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Author Topic: How do you protect objects from a high powered laser?  (Read 6278 times)

Offline Airthumbs

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History has been made with a anti missile device that can shoot a missile travelling at mach one by using a high powered laser.

What I find a little bit odd about this is.... would a very simple way to protect and object from a laser beam, no matter how powerful, be to cover it in a reflective surface?

This seems so obvious to me that I have to wonder what other targets the military really has in mind with a device like this. 

Would covering an object in a reflective surface, including ourselves, be enough to reflect this type of attack and render it utterly useless?

Zap zap!!


 

Offline Airthumbs

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How do you protect objects from a high powered laser?
« Reply #1 on: 08/07/2011 02:21:10 »
I have to say that if this is not so obvious and I have just ruined billions of dollars of research then I will remove my post if you guarantee every person in the world clean drinking water!  [^]
 

Offline grizelda

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How do you protect objects from a high powered laser?
« Reply #2 on: 08/07/2011 03:58:39 »
I read somewhere that a laser beam might originally have a thickness the size of a molecule, so unless you invent a reflective molecule and weave a blanket out of it, the laser will burn through.
 

Offline mlarsen77

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How do you protect objects from a high powered laser?
« Reply #3 on: 08/07/2011 04:49:06 »
Well.......I would think that because a reflective surface still can become hot to the touch, it is actually absorbing some of the energy before reflecting it. With enough intensity, the surface would eventually be damaged. I think the best defense would be one of two things......a multifaceted prismatic surface that would either by refraction redirect the beam until it was no longer headed towards the target, or diffuse the beam enough so that its effective frequency...density was no longer dangerous......   or......option 2......similar to the shuttle, white ceramic porous plating that when light hits it, it is both diffused, and any heat generated would be dissipated......
 

Offline CliffordK

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How do you protect objects from a high powered laser?
« Reply #4 on: 08/07/2011 05:41:49 »
A highly reflective coating would likely reflect much of the light.  If you could reduce the power by say 90%. or perhaps even 50%, that might be enough to render the laser ineffective.  With reflected light, the photon energy is not absorbed, so one would not expect a mirror to heat up as much in direct sunlight as a black box would.

A cone or cylinder shape (common on rockets) would tend to diffuse the light, but it would also cause a significant flash visible to observers.

Is there any way to incorporate a mirror designed to reflect the light back to the source?  Perhaps some kind of adjustable Fresnel type mirror?

I think there are supposed to be issues with lasers ionizing the air, and thus their utility on earth is more limited than it would be if deployed in space (for space to space operations).
 

Offline Airthumbs

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How do you protect objects from a high powered laser?
« Reply #5 on: 16/07/2011 17:56:06 »
A highly reflective coating would likely reflect much of the light.  If you could reduce the power by say 90%. or perhaps even 50%, that might be enough to render the laser ineffective.  With reflected light, the photon energy is not absorbed, so one would not expect a mirror to heat up as much in direct sunlight as a black box would.

A cone or cylinder shape (common on rockets) would tend to diffuse the light, but it would also cause a significant flash visible to observers.

Is there any way to incorporate a mirror designed to reflect the light back to the source?  Perhaps some kind of adjustable Fresnel type mirror?

I think there are supposed to be issues with lasers ionizing the air, and thus their utility on earth is more limited than it would be if deployed in space (for space to space operations).

Having listened to, in my opinion, the latest and most boring podcast in history with information sadly repeated from previous podcasts, it has to be cats eyes! (Seriously what a folly, who is that guy playing with Dam-buster models and how on earth does he get funding for a project like that)!!? Where are the naked scientists, have they had a fallout? Are they all on holiday? Do they know the BBC has stolen their format? Have they been shut down for naked antics?

I expect one solution might be to cover the surface of an object with cats eyes.  Not literally of course but the ones you find in roads.  Also by using this technique the light would be directed back at the source.  So for all you nutters with your finger on the trigger of an ICBM just stick cats eyes all over it!
 

Offline CZARCAR

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How do you protect objects from a high powered laser?
« Reply #6 on: 16/07/2011 21:04:05 »
& a tinfoil hat is wheres its at!
 

Offline CliffordK

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How do you protect objects from a high powered laser?
« Reply #7 on: 16/07/2011 21:12:51 »
If the ICBMS are already made out of aluminum or similar metal...  it wouldn't hurt to put a mirror polish on them.

Of course the other option is to give up on the idea of making better bombs.
 

Offline grizelda

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How do you protect objects from a high powered laser?
« Reply #8 on: 16/07/2011 23:05:49 »
If you have a religious destiny, then ICBM's are just the ticket to deal with anyone interfering with that destiny.
 

Offline SeanB

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How do you protect objects from a high powered laser?
« Reply #9 on: 17/07/2011 12:21:27 »
The laser can cut a hole if you can do the following:

Aim at a fast moving target many kilometers away.
compensate for air turbulence.
hit one spot on a rotating object
input more power than what is reflected, and what is dissipated when the beam is not on the same spot
Keep this up for the 15-20 seconds it takes to burn a hole through.


More likely is that a high powered laser can be used to overload the optical sighting system and either cause damage to the internal sensor, or cause the missile to lose visual correction ability and miss the target. So, radar tracking and inertial guidance are not affected by this.


Of course if the laser is capable of putting terawatt power into a 1 second pulse then it can vapuorise most items, along with a cylinder of air joining the 2 points.
 

Offline lightarrow

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How do you protect objects from a high powered laser?
« Reply #10 on: 26/07/2011 19:36:33 »
input more power than what is reflected,
This happens always, even with the most feeble light: the incident light is the sum of the absorbed and the reflected  :)
 

Offline lightarrow

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How do you protect objects from a high powered laser?
« Reply #11 on: 26/07/2011 19:49:14 »
would a very simple way to protect and object from a laser beam, no matter how powerful, be to cover it in a reflective surface?
"no matter how powerful" is a bit big statement. The reflectivity cannot be 100%. Even if it were 99.99%, that 0.01% of intensity absorbed can destroy the target if the beam intensity is high enough. I am speaking in general, of course, I have no idea of how powerful are those lasers.
Furthermore, the reflectivity of a material decreases with increasing temperature.
Last consideration: if in the (far) future will be possible to construct lasers emitting in the X-ray range, then no material could reflect it enough.
 

Offline SeanB

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How do you protect objects from a high powered laser?
« Reply #12 on: 26/07/2011 20:19:03 »
X-ray lasers have been built and tested, though they were not terribly effective, and had an unfortunate tendency to be single use devices. Not easy to make a multi shot unit when you need a small ( 20 kiloton or so) nuke to generate the plasma channel and get it hot enough to get population inversion. Mirrors that reflected were easy, just simple metal plate at each end, it shot a laser beam out of each end, lasting as long as it took to vapourise the unit.
 

Offline Airthumbs

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How do you protect objects from a high powered laser?
« Reply #13 on: 26/07/2011 22:31:02 »
This is so scary I wish I had not asked now!!   ;D
 

Offline SeanB

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How do you protect objects from a high powered laser?
« Reply #14 on: 27/07/2011 21:24:11 »
Funny enough it was funded by Ronnie Raygun.........
 

Offline lightarrow

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How do you protect objects from a high powered laser?
« Reply #15 on: 27/07/2011 21:42:38 »
X-ray lasers have been built and tested, though they were not terribly effective, and had an unfortunate tendency to be single use devices. Not easy to make a multi shot unit when you need a small ( 20 kiloton or so) nuke to generate the plasma channel and get it hot enough to get population inversion.
I know, I meant lasers which are managebles like the conventional ones.

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Mirrors that reflected were easy, just simple metal plate at each end, it shot a laser beam out of each end, lasting as long as it took to vapourise the unit.
Yes and the beam have to form an incidence angle almost equal to 90 with the metal plate surface, that is it have to be almost in the same plane (very grazing). It means that such a beam penetrates easily unless it is almost totally parallel to the surface.
 

Offline SeanB

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How do you protect objects from a high powered laser?
« Reply #16 on: 28/07/2011 20:42:42 »
A pocket solid state semiconductor laser is probably possible, but not in the near future. You can do UV diodes, and probably will be able to do a frequency doubling arrangement to make an X-ray LED, but a laser would be a little harder, not to mention a difficult item to package.
 

Offline Airthumbs

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How do you protect objects from a high powered laser?
« Reply #17 on: 29/07/2011 01:17:33 »
The worlds most powerful laser, upto 1.8 mega-joules, uses mirrors, and lots of them, to reflect and concentrate 192 high energy beams into one.  If it was the case that a mirror does not reflect light effectively and is damaged in the process then why on Earth would it be used in this device.  According to some of the above responses a mirror would be ineffective against such high powered lasers, I suspect that maybe the people who posted those reposnes have connections with the military and don't want the secret out!  ::)

I imagine that if the mirror was full of imperfections larger then the wavelength of the laser then as has been posted some of that energy would be refracted, absorbed into the material and may cause damage.  I am sure there are ways of creating a very effective reflective surface using modern technology that could be then employed as a defence. 

PS. My car is the one with the mirror on the roof, you aint zapping me!  :P
 

Offline lightarrow

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How do you protect objects from a high powered laser?
« Reply #18 on: 29/07/2011 15:14:07 »
The worlds most powerful laser, upto 1.8 mega-joules, uses mirrors, and lots of them, to reflect and concentrate 192 high energy beams into one.  If it was the case that a mirror does not reflect light effectively and is damaged in the process then why on Earth would it be used in this device.  According to some of the above responses a mirror would be ineffective against such high powered lasers,
Wait a moment. One thing is the laser energy, another is its power (it depends on the first and on the pulse duration) and still another is its intensity. You can have 1.8 MJ and the power that you want, but if it's dispersed in a large area (little intensity), it won't do a bit to anything. I imagine this is the case for those mirrors, or at least it's how I would do it: using mirrors to deflect a large beam and then mirrors to focus it into a thin one.
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PS. My car is the one with the mirror on the roof, you aint zapping me!  :P
For cars they have Masers, and your mirror on the roof does nothing to them  ;D

 

Offline Airthumbs

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How do you protect objects from a high powered laser?
« Reply #19 on: 29/07/2011 15:22:53 »
For cars they have Masers, and your mirror on the roof does nothing to them  ;D

You know that glass you get on the door of your microwave oven?  Would that work with the MASER?
At this rate my car is going to heavier then Obama's!!
 

Offline CliffordK

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How do you protect objects from a high powered laser?
« Reply #20 on: 29/07/2011 21:43:50 »
For your Police Radar, you need one of these.

http://www.roadsideamerica.com/tip/15600


While it absorbs much of the Radar Energy, the idea is to reflect the beam any direction except back to the source. 

Of course, if the idea is to avoid being vaporized, then you would choose a highly reflective finish so you would not absorb the energy.
 

Offline lightarrow

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How do you protect objects from a high powered laser?
« Reply #21 on: 30/07/2011 20:10:02 »
For cars they have Masers, and your mirror on the roof does nothing to them  ;D

You know that glass you get on the door of your microwave oven?  Would that work with the MASER?
Yes, certainly, for more than a millisecond  ;D
 

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How do you protect objects from a high powered laser?
« Reply #21 on: 30/07/2011 20:10:02 »

 

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