reflecting sunlight onto the Moon?

Here's an off-the-cuff thought which I lack the expertise to answer in
any detail:

What would it take to focus & reflect sunlight on a lunar colony from a
series of orbiting lunar satellites? I'm imagining something where one
satellite comes over the horizon, focuses light onto our moon base
(which is in the dark of course), then as it goes down, another
satellite comes up and takes over the job. (I'm assuming these
satellites have to be in a fairly low orbit since otherwise you wouldn't
be able to focus the light to sufficiently small spot.)

I'm willing to accept a period of darkness when the satellite over the
horizon passes through the Moon's shadow. I'm just trying to get some
light (and therefore heat and power) to the base for the majority of the
lunar night.

Can anyone fill in some more details for this idea?

Thanks,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

Joe Strout wrote:
Here's an off-the-cuff thought which I lack the expertise to answer in
any detail:

What would it take to focus & reflect sunlight on a lunar colony from a
series of orbiting lunar satellites? I'm imagining something where one
satellite comes over the horizon, focuses light onto our moon base
(which is in the dark of course), then as it goes down, another
satellite comes up and takes over the job. (I'm assuming these
satellites have to be in a fairly low orbit since otherwise you wouldn't
be able to focus the light to sufficiently small spot.)

Why?

I'm willing to accept a period of darkness when the satellite over the
horizon passes through the Moon's shadow. I'm just trying to get some
light (and therefore heat and power) to the base for the majority of the
lunar night.

Oh.

Can anyone fill in some more details for this idea?

It may be a case of filling in the hole for it to be buried in.
It's got some problems.
The moon has a diameter of 2000Km.
So, at best the light has to come at midnight around 2000Km.
The suns rays diverge at an angle of .01 radians, so the image of the
sun will be at least some 20Km in diameter by the time you get to the
base.
This is a good match only if your base is some 20Km square, using some
400Gw of power.
The reflectors on the satellites would need to be around 30Km or so
across.
This has big nasty problems from masscons in the moon.

What about another way.
If you built a polar station, you could probably get by with a string
of reflectors in polar orbit.

A 200m spot of sunlight, of some 30Mw power seems more likely
for a near-term base.
This can't be sent from much over 20Km distance.
Orbital velocity on the moon is around 2Km/s, so a reflector will be
in view for some 10 seconds, so you need some 180 of them.

The really horrible problem is how do you accurately slew a mirror
200m wide by well over 90 degrees in 10 seconds.
Add to this that you'r going to be needing large amounts of thrust
to keep in a 20Km orbit, and things just go downhill.

The moonbase on a circular railroad track around the moon starts to
look good

Joe Strout wrote:
Here's an off-the-cuff thought which I lack the expertise to answer in
any detail:

What would it take to focus & reflect sunlight on a lunar colony from a
series of orbiting lunar satellites? I'm imagining something where one
satellite comes over the horizon, focuses light onto our moon base
(which is in the dark of course), then as it goes down, another
satellite comes up and takes over the job. (I'm assuming these
satellites have to be in a fairly low orbit since otherwise you wouldn't
be able to focus the light to sufficiently small spot.)

I'm willing to accept a period of darkness when the satellite over the
horizon passes through the Moon's shadow. I'm just trying to get some
light (and therefore heat and power) to the base for the majority of the
lunar night.

Can anyone fill in some more details for this idea?


I'd vote for an sps satellite parked at the L1 point where they're
hoping to send the James Webb scope. That might be useful for colonists
during the long lunar night.



--
Hop David
http://clowder.net/hop/index.html

"Hop David" wrote in message ...

What would it take to focus & reflect sunlight on a lunar colony from a
series of orbiting lunar satellites? I'm imagining something where one
satellite comes over the horizon, focuses light onto our moon base
(which is in the dark of course), then as it goes down, another
satellite comes up and takes over the job. (I'm assuming these
satellites have to be in a fairly low orbit since otherwise you wouldn't
be able to focus the light to sufficiently small spot.)

I'd vote for an sps satellite parked at the L1 point where they're
hoping to send the James Webb scope. That might be useful for colonists
during the long lunar night.


The JWST is going to be parked at the Solar L2 point, 1.5 million km
out from the Earth-Moon barycenter, not the Lunar L1.


But I agree that an solar power satellite in L1, where there is always
sunlight except during Lunar and Solar eclipses, makes the most sense.
It would beam down the energy as short-wavelength microwaves. (You
don't need to use the wavelenghts you'd use on Earth because there's
no atmosphere to penetrate, so the rectenna could be smaller.)


I've read a few chapters from the Lunar Base Handbook, and one project
estimate is that the solar panels needed for supplying an initial base
would weigh only a ridiculous 1t while the equipment needed to *store*
enough power for surviving the Lunar night would weigh about 45t.

So finding a spot that's perpetually in sunlight isn't such a bad
idea, be it a mountain on the south pole or L1...



--
__ "A good leader knows when it's best to ignore the __
('__` screams for help and focus on the bigger picture." '__`)
//6(6; ©OOL mmiv :^)^\\
`\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/'

Ool wrote:
"Hop David" wrote in message ...


What would it take to focus & reflect sunlight on a lunar colony from a
series of orbiting lunar satellites? I'm imagining something where one
satellite comes over the horizon, focuses light onto our moon base
(which is in the dark of course), then as it goes down, another
satellite comes up and takes over the job. (I'm assuming these
satellites have to be in a fairly low orbit since otherwise you wouldn't
be able to focus the light to sufficiently small spot.)


I'd vote for an sps satellite parked at the L1 point where they're
hoping to send the James Webb scope. That might be useful for colonists
during the long lunar night.



The JWST is going to be parked at the Solar L2 point, 1.5 million km
out from the Earth-Moon barycenter, not the Lunar L1.

Doh! What was I thinking. Yes, right you are.



But I agree that an solar power satellite in L1, where there is always
sunlight except during Lunar and Solar eclipses, makes the most sense.
It would beam down the energy as short-wavelength microwaves. (You
don't need to use the wavelenghts you'd use on Earth because there's
no atmosphere to penetrate, so the rectenna could be smaller.)


I've read a few chapters from the Lunar Base Handbook, and one project
estimate is that the solar panels needed for supplying an initial base
would weigh only a ridiculous 1t while the equipment needed to *store*
enough power for surviving the Lunar night would weigh about 45t.

So finding a spot that's perpetually in sunlight isn't such a bad
idea, be it a mountain on the south pole or L1...

Is there such a mountain?



--
Hop David
http://clowder.net/hop/index.html

Ool wrote:
snip
I've read a few chapters from the Lunar Base Handbook, and one project
estimate is that the solar panels needed for supplying an initial base
would weigh only a ridiculous 1t while the equipment needed to *store*
enough power for surviving the Lunar night would weigh about 45t.

Solar panels are running at approaching 200W/Kg for the cutting-edge
designs (zero G)

100Kw (average) isn't a very huge amount of power.
For example, if you were wanting to run a greenhouse on it, it's enough
to light a room 10 meters square or so at a bit less than sunlight.

Heating and air conditioning can easily use this sort of power, not
to mention energy intensive stuff like trying to process crust.

The night is about a megasecond, so you'd need 100GJ of storage.
This is some 130t using lithium-ion cells. (good for over a decade)

So finding a spot that's perpetually in sunlight isn't such a bad
idea, be it a mountain on the south pole or L1...

"Hop David" wrote in message ...
Ool wrote:

So finding a spot that's perpetually in sunlight isn't such a bad
idea, be it a mountain on the south pole or L1...

Is there such a mountain?


I think the highest spots along the crater rims are in sunlight 86% of
the time. That would be 24 Earth days of light, 4 days of darkness.
It would diminish the need for heavy batteries or flywheels considera-
bly...

But I'm not sure you could get that much sunlight all in one spot and
wouldn't have to connect several sites with kilometers of power ca-
bles...

(It also depends on whether it's Lunar summer or winter. The Moon's
axial tilt is 1.6°.)


--
__ "A good leader knows when it's best to ignore the __
('__` screams for help and focus on the bigger picture." '__`)
//6(6; ©OOL mmiv :^)^\\
`\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/'

In article ,
Hop David wrote:
So finding a spot that's perpetually in sunlight isn't such a bad
idea, be it a mountain on the south pole or L1...

Is there such a mountain?

Nobody is certain, actually. We do not have good topographic maps of the
lunar polar regions. (Clementine's elliptical orbit never passed low
enough over the poles to get laser-altimeter data there.) Nor do we have
good overhead photography over the full range of lunar seasons -- the Moon
*does* have a little bit of axial tilt, so a mountain that's in continuous
sunlight in polar summer might get some darkness in polar winter.

Even if you can't get continuous light on the surface, you can probably
come close enough that a modest tower would put a solar array up in
continuous light.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

is there no advantage to using a nice nuclear reactor to provide power?..
perhaps use solar heat for processing ores etc.. then take a break during
the dark period.

I would want redundant reactors for life support..

On Fri, 07 May 2004 15:45:31 -0500, Joe Strout wrote:

What would it take to focus & reflect sunlight on a lunar colony from a
series of orbiting lunar satellites?

Herm
Astropics http://home.att.net/~hermperez

"Ian Stirling" wrote in message ...
Ool wrote:

I've read a few chapters from the Lunar Base Handbook, and one project
estimate is that the solar panels needed for supplying an initial base
would weigh only a ridiculous 1t while the equipment needed to *store*
enough power for surviving the Lunar night would weigh about 45t.

Solar panels are running at approaching 200W/Kg for the cutting-edge
designs (zero G)

100Kw (average) isn't a very huge amount of power.
For example, if you were wanting to run a greenhouse on it, it's enough
to light a room 10 meters square or so at a bit less than sunlight.

The concept of a *first* base would include bringing one's own junk
food.

Heating and air conditioning can easily use this sort of power, not

The idea is to live in an inflatable habitat buried under an insulat-
ing layer of regolith. (Which is very insulating. Only about half a
meter down in the ground there's a stable -20°C, as opposed to -140°C
or +100°C on the surface.)

to mention energy intensive stuff like trying to process crust.

That would be done during the day, using solar electric and solar
thermal energy.

The night is about a megasecond, so you'd need 100GJ of storage.
This is some 130t using lithium-ion cells. (good for over a decade)

If there is a simple way of fusing regolith into highly thermally con-
ductive slabs of black glass it could possibly be used for a heat
source (or, alternatively, a heat sink) that would stay warm (or cold)
all during the night (or day) by exposing it during the day (or night)
while covering it up the rest of the time with insulating metal foil
and/or regolith.

Such a solution would have the advantage of being rather low-tech and
of not requiring much mass from Earth by making use of Lunar material
for energy storage in the form of temperature difference...



--
__ “A good leader knows when it’s best to ignore the __
('__` screams for help and focus on the bigger picture.� '__`)
//6(6; ©OOL mmiv :^)^\\
`\_-/ http://home.t-online.de/home/ulrich....lmann/redbaron \-_/'