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Moon Base L2 for Solar Sail Assembly Line



 
 
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  #4  
Old February 8th 16, 03:42 PM posted to sci.space.policy
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Default Moon Base L2 for Solar Sail Assembly Line

On Monday, February 8, 2016 at 8:26:44 AM UTC-5, Greg (Strider) Moore wrote:
"Alain Fournier" wrote in message ...

On Feb/7/2016 7:53 PM, wrote :
Moon Base L2
Douglas Eagleson


I read somewhere that L2 was to be usable for launching solar sails. L2
is the geostationary
lagrangian point on the far side of the moon.

I was rumaging the issue. L2 exhibits a well like location behavior. An
object placed there tends to settle.


No. L2 is an unstable equilibrium point. An object placed there will tend
to drift away. An object can be kept there with minimal station keeping to
maintain position. Only L4 and L5 have stable equilibrium.


Alain Fournier


Wikipedia seems to indicate otherwise, and this is my recollection as well:

https://en.wikipedia.org/wiki/Lagran...ipotential.jpg




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Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net


Thanks for the reference. Just to clarify. The well field occurs when the moon is on the moon-earth-sun centerline. It is a window of usable proportions. It is a matter of the distortion of the centering forces.

L4 and L5 are also transiently existing.

L4 is also a good point to launch solar sails. Or is it? They are theory fields of enticement only. But boosting a solar sail from low earth orbit up to L4 is also the transient field usage. It is a big deal to define the points of minimal energy usage to leave the earth-moon system.
  #5  
Old February 9th 16, 05:54 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default Moon Base L2 for Solar Sail Assembly Line

In article . com,
says...

L4 is also a good point to launch solar sails. Or is it?


Since there isn't even a McDonalds there, what is the point of staging a
launch at a LaGrange point since you'll need to spend fuel to get there,
so there are no real savings and no resources there. And bring supplies
there will cost a lot more fuel, and any EVA there also has the
radiation problem since you're above Van Allen.


Setting aside the issue of lack of a stable point or orbit around L2 for
a moment...

If you're using materials (including fuel and oxidizer) obtained from
the moon, there could be an advantage because the moon's gravity is far
less, so it ought to take much less delta-V to take materials from the
lunar surface to L2 than from the earth's surface to L2.

In LEO, you have a constant sun/dark cycle every 90 minutes. This lets
you charge batteries and then cool down 45 minutes later when it goes dark.


This also creates all sorts of cyclic thermal stresses to deal with. It
also means you need fairly heavy batteries to store electricity when
your solar arrays are in darkness. Plus, if you assemble a frail craft
like a solar sail in LEO, getting it out of LEO and through the van-
Allen radiation belts quickly is a problem.

What sort of orbital periods are we talking about at LaGrange ? What
percentage of time is spent in the dark vs sun ? Would there be issues
with cooling (long periods of sun) or battery autonomy (long periods of
dark) ?


Put it in a halo orbit around L2 and you'd have virtually no periods of
darkness. People have thought about these things and written papers on
the subject:

A Lunar L2 Navigation, Communication, and Gravity Mission
Keric Hill, Jeffrey Parker, George H. Born, and Nicole Demandante
University of Colorado, Boulder, Colorado 80309
http://ccar.colorado.edu/geryon/pape...AA-06-6662.pdf

Jeff
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These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #6  
Old February 9th 16, 06:02 PM posted to sci.space.policy
Rick Jones[_6_]
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Default Moon Base L2 for Solar Sail Assembly Line

Jeff Findley wrote:
Plus, if you assemble a frail craft like a solar sail in LEO,
getting it out of LEO and through the van- Allen radiation belts
quickly is a problem.


Are materials commonly considered for solar sails that sensitive to
radiation, or is it more just a slow trip through the belts in general
and the effects on the electronics whether the propulsion was solar
sail or not?

rick jones
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these opinions are mine, all mine; HPE might not want them anyway...
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  #8  
Old February 9th 16, 10:06 PM posted to sci.space.policy
Bob Haller
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Posts: 3,197
Default Moon Base L2 for Solar Sail Assembly Line

On Tuesday, February 9, 2016 at 11:55:35 AM UTC-5, Jeff Findley wrote:
In article . com,
says...

L4 is also a good point to launch solar sails. Or is it?


Since there isn't even a McDonalds there, what is the point of staging a
launch at a LaGrange point since you'll need to spend fuel to get there,
so there are no real savings and no resources there. And bring supplies
there will cost a lot more fuel, and any EVA there also has the
radiation problem since you're above Van Allen.


Setting aside the issue of lack of a stable point or orbit around L2 for
a moment...

If you're using materials (including fuel and oxidizer) obtained from
the moon, there could be an advantage because the moon's gravity is far
less, so it ought to take much less delta-V to take materials from the
lunar surface to L2 than from the earth's surface to L2.

In LEO, you have a constant sun/dark cycle every 90 minutes. This lets
you charge batteries and then cool down 45 minutes later when it goes dark.


This also creates all sorts of cyclic thermal stresses to deal with. It
also means you need fairly heavy batteries to store electricity when
your solar arrays are in darkness. Plus, if you assemble a frail craft
like a solar sail in LEO, getting it out of LEO and through the van-
Allen radiation belts quickly is a problem.

What sort of orbital periods are we talking about at LaGrange ? What
percentage of time is spent in the dark vs sun ? Would there be issues
with cooling (long periods of sun) or battery autonomy (long periods of
dark) ?


Put it in a halo orbit around L2 and you'd have virtually no periods of
darkness. People have thought about these things and written papers on
the subject:

A Lunar L2 Navigation, Communication, and Gravity Mission
Keric Hill, Jeffrey Parker, George H. Born, and Nicole Demandante
University of Colorado, Boulder, Colorado 80309
http://ccar.colorado.edu/geryon/pape...AA-06-6662.pdf

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.


space xs lower cost to orbit may make doing things on cite more costly
  #10  
Old February 10th 16, 07:32 AM posted to sci.space.policy
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Default Moon Base L2 for Solar Sail Assembly Line

Will we even be using Solar Sails in the future, or will they be superceded by E-Sails?:

http://www.space.com/31063-electric-...ploration.html

Quote:

"The HERTS team's work suggests that e-sailing craft can continue accelerating
far beyond the point that solar-sail probes lose steam, Johnson said. For this
reason, an e-sail could get a probe out to the heliopause -- the edge of the
sun's sphere of influence, where the solar wind hits the interstellar medium --
in 10 years, twice as fast as a solar sail could, HERTS team members have said."

 




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