Dear Group,
For the two following SRM proposals:
1/ orbital sunshades
2/ marine cloud brightening
Can please some one list:
a) the comparative costs
b) the technical feasibility
c) the possibilities of rapid reversibility
d) and the pros & cons
Thanks
R. de Richter
2016-12-14 3:55 GMT+01:00 Michael Hayes <voglerl...@gmail.com>:
Hi Folks,
The problem of launching such massive weight, if solved, would itself
provide a great deal of climate change mitigation/adaptation benefits
beyond Dyson Dots. And so, it is the launch economics which is my
primary focus concerning any space based system. Interestingly,
trans-atmospheric tubes are being proposed for use as heat transfer
systems and the basic conduit design may actually lend itself to the
creation of an atmospherically shielded launch system.
In brief, we have the high-tech materials/control systems needed for
the heat transfer conduit and could install any one of a number of
candidate propulsion systems in the heat tube for launching payloads.
Simply eliminating air resistance during launch can go a long way in
reducing costs. With proper funding such a launch system could be field
tested within a few years.
Michael
On Tuesday, December 13, 2016 at 6:13:42 PM UTC-8, Robert G Kennedy
III, PE wrote:
No, Andrew it would be rather short-lived, decades, say, and even that
would require active position maintenance. Remember, the
sausage-shaped
region around L1 is metastable, not truly stable. So something has to
work, albeit not very hard but all the time, to keep itself there. But
at least the "fuel" would be free--the sails would manipulate the very
photons they're intercepting to keep thmselves on station.
Modulating the shade Earth gets is a totally reversible process, just
like the natural Solar Max/Min. The effect of a school the size of
Texas (say, 1,000,000 km^2) is about 1 part in 400, roughly 3X the
magnitude of the existing Solar Max/Min cycle, which is 1 part in a
1000. To reduce or turn off the cooling effect, the authorities simply
shift the parasol a few 10's of thousands of km sideways off the
Sun-Earth line. Such a shift is small compared to the zone of
metastability around L1, which is on the order of a few 100,000 km
transverse dimension by maybe 1,000,000 km long.
The umbral shadow cone peters out long before it reaches the Earth.
The
shadow that reaches the earth is penumbral, not umbral. At such a
range
(Mike is correct, L1 is 1.5M km from us, and the shades would orbit
some
distance even further inside that), the shading is uniform across the
shadow. Very light, about 1 part in 400, which would not even be
perceptible on bare skin. I think it is important that any
intervention
be minimally intrusive, and that it be as uniform across the world.
For
worldwide political acceptance, climate engineering must not be more of
a burden on some than on others. Which is why I am quite skeptical
about regional solutions--that way lies mischief.
L1 is far far away from traffic lanes for spacecraft. Nothing goes
there now except the occasional solar observatory, and no one is likely
to go there unless it's the construction crew to deploy these things.
Also, the velocity gradients around any libration point are very
shallow. The relative velocity of objects moving in halo orbits around
the Lagrangian points would be on the order of meters or tens of meters
per second. A very slow motion ballet.
Robert G. Kennedy III, PE
www.ultimax.com
1994 AAAS/ASME Congressional Fellow
U.S. House Subcommittee on Space
On 2016-12-13 17:19, Andrew Lockley wrote:
Such a system may outlast civilisation. How would it self correct or
self destruct as CO2 levels fell?
Would it endanger observational satellites or passing spaceships?
A
On 13 Dec 2016 22:13, "Michael MacCracken" <mmac...@comcast.net>
wrote:
Dear Robert--Very interesting. Given the time scale involved, maybe
what to be thinking about, in global climate intervention sense, is
stratospheric aerosols first as this can be done quickly, but they
have
a number of disadvantages, including the problem that backscattering
is
only about 10% efficient--so about 10 times as much energy is taken
out
of the direct beam and into the forward scattering part of the beam,
are limited as the need to reflect more energy rises to counterbalance
an ongoing GHG increase, etc., and then Dyson Dots are the exit
strategy, there problem being that it will take longer than we can
wait
to get started, but they do not have the forward scatter problem nor
is
there the limit on how large the intervention can be once one builds
such a system--plus their effect can be more easily varied in time.
And actually, if one wants a really systematic approach, one would
start by limiting regional influences using tropospheric approaches to
gain a better understanding, etc., then work up to stratospheric
aerosols and then to Dyson dots.
Mike MacCracken
On 12/13/16 3:57 PM, ro...@ultimax.com wrote:
Hi, there, everybody and greetings from Dar es Salaam. I'm here in
Tanzania on a geothermal job.
Over a year ago, I posted a PDF of the full paper from JBIS to this
group, but no comment ensued. Look for the keywords "Dyson Dots".
We (R.G.Kennedy, E.Hughes, K.I. Roy, D.E.Fields) have been working on
this for ~16 years, and published in Acta Astronautica, JBIS, the
Russian Academy of Sciences/Rosgidromet, Stanford's EE380 lecture
series, Asilomar, and many other venues. A couple months ago, Mr.
Bart
Leahy reached out to us to do a more popular treatment of the subject.
Yes, Dr. McCracken, Jim Early is fully aware of our work and was in my
living room in Oak Ridge TN two years ago in November 2014, where he
got to meet all the authors of that latest version "Dyson Dots". It
was
on the 25th anniversary, to the hour, of the Wall coming down. Kinda
cool evening, that.
A couple important points about orbital dynamics, and one about cost,
that Mr. Leahy didn't have room to cover in a mere 1000-word limit:
(1) a fleet of sunshades is not *at* L1, they go around the Sun in
"radiation-levitated non-Keplerian orbits" significantly inside of L1,
1-2 million km depending on their specific mass density [kg/m^2]. The
lighter a sunshade-sail is, the further inside it has to go. Wherever
that point is, four forces in metastable balance: the two opposing
gravitational pulls of the Earth and the Sun, the centripetal force of
the shade's path around the Sun, and light pressure.
(2) L1, L2, and L3, and the regions of space near them, are
metastable,
not truly stable like L4 and L5. Therefore, the sunshade must
continually monitor and adjust its position, by modulating light
pressure. The Japanese IKAROS sail of 2010? showed that that is
possible.
(3) Using the space launch methods that we are limited to today, and
building a fleet of shades big enough to do the job (collective
shading
area is the size of Texas, mass of a good 100 megatonnes) with only
terrestrial resources, would be fabulously expensive. Multiples of
gross world product. Therefore, either these things get built in
space
with offworld materials, or they don't get built at all.
Most geoengineering schemes are invoked by some kind of fiat. The
clean-power-from-space facet of Dyson Dots is a way we proposed for
the
scheme to organically pay for itself. HELIOS is just the sunshading
part, i.e., Dyson Dots with the space-based power element removed.
Robert G. Kennedy III, PE
www.ultimax.com
1994 AAAS/ASME Congressional Fellow
U.S. House Subcommittee on Space
[snippissimo]
--
Robert G Kennedy III, PE
www.ultimax.com
--
You received this message because you are subscribed to the Google
Groups "geoengineering" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to geoengineering+unsubscr...@googlegroups.com.
To post to this group, send email to geoengineering@googlegroups.com.
Visit this group at https://groups.google.com/group/geoengineering.
For more options, visit https://groups.google.com/d/optout.
