# Thread: 100% conversion of mass into energy

1. kzb
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## 100% conversion of mass into energy

All I have to do to achieve this is compress mass into micro black holes.

All the mass will then be radiated as Hawking radiation, thereby converting all the compressed mass into energy with 100% efficiency (not counting the energy needed to compress the matter into micro black holes).

Is that correct?

2. Well, there is the issue that Hawking radiation hasn’t been observed and it gets into an area of physics (the intersection of relativity theory and quantum physics) that isn’t fully established.

Then, if valid, there would be the practical issues, like the energy needed to create the micro black hole, and what would come out of the black hole, which could be a variety of particles and gamma radiation. Much of it might not be terribly useful, like neutrinos, or too nasty to deal with.

3. Originally Posted by kzb
All I have to do to achieve this is compress mass into micro black holes.

All the mass will then be radiated as Hawking radiation, thereby converting all the compressed mass into energy with 100% efficiency (not counting the energy needed to compress the matter into micro black holes).

Is that correct?
The matter that actually enters the MBH would, if Hawking radiation pans out, be converted to annihilating M/AM particles which would yield energy. But the compressed matter around the hole that has not yet entered would also be reacting to your pressure, producing various forms of radiation and heat. So you'd get less than 100% efficiency in practice.

4. kzb
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Originally Posted by Noclevername
The matter that actually enters the MBH would, if Hawking radiation pans out, be converted to annihilating M/AM particles which would yield energy. But the compressed matter around the hole that has not yet entered would also be reacting to your pressure, producing various forms of radiation and heat. So you'd get less than 100% efficiency in practice.
Yes I am quite prepared for it to be less than 100% in practice, nothing is ever 100% efficient.

However, hydrogen fusion converts only 0.7% of mass into energy, so it is going to beat that.

Antimatter/matter reaction gives off a large proportion of its energy as neutrinos, so that energy is lost.

Also, there was fear that the LMC would produce black holes, so it must have some feasibility to it.

5. Originally Posted by kzb
Also, there was fear that the LMC would produce black holes, so it must have some feasibility to it.
Subatomic black holes, that if HR is a thing would immediately evaporate. Building a useful sized black hole is well outside our capacity.

6. If we do make black holes here, would they not tunnel to the Earth’ centre? So we don’t know for sure if atom sized black holes get made accidentally?

7. Originally Posted by profloater
If we do make black holes here, would they not tunnel to the Earth’ centre? So we don’t know for sure if atom sized black holes get made accidentally?
Would they? We don't know much about how subatomic particles interact with gravity and other forces.

8. kzb
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Originally Posted by Noclevername
Subatomic black holes, that if HR is a thing would immediately evaporate. Building a useful sized black hole is well outside our capacity.
Immediate evaporation is exactly what is needed for a black hole rocket.

9. kzb
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Duplicate post

10. kzb
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Originally Posted by profloater
If we do make black holes here, would they not tunnel to the Earth’ centre? So we don’t know for sure if atom sized black holes get made accidentally?
They are meant to disappear in a shower of particles. They wouldn't live long enough to get far. None have been observed in the LHC though.

11. Originally Posted by kzb
Immediate evaporation is exactly what is needed for a black hole rocket.
Gradual evaporation of a macro scale hole is what would be needed for a rocket. We are nowhere near that.

ADDED: Tiny, undetectable BH that disappear as soon as they're created are of no practical use. Unless your rocket carries a miles-wide particle accelerator.
Last edited by Noclevername; 2020-Oct-19 at 10:55 PM.

12. Order of Kilopi
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## Don't You Just Hate It When They Say "Whoops"

Originally Posted by kzb
All I have to do to achieve this is compress mass into micro black holes.

All the mass will then be radiated as Hawking radiation, thereby converting all the compressed mass into energy with 100% efficiency (not counting the energy needed to compress the matter into micro black holes).

Is that correct?
Do us a favor. Don't do this at home.

13. kzb
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Originally Posted by Noclevername
Gradual evaporation of a macro scale hole is what would be needed for a rocket. We are nowhere near that.

ADDED: Tiny, undetectable BH that disappear as soon as they're created are of no practical use. Unless your rocket carries a miles-wide particle accelerator.
I was thinking there could be some breakthrough technology which miniaturizes particle accelerators, or some easy way of making micro black holes is found.

Really I was just asking the question. Having asked it I now realize this is not a new idea and indeed dates back to the 1970's. But I still don't think it gets any attention as an idea for space drives.

14. Originally Posted by kzb
Really I was just asking the question. Having asked it I now realize this is not a new idea and indeed dates back to the 1970's. But I still don't think it gets any attention as an idea for space drives.
It has in science fiction and a bit in futurism/technological speculation. For instance, Charles Sheffield had a number of stories with ships using mini black holes. Arthur C. Clarke had it in Imperial Earth. Early stories didn’t assume Hawking radiation, though.

15. Originally Posted by kzb
Yes I am quite prepared for it to be less than 100% in practice, nothing is ever 100% efficient.

However, hydrogen fusion converts only 0.7% of mass into energy, so it is going to beat that.

Antimatter/matter reaction gives off a large proportion of its energy as neutrinos, so that energy is lost.
So could a mini black hole. Matter/anti-matter is much more approachable with not insanely futuristic technology. One thought is to use a small amount of anti matter to make a fusion drive more feasible. Storing small amounts of anti-matter is possible.

Also, there was fear that the LMC would produce black holes, so it must have some feasibility to it.
That was considered an unlikely possibility based on rather speculative physics, which appears to not have been correct.

16. I think there's something in this idea that's missing the point.

100% energy conversion isn't in-and-of-itself the end-goal, as far as powering a spaceship goes.

If it takes a billion years to extract that energy, then it's useless in a propulsion system.
At the other end of the scale, if it evaporates before you can even get it into the spaceship, then it's useless in a propulsion system.

The goal is to have access to an arbitrarily large amount of energy in an arbitrarily short amount of time. (Sort of like specific impulse of a fuel source, but I don't think that's the right term.)

With that in-mind, I don't see any way, even in theory, you could use the radiation from any sized black hole to directly power a spaceship (thought that doesn't rule out indirect utilization).
Last edited by DaveC426913; 2020-Oct-20 at 01:03 AM.

17. Originally Posted by profloater
If we do make black holes here, would they not tunnel to the Earth’ centre? So we don’t know for sure if atom sized black holes get made accidentally?
Back in the LHC safety studies, scientists considered various possibilities like black holes and strangelets and if they could pose a risk. Basically, they considered that there are higher energy events happening constantly in nature, and looked at worlds, stars, even neutron stars (because they are very dense so would tend to stop almost anything interesting hitting them). They could find no evidence of any such being eaten by mini black holes or strangelets, so that was in large part their argument for why it couldn’t happen here.

Incidentally, an atom sized black hole would be quite large given they were smashing subatomic particles.

18. Originally Posted by DaveC426913
I think there's something in this idea that's missing the point.

100% energy conversion isn't in-and-of-itself the end-goal, as far as powering a spaceship goes.

If it takes a billion years to extract that energy, then it's useless in a propulsion system.
At the other end of the scale, if it evaporates before you can even get it into the spaceship, then it's useless in a propulsion system.

The goal is to have access to an arbitrarily large amount of energy in an arbitrarily short amount of time. (Sort of like specific impulse of a fuel source, but I don't think that's the right term.)

With that in-mind, I don't see any way, even in theory, you could use the radiation from any sized black hole to power a spaceship.
At least a couple methods have been proposed. If Hawking radiation exists, it would be irrelevant for even a black hole with the mass of a large asteroid, but a lower mass black hole could produce immense energy. In fact, the biggest problem with a small black hole in this scenario is that you can’t turn it off. You can either maintain its mass by feeding it (which can be tricky due to radiation pressure) or you can let it fully evaporate, which would be like being next to a very large nuclear explosion.

In theory, it is possible to keep a charge on a black hole and manipulate it that way, but I’d suspect Hawking radiation would make that difficult (I would suspect it would tend towards a neutral charge). So you have a lot of emitted energy which could be directed, or used to heat a gas, and a possible way to control the black hole. I fully expect though that you wouldn’t do this unless you had a very large ship.

Another method would be by using the Penrose process. Essentially you feed matter to a rotating black hole, the BH absorbs half of it, and the rest is ejected with a lot of excess velocity. This could work even with a classical black hole (no Hawking radiation). You could potentially use the black hole itself to accelerate a spacecraft if it is large enough by sending the ship in close orbit, and dropping part of the ship’s mass.

19. kzb
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Originally Posted by DaveC426913
I think there's something in this idea that's missing the point.

100% energy conversion isn't in-and-of-itself the end-goal, as far as powering a spaceship goes.

If it takes a billion years to extract that energy, then it's useless in a propulsion system.
At the other end of the scale, if it evaporates before you can even get it into the spaceship, then it's useless in a propulsion system.

The goal is to have access to an arbitrarily large amount of energy in an arbitrarily short amount of time. (Sort of like specific impulse of a fuel source, but I don't think that's the right term.)

With that in-mind, I don't see any way, even in theory, you could use the radiation from any sized black hole to directly power a spaceship (thought that doesn't rule out indirect utilization).
I am envisaging continuous on-board production of nano-black holes that evaporate in a tiny fraction of a microsecond. Not using one larger black hole, which seems to be the usual concept.

20. kzb
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Originally Posted by Van Rijn
It has in science fiction and a bit in futurism/technological speculation. For instance, Charles Sheffield had a number of stories with ships using mini black holes. Arthur C. Clarke had it in Imperial Earth. Early stories didn’t assume Hawking radiation, though.
Yes I've read Imperial Earth, and the space drive concept is quite different to "my" idea. As you say, it was not based on Hawking radiation, it used one re-usable black hole to accelerate propellant.

BTW, I wonder if Hawking radiation would make Arthur C Clarke's space drive concept impossible?

21. kzb
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Originally Posted by Van Rijn
So could a mini black hole. Matter/anti-matter is much more approachable with not insanely futuristic technology. One thought is to use a small amount of anti matter to make a fusion drive more feasible. Storing small amounts of anti-matter is possible.

That was considered an unlikely possibility based on rather speculative physics, which appears to not have been correct.
A large fraction of the antimatter/matter reaction is carried off by neutrinos, so is not usable. Hawking radiation is supposed to be photons. Although the expected showers of particles from BH's in the LHC confuses that picture.

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