The USA's "Star Wars" program is looking at laser weapons to explode
missiles.  What if the missiles were covered in a mirrored surface? 
Would the killer lasers reflect off harmlessly?  Would this simple
solution make all that weapon technology useless?

Greetings Haphazard, and thank you for your interesting question.
Someone thought of the same thing as you did. I wonder if the person
who wrote this message was you as well:

Message on March 29, 1999 - <nettime> hardware speculations digest
[human being, mediafilter]
http://amsterdam.nettime.org/Lists-Archives/nettime-l-9903/msg00127.html

I disagree with his opinion though, since the thought that a mirror
always reflects a laser is quite an urban legend.

In the Military Analysis Network page listed below, note what is said
in the “Characteristics of materials” subtitle: “If light rays strike
a mirror, almost all of the energy incident on the mirror will be
reflected.” *Almost all*, but not really ALL of the energy is
reflected. It is possible if the laser beam has enough strength, some
of the energy may even penetrate the mirror and cause damage to the
missile. A laser is not only light, but also has some force and even
heat in it, so that force can shatter or melt the glass.

I also feel that a missile with mirrors all over would also be
unlikely, since a missile at launch and in flight is subject to
serious vibration and shock, which glass today certainly wouldn’t
stand up to. If you’re thinking of high stress glass like that of jet
cockpits, then there is the wear and tear of drag on the missile could
erode the mirror surfaces and reduce reflectivity. Of course the jet
cockpit has minimal glass and doesn’t go through the same stress as a
missile. Also, there is always one opening a mirror can’t cover in the
missile, which is the exhaust. A laser through there could knock out
the missile.

You might also note that some laser weapon systems use mirrors (mostly
ground-based and airborne laser systems). These mirrors are actually
meant for focusing the laser beam, probably since it loses power when
it travels in an atmosphere. They would also be definitely attuned to
the wavelength of the laser, so they wouldn’t break. These mirrors are
used mainly to correct deviations in the path of the laser. Using an
ordinary mirror as a laser though would be relegated to the realm of
fantasy. If shield mirrors would be used, they might have to be made
of an outlandish material that would also be very expensive.

Sources:
Military Analysis Network - Laser Fundamentals
http://www.fas.org/man/dod-101/navy/docs/laser/fundamentals.htm

A - SOL:LASER COUNTERMEASURES STUDY (11/30/95)
http://www.fbodaily.com/cbd/archive/1995/11(November)/30-Nov-1995/Asol001.htm

Phun Physics - Laser light show Demonstration
http://phun.physics.virginia.edu/demos/laser.html
- The laser here is different from what is used in satellite-based
laser weapon systems.

Homebuilt Lasers Page - Lasing Mechanisms
http://www.technology.niagarac.on.ca/people/mcsele/lasers/Mechanism.htm

Links to documents on space lasers:
Space Based Laser concepts
http://210.79.226.16:81/cetin2/report/tmd/nmdzl/sbl/sbl.htm

Laser Options for National Missile Defense
http://www.fas.org/spp/starwars/program/docs/98-165.htm

Space Based Laser profile
http://en.afit.edu/enp/de/sbl.pdf

A Brief History of the Missile Defense System
http://members.fortunecity.com/volcanopele/Factual_Report.htm

Space.com - Space Laser project heats up
http://www.space.com/businesstechnology/technology/space_laser_001127.html

Schedule for Airborne Laser testing
http://www.airbornelaser.com/special/abl/schedules/milestones.html

Search terms used:
laser reflect mirror mechanics
laser reflect mirror physics
laser countermeasures
laser missile mirror/mirrors

Other research tools: personal knowledge

I hoe this has been a satisfactory answer. If you have a problem with
this answer, do please post a request for clarification. Thank you.

Great answer, and nice to have links to sources.  Thanks!

The idea of mirrors does seem viable if you want to find more about
the system head towars the lockheed web site, though the starwars
project mainly is a 3d radar based systems which finds a target
indentifies it and then launches a counter missile towards the target
to make a direct hit with the offending missle.

There are two things to consider:

(1) What you mean by a "mirror". A mirror reflects light at a range of
wavelengths (colours). Different Lasers can be produce light at
different wavelengths, many of which  are not visible to the eye and
not necessarily reflected by a mirror. By choosing a laser at a
particular wavelength (even lower wavelength than ultra violet) the
"mirror" may not be effective. Lasers emit light at one specific
wavelength so I guess that the "star wars" weapon would consist of
several lasers of different wavelengths (or a tunable laser) so that
it could not easily be reflected in this way.

(2) The total energy in the laser pulse. If the pulse of energy
(light) from the laser was high enough then it could destroy the
missile even if it reflected a high percentage of the laser light.

A highly reflective surface all over the missle might require 20 times
more laser energy to pierce the skin of the missle. I don't think more
than about 95% reflectivity is possible. Because the missle is very
fast, tiny dust particles in the air quickly degrade the mirror
surface. I presume a tiny robot is possible that polishes the surfaces
as the missle flies.  With an exta minute of advance warning, it
should be possible to exploded a dust bomb ahead of the missle which
releases very abrasive dust, which might also blind the missle causing
it to miss its target.  Neil

The question/answers/comments seems to skirt the topic of the
producability of such a device. A mirrored-missile would cost so much
to produce that it wouldn't be viable. Nonetheless...

The comments made above that the mirrored surface would not last in
the atmosphere are quite true. Especially when you consider that a
typical ICBM (which is what the "star wars" system is supposed to
protect against) travels supersonically, and ideally hypersonically to
try to avoid getting hit by a laser or missile before striking its
target.

krobert-ga

It seems that a glass mirror would not be possible but perhaps having
the missle housed in a polished steel (like chrome) coating might
reduce the engery assorbed from the laser.

I must make a correction here. My sentence in the third large
paragraph which reads, "Using an ordinary mirror as a laser though..."
should read "Using an ordinary mirror as a deflector/shield..."

While these ideas are interesting, to the best of my knowledge the
issue of laser-based damage to high-speed missles was addressed
shortly after the concept was espoused.  The answer, as I remember it,
was relatively straightforward:  the use of refractive material
embedded in the missile housing's coating, together with a design
makes the missile spin at a high rate has it travels.  Apparently the
comination was sufficient, and I do not belive that anyone is intently
pursuing anti-missile lasers from a damage perspective since.

I would be interested and grateful to learn of any concrete
information to the contrary-

Cheers,
Matt