Space-Based Solar Power: Continuing the Renewable Revolution Published Aug. 22, 2024 By Maj. Justin Sadowski Wild Blue Yonder--Maxwell AFB -- A little over 50 years ago, the Arab oil embargoes of the 1970s shook the world’s developed economies and sent the US into a recession. These shockwaves convinced the US government to strive to avoid allowing its energy market to rely too heavily on a small number of foreign suppliers, especially those in volatile regions such as the Middle East. Although much of the US consumption of petroleum products goes toward transportation, some of it is burned to power our nation’s electrical grid. Fossil fuels (including natural gas and coal) are currently responsible for about 60% of the electrical generation in the US. They produce power by way of gas or steam turbine plants and possess a heavy carbon footprint. Even after years of investment, renewable energy production via solar and wind has only reached 14% of the total US electrical generation as of 2022 (which is the latest corrected full-year reported by the US Energy Information Agency – 2023’s data to be released Oct 2024).[1] Much of this interest/investment is in the hope that this “green” power will reduce the grid’s reliance on fossil fuels and drive toward solving climate change instead of contributing to it. However, the wind doesn’t always blow, and the sun occasionally disappears behind cloud cover, forcing power grids to rely on quick-reacting fossil fuel powerplants to shoulder the load. Even worse, as many an elementary student will point out, the sun tends to sink below the horizon in most parts of the US during the night. While some of these short-cycle natural constraints can be ameliorated by grid-level energy storage, long-cycle or seasonal effects will still challenge a grid that is largely reliant upon wind and traditional solar power. While there are many on-going debates as to how to update the grid to be both resilient and carbon-neutral, they tend to revolve around other forms of terrestrial-based power generation (such as nuclear or hydro pumped storage). As it turns out, part of the solution may come from above – through space-based solar power (hereafter referred to as simply ‘space solar’). Outside the Earth’s atmosphere, solar collection can continue unperturbed by weather effects, seasonal orbital fluctuations, and attenuation/reflection by the atmosphere. According to NASA, only about half of the solar irradiance that reaches Earth makes it to the surface,[2] so why not harvest this energy on the other side of this barrier? At first blush, the engineering challenges of fielding a grid-scale on-orbit power farm seem laughably daunting. After all, how much steel would it take to run a high-voltage power line to a geosynchronous satellite? For those with a penchant for ridiculous math, long-line transmission cables are mostly aluminum, with less-conductive but higher-strength steel used for the core, so you’re looking at “only” around 180,000 kg of cable. And what about the expense of space launch? It would be quite reasonable for one to think that these hurdles would keep any concepts of space solar purely within the realm of science fiction. However, three revolutions in engineering are making space solar not just achievable, but an important consideration in the future power generation architecture discussion. First, space launch costs continue to fall thanks to the work of the private sector (e.g. SpaceX). According to data published by Aerospace Corporation, launch costs for heavy launch options have decreased in a fashion closely resembling exponential decay since the 1980s.[3] While it is reasonable to assume there will be some law of diminishing returns on launch cost scaling and optimization, these costs are already no longer within the sole purview of nation-states. This revolution kindles hope for launching space solar materials at a scale relevant to grid-level power supply. Second, power-beaming has experienced a renaissance in funding and development, obviating the need for space-to-ground power cabling. Although not widely known, wireless power transmission, or power-beaming, is an idea that’s been around (at least) since Nikola Tesla began practical experiments building on Michael Faraday’s concept of electromagnetic induction in the 1890s.[4] In fact, NASA’s experiment at Goldstone in 1975 transmitted 34kW of electrical power over 1.5km! In the nearly 50 years since then, concurrent improvements in optics for data transmission and in microwave and millimeter wave devices (due in large part to the global explosion in cell phone usage) have added new efficiencies to the mechanics of power beaming. Finally, the green revolution has led to significantly cheaper and more efficient solar cells for terrestrial applications, which can likewise be adapted for use in space solar. The costs for a utility-scale photovoltaic modules went from ~$2.50 per Watt in 2010 to ~$0.50 per Watt in 2020, according to data from the US National Renewable Energy Laboratory.[5] While these price improvements are significant, the efficiency leaps are equally important, as moving from 20% to 30% conversion efficiency (the median of the technology for the early 2000s and today, respectively)[6] provides a theoretical 50% increase in power output from the same collector area. This, then, would either lower launch costs (less collector area needed) or provide a bigger return on investment for the same. With the basic science already demonstrated, “all” that remains is to work through the engineering and policy challenges of stitching these three revolutions together into an economically viable product. However, until these hurdles are overcome (and especially until policies are put in place), it is unlikely that private industry or public-private power utilities will be willing to invest significantly in space solar, potentially leaving the US behind the power curve as other nations (China, members of the EU, Japan, and the UK) continue making progress. Luckily, the US has the Department of Defense (DoD), an organization which traditionally values operational utility over commercial viability. Over the years, the DoD has been a champion of new technologies which then spun off into commercial products (the internet, Jeeps, duct tape, super glue, GPS, and aerosol bug spray, just to name a few).[7] As the international rules-based order continues to be challenged around the world, the US military’s reliance on forward-deployed, enduring base locations leaves these forces at risk should a shooting war start. To address these challenges, the Air Force has introduced Agile Combat Employment to disperse its forces to complicate adversarial targeting, but this also creates commensurate sustainment and logistics challenges. The Marine Corps is pursuing Force Design 2030, a tenet of which is to improve sustainment of forces in the field. Marine units will be expected to operate from austere locations, ranging from small islands to remote forward operating bases, each of which presents its own logistical challenges. The Army maintains that the battlefield of the future will be faster, more lethal, and distributed, thereby implying their forces and logistics must be as well. With its penchant for ever-more-power-hungry technology, the DoD has many good reasons for pursuing space solar to augment their forces in the field. Space solar can beam down to isolated or dispersed units, keeping them powered without the telltale and vulnerable trail of logistics required for generator fuel. This advantage is even more significant for covert or rapidly relocating units who won’t be able to bring generators at all but still require power for their gear. Although these are predominately tactical/operational reasons the DoD should invest in space solar for the battlefields of the 21st Century, Dr. Paul Jaffe of Naval Research Laboratory takes the discussion up a level by simply stating: “if we don’t lead, others will.”[8] Supposing the United States doesn’t want to find itself in catch-up mode in the era of Great Power Competition, the time for investment is now. Given the unique opportunities associated with space solar, the DoD is well-suited to take the lead in this investment. Maj Justin ‘Pixar’ Sadowski is a developmental engineer in the United States Space Force and presently a DAF Fellow assigned to Argonne National Lab, Lemont, IL. The author would like to thank the Interagency Advanced Power Working Group, NRL, Dr. Philip Lubin of UCSB, and Dr. Roger Blomquist of Argonne National Laboratory for their discussions on these topics. The views expressed herein are those of the author, and do not necessarily reflect the official policy or position of the Space Force, the Department of Defense, or the U.S. Government. [1] “Electric Power Annual 2022,” U.S. Energy Information Administration, accessed July 8, 2023. [2] “Earth’s Energy Budget,” NASA’s Earth Observatory, January 14, 2009. [3] Thomas Roberts, “Space Launch to Low Earth Orbit: How Much Does It Cost?,” Aerospace Corporation, September 1, 2022. [4] Dale Wilson, “A Century After Tesla, Wireless Power Transfer May Finally Be Delivering,” EE Power, July 11, 2022. [5] “Documenting a Decade of Cost Declines for PV Systems,” National Renewable Energy Laboratory, February 10, 2021, [6] “Best Research-Cell Efficiency Chart,” National Renewable Energy Laboratory, July 8, 2024. [7] “Military Inventions That We Use Every Day,” North Atlantic Treaty Organization, accessed January 5, 2024, [8] Elias Wilcoski, “Power Beaming & Space Solar,” presentation, Interagency Advanced Power Group, virtual, November 9, 2023.