Low Mass Spinning Space Mirrors

13 views
Skip to first unread message

John Hampson

unread,
Apr 21, 2009, 9:17:32 AM4/21/09
to geoengineering
The idea of reflecting sunlight using mirrors at the Earth-Sun L1
Lagrange point is well established. It appears to be based on
manufacturing mirrors on the Moon from refined regolith and launching
them for assembly at L1: this is to reduce the launch costs of a
massive mirror.

But has consideration been given to launching very low mass mirrors
directly from Earth? Many large mirrors (say 100m diameter) made from
thin reflective sheet (like space blanket) could be launched directly
from Earth. The problems arise when you try to wallpaper a vacuum
with them and then maintain their shape, orientation and position.

A rotating space-station, similar to the one in the film 2001 could be
used for this purpose. The sheet would be unfurled across the sunward
face of the space station and the rotational forces would stretch and
maintain the mirrors shape, keeping it rigid. Once the mirror was
stable the space station would detach and move on to the next piece of
vacuum to be wallpapered, leaving hundreds of spinning mirrors in its
wake.

Two types of mirror might be considered. A “passive mirror” would
float away to be recovered and reused once out of position. To
maintain its orientation it could be convex shaped against the solar
wind and it might initially be launched against the solar wind using
puffs of thruster gas from the space station to extend its life.

A better option would involve an “active mirror” having a number of
solar-powered miniature ion-thrusters installed around its outer
edge. These would maintain the mirrors rotation, orientation and
position in space. This would avoid (or at least reduce) the
hazardous activity of recovering out of position mirrors.

Active mirrors would be flexible because they could be remote-
controlled and might be useful in Earth orbit to reduce warming,
manipulate the weather and even replace street lighting in urban
areas. At Lagrange points L4 and L5 they could reflect sunlight
towards Earth in the event of cooling brought on by natural disaster
(volcanic eruption or asteroid impact).

A spinning Earth orbit space station built for scientific purposes
could include facilities to unfurl mirrors at relatively little extra
cost. An entire fleet of low mass mirrors sent to this station might
require less launch mass than is needed just to build a Moon base and
could be a flexible and relatively low cost means to control global
warming.

John Hampson

Alvia Gaskill

unread,
Apr 22, 2009, 4:33:06 AM4/22/09
to geoengineering
What you have described includes Roger Angel's proposal to launch
remote controlled refractors from the surface of the Earth to the L1
point. All of these ideas involve advanced technologies most likely
not available until the second half of the 21st century. Think about
how primitive the ISS and its associated delivery systems are and the
difficulty with launching and controlling satellites is today. I
hadn't seen the idea of increasing the amount of sunlight reaching the
Earth before as almost all of the current discussion is on reducing
sunlight. Boosting the solar radiation could be helpful in
terraforming other planets or moons and longer term may play an
important role in colonization of these worlds. What we learn from
geoengineering to stop global warming may pay dividends for thousands
of years.

Andrew Lockley

unread,
Apr 22, 2009, 5:34:52 AM4/22/09
to agas...@nc.rr.com, geoengineering
When Angel's idea was discussed on discovery channel, the idea was to use small and relatively fragile mirrors, which is fraught with problems.

Conversely, the thin, flexible films required for this technique are readily available, such as in the aptly-named 'space blankets' used for keeping disaster victims warm.  The material used for crisp packets (potato chips) also have the necessary properties.  Both are far stronger than would be needed for such an application. I'm unsure as to how thin and light such a material could be made. 

Making a large 'star' out of long strips of such a material should be relatively easy.  Small weights, similar to an electrical wire, could be fixed to the perimeter to keep the material taught as it spins.  The techniques for spinning-up satellites are well established, and even a low torque should result in a good unfurl given time.  Whether the resulting structure will 'drift' or 'wrinkle' remains to be determined.

I've always maintained a deep loathing for space-based geoengineering, as I've regarded it as an impractical fantasy.  However, when you consider  how lightweight and permanent such a structure could be, it doesn't seem quite so silly anymore.  In the short term, wrapping deserts and glaciers would obviously be cheaper, but the maintenance, degradation and environmental impacts would all be significant.  I think it would be worth considering how big a single star could be made.

I understand that it's possible to create small-scale experiments and piggyback them on existing missions.  Would this be one worth testing?

A

2009/4/22 Alvia Gaskill <agas...@nc.rr.com>

Ken Caldeira

unread,
Apr 22, 2009, 5:56:38 AM4/22/09
to andrew....@gmail.com, agas...@nc.rr.com, geoengineering
See attached and following for relevant discussion.

http://globalecology.stanford.edu/DGE/CIWDGE/labs/caldeiralab/Caldeira%20downloads/Teller_etal_LLNL231636_1997.pdf

___________________________________________________
Ken Caldeira

Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA

kcal...@ciw.edu; kcal...@stanford.edu
http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
+1 650 704 7212; fax: +1 650 462 5968  
Early_JBritInterplanetSoc1989.pdf

dsw_s

unread,
Apr 22, 2009, 8:20:54 PM4/22/09
to geoengineering
Having a mirror sit there doesn't seem more advanced than having life
support and equipment to do experiments with. Note also that part of
the reason launch costs are so high is that the payloads currently
worth launching are either people or very expensive one-of-a-kind high-
tech satellites, so the tolerance for failure is very low. Loosening
the requirements could give some cost savings.

On Apr 22, 5:56 am, Ken Caldeira
<kcalde...@globalecology.stanford.edu> wrote:
> See attached and following for relevant discussion.
>
> http://globalecology.stanford.edu/DGE/CIWDGE/labs/caldeiralab/Caldeir...
>
> ___________________________________________________
> Ken Caldeira
>
> Carnegie Institution Dept of Global Ecology
> 260 Panama Street, Stanford, CA 94305 USA
>
> kcalde...@ciw.edu; kcalde...@stanford.eduhttp://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
> +1 650 704 7212; fax: +1 650 462 5968
>
> On Wed, Apr 22, 2009 at 10:34 AM, Andrew Lockley
> <andrew.lock...@gmail.com>wrote:
>
> > When Angel's idea was discussed on discovery channel, the idea was to use
> > small and relatively fragile mirrors, which is fraught with problems.
> > Conversely, the thin, flexible films required for this technique are
> > readily available, such as in the aptly-named 'space blankets' used for
> > keeping disaster victims warm.  The material used for crisp packets (potato
> > chips) also have the necessary properties.  Both are far stronger than would
> > be needed for such an application. I'm unsure as to how thin and light such
> > a material could be made.
>
> > Making a large 'star' out of long strips of such a material should be
> > relatively easy.  Small weights, similar to an electrical wire, could be
> > fixed to the perimeter to keep the material taught as it spins.  The
> > techniques for spinning-up satellites are well established, and even a low
> > torque should result in a good unfurl given time.  Whether the resulting
> > structure will 'drift' or 'wrinkle' remains to be determined.
>
> > I've always maintained a deep loathing for space-based geoengineering, as
> > I've regarded it as an impractical fantasy.  However, when you consider  how
> > lightweight and permanent such a structure could be, it doesn't seem quite
> > so silly anymore.  In the short term, wrapping deserts and glaciers would
> > obviously be cheaper, but the maintenance, degradation and environmental
> > impacts would all be significant.  I think it would be worth considering how
> > big a single star could be made.
>
> > I understand that it's possible to create small-scale experiments and
> > piggyback them on existing missions.  Would this be one worth testing?
>
> > A
>
> > 2009/4/22 Alvia Gaskill <agask...@nc.rr.com>
>  Early_JBritInterplanetSoc1989.pdf
> 2766KViewDownload
Reply all
Reply to author
Forward
0 new messages