, starting with destruction, then following up with conquering, and exploration coming somewhere before constructive applications at the far end.
As apes we just can't keep holding back till we can build houses or something with it, when we also could just throw that stone at something. Especially before someone else does :)
Seems reasonable might have some way of dealing with that when they’re able to accelerate sizable objects to multiple percents c.
My understanding is that space is so big and empty that the odds of you actually hitting anything is quite small.
At these velocities, even a spec of sand is a major hazard. And the distances covered in these shorts of journeys would pretty much guarantee a collision of that sort. (Random search showed a 13mg grain of sand at .999c is equivalent to 1700 tons of TNT).
Even interstellar/stellar wind would have enough molecules of gas to cause some crazy erosion/damage.
Even interstellar/stellar wind would have enough molecules of gas to cause some crazy erosion/damage.
I'd imagine that simply interacting with stray hydrogen atoms faffing about in interstellar space would cause significant damage over time?
Sounds about right.
In the interstellar medium, matter is primarily in molecular form and reaches number densities of 10^12 molecules (mostly composed of) hydrogen, then helium, oxygen, nitrogen) per cubic meter (1 trillion molecules per cubic meter).[1]
So, what, about a picogram per cubic meter.
If your ship has a cross-sectional area of one square meter, and Alpha Centauri is 40,000,000,000,000 meters away [2] (and you thought it was a long way to the shop if you want a Chiko Roll), you’ll have to manage with 2.62^23 tonnes of mostly hydrogen in the way.
The interstellar medium is also about 1% dust, so about 2.6^21 tonnes of solid matter.
Someone check my mass maths.
1. https://en.m.wikipedia.org/wiki/Interstellar_medium
2. Google Search AI Overview
In the interstellar medium, matter is primarily in molecular form and reaches number densities of 10^12 molecules (mostly composed of) hydrogen, then helium, oxygen, nitrogen) per cubic meter (1 trillion molecules per cubic meter).[1]
So, what, about a picogram per cubic meter.
If your ship has a cross-sectional area of one square meter, and Alpha Centauri is 40,000,000,000,000 meters away [2] (and you thought it was a long way to the shop if you want a Chiko Roll), you’ll have to manage with 2.62^23 tonnes of mostly hydrogen in the way.
The interstellar medium is also about 1% dust, so about 2.6^21 tonnes of solid matter.
Someone check my mass maths.
1. https://en.m.wikipedia.org/wiki/Interstellar_medium
2. Google Search AI Overview
ChatGPT’s math says that a picogram at 0.999c delivers about the energy of a strong human punch. Aside from issues of metal fatigue that wouldn’t seem like the thing to be most concerned with regardless of distance - the effect to me would seem closer to space rain (assuming you could dissipate the heat which seems like the bigger problem).
Dust is a concern but again the typical dust particle size would be about the power of a gun shot of a small caliber rifle. A problem to deal with but a rarer event still. Of course another challenge would be larger dust particles which while improbable are still possible which largely rules out humans in these craft. But that goes without saying since the acceleration to get to that speed would be unlikely something humans could withstand anyway.
Dust is a concern but again the typical dust particle size would be about the power of a gun shot of a small caliber rifle. A problem to deal with but a rarer event still. Of course another challenge would be larger dust particles which while improbable are still possible which largely rules out humans in these craft. But that goes without saying since the acceleration to get to that speed would be unlikely something humans could withstand anyway.
Right, but a .357 round delivers roughly the same kinetic energy as nunchucks and particle accelerators are also a thing, which is to say delivery of a human punch to a cross section of area the size of a hydrogen atom is going to have permanent negative impacts to whatever is on the receiving end. I'm imagining the front of the craft ablating at the atomic level and throwing off some wild-ass radiation in the process?
I wonder if it would be possible to push it out of the way with some kind of charged field ahead of the space craft. But even if that's the case it would act like air and cause deceleration.
Could they just send lots of ships on the same path and specifically design them to break apart outward if destroyed, eg spin them at very high rates, to basically sweep the path clean, or would most of the particles in the path only be there because they happened to move into the path momentarily? I don’t know much about the velocities of interstellar particles.
Isn't some of that matter/gas moving at really high speeds anyway?
Deflector shields of course
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.
This is assuming that you have to be conscious during the trip. Antimatter storage is a lot more scifi than human hibernation.
I think the opposite is true.
We do know how to inefficiently create and store antimatter, we don’t have any idea how to cause human hibernation.
To me getting two dozen of orders of magnitude better at something is clearly hard, but that still beats trying to do something we don’t have a clue how to start. For human hibernation step 1 is probably serious genetic engineering and there’s going to be other steps.
We do know how to inefficiently create and store antimatter, we don’t have any idea how to cause human hibernation.
To me getting two dozen of orders of magnitude better at something is clearly hard, but that still beats trying to do something we don’t have a clue how to start. For human hibernation step 1 is probably serious genetic engineering and there’s going to be other steps.
Inefficiently in the context of antimatter storage makes every industrial accident since the dawn of time combined seem like a kid spilling their juice.
The inefficiencies around storage are a practical not a safety concern. Once cooled we can contain the particles just fine the issue is only 0.1% get trapped and the apparatus is vastly larger than the mass of antimatter stored.
If you look at particle accelerators, the anti-matter storage is still very much experimental with anti-hydrogen storage holding it for less than 20s at most. We can trap individual particles (e.g. protons) for a long time but things get exponentially more complicated as you increase the size of the system.
Hell, we can't even store hydrogen without leakage issues and with anti-hydrogen any leakage is very bad.
Hell, we can't even store hydrogen without leakage issues and with anti-hydrogen any leakage is very bad.
To put that into number that people can understand, to accelerate 1kg of matter to 94% the speed of light you need 1kg of antimatter. That is the equivalent of the tsar bomb. So the storage facility would need to withstand that type of explosion 1000 times over for every kg of antimatter it produces.
World ending doesn't begin to describe what that looks like.
World ending doesn't begin to describe what that looks like.
That assumes the energy is released in a fraction of a second which would preclude cooling the antimatter.
Do the same thing over a year in many different devices and you’re basically dealing with a normal nuclear power plant’s output.
Do the same thing over a year in many different devices and you’re basically dealing with a normal nuclear power plant’s output.
I imagine you will want to send more than 1kg worth of payload.
We can freeze and reanimate living things only five or so orders of magnitude removed from humans; if we're just talking hibernation, it's as little as two.
How many orders of magnitude more complicated is a human mind than a cell? Infinity, I'd guess.
Maybe, but there are mammals that can survive deep hibernation and near-total suspension. In pure biological/biochemical terms I don't see any reason to think we're much more than 100 times more complex than a rodent, or 1000 times more complex than the various fish and amphibian species who can survive their bodies reaching near-zero temperatures.
They've put pigs into suspended animation for an hour or two, I'm not sure what the upper bound is on that or how much further it's possible to go with it. Ditto organ deep-cooling. So while it's not feasible now, it feels like we need "only" 100x or so improvement to make it viable.
They've put pigs into suspended animation for an hour or two, I'm not sure what the upper bound is on that or how much further it's possible to go with it. Ditto organ deep-cooling. So while it's not feasible now, it feels like we need "only" 100x or so improvement to make it viable.
Unfortunately, it only takes one thing to make it not work.
Everybody forgets about tardigrades, but they will be here when we are long passed from all memory.
[deleted]
The problem with human hibernation is that it is almost impossible to ethically test.
What medical ethics board is going to approve a research project "put healthy experimental subject in coma for 5 years, observe what they are like when they wake up?"
Reminds me of https://en.wikipedia.org/wiki/Deep_sleep_therapy and https://en.wikipedia.org/wiki/Chelmsford_Royal_Commission
I think this is an example of a technology which, if it is ever developed, is most likely to be developed by some kind of totalitarian regime which has no ethical qualms about human experimentation.
What medical ethics board is going to approve a research project "put healthy experimental subject in coma for 5 years, observe what they are like when they wake up?"
Reminds me of https://en.wikipedia.org/wiki/Deep_sleep_therapy and https://en.wikipedia.org/wiki/Chelmsford_Royal_Commission
I think this is an example of a technology which, if it is ever developed, is most likely to be developed by some kind of totalitarian regime which has no ethical qualms about human experimentation.
Heinlein story time! Door into Summer
https://en.wikipedia.org/wiki/The_Door_into_Summer
Protagonist signs their life away for a 'cold sleep' that will allow them to wake up many years later. Tech is iffy. They do it because they are desperate, and the interest gained over time should make them rich (doesn't happen of course).
That's not really how hibernation works in mammals, they have to raise their body temperature and come out of hibernation every couple weeks, the leading theory is this is to (ironically) catch up on sleep.
Inducing torpor would have major medical uses in surgical and emergency medicine, it's not just useful for passing the time.
Inducing torpor would have major medical uses in surgical and emergency medicine, it's not just useful for passing the time.
People with incurable diseases or just strange individuals can volunteer for such experiments. After that, if they write about their experiences, it could be featured first on Hacker News.
At .99c, the Lorentz factor is only about 7, so 1 year of ship time for 7 years of earth time.
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_...
[1] https://www.reddit.com/r/dataisbeautiful/comments/s4tbry/oc_...
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.
That's exactly the point. The limiting factor to space travel is how to achieve acceleration, and not the acceleration limits of the human body.
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.
No, they would have as much mass as the black hole plus the energy of the photons (they still distort spacetime and exert a gravitational force, and have inertial mass) and you still have to move that mass with you. You may have increased your fuel density, but you haven’t reduced its mass compared to antimattter, and you still have not dodged the relativistic rocket equation.
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.
The title of the graph says it is for accelerating half way, then decelerating the other half
The CMB becomes deadly well before these speeds (the rear facing light burns you; the forward facing light nukes you). That's not even accounting for objects in space, or the light from stars, which will be amplified according to the Lorentz factor.
EDIT: here's a small discussion: https://physics.stackexchange.com/a/196171 There's a whole PBS SpaceTime episode about this, but I can't find it, rn.
EDIT: here's a small discussion: https://physics.stackexchange.com/a/196171 There's a whole PBS SpaceTime episode about this, but I can't find it, rn.
And at high enough speeds, you don’t want to be carrying anything metal with you, eddy currents as you pass through magnetic fields will melt your wedding ring.
A mere engineering problem.
[deleted]
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.
Yep. Interstellar space is pretty famously big.
You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
Space is big.
Space is dark.
It’s never hard to find a place to park
- Burma Shave
- Burma Shave
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. :)
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. :)
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.
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.
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.
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.
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.
At sufficiently relativistic speeds, it wouldn’t just be “like” an explosion - you would have instant nuclear fusion at impact.
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.
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.
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.
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.
We just have to get creative, or discover some new physics :-)
In addition to the ark-ship colony, or the cryosleep slow ship:
1. Assuming it's a stream of robotic probes doing flybys, without decelerating, we have the Breakthrough Starshot approach. Maybe there's a way to use the target system's sun for solar sail braking? Send smart enough robots that have agency, that can do the exploring for us.
2. For human travel - it could just be a bunch of frozen embryos with a robotic nursemaid, accelerated via external propulsion and decelerated via nukes / high-g aerobraking... (Raised by Wolves had a cool introduction like this in the first episode - then went quickly downhill)
3. ...
In addition to the ark-ship colony, or the cryosleep slow ship:
1. Assuming it's a stream of robotic probes doing flybys, without decelerating, we have the Breakthrough Starshot approach. Maybe there's a way to use the target system's sun for solar sail braking? Send smart enough robots that have agency, that can do the exploring for us.
2. For human travel - it could just be a bunch of frozen embryos with a robotic nursemaid, accelerated via external propulsion and decelerated via nukes / high-g aerobraking... (Raised by Wolves had a cool introduction like this in the first episode - then went quickly downhill)
3. ...
"we need new physics" basically means "I hope this isn't true". I get it. I think many of us would like to wander the stars in a reasonable timeframe but there's simply no evidence the Universe works this way.
As for cryosleep, this curently seems unlikely but not impossible. For one thing, the decay of radioactive elements in your body (primarily Carbon-14) would give you about a lethal dose of radiation after about a century. Some organisms have natural antifreeze and other means of surviving low temperatures. We do not. Freezing water tears our cells to shreds.
Cryobabies and artifical wombs are another vector. This is nontrivial too but also, woould you trust the automation? Some AI might have to raise humans hundreds or thousands of years in the future without any context of what's happened in that time. We might be able to communicate with such a ship and update it but should it trust such updates?
You're also creating a whole bunch of people who haven't consented to never see Earth. Generation ships have this problem too to some degree. That has questionable ethics.
As for using the target star to decelerate, that's entirely possible. It's just a solar sail. And that might be the only way we could do interstellar travel anyway because of the reaction mass problem. But solar sails can only accelerate so fast. Travel too fast and you might not have time to decelerate as well. So you're still looking at hundreds of years most likely.
It really seems like we need radical life extension while maintaining quality of life to make these time frames reasonable (relatively). That actually does seem doable.
As for cryosleep, this curently seems unlikely but not impossible. For one thing, the decay of radioactive elements in your body (primarily Carbon-14) would give you about a lethal dose of radiation after about a century. Some organisms have natural antifreeze and other means of surviving low temperatures. We do not. Freezing water tears our cells to shreds.
Cryobabies and artifical wombs are another vector. This is nontrivial too but also, woould you trust the automation? Some AI might have to raise humans hundreds or thousands of years in the future without any context of what's happened in that time. We might be able to communicate with such a ship and update it but should it trust such updates?
You're also creating a whole bunch of people who haven't consented to never see Earth. Generation ships have this problem too to some degree. That has questionable ethics.
As for using the target star to decelerate, that's entirely possible. It's just a solar sail. And that might be the only way we could do interstellar travel anyway because of the reaction mass problem. But solar sails can only accelerate so fast. Travel too fast and you might not have time to decelerate as well. So you're still looking at hundreds of years most likely.
It really seems like we need radical life extension while maintaining quality of life to make these time frames reasonable (relatively). That actually does seem doable.
I agree with most of this, but the ethics question intrigues me: did any human ever have a chance to consent to the circumstances they were born into?
> there is a kind of relativistic Tsiolkovsky equation for mass-energy propulsion vehicles that carry their own fuel
Yes, it's called the relativistic rocket equation.
https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/...
Yes, it's called the relativistic rocket equation.
https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/...
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.
would be real nice to have a small device in your pocket that works at nano scale and converts input matter into output antimatter. Like feed it rock powder and you get antimatter rock powder. Would be real nice such a device could be made
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.
[deleted]
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.
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.
Or vice versa you can store the energy of 1.5 little boy atomic bombs into a handy gram of antimatter ...
The Sun outputs the energy equivalent of over 4 million tons of matter every second. The same as the energy of over a billion hydrogen bombs every second.
Only a tiny amount reaches the Earth, and we use only a tiny amount of that. But if we could capture even a small percentage of the total energy of the Sun we could produce antimatter by the ton.
Only a tiny amount reaches the Earth, and we use only a tiny amount of that. But if we could capture even a small percentage of the total energy of the Sun we could produce antimatter by the ton.
I always liked the star gate universe (?) series where the ships skimmed the stars they passed to charge up. We’ve essentially got a bunch of EV chargers dotted around the universe, although galaxy to galaxy might have some range anxiety.
> 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.
Is there something I'm missing here? Proxima Centauri is 4+ light-years from us and firmly out of the solar system.
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.
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.
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.
I read this book after seeing this comment. It was a fun book, thank you!
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.
Here's some further calculations for a 1G space ship: https://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/.... 3.6 years to Proxima Centauri if you want to stop.
> this is absolutely possible by the laws of physics
Not with antimatter rockets, it's not. Even though antimatter is extremely energy dense, the rocket equation still applies. You need reaction mass.
If you use laser beams as your rocket exhaust, then you get maximal efficiency (exhaust velocity is C), but very low thrust. That's not going to get you anywhere in days or weeks.
If you use stored matter (hydrogen, say) as your rocket exhaust, then you'd get better thrust, but all sorts of other issues come into play. Radiating all that waste heat. Running out of reaction mass. Again, there's not a practical design that could get you anywhere near a nearby star in "days or weeks", even if you assume "perfect" materials, efficiency, etc.
> If you're on a ship with sufficient fuel, you can keep accelerating forever
Um, no.
Not with antimatter rockets, it's not. Even though antimatter is extremely energy dense, the rocket equation still applies. You need reaction mass.
If you use laser beams as your rocket exhaust, then you get maximal efficiency (exhaust velocity is C), but very low thrust. That's not going to get you anywhere in days or weeks.
If you use stored matter (hydrogen, say) as your rocket exhaust, then you'd get better thrust, but all sorts of other issues come into play. Radiating all that waste heat. Running out of reaction mass. Again, there's not a practical design that could get you anywhere near a nearby star in "days or weeks", even if you assume "perfect" materials, efficiency, etc.
> If you're on a ship with sufficient fuel, you can keep accelerating forever
Um, no.
Yeah, forever is an overstatement since we know there's not sufficient fuel for that. However, my main point was there's not a global speed limit in the sense that a traveler would be prevented from accelerating at some point because they were "near the speed of light".
That's pretty mind boggling and quite different from "you can never reach the speed of light therefore you could never travel across the Milky Way in a human lifetime".
If you could carry sufficient fuel to accelerate at 9.8 m/s for 12 years you could travel across the Milky Way galaxy (112000 light years). You would be 12 years older but 112000 light years away from where you started. That's amazing to me.
It's a given that this is impractical.
That's pretty mind boggling and quite different from "you can never reach the speed of light therefore you could never travel across the Milky Way in a human lifetime".
If you could carry sufficient fuel to accelerate at 9.8 m/s for 12 years you could travel across the Milky Way galaxy (112000 light years). You would be 12 years older but 112000 light years away from where you started. That's amazing to me.
It's a given that this is impractical.
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...
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...
Traverse the solar system to reach the nearby star (the sun) maybe?
Why would carbon emissions be an issue in space propulsion?
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 could only be an issue for the launch.
I guess its just a keyword they have to put in for grants/funding purposes.
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.
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.
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.
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.
This is only slightly less practical than a black hole starship.
https://en.m.wikipedia.org/wiki/Black_hole_starship
https://en.m.wikipedia.org/wiki/Black_hole_starship
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.
I wouldnt want to work at the IAA right now.
I wouldnt want to work at the IAA right now.
> 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
Countries on a budget do not have the resources to create a CERN-like accelerator. In a relative sense, building a nuke with enriched uranium is the "cheap" option compared to amassing enough antimatter for even a kiloton yield.
> Thanks russia, thanks china, thanks usa - one world locked in a eternal Mexican standoff it is
We've been in this spot since the 60s. Nukes got the ball rolling and ICBMs hammered in the idea that you cannot escape nukes if your enemy doesn't want you to.
> Future generations are going to look at the collapse of Assads regime as the last "downfalls" without nail-biting.
Perhaps if they all live under rocks. The past 10 years of the Syrian revolution were absolutely a nailbiter, with Assad torturing, systematically executing and mass-burying his own citizens and political opposition. There were stockpiles of chemical weapons, underground concentration camps and Putin could launch an missile attack or airstrike with a phone call and enough money offered.
Syria's citizens only knew they were safe when Assad ran out of money. They suffered under Russia's oppression for 10 long years and thousands of people died horrific and unjust deaths. If anything, the fact that Assad was allowed to keep Syria this long is a condemnation of western diplomacy as a whole.
Countries on a budget do not have the resources to create a CERN-like accelerator. In a relative sense, building a nuke with enriched uranium is the "cheap" option compared to amassing enough antimatter for even a kiloton yield.
> Thanks russia, thanks china, thanks usa - one world locked in a eternal Mexican standoff it is
We've been in this spot since the 60s. Nukes got the ball rolling and ICBMs hammered in the idea that you cannot escape nukes if your enemy doesn't want you to.
> Future generations are going to look at the collapse of Assads regime as the last "downfalls" without nail-biting.
Perhaps if they all live under rocks. The past 10 years of the Syrian revolution were absolutely a nailbiter, with Assad torturing, systematically executing and mass-burying his own citizens and political opposition. There were stockpiles of chemical weapons, underground concentration camps and Putin could launch an missile attack or airstrike with a phone call and enough money offered.
Syria's citizens only knew they were safe when Assad ran out of money. They suffered under Russia's oppression for 10 long years and thousands of people died horrific and unjust deaths. If anything, the fact that Assad was allowed to keep Syria this long is a condemnation of western diplomacy as a whole.
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.
There's some possible ideas for how to do it out there, but obviously we kind of lack enough antimatter to go experimenting.
From Fermilab’s antimatter factory:
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.
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.
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.
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.
> 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.
It's much worse than that. At those speeds, the cosmic background radiation would get blue-shifted to the point that you'd be constantly bathed in x-rays and gamma rays.
It's much worse than that. At those speeds, the cosmic background radiation would get blue-shifted to the point that you'd be constantly bathed in x-rays and gamma rays.
> I suppose the only way to be sure is to build a prototype and try it.
Not in our planet's back yard. Maybe behind the moon.
Not in our planet's back yard. Maybe behind the moon.
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.
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.
The pions coming out of the reaction are moving at relativistic velocities and provide far more specific impulse.
Helpful "high-res" graphical abstract: https://ars.els-cdn.com/content/image/1-s2.0-S26662027240045...
I am just thinking out loud and stupid but this could be something like the Cold Fusion/LENR or be actually something useful.
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.
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.
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"
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"
You can start by getting nuclear rockets to work
And imattwr is at the end of a tech tree that we have not started
And imattwr is at the end of a tech tree that we have not started
Is this reputable journal?
Short answer: it's not happening yet.
> A general conclusion was drawn that antimatter technology and its development for propulsion is still in its theoretical stages.
> A general conclusion was drawn that antimatter technology and its development for propulsion is still in its theoretical stages.
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).
If I don't change position, then I'm not traveling. Information about me is not me.
I don't think we really know what "me" is yet, to any useful degree. We have no idea what causes our consciousness, or where it "lives" (if anywhere). We don't know if Star Trek-style transporters would actually kill you and create a new you somewhere else. We don't know if it's possible to transmit your consciousness elsewhere, leaving your body behind, a la Altered Carbon.
Sometimes we think of these as philosophical questions, but in many ways they are questions for science that we don't know how to tackle.
Sometimes we think of these as philosophical questions, but in many ways they are questions for science that we don't know how to tackle.
Define „I“. Are you mass (obviously) and information?
I'm talking about information that you „have“ in the sense of the one that is part, or maybe more importantly, makes up your mind. If we were able to entangle it with a (partial) information set somewhere else in space then we could achieve what I would call information traveling. And since at quantum level there seems to be something very similar, I hope this would allow us „traveling without mass“.
Entanglement doesn't mean information actually travels from point A to point B. Imagine it like tearing paper into 2 pieces without looking at it. Then both pieces are taken away. And then you look at the exact shape of the cut - and you know that the other piece of paper mirrors it exactly. There was no actual travel of information, you had it the whole time - you just looked at it when it was convenient. Quantum entanglement is nicer than that because it can also guarantee single usage (or the key doesn't work) but it's not a magical telecommunication channel, you still need radio/laser/...
Thanks for the paper analogy. First, I don't agree that if we bring the other half of the paper away that no information has traveled. What else is the shape of the cut than information? Second, do we know that no dual of entanglement exists, meaning that we start from one piece of the paper (far way) that we can somehow select and (re-)create the other half "here", thus being able to see its shape "here", all this not subject to the laws of mass physics? Sure this is all just thinking going on in my mind and I'm really not an expert in all these things; not at all. I just have questions that sometimes provoke ideas; which might be naive (due to lack of information).
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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.