Researchers investigating large sunshades to combat global warming
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.
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.
“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.
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
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.