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
On Monday, December 12, 2016 at 1:58:24 PM UTC-5, Andrew Lockley wrote:
http://www.spaceflightinsider.com/missions/commercial/researchers-investigating-large-sunshades-combat-global-warming/
<http://www.spaceflightinsider.com/missions/commercial/researchers-investigating-large-sunshades-combat-global-warming/>
RESEARCHERS INVESTIGATING LARGE SUNSHADES TO COMBAT GLOBAL WARMING
BART LEAHY
DECEMBER 11TH, 2016
A group of concerned engineers and scientists is investigating a
space-based method to offset global warming. Their concept is called
Heliocentric Earth-Lagrangian Interception of Sunlight (HELIOS), a
flotilla of perhaps many thousands of kilometer-square sun sails
that,
once placed at the Sun-Earth Lagrange (SEL1) point, would reduce the
amount of sunlight striking the Earth.
THINKING BIG
________________________________
HELIOS was born out of a pair of papers presented at the Tennessee
Valley Interstellar Workshop (TVIW) and later in the Journal of the
British Interplanetary Society (JBIS). Those papers focused on
geoengineering, the deliberate large-scale modification of the
Earth’s
climate through artificial means. Arguably, human beings have already
been performing accidental geoengineering over the last 200 years by
increasing the amount of carbon dioxide in the atmosphere through
burning fossil fuels.
The paper presenter, Robert G. Kennedy III, proposed building “Dyson
Dots” – a much smaller version of a conceptual swarm of solar
collectors proposed by physicist Freeman Dyson to capture the entire
energy output of a star, now called a “Dyson Sphere”.
These “dots” would consist of multiple reflectors and block an area
approximately 386,000 square miles (over 1,000,000 square kilometers)
in extent, nearly the size of the state of Texas. The reflectors
would
be placed near L1 to ensure a stable orbit. At this distance, the Dot
would reduce the amount of sunlight (insolation) the Earth
receives by
as much as one-quarter of one percent. Is that enough to make a
difference? Kennedy and the other members of the HELIOS team think
so.
image:
http://www.spaceflightinsider.com/wp-content/uploads/2016/12/L1-Positioning-655x346-1.png
<http://www.spaceflightinsider.com/wp-content/uploads/2016/12/L1-Positioning-655x346-1.png>
Large sunshades placed at the Sun-Earth Lagrange Point 1 (L1 in this
image) could reduce the amount of sunlight Earth receives by just
enough to offset any effects caused by global warming. Image Credit:
R. Kennedy / Ultimax Group and D. Hughes / www.debbiehughes.com
<http://www.debbiehughes.com>
“This reduction would bring down Earth’s average global
temperature by
as much as 2.7 degrees Fahrenheit (1.5 degrees Celsius),
approximately
the same change that brought about the “Little Ice Age”
(approximately
1550–1850 C.E.).”
The goal is not to produce an ice age. Instead, HELIOS would combat
the anticipated global temperature rise by precisely offsetting it
with artificial cooling.
THE BIG PICTURE
________________________________
“The initial study assumed the shade just appeared, all in one
piece,”
Kennedy explained. “In reality, it will be assembled from smaller
sunshades. Nobody’s going to build a 100-megatonne piece of tinfoil
the size of Texas in one go, especially the first time. An actual
project would be incrementally built, incrementally deployed, incur
[an] incremental expense, and yield incremental benefits.”
In the long term, learning to build megastructures like the Dyson Dot
would advance the progress of solar-sail propulsion. Solar sails are
one possible method of transport within the solar system and to other
stars.
“Also, we’re certain the sunshades would have to be manufactured in
space, with off-world resources,” Kennedy said.
HELIOS could spur the in-space economy, as it will require access to
in situ magnesium – which is three times more common off Earth than
aluminum – as well as silicon, carbon, and iron. In addition to
resources, of course, the array requires advanced, industrial-scale
in-space manufacturing capabilities.
Lastly, a Dyson Dot could act like a conventional household or
satellite solar panel, converting solar radiation into electricity.
The solar energy collected from the Dyson Dot network could be
transmitted to Earth through space via a series of relays, supplying
over 10,000 gigawatts per year – Earth’s entire electric power
demand.
Before that, HELIOS, the first-generation sunshield without the power
generation capability, has to help address the global warming
problem.
HELIOS’ NEXT STEPS
________________________________
Obviously, a project as ambitious as HELIOS will be difficult and
expensive, so the group’s initial priority will be financing. This
means attracting the interest of venture capitalists or angel
investors as well as getting their ideas into the public
consciousness
(full disclosure: the author of this article is the HELIOS team’s
outreach consultant).
Technically, the initial steps for developing HELIOS will include
defining the system architecture, defining its physical
characteristics, and determining its actual environmental
performance.
The team will also need to do a due-diligence review on the system.
For example, they must determine the Technology Readiness Level (TRL)
of the major system components and develop a roadmap for development
and TRL advancement.
Along the way, the team will develop multiple deployment strategies
for the sunshade, looking for incremental, affordable ways to do it.
Once the high-level strategizing is complete, the HELIOS team will
focus on developing proof-of-concept technologies, such as packaging
and deployment mechanisms for large-scale solar sails. And – of
interest to any investors – they need to provide a solid estimate of
benefits, implementation costs, and timeline.
How much would the overall system cost? That’s one of the things the
initial architecture studies will determine.
“Odds are, with current lift methods, the cost would be astronomical,
though it would probably still be cheaper than moving everybody on
the
seacoasts 50 miles inland as sea levels rise,” said HELIOS team
member
Ken Roy.
A space-based geoengineering solution to global warming could be done
incrementally and, more importantly, could be quickly reversible
should any negative side effects arise along the way.
Obviously, the HELIOS team is taking the long view, but their
proposed
hardware offers the long-term potential to address both global
warming
and future energy production. A healthy planet with abundant energy
for future generations, they maintain, would be an excellent
return on
investment.
Individuals interested in working with the HELIOS group can contact
Robert Kennedy or Victoria Coverstone.
Read more at
http://www.spaceflightinsider.com/missions/commercial/researchers-investigating-large-sunshades-combat-global-warming/#iy0q5rLvBB60aB7V.99
<http://www.spaceflightinsider.com/missions/commercial/researchers-investigating-large-sunshades-combat-global-warming/#iy0q5rLvBB60aB7V.99>
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