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Laser writing on the moon



 
 
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  #1  
Old April 1st 08, 11:05 PM posted to sci.space.history
Mike Ross[_3_]
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Posts: 31
Default Laser writing on the moon

I thought I saw recently somewhere a plan to use a laser to put ads on the
moon. Is that really possible? Seems like the power levels required would
be prohibitive, or at least dangerous to anything passing through the beam.

Should some group decide to such a thing, I wonder how hard it would be to
find the source of the laser?
--
************************************************** ************
Mike Ross, PE * 20+ yrs at JSC in Shuttle & ISS robotics
Opinions expressed herein would probably appall NASA
************************************************** ************
  #2  
Old April 2nd 08, 01:18 AM posted to sci.space.history
BradGuth
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Posts: 21,544
Default Laser writing on the moon

On Apr 1, 2:05 pm, Mike Ross
wrote:
I thought I saw recently somewhere a plan to use a laser to put ads on the
moon. Is that really possible? Seems like the power levels required would
be prohibitive, or at least dangerous to anything passing through the beam.

Should some group decide to such a thing, I wonder how hard it would be to
find the source of the laser?
--
************************************************** ************
Mike Ross, PE * 20+ yrs at JSC in Shuttle & ISS robotics
Opinions expressed herein would probably appall NASA
************************************************** ************


Not a power or safety problem if such photons were transmitted from
within the moon's L1, roughly a little better than 58,000 km away from
the moon.

However, that moon is nearly as dark as coal, most of it covered in a
deep and crystal dry layer of fluffy and electrostatic charged dust
(hardly reflective in the visual spectrum, but fairly IR good to go),
so that you'd need nearly 10 fold as much laser cannon beam energy as
you'd think.
.. - Brad Guth
  #3  
Old April 2nd 08, 07:15 AM posted to sci.space.history
Damon Hill[_4_]
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Posts: 566
Default Laser writing on the moon

Mike Ross wrote in
:

I thought I saw recently somewhere a plan to use a laser to put ads on
the moon. Is that really possible? Seems like the power levels
required would be prohibitive, or at least dangerous to anything
passing through the beam.

Should some group decide to such a thing, I wonder how hard it would
be to find the source of the laser?


Given the low albedo, the size of the area that'd need to be illuminated
and distance of the target...yeah. Serious power. Got to keep the
beam from spreading too much and the earth's atmosphere might tend to
scatter the beam a bit, too.

Even so, surely someone's tried this...?

--Damon
  #4  
Old April 2nd 08, 06:00 PM posted to sci.space.history
Joseph Nebus
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Posts: 306
Default Laser writing on the moon

Damon Hill writes:

Mike Ross wrote in
:


I thought I saw recently somewhere a plan to use a laser to put ads on
the moon. Is that really possible? Seems like the power levels
required would be prohibitive, or at least dangerous to anything
passing through the beam.

Should some group decide to such a thing, I wonder how hard it would
be to find the source of the laser?


Given the low albedo, the size of the area that'd need to be illuminated
and distance of the target...yeah. Serious power. Got to keep the
beam from spreading too much and the earth's atmosphere might tend to
scatter the beam a bit, too.


Even so, surely someone's tried this...?


An article for Nature that I dug up when this was discussed a
couple weeks back on rec.arts.sf.written claimed that the signal loss
on a laser bouncing from Earth, to the reflectors on the Moon, back to
the Earth, is something like 10^{-21} -- and remember, that's to the
spots on the moon designed to reflect as perfectly for the mass as
humans could manage, circa 1970. I'm sure I can find it again, but it
wasn't a particularly tricky Google search for it.

Considering that most of the Moon has a vastly lower albedo,
and that you would need to send up enough light that what's reflected
stands out against the full moon's intensity -- and to complicate
things, that the logo is a light green, which is harder to read on the
basically-white background than, say, red would be -- and ... I don't
have a quick way to calculate what power is needed, but feel safe to
say nobody's got a laser that'll do that.

--
Joseph Nebus
------------------------------------------------------------------------------
  #5  
Old April 2nd 08, 07:11 PM posted to sci.space.history
BradGuth
external usenet poster
 
Posts: 21,544
Default Laser writing on the moon

On Apr 1, 10:15 pm, Damon Hill wrote:
Mike Ross wrote m:

I thought I saw recently somewhere a plan to use a laser to put ads on
the moon. Is that really possible? Seems like the power levels
required would be prohibitive, or at least dangerous to anything
passing through the beam.


Should some group decide to such a thing, I wonder how hard it would
be to find the source of the laser?


Given the low albedo, the size of the area that'd need to be illuminated
and distance of the target...yeah. Serious power. Got to keep the
beam from spreading too much and the earth's atmosphere might tend to
scatter the beam a bit, too.

Even so, surely someone's tried this...?

--Damon


What's your dumbfounded problem?
There's not a beam spreading or all that much energy demand if
transmitted from the moon's L1.
.. - Brad Guth

  #6  
Old April 2nd 08, 07:17 PM posted to sci.space.history
BradGuth
external usenet poster
 
Posts: 21,544
Default Laser writing on the moon

On Apr 2, 9:00 am, (Joseph Nebus) wrote:
Damon Hill writes:
Mike Ross wrote in
:
I thought I saw recently somewhere a plan to use a laser to put ads on
the moon. Is that really possible? Seems like the power levels
required would be prohibitive, or at least dangerous to anything
passing through the beam.


Should some group decide to such a thing, I wonder how hard it would
be to find the source of the laser?

Given the low albedo, the size of the area that'd need to be illuminated
and distance of the target...yeah. Serious power. Got to keep the
beam from spreading too much and the earth's atmosphere might tend to
scatter the beam a bit, too.
Even so, surely someone's tried this...?


An article for Nature that I dug up when this was discussed a
couple weeks back on rec.arts.sf.written claimed that the signal loss
on a laser bouncing from Earth, to the reflectors on the Moon, back to
the Earth, is something like 10^{-21} -- and remember, that's to the
spots on the moon designed to reflect as perfectly for the mass as
humans could manage, circa 1970. I'm sure I can find it again, but it
wasn't a particularly tricky Google search for it.

Considering that most of the Moon has a vastly lower albedo,
and that you would need to send up enough light that what's reflected
stands out against the full moon's intensity -- and to complicate
things, that the logo is a light green, which is harder to read on the
basically-white background than, say, red would be -- and ... I don't
have a quick way to calculate what power is needed, but feel safe to
say nobody's got a laser that'll do that.

--
Joseph Nebus
------------------------------------------------------------------------------


Then simply laser illuminate upon the physically dark moon as of
otherwise being earthshine dark, and otherwise by way of simply using
the moon's L1 as the efficient station-keeping location for those
laser cannons, and of easily creating every viable color you'd like
(including UV and IR if you'd like).
.. - Brad Guth
  #7  
Old April 10th 08, 02:47 AM posted to sci.space.history
NTL Newsgroups
external usenet poster
 
Posts: 1
Default Laser writing on the moon

Im sure there is not a single laser that could undertake this task, but how
about hundreds or even thousands of lasers, all working in sync might work.

Dan.

"BradGuth" wrote in message
...
On Apr 1, 10:15 pm, Damon Hill wrote:
Mike Ross wrote
m:

I thought I saw recently somewhere a plan to use a laser to put ads on
the moon. Is that really possible? Seems like the power levels
required would be prohibitive, or at least dangerous to anything
passing through the beam.


Should some group decide to such a thing, I wonder how hard it would
be to find the source of the laser?


Given the low albedo, the size of the area that'd need to be illuminated
and distance of the target...yeah. Serious power. Got to keep the
beam from spreading too much and the earth's atmosphere might tend to
scatter the beam a bit, too.

Even so, surely someone's tried this...?

--Damon


What's your dumbfounded problem?
There's not a beam spreading or all that much energy demand if
transmitted from the moon's L1.
. - Brad Guth


  #8  
Old April 10th 08, 03:57 AM posted to sci.space.history
BradGuth
external usenet poster
 
Posts: 21,544
Default Laser writing on the moon

On Apr 9, 6:47 pm, "NTL Newsgroups" wrote:
Im sure there is not a single laser that could undertake this task, but how
about hundreds or even thousands of lasers, all working in sync might work.

Dan.


As transmitted from the moon's L1 that's roughly 58,000 km away from
the moon, and depending on how large of pattern gets projected onto
the dark earthshine illuminated moon (say not more than illuminating a
1,000 km diameter), there is sufficient laser cannon capability if an
array of 10 such commercial laser projections were utilized .

The reflected light of the visual spectrum would still be fairly dim
to the naked eye, unless IR counts, because IR reflects off the moon
at the albedo efficiency of 33 to 50%.
.. - Brad Guth
  #9  
Old April 10th 08, 08:04 AM posted to sci.space.history
Pat Flannery
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Posts: 18,465
Default Laser writing on the moon



NTL Newsgroups wrote:
Im sure there is not a single laser that could undertake this task,
but how about hundreds or even thousands of lasers, all working in
sync might work.

Dan.


Several years back somebody came up with a scheme where as many people
around the world as possible were supposed to aim their laser pointers
at the Moon simultaneously.
It wouldn't have worked, but it was kind of a fun idea.

Pat
  #10  
Old April 10th 08, 05:26 PM posted to sci.space.history
BradGuth
external usenet poster
 
Posts: 21,544
Default Laser writing on the moon

On Apr 10, 12:04 am, Pat Flannery wrote:
NTL Newsgroups wrote:
Im sure there is not a single laser that could undertake this task,
but how about hundreds or even thousands of lasers, all working in
sync might work.


Dan.


Several years back somebody came up with a scheme where as many people
around the world as possible were supposed to aim their laser pointers
at the Moon simultaneously.
It wouldn't have worked, but it was kind of a fun idea.

Pat


A sufficient battery or array of green power lasers in the commercial
range of several watts each, as such could rather easily make a
sustained 100 km diameter spot on the physically dark lunar surface
visible to the naked human eye, although red lasers would actually
reflect more efficiently. Laser tracking would be most difficult for
the majority of the public armatures, but not insurmountable.

Using 1/10 second pulsed laser shots at much greater intensity would
be more doable.
.. - Brad Guth
 




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