Neutrinos... A Safe Power Or Drive Source?

[Spacescifi]

I know little about neutrinos other than that they pass through everything all the time. What if we could capture and store a bunch of them to use as an energy source?

 

Would that make it safe? Scenario means we must both have a means to capture and absorb large amounts of neutrinos as will as release them as heat or radiant energy.

Could this be a safer alternative to fusion or antimatter? Only requires high tech?

[Spacescifi]

Edit: Interestingly you could use them in a beam to communucate through solid rock. Want to send a message through to the other side of the planet? No problem! Use a a neutrino radio and so long someone on the other side of the planet has a neutrino receiver and you aimed right you're golden.

[NFUN]

if you stored neutrinos they're not moving so they're no better fuel than anything else. ion thrusters take considerably less magic to build and less magic to generate thrust from

[StrandedonEarth]

I don’t see how a chargeless, essentially massless particle would be useful for power or propulsion. However, in the Nivenverse, they are used for “deep radar” scans, which can see through planets much like your neutrino radio concept. 

[sevenperforce]

9 hours ago, Spacescifi said:

I know little about neutrinos other than that they pass through everything all the time. What if we could capture and store a bunch of them to use as an energy source?

You'd have to capture a lot of them.

100 trillion neutrinos pass through the human body every second. A circular neutrino dish 1 kilometer wide would get hit with 785 quadrillion neutrinos every second. If that gigantic neutrino dish could somehow catch 100% of the neutrinos passing through it, it would take 283 million years for it to collect one kilogram of neutrinos.

[kerbiloid]

4 minutes ago, sevenperforce said:

100 trillion neutrinos pass through the human body every second.

(Starts scratching).

***

We need a  neutrino kugelblitz blackhole drive.

[Shpaget]

Why neutrinos specifically? Do you have any reason to think neutrinos would perform? 

Why not some other random particle? May I suggest quarks?  They start with a "Q", same as "quantum", and that may attract attention. Perhaps the charm flavour? It even sounds magical.

 

[KSK]

1 hour ago, Shpaget said:

Why neutrinos specifically? Do you have any reason to think neutrinos would perform? 

Why not some other random particle? May I suggest quarks?  They start with a "Q", same as "quantum", and that may attract attention. Perhaps the charm flavour? It even sounds magical.

 

Nah - sounds a bit strange to me. It’s been a trying week though so I’m likely up side  down and bottom over top.

[K^2]

10 hours ago, NFUN said:

if you stored neutrinos they're not moving so they're no better fuel than anything else. ion thrusters take considerably less magic to build and less magic to generate thrust from

Well, I can see one use case for a neutrino thruster. Imagine you had an efficient mass-to-energy conversion that you wanted to use for a drive. Photon drive is a natural choice, but suppose you want to go to a hover over a colony's landing platform. Well, a 100kN thruster you'd want for a modest shuttle is a 30TW beam. You can cover that landing pad with your best reflective material, and it will still melt like a stick of butter in front of a blow torch. That's not ideal. And forget about using it in the atmosphere. Air might not burn exactly, but with tens of terawatts of input, even with the tiny absorption you're likely to get, it's still going to be a plasma tornado. You just can't use a drive like this anywhere outside of deep space.

If you could generate a neutrino beam instead, even at these ludicrous energies, it's going to be safe to walk under. For all intents and purposes, that shuttle's going to hover in the air like it's on grav plates, with no noise, no dust, no moving parts at all. Just 10 tons of pure thrust pushing against the engines that can be fully concealed within the body of the craft. The cross-section is just that small for weak interactions. Other than the fact that you still need an energy source to fuel all of that somehow, such a drive might as well be reactionless.

Of course, all of that said, that's also precisely why it's so hard to imagine something like this working. The weakness of interaction is what makes production of neutrinos so difficult. And for something like this, you need to be ridiculously close to 100% efficiency, or you're just going to die on thermals. You might be able to dissipate, what, a few MW of heat from a landing shuttle without causing problems? So you need to be better than 99.9999% efficient. Something like Mossbauer Effect might give you a recoil into the lattice at the right sort of efficiency. But now we're trying to invent a Mossbauer neutrino laser (naser?) that also has power in terawatts instead of milliwatts, which is what you usually get with these kinds of techniques even with optical devices? Yeah, I don't know what sort of quantum wizardry might even approach these sorts of magicks.

A graviton drive might be more plausible. Same benefits, different particle. And at least, we have an idea how to couple something very strongly to a gravity field, because gravitational field isn't strictly linear. All you need is a lattice of tiny black holes and you're in business. And the fact that this seems plausible in comparison should speak volumes about how miraculous the neutrino drive would have to be. But, you know, would be neat if we could have it.

[darthgently]

Reading "naser" made my day.

Watch out! He's got a naser rifle!  Oh yeah, nevermind.  Stand down.

[Spacescifi]

1 hour ago, K^2 said:

Well, I can see one use case for a neutrino thruster. Imagine you had an efficient mass-to-energy conversion that you wanted to use for a drive. Photon drive is a natural choice, but suppose you want to go to a hover over a colony's landing platform. Well, a 100kN thruster you'd want for a modest shuttle is a 30TW beam. You can cover that landing pad with your best reflective material, and it will still melt like a stick of butter in front of a blow torch. That's not ideal. And forget about using it in the atmosphere. Air might not burn exactly, but with tens of terawatts of input, even with the tiny absorption you're likely to get, it's still going to be a plasma tornado. You just can't use a drive like this anywhere outside of deep space.

If you could generate a neutrino beam instead, even at these ludicrous energies, it's going to be safe to walk under. For all intents and purposes, that shuttle's going to hover in the air like it's on grav plates, with no noise, no dust, no moving parts at all. Just 10 tons of pure thrust pushing against the engines that can be fully concealed within the body of the craft. The cross-section is just that small for weak interactions. Other than the fact that you still need an energy source to fuel all of that somehow, such a drive might as well be reactionless.

Of course, all of that said, that's also precisely why it's so hard to imagine something like this working. The weakness of interaction is what makes production of neutrinos so difficult. And for something like this, you need to be ridiculously close to 100% efficiency, or you're just going to die on thermals. You might be able to dissipate, what, a few MW of heat from a landing shuttle without causing problems? So you need to be better than 99.9999% efficient. Something like Mossbauer Effect might give you a recoil into the lattice at the right sort of efficiency. But now we're trying to invent a Mossbauer neutrino laser (naser?) that also has power in terawatts instead of milliwatts, which is what you usually get with these kinds of techniques even with optical devices? Yeah, I don't know what sort of quantum wizardry might even approach these sorts of magicks.

A graviton drive might be more plausible. Same benefits, different particle. And at least, we have an idea how to couple something very strongly to a gravity field, because gravitational field isn't strictly linear. All you need is a lattice of tiny black holes and you're in business. And the fact that this seems plausible in comparison should speak volumes about how miraculous the neutrino drive would have to be. But, you know, would be neat if we could have it.

 

Neutrino emission... so THAT is how Superman and Supergirl fly lol.

 

[darthgently]

Naser:  nerf gun of particle beam weapons.

[kerbiloid]

We need a way to make the neutrons decay oriented , so all antineutrinos will be flying in same direction.

[K^2]

11 hours ago, kerbiloid said:

We need a way to make the neutrons decay oriented , so all antineutrinos will be flying in same direction.

They'll orient neatly in a strong magnetic field. And this would absolutely work. Get a bunch of baryonic matter that beta-decays - neutrons being probably the most energy-efficient, but something like tritium would be easier to store, shove it in a strong magnetic field, enclose it to prevent any leaks, and it will produce thrust by emitting more neutrinos in one direction than the others.

It's also going to have an absolutely abysmal efficiency, since only a tiny amount of decay energy is going into neutrino production, and they aren't emitted in a single line - merely preferentially kicked out more in one direction than the others. Neutron decay releases a few hundred keV of energy, of which a few eV go to neutrinos. So we're looking at something like 10^-3 efficiency here, and then the recoil momentum bias is less than 10% (I don't recall the exact number, and this will pain me to look up, as this is starting to get a bit obscure, but lets just take 10% as an upper bound). So for every 1N of thrust, you'd be releasing something like 300GW+ of power as electron recoil, which in this case is just guaranteed to be heat.

Which on one hand is really cool. Yeah, 300GW is energy production of a medium sized country, but I can imagine some sort of a huge colony ship producing that much power for various uses, and 1N of thrust will probably be measurable even at that scale. So with the right type of a reactors you can magnetize it and get a little bit of thrust out of it. On the other, I wouldn't call it practical, because you're dumping waste heat to space anyways, and if you paint your radiator panels black on only one side, you'll be literally getting a lot more thrust from asymmetric IR radiation than the neutrino flux.

So that's why I brought up the efficiency in the initial post. To make this kind of propulsion practical over photon drive, it has to be really, really efficient, and I just don't see a practical way of achieving that.

[DerkyJerkyWreaksHavoc]

On 4/6/2023 at 8:08 AM, NFUN said:

if you stored neutrinos they're not moving so they're no better fuel than anything else. ion thrusters take considerably less magic to build and less magic to generate thrust from

Correction: Ion engines require no magic to build and no magic to generate thrust from. It may blow a couple of fuses though

Spoiler

 

[NFUN]

you can't tell me the hall effect isn't magic

[K^2]

1 hour ago, NFUN said:

you can't tell me the hall effect isn't magic

I learned the hard way that anything magnet is always magic. You might think you can explain magnets. Then you try. And then you fail, as the explanation devolves into a number of tangential topics. And you try again, trying to stay on target this time, and you fail some more. And then you start wondering if you understand magnets. At which point, it might be easy to fall in a despair. But then you watch Richard Feynman be asked about magnets, and instead of explaining it, he goes into several minutes of diversion on whether you can know why something is at all on the fundamental level, finally giving hand-waving non-explanation to magnets. And then you just settle on, "Magnets are magic." Of course, there is science to them. And of course, any given question about them can be rigorously and mathematically answered, but then there is nuance upon nuance, relativistic and quantum effects, and even some quantum relativistic effects, and you're scraping the very fundamentals of what is cosmos, and you still have gaps in what you're covering about the magnets. All the meanwhile, Gandalf, the smug so-and-so that he is, stands there smirking at you, smoking his pipe, because he figured out long ago that you just call it magic and move on.

Magnets are magic. Hall effect is most certainly magic. Hall effect in superconductors? Look, I'll just put it this way, the best quantum computers we got are just a chainmail of tiny superconducting magnets connected to each other via Hall effect. They can't do general computation very well, but they're fantastic for quantum annealing, so people are running neural nets on these. People jest about the thinking sand inside computers. These frigid ceramic donuts are going to out-Hall-effect our brains at this rate. Not only is it magic, it's the highest form of magic. I will be taking no more questions on the matter.

[Kerbart]

3 minutes ago, K^2 said:

I learned the hard way that anything magnet is always magic. You might think you can explain magnets. Then you try. And then you fail, as the explanation devolves into a number of tangential topics.

I was under the impression that topic was settled by the Insane Clown Posse?

[NFUN]

24 minutes ago, K^2 said:

I learned the hard way that anything magnet is always magic. You might think you can explain magnets. Then you try. And then you fail, as the explanation devolves into a number of tangential topics. And you try again, trying to stay on target this time, and you fail some more. And then you start wondering if you understand magnets. At which point, it might be easy to fall in a despair. But then you watch Richard Feynman be asked about magnets, and instead of explaining it, he goes into several minutes of diversion on whether you can know why something is at all on the fundamental level, finally giving hand-waving non-explanation to magnets. And then you just settle on, "Magnets are magic." Of course, there is science to them. And of course, any given question about them can be rigorously and mathematically answered, but then there is nuance upon nuance, relativistic and quantum effects, and even some quantum relativistic effects, and you're scraping the very fundamentals of what is cosmos, and you still have gaps in what you're covering about the magnets. All the meanwhile, Gandalf, the smug so-and-so that he is, stands there smirking at you, smoking his pipe, because he figured out long ago that you just call it magic and move on.

Magnets are magic. Hall effect is most certainly magic. Hall effect in superconductors? Look, I'll just put it this way, the best quantum computers we got are just a chainmail of tiny superconducting magnets connected to each other via Hall effect. They can't do general computation very well, but they're fantastic for quantum annealing, so people are running neural nets on these. People jest about the thinking sand inside computers. These frigid ceramic donuts are going to out-Hall-effect our brains at this rate. Not only is it magic, it's the highest form of magic. I will be taking no more questions on the matter.

When the simplest explanation for magnetism is "because special relativity", you know you're screwed

 

Quantum annealing is a meme though

[K^2]

9 minutes ago, NFUN said:

When the simplest explanation for magnetism is "because special relativity", you know you're screwed

And with magnets, magnetism itself is a warm-up exercise. Because that naturally flows into, "Oh, so when a current flows, there is a magnetic field.? - "Yes." - "So in this magnetized chunk of iron, there are current flows?" - "Well, no, the magnetic field in iron is produced by point objects." And then you have to talk about the spin. And intrinsic degrees of freedom that lead to it. And why that particular hammerspace happens to induce magnetism in the real space, which in itself a wonderful topic. And then how all of this conspires to give an entire atom a magnetic moment, because of course Pauli exclusion is involved. And when that explanation is finally wrapped up, that is usually followed up with, "Well, don't a lot of atomic nuclei have a magnetic moment? Why isn't nearly everything a magnet?" And this is where you break down and cry, because now statistical mechanics is added to the mix. We have quantum mechanics, relativity, and statistical mechanics contributing. The trifecta of all that is modern physics. Welcome to the nightmare, enjoy your stay, don't forget to visit the gift shop on the way out. We have fridge magnets that just say, "MAGIC!"

[sevenperforce]

On 4/6/2023 at 6:29 PM, K^2 said:

If you could generate a neutrino beam instead, even at these ludicrous energies, it's going to be safe to walk under. For all intents and purposes, that shuttle's going to hover in the air like it's on grav plates, with no noise, no dust, no moving parts at all. Just 10 tons of pure thrust pushing against the engines that can be fully concealed within the body of the craft. The cross-section is just that small for weak interactions. Other than the fact that you still need an energy source to fuel all of that somehow, such a drive might as well be reactionless.

Hmmmm, I feel like I need to sanity check this. Because despite the low cross-section, there's still such a thing as a lethal dose of neutrino radiation.

Let's use the Raptor engine as an analogue: 230 metric tonnes of thrust coming out of a circle 1.3 meters in diameter. Because neutrinos are highly relativistic, their momentum is simply equal to E/c. Assuming that we are using neutrinos from free neutron decay, average energy will be 0.5 MeV which translates to a momentum impulse of 2.67e-28 kg*m/s per neutrino. Requisite propellant production rate will therefore be 8.45e33 neutrinos per second, or a neutrino radiation density of 6.37e33 neutrinos per square meter per second. That's on the order of 10²² times the solar neutrino flux at Earth's surface.

Due to the low cross-section, we ordinarily only have an interaction with one solar neutrino every few years -- let's say 2 years as a baseline. If you're standing under this rocket as it's running, you're having 10²² times that many interactions, which comes to 1.58e14 interactions per second. Each interaction dumps 0.5 MeV into you, which comes to the oddly normal-sounding 12.7 W of power being deposited into your body.

For a 100 kilogram adult, that comes to 0.127 W/kg which is the SI unit of absorbed ironizing radiation, expressed as Grays per second. The actual biological impact of radiation, measured in Sieverts, is equal to Grays times Q, where Q is a "quality factor" denoting the way that a particular type of radiation interacts with the body. According to this old paper, the quality factor for neutrino radiation is around 30.

So: while the actual energy transferred to the launch pad by the exhaust from a neutrino rocket thruster would be rather low, you still wouldn't want to stand underneath it, as it would give you a lethal radiation dose in roughly 0.017 seconds.

[kerbiloid]

Aand now about a neutrino steam engine, using the pressure of neutrino gas to move the piston...

[K^2]

1 hour ago, sevenperforce said:

Assuming that we are using neutrinos from free neutron decay, average energy will be 0.5 MeV which translates to a momentum impulse of 2.67e-28 kg*m/s per neutrino.

I honestly haven't even considered the neutrinos being ionizing and whether that can contribute to a radiation hazard. Thanks for running the numbers! So I guess, we have to add "non ionizing" to the list of requirements to this magical engine.

The reason I didn't put much thought into the neutrino energy is that decay of any sort will produce so much waste heat that there is no plausible way to manage it. You have to be incredibly near 100% efficiency on whatever means of neutrino production you go with to make this practical. Given that, I don't know if there is any reason to think that 0.5MeV neutrinos are going to be any easier to produce than 0.1eV neutrinos. And if you can dial down the neutrino energy, you can get to the point where it's non-ionizing. Since they are not entirely massless (theoretically, but well-established), you do expect a roll-off, but our upper bound on mass is below 0.13eV, so even with room-temperature neutrinos (a little under 0.03eV), you'll still have at least about a third of maximum thrust. Likely a lot more.

For non-ionizing, less than about 1W/kg will be absorbed easily enough short term. Human body is capable of producing more than that internally. But this does bring up an interesting point. I didn't bother computing the energy density at which a low energy neutrino beam will still absolutely cook you, and based on your numbers, it's not as absurd as I might have thought. Which brings us to potentially the best possible use for an overpowered neutrino beam, achieving the goal that has been eluding humanity for millennia. A piece of technology that should be in every house, and now, maybe, we can hope that one day it will.

We can finally have an oven that heats your food evenly throughout its entire volume.

[Shpaget]

1 hour ago, K^2 said:

A piece of technology that should be in every house

Pff, such wastefulness. You only need one for the entire planet* and it can be anywhere in the world** and just as capable of heating up your TV dinner. 

*Queue time may vary depending on global demand.

**Subject to accuracy of the targeting device.

[Codraroll]

On 4/6/2023 at 11:42 AM, Spacescifi said:

Edit: Interestingly you could use them in a beam to communucate through solid rock. Want to send a message through to the other side of the planet? No problem! Use a a neutrino radio and so long someone on the other side of the planet has a neutrino receiver and you aimed right you're golden.

This is one of those things that appear to make sense until you connect the dots. 

First, neutrinos are generated by radioactive decay. Good luck creating a modulated signal from that process. I guess you could have some type of nuclear reaction run full blast at all time, and just flicker the shielding like one of those old naval Morse code signal lamps, but that seems kind of difficult to do at a rate that would give the signal any reasonable bandwidth. After all, it'd be a shield that stops neutrinos, it sounds like you need approximately all the power you can get, which leaves little room for finesse.

But more importantly, there's the matter of the neutrino receiver. You have already noted that you can put a planet in the way of the neutrino beam, and the two won't interact at all. That makes it tricky to create an antenna. A hundred trillion neutrinos pass through a volume the size of a human body every second, but it takes years between each time one of them interacts with an atom. Just to observe this phenomenon, you need to fill a giant volume with a clear liquid, line its walls with detectors, and wait. The Ice Cube detector is a cubic kilometer in size, and detects about 275 neutrinos per day - out of approximately a trillion trillions that pass through it every second. That's not a very good rate of interception.

That also implies that if you ever were to build a receiver that detects neutrinos at an appreciable rate to facilitate communication, any signals would completely drown in the deluge of solar neutrinos that would ping the receiver constantly. Imagine the Niagara falls with ping-pong balls instead of water. Then you try to communicate with a friend downstream by taking a few more ping-pong balls, writing a single letter on each, and throwing them in one by one. He'd have a vastly better chance of picking up your communicated message than a neutrino receiver would have to collect the intended signal among all the solar neutrinos out there.