Spaceflight Insider

Researchers investigating large sunshades to combat global warming

Earth via Exp47

Photo Credit: NASA

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, based on a 1984 paper by scientist and science fiction author Robert L. Forward among others cited below, 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.

L1 Sunshades

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

“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.

Additional Reading

Forward, R.L. 1984. “Roundtrip Interstellar Travel Using Laser-Pushed Lightsails,” J. Spacecraft, Vol 21, March April. pp. 187ff
Early, J. T., 1989: Space-based solar screen to offset the greenhouse effect, Journal of the British Interplanetary Society 42, 567-569.
Roy, Ken. I. 2001. “Solar Sails: An Answer to Global Warming?” presented at STAIF 2001 Albuquerque NM February 11-14.)

Angel, R., 2006: Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1), Proceedings of the National Academy of Sciences 103, 17184-17189

Genta, Giancarlo, ed. K.I. Roy, R.G. Kennedy and D.E. Fields. “Dyson Dots”. Proceedings of the Seventh IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions: Missions  to  the  outer  solar  system  and  beyond. International Academy Of Astronautics, Aosta, Italy,    July 11-14, 2011.
This article was edited at 4:06 p.m. EDT on Thursday, Jan. 5 2017 to update the original source of the technical concept and to include additional sources.

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Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.

Reader Comments

Sounds very nice but it’s way too late. The ice cap is melting and teh methane release has begun.

How about using asteroid material? Is that what the article meant when it spoke of off-world manufacturing? There must be a reason why no one speaks of an orbiting shield around the world. A band of dust like Saturn’s rings or even other orbits. That should be a lot cheaper and controllable.

Ben Helvensteijn

Ever heard of styrofoam? It falls apart in unnamed numbers of little spherules. Murphy’s Law next to guarantees that a similar outcome results for these large reflectors, ending up as what could be called the man-made snipbits belt.
I dare anyone to argue that such is not going to happen after years of bombardment by high energy radiation.
Given that predictable outcome, the ‘quickly reversible’ argument guaranteed befalls the same fate as described above for these “fancy” shields.

The “Dyson Dot”swarm is an interesting variant on the traditional Megastructure model for the ‘parasol’concept. However, do we need to posit a hands-on construction site for this? How about:

Park a base/hub at the L1 point between Earth and Sol (wouldn’t need more than a few solar-electric thrusters and some attitude wheels to maintain station-keeping). Unfold an orb-spinner-like scaffold around it, and activate a semi-autonomous swarm of bots that use a [insert results of Materials Engineering research] substrate to fab an ever-expanding shade, slinging substrate refill pods as needed, to rendezvous autonomously with the thing.

Over time, largely hands-off, it grows to the desired dimensions, slowly enough to measure the effects here on the homeworld.

The beauty of this is that it is wholly non-invasive on the biosphere, and it could be designed such that sections of it would have the ability to fold back and so dynamically regulate the amount of solar flux that gets intercepted, so you don’t have to Commit to any given value (since complex systems like climate are *inherently* unpredictable in detail).

That’s the Meat. Here’s the gravy:

Cover the Sunward-facing side of it with solar collectors, and fit the earth-facing side of the hub with microwave emitters (probably have to collimate them as masers, given the range), aimed at rectenna arrays in high polar orbits, which then beam power more precisely to groundside receivers. Now you’ve got a power source to make Freeman Dyson grin!

Sure, energy wastage would be appalling, but even the comparative trickle that reaches us would be Game-Changing. This would remain the case, even with the power you’d have to divert to the solar-electric thrusters that would be needed to compensate for how very badly it would want to become a big-ass solar sail, headed our way (but, lest this make folks nervous, we’re talking about something that, while many, MANY klicks across, would still be flimsy enough that it’d do little more than make a SUPERB fireworks display were it to hit atmo).

Extra-EXTRA gravy: the whole business would be inherently well-suited to charge up as a honking big electromagnet, providing an added level of protection (in addition to earth’s native magnetosphere) against solar flares and CMEs, deflecting inbound solar particles to the benefit of earthbound and orbital assets.

Shiny, eh?

Whoops! Almost forgot:that big power-transmitting maser could be angled off-axis, should it be required to ablate the surface of (and thus, in effect, create remote “thrusters” on) any pesky primordial orbiting ordnance that might wanna go all
Chicxulub on our buttocks).

Reckon it could also give a nice long boost to a sail-based interstellar probe we might want to use to send a care package to the Na’vi or somesuch…

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