7 ms·

The idea is kind of cool, but doesn't sound very practical. The beam width is my concern. If it's really narrow, then we have to know exactly where every nuclea

by ufmace 6y ago

The idea is kind of cool, but doesn't sound very practical. The beam width is my concern. If it's really narrow, then we have to know exactly where every nuclear warhead is to hit it. If it's really wide, then the power draw will be that much more immense, plus a huge risk of collateral damage to any life, human or otherwise, that happens to get in the path of the beam. Not to mention that the prospect of detonating every nuke in the world, even at only 3% or so of normal yield, sounds pretty destructive too. If we're gonna get rid of some nukes, how about Megatons to Megawatts instead? https://en.wikipedia.org/wiki/Megatons_to_Megawatts_Program https://en.wikipedia.org/wiki/Megatons_to_Megawatts_Program

rbanffy 6y ago
I'd assume Selenites will want to have such a weapon pointed towards Earth in case Earthlings decide to act up. They'll have a lot of solar power to play with too. And it's much neater than throwing rocks too. And faster.
- lsllc 6y ago
  At least the Trisolarians can use their sophons to prevent such a thing.
jessriedel 6y ago
> plus a huge risk of collateral damage to any life, human or otherwise, that happens to get in the path of the beam. Why? This doesn't actually deposit that much energy directly in any given volume. The beam is about a meter wide and the power is about a kilowatt (1000 joules per second). The authors say > This is equivalent to about 1 Sv/sec. We note that this value of the radiation dose is very large, compared with the U.S. Federal off-site limit of 1 mSv/year. but that seems wrong. Up to a dimensionless factor Q that adjusts for biological details, a sievert (Sv) is 1 joule of radiation energy deposited per kilogram. But that neutrino beam has a mean-free-path of the diameter of the Earth! That means it is roughly distributing the kilowatt of energy over 1 m^2 * 13,000 km ~= 1e7 m^3. At the density of water, that's 1e10 kg, so the deposited power is about a 1e-7 watts per kilogram, or roughly 100 nano sieverts per second. You'd have to point the beam at someone for 3 hours straight to exceed the (conservative) federal limit.
- function_seven 6y ago
  My reading of the paper shows they already factored that into the equation. So at the target, in the 1m² cross-section, 1,000 W of energy is being delivered. It takes about 50,000,000,000 W at the beam generator to achieve that.
  - 3pt14159 6y ago
    If it's just 50 gigawatts it is potentially viable, considering the stakes of nuclear warfare. The precise locations of most stationary nuclear weapons systems are already known, though this would run into some trouble finding nukes on submarines unless they were detected by submerged drones or subullites. I'd look into it.
    - CSSer 6y ago
      > most Sounds really perilous. If even one is missed isn’t its risk of usage now astronomically higher?
      - 3pt14159 6y ago
        Well I don't think anyone in charge is really happy about how nuclear weapons are handled these days, but generally speaking I'd say that most people don't want to use them, but they're forced into over-worrying about attack vectors because that's the nature of MAD. Even so, there are so many ways of doing so much damage to an adversary right now I doubt if a major nuclear power would actually deploy[0] offensive neutrino weapons outside of an actual war. [0] There is a difference between use and deploy in military terminology.
  - jessriedel 6y ago
    Which part of the paper? I don't know why they would quote power per unit area for a beam that is clearly depositing it proportional to volume. What is the assumed depth?
    - 6y ago
dpq 6y ago
This immediately reminded me a very old book by Bob Shaw: https://en.wikipedia.org/wiki/Ground_Zero_Man https://en.wikipedia.org/wiki/Ground_Zero_Man The tech in the book was no less fictitious but sounded kinda cool: a neutron resonator, with a beam being targeted on the Moon and being reflected to the Earth, widening sufficiently to cover the whole planet (no idea how or why it would affect warheads on the other side).

by ufmace 6y ago

rbanffy 6y ago

I'd assume Selenites will want to have such a weapon pointed towards Earth in case Earthlings decide to act up. They'll have a lot of solar power to play with too. And it's much neater than throwing rocks too. And faster.

lsllc 6y ago
At least the Trisolarians can use their sophons to prevent such a thing.

jessriedel 6y ago

> plus a huge risk of collateral damage to any life, human or otherwise, that happens to get in the path of the beam. Why? This doesn't actually deposit that much energy directly in any given volume. The beam is about a meter wide and the power is about a kilowatt (1000 joules per second). The authors say > This is equivalent to about 1 Sv/sec. We note that this value of the radiation dose is very large, compared with the U.S. Federal off-site limit of 1 mSv/year. but that seems wrong. Up to a dimensionless factor Q that adjusts for biological details, a sievert (Sv) is 1 joule of radiation energy deposited per kilogram. But that neutrino beam has a mean-free-path of the diameter of the Earth! That means it is roughly distributing the kilowatt of energy over 1 m^2 * 13,000 km ~= 1e7 m^3. At the density of water, that's 1e10 kg, so the deposited power is about a 1e-7 watts per kilogram, or roughly 100 nano sieverts per second. You'd have to point the beam at someone for 3 hours straight to exceed the (conservative) federal limit.

function_seven 6y ago
My reading of the paper shows they already factored that into the equation. So at the target, in the 1m² cross-section, 1,000 W of energy is being delivered. It takes about 50,000,000,000 W at the beam generator to achieve that.
- 3pt14159 6y ago
  If it's just 50 gigawatts it is potentially viable, considering the stakes of nuclear warfare. The precise locations of most stationary nuclear weapons systems are already known, though this would run into some trouble finding nukes on submarines unless they were detected by submerged drones or subullites. I'd look into it.
  - CSSer 6y ago
    > most Sounds really perilous. If even one is missed isn’t its risk of usage now astronomically higher?
    - 3pt14159 6y ago
      Well I don't think anyone in charge is really happy about how nuclear weapons are handled these days, but generally speaking I'd say that most people don't want to use them, but they're forced into over-worrying about attack vectors because that's the nature of MAD. Even so, there are so many ways of doing so much damage to an adversary right now I doubt if a major nuclear power would actually deploy[0] offensive neutrino weapons outside of an actual war. [0] There is a difference between use and deploy in military terminology.
- jessriedel 6y ago
  Which part of the paper? I don't know why they would quote power per unit area for a beam that is clearly depositing it proportional to volume. What is the assumed depth?
  - 6y ago

dpq 6y ago

This immediately reminded me a very old book by Bob Shaw: https://en.wikipedia.org/wiki/Ground_Zero_Man https://en.wikipedia.org/wiki/Ground_Zero_Man The tech in the book was no less fictitious but sounded kinda cool: a neutron resonator, with a beam being targeted on the Moon and being reflected to the Earth, widening sufficiently to cover the whole planet (no idea how or why it would affect warheads on the other side).