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Comment: Re:This might alienate anti-ISI* Muslims. (Score 1) 225

by joe_frisch (#48569227) Attached to: US Navy Authorizes Use of Laser In Combat

The only demo I saw of one of these was against a small boat.

Missiles might be a valid target, but they could be designed to be very laser resistant - picture a reentry shield......

I don't really see much use for these anyway - "won't work in rain and fog" is a pretty big problem.

Comment: Re: This might alienate anti-ISI* Muslims. (Score 1) 225

by joe_frisch (#48569151) Attached to: US Navy Authorizes Use of Laser In Combat

A modestly shiny piece of metal will do quite a good job of reflecting. You won't get a coherent beam but a diffuse spot that will still blind at a long distance. think of the sun reflecting off of a modestly well polished metal surface. Something you could easily get with a buffing wheel.

Or for more humor value - a disco ball......

Comment: Re:This might alienate anti-ISI* Muslims. (Score 1) 225

by joe_frisch (#48569061) Attached to: US Navy Authorizes Use of Laser In Combat

I'm worried about a reflector on the target ship. If I were planning a terrorist attack on a US navy ship, after reading this, I'd mount an optical retro-reflectors. (though of course that makes you more radar-visible... The retroreflectors are a big hazard to crew on the firing ship. They don't need to be very good if you are just trying to blind, not do physical damage.

The blinding problem is more an issue if the ship is in harbor somewhere. There is also the risk of a clever terrorist on a boat reflecting the beam toward a nearby (few kilometers) set of civilians - say a crowded beach.......

Reasonable precautions can avoid these scenarios, but the precautions need to be taken very seriously. I don't want to hear that we accidentally blinded hundreds of innocent families on a beach somewhere.....

(I just hope that the US realizes the risk before the terrorists recognize the opportunity). Otherwise I wouldn't even post ideas like this on a public board.

Comment: Re:This might alienate anti-ISI* Muslims. (Score 1) 225

by joe_frisch (#48568853) Attached to: US Navy Authorizes Use of Laser In Combat

This could get sticky. The most effective property of the lasers may be that they blind, even though that isn't their stated function. Similarly to using white phosphorus against humans, the legality is debated.

Everyone on a ship with the laser will need eye protection all the time. Crude metal corner cubes will be pretty effective and since the goal of the weapon is rapid response, the crew will need to always be ready, or they risk blinding their own people. It will have a really tough time burning through a 1/4" thick aluminum corner cube.

Note - it isn't clear from the article whether the laser operates at a wavelength that is likely to cause blindness. Various hints suggest it is Nd (or maybe Yb) based which would be ~1um and is in a wavelength range that can easily cause blindness (it is focused by the eye). The powers required for blinding are dramatically lower then the power required to do physical damage, so its range as a blinding weapon (intentional or not) will be much longer than its range for physical damage. The risk of blinding bystanders from scatter may be significant.

If it is ~1um micron wavelength the beam will be invisible and targets may not be aware of how they were damaged or blinded.

Comment: Re:It's allowed... (Score 4, Insightful) 772

by joe_frisch (#48560023) Attached to: CIA Lied Over Brutal Interrogations

Generally fighting fire with water or other fire retardants is the preferred method.

It is in the very nature of evil that it "gets results". The entire point of morality is that there are things you will not do even if they are in your interest.

As an American citizen, I do not in any way approve of the use of torture. I am willing to accept the higher risk of death by terrorism, assuming the risk even is higher, in return for the country behaving in a moral fashion. I am willing to trade my safety for doing what is right. No torture, no indefinite detention, no extra-judicial killings.

  If I knew a legal way to stop the US from using torture, I would.

We have become the things we always claimed that we opposed in the world.

Comment: Re:What about efficiency? (Score 1) 90

by joe_frisch (#48559043) Attached to: Berkeley Lab Builds World Record Tabletop-Size Particle Accelerator

Superconducting linacs can be quite efficient - 10s of %. Electric costs are not a major driver for most accelerators so typically they are not that good in order to save construction costs. You could probably design >50% wall plug -> beam efficiency accelerator if you wanted to.

Laser accelerators are not that good at converting laser energy to beam energy. I don't know the numbers, but above ~10% would surprise me. Then the high drive lasers are very inefficient (these are not diode laesrs!). Both those can be improved, but I would be surprised if the final efficiency were as high as for a conventional superconducting linac.

For low power beam applications that may not be a significant disadvantage and the short length is of course a big advantage. (though the drive laser is big).

Comment: Engineering == use the correct technology (Score 1) 197

by joe_frisch (#48537105) Attached to: Orion Capsule Safely Recovered, Complete With 12-Year-Old Computer Guts

If older computers can do the job and are known to be reliable in this environment, then using them is the correct choice. We sent people to the moon, and Voyager to multiple outer planets with much older computer technology.

If newer computers would provide improved performance IN THIS APPLICATION then they are worth considering.

Comment: Re:Even if their wet? (Score 3, Funny) 194

by joe_frisch (#48535735) Attached to: Trains May Soon Come Equipped With Debris-Zapping Lasers

We need to test all the competing technologies for this to pick the best:

1) high power lasers.
2). Flame throwers
3). High power plasma discharges.
4). rocket-propelled Anti-leaf attack drones
5). Jets of ClF3
6) Anti-proton beams.
7). Brushes
8) US only: a guy walking ahead of the train with a broom.

then we can see which is the most cost effective and safe - and get some cool youtube videos as well.

Comment: Re:Sauce for the goose; sauce for the gander (Score 3, Informative) 528

by joe_frisch (#48527671) Attached to: The Sony Pictures Hack Was Even Worse Than Everyone Thought

I feel sorry for their employees who's information was compromised, but I can't say the same about the company. They are still on my "do not buy" list, and I buy a lot of the sort of things that they sell. Still waiting for an apology for the rootkit.

Comment: Re:You will not go to wormhole today. (Score 1) 289

by joe_frisch (#48495219) Attached to: Physicist Kip Thorne On the Physics of "Interstellar"

Depends on what you mean by "small scales". Relativity works to the length scales accessible by accelerators (1 TeV, or something like 1e-18M - and probably extrapolated a lot further). There are issues with quantum gravity but they only become significant at energy scales approaching plank energy - far beyond any conceivable technology. There are also possible issues with relativity at cosmological scales.

The problem is that relativity seems completely under all technologically reachable conditions. Star drives just don't seem possible.

We *could* be missing something, but it is very difficult to imagine a set of rules that allow FTL or other fun stuff, but which would not have been noticed in present day measurements that range for accelerator scales to cosmological scales.

Comment: Re:These idiots are going to ruin it for everyone (Score 1) 132

by joe_frisch (#48380453) Attached to: Drone Sightings Near Other Aircraft Up Dramatically

Maybe this suggests a technical solution.
Equip drones with GPS and nav databases so that they will not fly in controlled airspace. (with the ability to override with some sort of approval).

There are flights in uncontrolled airspace but it is much less of an issue.

Comment: Re:Not exactly (Score 2) 161

by joe_frisch (#48322941) Attached to: New Particle Collider Is One Foot Long

Its a good question .
I don't understand astrophysical shocks, but see: http://www.slac.stanford.edu/e...
As far as I can tell the rely on magnetic fields bending the particles back into the shock.

When relativistic particle trajectories are bent by magnetic fields, they emit synchrotron radiation which increases rapidly with increasing particle energy.

Longitudinal fields don't do the same thing. There is a tiny amount of radiation, but it is not strongly dependent on particle energy. I believe this is because Lorentz contraction increases transverse, but not longitudinal electromagnetic fields: http://en.wikipedia.org/wiki/C...

Ideally the fields in the plasma accelerator are longitudinal on axis. If the particle enters slightly off axis it will get a transverse kick and will radiate synchrotron radiation, and we do see that. For very high energies that radiation might be large, but the effect would be to damp the transverse motion of the particle, but not affect the longitudinal acceleration.

  I know that the plasma wakefield people are seriously thinking about TeV scale machines: https://accelconf.web.cern.ch/...

It is possible that the concept fails at some much higher energy.

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