Conceptual illustration depicting the design features of a Korean Space Solar Power Satellite (K-SSPS) Credits: Joon-Min Choi, Su-Jin Choi, Sang-Hwa Yi via Creative Commons License CC by 4.0
Researchers from the Korea Aerospace Research Institute (KARI) and the Korea Electrotechnology Research Institute (KERI) describe a concept for a Korean Space Solar Power Satellite in a new publication called the Journal of Space Solar Power and Wireless Transmission. Dubbed K-SSPS, its components would be launched with reusable rockets, robotically assembled and tested in LEO, then boosted to geostationary orbit (GEO) using solar electric thrusters powered by its own solar cell array.
The baseline conceptual design for K-SSPS provides 2GW of delivered power to the ground collected by a 4km diameter rectenna located in the Demilitarized Zone. There is sufficient space in this region for 60 rectennas of this size for a total collected power of 120 GW. In terms of electricity generation, such a system would provide a terawatt-hour of electricity per year which exceeds South Korea’s electricity consumption in 2021.
This study also addresses disposal of the system after its useful life estimated to be about three decades, Since such massive systems spanning an area measuring several square kilometers would present a rather large cross section increasing the risk of collision with other decommissioned satellites in the usual graveyard orbit located 235 km above GEO, the authors propose a novel but controversial approach: controlled crash landing the spent satellite in a safe zone on the far side of the Moon. This would enable future colonies on the Moon to harvest these valuable Earth-sourced materials from the impact zone, recycling them into useful commodities to help sustain lunar operations. Care would have to be taken to ensure that the structure is guided to a designated area far from established infrastructure, most of which (if not all) would be located on the near side facing Earth. Not considered in the study was recycling and/or repurposing the K-SSPS materials in space using material processing technology like Cislunar Industries’ Modular Space Foundry (previously Microspace Foundry).
South Korea’s space agency, the Korea Aerospace Research Institute (KARI), has set a goal of a test system deployment in LEO by 2040, with a full scale system in GEO by 2050. Since this effort will take considerable development time and significant financial investment, KARI plans a small-scale two-satellite pilot system demonstration in LEO within the next decade to validate the wireless power transmission technology and the deployment mechanisms. The pilot system, which was described in a paper presented at the 73rd International Astronautical Congress in September 2022, will be placed in a sun synchronous orbit and features a solar panel equipped antenna array beaming power to a receiver satellite 100m away, in a sun synchronous orbit.
Diagram depicting the operational concepts planned over the mission life of the KARI pilot space solar power demonstration. Credits: Joon-Min Choi, Su-Jin Choi, Sang-Hwa Yi via Creative Commons License CC by 4.0
KARI and KIRI have described their case studies on a space solar power program as a renewable energy option for Korea to help address global efforts to achieve net zero greenhouse gas emissions by 2050. This paper summarizes their concept design for a 2GW space solar satellite highlighting gaps in the economic and technological knowledge needed for success, proposed a responsible and sustainable disposal method, and outlined an achievable architecture for a near term pilot demonstration within a decade. Korea joins other global development efforts that SSP has been following with their own unique approach to space-based solar power (SBSP).
However, doubters have been surfacing recently highlighting the significant engineering and economic challenges that need to be addressed for SBSP to be competitive with ground-based renewable energy sources and backup storage systems, the technology of which are rapidly developing and improving. One skeptic, former European Space Agency engineer Henri Barde, published an article in IEEE Spectrum arguing that among other things, designers will have a significant challenge shaping and aiming the microwave beam of a kilometer-scale phased array antennae. In his opinion, this and other engineering obstacles will not be solved until fusion energy will be commercially available. In a rebuttal on LinkedIn, CEO of SBSP startup Virtus Solis John Bucknell responded that his company has proprietary software that can simulate greater than 2km transmission apertures and that SBSP is in the engineering phase while fusion is still in R&D, the complexity of which makes capital and operating costs a big unknown for commercialization.
NASA has yet again kicked the can down the road, claiming in their most recent study that expected greenhouse gas emissions and the cost of space hardware for current design options will be on a par with existing renewable electricity technologies and therefore recommends further study to close several technology gaps for SBSP to make economic sense. The next few years will be critical for engineering testing, not only for Korea’s pilot satellite, but Virtus Solis‘s in-space plans and Northrup Grumman’s end-to-end test in 2025 of their Space Solar Power Incremental Demonstrations and Research prototype system. Once in-space prototype testing demonstrates sufficient feasibility to retire technical risks, venture capital investors may feel comfortable funding subsequent operational phases toward profitable commercialization.
Conceptual illustration of ESA’s SOLARIS space based solar power system. Credits: ESA
This year there were a lot of announcements and commentary regarding government support for studies that may lead to actual development activities for space solar power. These events, as well as some efforts by private companies, have been prompted by global initiatives to reduce carbon emissions toward net zero by midcentury in the hope of mitigating climate change.
Last January Japan codified into law an aggressive timetable to launch an end-to-end space solar power demonstration flight in LEO by 2025. From an English translation of Japan’s Basic Space Law provided by the National Space Society, the exact text reads “Each ministry will work together to promote the realization of space solar power generation. Concerning microwave-type space solar power generation technology, the aim will be to demonstrate by 2025 energy transmission from low Earth orbit to the ground.” If implemented on time, this would be the first such technical demonstration to be performed from space. Also, the fact that the initiative is codified into Japan’s laws means they are serious.
At a Royal Aeronautical Society conference last April in London called Toward a Space Enabled Net-Zero Earth, chairman of the Space Energy Initiative Martin Soltau outlined a 12-year timeline that would provide gigawatts of power from space for the UK by 2035. The Initiative, which is a collection of over 50 British technology organizations, has selected a space solar power satellite design called CASSIOPeiA after a cost benefit analysis performed by Frazer-Nash Consultancy initially covered by SSP. Incidentally, links to the final report by Frazer-Nash Consultancy completed in September 2021 and to the CASSIOPeiA system are available on the SSP Space Solar Power page.
At the International Space Development Conference in Washington D.C. last May, Nickolai Joseph of the NASA Office of Technology Policy, and Strategy (OTPS) announced an effort by the space agency to reexamine space based solar power. The purpose of the study is to assess the degree to which NASA should support its development. Joseph said the report was to be completed by the end of September but as this post goes to press, it had not been released. Head of the OTPS, Bhavya Lal, tweeted last month that the report was in final review but this Tweet has been deleted without explanation. We are still waiting.
Three items on space solar power came up in September. First, John Bucknell returned to The Space Show to give an update on Virtus Solis, his space-based power system that SSP covered previously in an interview. With the novel approach of a Molynia sun-synchronous orbit, Bucknell claims that Virtus Solis will provide baseload capacity at far lower cost. In addition, the choice of orbits allow sharing orbital assets globally enabling solutions for multiple countries and regions. Bucknell hopes to have a working prototype to test in space within the next few years.
Schematic illustration of a three-array Virtus Solis constellation in Molniya orbits serving Earth’s Northern Hemisphere and a two-array constellation serving the Southern Hemisphere of Luna. Credits: Virtus Solis
Later in the month, the American Foreign Policy Council published a position paper on space based solar power in the organization’s publication Space Policy Review. From the introduction, author Cody Retherford writes that space solar power “…satellites are a critical future technology that have the potential to provide energy security, drive sustainable economic growth, support advanced military and space exploration capabilities, and help fight ongoing climate change.”
Overview of Space-based Solar Power from Figure 1 in American Foreign Policy Council report. Credits: AFPC and U.S. Department of Energy.
Also in September, the European Space Agency proposed a preparatory program called SOLARIS to inform a future decision by Europe on space-based solar power. The proposal was submitted for consideration in November at the ESA Council at Ministerial Level held in Paris.
The goal of SOLARIS, conceptualized in the illustration at the top of this post, would be to lay the groundwork for a possible decision in 2025 to move forward on a full development program to realize the technical, political and programmatic viability of a space solar power system for terrestrial needs.
Upon the conclusion of the ESA Council at Ministerial Level meeting SOLARIS was approved as a program. The Council confirmed full subscription to the General Support Technology Programme, Element-1, which requested funding for SOLARIS development. The activities performed under Element 1 support maturing technologies, building components, creating engineering tools and developing test beds for ESA missions, from engineering prototype up to qualification. Still to be determined: how much funding will be allocated by each member of the EU.
Then in October an article published in Science asks the question “Has a new dawn arrived for space-based solar power?” The authors bring to light what many advocates have already realized: that better technology and falling launch costs have revived interest in the technology. Also in October, MIT Technology Review issued a report “Power Beaming Comes of Age”. Based on interviews with researchers, physicists, and senior executives of power beaming companies, the report evaluated the economic and environmental impact of wireless power transmission to flush out the challenges of making the technology reliable, effective and secure.
China announced in November that it plans to test space solar power technologies outside its Tiangong space station. Using the robotic arms attached to the station, they plan to evaluate on-orbit assembly techniques for a space-based solar power test facility which will eventually then orbit independently to verify solar energy collection and wireless power transmission. The China Academy of Space Technology has already articulated plans for development of their own space solar power system culminating in a 2 Gigawatt facility in geostationary orbit by 2050.
To cap off the year, aerospace engineer and founder of The Spacefaring Institute Mike Snead published a four-part series on evaluation of green energy alternatives including space solar power which he calls Astroelectricity. In the first part, he covers the history of humanity’s energy use and the dawn of fossil fuel use over the last century pointing out the fragility of the current system with respect to energy security. A gradual transition to fossil fuel free alternatives is needed to provide enough time for technology development and conversion over to green energy sources while not creating shocks to an economy based mostly on coal, oil and gas.
Next, nuclear power is addressed (and dismissed) as a green alternative with the next generation of smaller modular fission nuclear reactors currently under development. Due to waste heat challenges and nuclear weapons proliferation issues plus problems with scaling up enough of these power plants as base load supply to supplement intermittent wind and solar, this alternative is rejected as a viable green alternative. No mention is made of some the numerous fusion energy development activities in process or the promise of thorium molten salt reactors, so some readers may take issue with Snead’s position on this point.
In the third installment, if it is assumed that nuclear power is not a viable option, Snead examines to what extent wind and terrestrial based solar power has to be scaled up to replace fossil fuels in the latter part of this century given population growth and resulting energy needs. Not surprisingly, given the intermittent nature of wind and solar he finds these sources lacking, and they “… are not practicable options for America to go green.” Enter space solar power to fill the void.
In the last article in his series, Snead provides guidance for establishing a national energy security strategy for an orderly transition to green energy. He concludes that, “With America’s terrestrial options for going green not providing practicable solutions, the time for America to develop space solar power-generated astroelectricity has arrived. America now needs to pursue space solar power-generated astroelectricity to ensure that our children and grandchildren enjoy an orderly, prosperous transition to green energy.”
Finally, we close out the year with this: Northrop Grumman announced plans for an end to end space to ground demo flight in 2025 of their Space Solar Power Incremental Demonstrations and Research (SSPIDR) project funded by the Air Force Research Laboratory. SSP reported on the SSPIDR system previously. This development sets up a race between Japan, Virtus Solis (both mentioned above) and the U.S. government to be the first to beam power from space to the ground by the middle of this decade.
Conceptual illustration of a Virtus Solis satellite array beaming power to central California (not to scale). Credits: Virtus Solis Technologies. NOTE: all images in this post are credited to Virtus Solis Technologies
Ever since I was in high school space solar power has been the holy grail of space advocates. I even wrote a report on the topic based on Peter Glaser’s vision in my high school physics class before Gerard K. O’Neill popularized the concept in The High Frontier leveraging it as the economic engine behind orbiting space settlements. But the technology was far from mature back then, and O’Neill knew back in 1976 the other main reason why after all these years space solar power has not been realized:
“If satellite solar power is an alternative as attractive as this discussion indicates, the question is, why is it not being supported and pushed in vigorous way? The answer can be summarized in one phrase: lift costs.” – Gerard K. O’Neill, The High Frontier
John Bucknell, CEO and Founder of Virtus Solis, the company behind the first design to cost space solar power system (SSPS), believes that recent technological advances, not the least of which are plummeting launch costs, will change all that. He claims that his approach will be able to undercut fossil fuel power plants on price. He recently appeared on The Space Show (TSS) with Dr. David Livingston discussing his new venture. SSP reached out to him for an exclusive interview and a deep dive on his approach, the market for space solar power and its impact on space development.
SSP: Technological advancements of all the elements of a space solar power system have gradually matured over the last few decades such that size, mass and costs have been reduced to the point where there are now experiments in space to demonstrate feasibility. For example, SSP has been following the first test of the Naval Research Laboratory’s Photovoltaic Radio-frequency Antenna Module (PRAM) aboard the Air Force’s X37 Orbital test vehicle. Caltech’s Space-based Solar Power Project (SSPP) has been working on a tile configuration that combines the photovoltaic (PV) solar power collection, conversion to radio frequency power, and transmission through antennas in a compact module. According to your write-up in Next Big Future on a talk given to the Power Satellite Economics Group by the SSPP project manager Dr. Rich Madonna, they plan a flight demonstration of the tile configuration this December. The Air Force Research Laboratory’s Space Solar Power Incremental Demonstrations and Research (SSPIDR) project also plans a flight demonstration later this year with an as yet unannounced configuration. Which configuration of this critical element (PRAM or tile) do you think is the most cost effective and can you say if your system will be using one of these two configurations or some other alternative?
Bucknell: There is a lot of merit to the tile configuration as it shares much of it’s manufacturing process with existing printed circuit board (PCB) construction techniques. The PRAM itself is a version of the tile, but as it was Dr. Paul Jaffe’s doctoral dissertation prototype (from 2013) it did not use PCB techniques and should not be considered an intended SSPS architecture. Details of Caltech’s latest design aren’t released, but it appears they intend to deploy a flexible membrane version of the tile to allow automated deployment. Similar story with SSPIDR. As space solar power is a manufacturing play as much as anything, you would choose known large scale manufacturing techniques as your basis for scaling if you intend earth-based manufacturing – which we do. So yes, we are planning a version of the tile configuration.
SSP: You’ve said that the TRL levels of most of the elements of an SSPS are fairly mature but that the wireless power transmission of a full up phased array antenna from space to Earth is at TRL 5-6. The Air Force Research Laboratory (AFRL) plans a prototype flight as the next phase of the SSPIDR project with demonstration of wireless power transmission from LEO to Earth in 2023. What is your timeline for launching a demo and will it beat the Air Force?
Bucknell: Our timescales are similar for a demonstrator, but I suspect the objectives of a military-focused solution would be different than ours. We would plan a LEO technology demonstrator meeting most of the performance metrics required for a MEO commercial deployment.
SSP: Your solution is composed of mass produced, factory-built components including satellites that will be launched repeatedly as needed to build out orbital arrays. Will multiple satellites be launched in one payload or will each module be launched on its own? What is the mass upper limit of each payload and how many launches are needed for the entire system?
Bucknell: We intend a modular solution, such that very few variants are required for all missions. A good performance metric for a SSP satellite would be W/kg – and we believe we can approach 500 W/kg for our satellites (Caltech has demonstrated over 1000 W/kg for their solution). With known launchers and their payloads a 100MW system would take three launches of a Starship, with less capable launchers requiring many more. Since launch cost is inversely related to payload mass, we expect Starship to be the least expensive option although having a competitive launch landscape will help that aspect of the economics with forthcoming launchers from Relativity Space, Astra and Rocket Lab being possibilities.
SSP: The way you have described the Virtus Solis system, it sounds like once your elements are in orbit, additional steps are needed to coordinate them into a functional collector/phased array. Presumably, this requires some sort of on-orbit assembly or automated in-space maneuvering of the modules into the final configuration. I know you are in stealth mode at this point, but can you reveal any details about how the system all comes together?
Bucknell: An on-orbit robotic assembly step is necessary, although the robotic sophistication required is intentionally very low.
SSP: Your system is composed of a constellation of collection/transmitter units placed in multiple elliptical Molniya sun-synchronous orbits with perigee 800-km, apogee 35,000-km and high inclination (e.g. > 60 degrees). I understand this allows the PV collectors to always face the sun while the microwave array can transmit to the target area without the need for physical steering, which simplifies the design of the spacecraft. Upon launch, will the elements be placed in this orbit right away or will they be “assembled” in LEO and then moved to the destination orbit. Do the individual elements or each system assembly as a whole have on-board propulsion?
Bucknell: The concept of operations is array assembly in final orbit, mostly to avoid debris raising from lower orbits.
Schematic illustration of a three-array Virtus Solis constellation in Molniya orbits serving Earth’s Northern Hemisphere and a two-array constellation serving the Southern Hemisphere of Luna
SSP: The primary objective of the AFRL SSPIDR project is delivery of power to forward deployed expeditionary forces on Earth which would assure energy supply with reduced risk and lower logistical costs. It sounds like your system would not work for this application given the need for 2-km diameter rectenna. Could this potential market be a point of entry for your system if it were scaled down or reconfigured in some way?
Bucknell: Wireless Power Transmission (WPT) at orbital to surface distances suffer from diffraction limits, which is true for optics of all kinds. It is not physically possible to place all the power on a small receiver, and therefore the military will likely accept that constraint. As a commercial enterprise, we could not afford to not collect the expensively-acquired and transmitted energy to the ground station. There are also health and safety considerations for higher intensity WPT systems – ours cannot exceed the intensity of sunlight for example, and therefore is not weaponizable.
SSP: You said on TSS that your strategy would, at least initially, bypass utilities in favor of independent power producers. What criteria is required to qualify your system for adoption by these organizations? You mentioned you have already started discussions with one such group. Can you provide any further details about how they would incorporate an SSPS into their existing assets?
Bucknell: One of the key features of space solar power is on-demand dispatchability. Grid-tied space solar power generation has the benefit of being able to bid into existing grids when generation is needed and task the asset to other sites when demand is low. This all assumes that penetration will be gradual, but some potential customers might desire baseload capacity in which case there is not as much need for dispatchability. Each customer’s optimal generation profile is likely to be unique so it is preferable to attempt to match that with a flexible system.
Conceptual illustration of a 1GW Virtus Solis rectenna array next to Topaz Solar Farm of 550MW capacity in San Luis Obispo County, California
SSP: Other companies have alternative SSPS designs planned for this market. For example, SPS – ALPHA by Solar Space Technologies in Australia and CASSIOPeiA by International Electric Company in theUK. How does Virtus Solis differentiate itself from the competition?
Bucknell: From a product perspective, we are able to provide baseload capacity at far lower cost. Also, we intentionally selected orbits to not only reduce costs but to induce sharing of the orbital assets across the globe such that this is not a solution just for one country or region.
SSP: How big is the likely commercial market for your product/services going to be by the time you are ready to start commercial operations? Can you share some of your assumptions and how they are derived?
Bucknell: Recent data indicates that electrical generation infrastructure worldwide is about $1.5T annually. If you add fossil fuel prospecting, it is $3.5T. Total worldwide generation market size is about $8T. All of this is derived from BP’s “Statistical Review of World Energy – June 2018” and the report from the International Energy Agency “World Energy Investment 2018”
SSP: For your company to start operations, what total funding will be required, and will it come from a combination of government and private sources, or will you be securing funding only from private investors?
Bucknell: As a startup, especially in hardware, funding comes from where you can get it. To date no governmental funding opportunities have matched our technology, but that might change. Our early raise has been from angel investors and venture capital firms. Over the course of the research and development efforts, we expect demand for capital will be below $100M over the next several years but accurately forecasting the future is challenging. We would note this level of required investment is far below our competition.
SSP: For hiring your management team, since this business is not mature, what analogous industries would you be looking at to recruit top talent?
Bucknell: Everything in our systems exist today elsewhere. The wireless data industry (5G for example) has the tools and experience for developing radio frequency antennas and associated broadcast hardware. The automotive industry has extensive experience with manufacturing electronics at low cost in high volumes, including power and control electronics. Controls software engineering is a large field in aerospace and automotive, but in a large distributed system like ours the controls software will extend far beyond guidance, navigation and control (GNC).
SSP: O’Neill envisioned the production of SSPSs as the market driver for space settlements, in addition to replication of more space colonies. This approach seems to have gathered less steam over the years as economics, technological improvements, and safety concerns have taken people out of the equation to build SSPSs in space. In a recent article in the German online publication 1E9 Magazine you talked about SSPSs being useful for settlements on the Moon and Mars. What role do you see them playing in free space settlements and could they still help realize O’Neill’s vision?
Bucknell: We stand at a cross-roads for in-space infrastructure. For the first time access to space costs look to be low enough to make viable commercial reasons to deploy large amounts of infrastructure into cislunar space and beyond. To date the infrastructure beyond earth observation and telecom has been deployed to mostly satisfy nation-state needs for science unable to be performed anywhere else as well as exploration missions (also a form of science). However, there has to be a strong pull/demand to spur the construction of access to space hardware (heavy lift rockets) that consequently lowers the cost further through economies of scale. As I described in my Space Show interview there are only a few commercial in-space businesses that are viable with today’s launch costs. We have had telecom for a long time, followed closely by military and then commercial earth observation. Now we have a large constellation of “internet of space”. Even with those applications, there is not a large pull to scale reusable launch vehicle production – as reusability is counter-productive for economies of scale. A large, self-supporting in-space infrastructure would be needed to bootstrap launch production sufficiently to self-fulfil low cost access to space – Space Solar Power is that infrastructure. Space tourism, asteroid mining and others do not have scale nor potential lofted mass to scale the launch market adequately. In that way, O’Neill’s vision is right – and the follow-on markets can leverage the largely paid-for launch infrastructure to make themselves viable. Space solar power will be the enabler for humanity to live and work off-Earth, and Virtus Solis is leading the way.
