Developing solar power satellites (SPS) as a major energy source for Earth will involve multiple orbital demonstrators. Satellites in low Earth orbits (LEO) will have far lower costs than demonstrators in geostationary orbit (GEO) or High Elliptical Orbits (HEO), but they have the major disadvantage that they can deliver power to a receiving and rectifying antenna (rectenna) for only a few minutes, and only once every few days. However, Equatorial Low Earth Orbits (ELEO) offer the unique ability to effectively deliver power to the same rectennas about 12 times every day.
The Space Option Star in Equatorial Low Earth Orbit (SOS-ELEO) is a Gravity Gradient Stabilized Planar Phased-Array Solar Power Satellite (SPS) which will be an early demonstration of Space-Based Solar Power (SBSP) and a powerful communication event to alert the world population and their leaders about the Space Energy Option as a feasible near-term solution to address the energy and climate crises on Earth. It is designed to be launched with an Ariane 64 from Kourou, French Guiana and deployed into a 1,000 km Equatorial Low Earth Orbit (ELEO) and deliver approximately 1 MW of electrical power to multiple locations near the Equator.
Mission Background:
The idea of deploying a Solar Power Satellite (SPS) in an Equatorial Low Earth Orbit was first introduced in Japan during the 1990s as the SPS 2000 project which won the SPS91 prize.
In 2003, the European Space Agency (ESA) contracted Arthur Woods and Dr. Marco C. Bernasconi to re-examine the technology for large expandable structures in light of any new technological developments for the purpose of celebrating the 2016 Winter Olympics. The study included the examination in some technical detail of a large icosahedron to be built utilizing the chemically rigidized expandable structures (CRES) technology that had been underdevelopment in the United States and in Europe for over thirty years, although not yet used for a space structure of this dimension. ESA Contract No.16188/02/NL/MV.
In 2020, the European Space Agency issued a call for new mission ideas in their Campaign: What’s next? New space mission ideas and concepts. 201 ideas were submitted, and a number were selected for further consideration and development. Of the published concepts, 4 energy from space projects were selected including ESA’s own space power proposal. The Space Option Star selected by ESA as a possible future mission in the category ‘Technology Demonstrator’.
Link to the ESA OSIP website: https://bitl.to/3WdD
In June, 2021, Arthur Woods and Dr. Marco C. Bernasconi published the article “SOS – The Space Option Star: Addressing the Energy Dilemma” in Leonardo – The Journal of the International Society for the Arts, Sciences and Technology. Volume 54, No. 6.
Link to PDF: https://spaceoptionstar.space/space_option_star_leonardo_article.php
In March 2024, Astrostrom and Tallinn University of Technology (TalTech) in Estonia, signed a Memorandum of Understanding to further the development of Monograin Layer (MGL) thin-film photovoltaic technology for space applications. (See MGL description below)
In April 2024, Dr. Patrick Collins, who collaborated with the Japanese SPS200 project, presented ‘Advantages of Equatorial Orbits for SPS Demonstrator Satellites’ at the ESA/UK International Conference on Energy from Space 2024.
Dr. Patrick Collins at the ESA/UK International Conference on Energy from Space 2024
In September 2024, the mission concept “ELEO SPS Demonstrator in Equatorial Low Earth Orbit for European SPS Programmes” was selected as a study topic by the Swiss Federal Institute of Technology Zürich (ETHZ), Space Masters program. The resulting 106 page study detailed a mission scenario for deploying a 100 kW SPS demonstrator in ELEO with a high technical readiness level, as well as identifying the potential users and rectenna locations along the equatorial path. The study also evaluated different orbital altitudes to minimize Earth shadow effects and maximize power-to-rectenna ratios and cut-off times over the oceans.
Astrostrom is currently developing SOS in ELEO as a large-scale early SPS demonstration project.
SOS Communication Mission:
The SOS will utilize an inflatable laminated membrane technology incorporating a thin-film photovoltaic outer surface. Once in orbit, the reflective, faceted icosahedron shape of the SOS will both collect sunlight to generate electricity and reflect sunlight causing it to appear as a blinking star in the night sky. In addition to the visibility aspects which will make SOS a significant global communication event available to much of the world’s population, interactive components will enable communication with SOS at public locations around the world such as art and science museums and schools. Furthermore, Astrostrom is proposing a multi-national approach to SOS-ELEO mission, in order to emphasize that environmentally clean energy from space should be developed in an equitable, economical, and socially just manner.
In addition to the SOS being an acronym for the Space Option Star project, S.O.S. is an internationally recognized distress signal used to indicate that someone is in urgent need of help or assistance. This project will send the message that humanity must urgently address the climate and energy crises with new sources of clean and plentiful energy. As a ‘Star in the Sky’, the Space Option Star will announce the coming of the Space Energy Age.
SOS Technological Mission:
An Ariane 64 equipped with the 20-meter upper stage launched from the European equatorial launch site at Kourou would be able to deliver the SOS and other SPSs into an equatorial orbit. The space centre in Kourou is just 5 degrees from the equator (5°14’14”N) and is the most optimal launch location for this mission. The Alcântara Space Center in Brazil (5°14’14.6”N) would be another potential launch site depending on the capability of the launch vehicle.
The technical mission of the SOS will be to collect sunlight, convert it into microwave energy and then transmit this energy via a concentrated beam to receiving antennas (rectennas) located in various countries along the equator. Astrostrom has been collaborating with the Tallinn University of Technology (TalTech) in Estonia in the development of Monograin Layer (MGL) photovoltaics for Solar Power Satellites to be eventually produced from lunar materials although MGL photovoltaics are currently commercially available. Perovskite photovoltaics is another thin-film solar technology that could be utilized on the SOS. Either solar technology or perhaps both thin-film technologies could be incorporated into the Space Option Star demonstrator.
The deployment of the SOS will utilize a technology called chemically-rigidized expandable structures (CRES). In the late 80’s and early 90’s this technology was under development at Contraves Space A.G. in Switzerland which was funded by the European Space Agency (ESA). Recently, several companies in Europe and in the U.S. have renewed their development of this type of technology. CRES technology will be used to form the backbone of the icosahedron derived shape of the SOS as well as the transmitter antenna. The CRES material is a laminated sandwich of metallic coated Kapton and Kevlar which has been impregnated with a UV sensitive resin. The material is very lightweight and flexible permitting it to be easily folded and packaged. Once it is inflated in space, the CRES material must “cure” in sunlight which causes the resin to harden and the membrane to rigidize which stabilizes the shape of the inflated object. Compared with assembling large structures in space with autonomous robots which most large SPS systems require, this approach will ease the deployment of the satellite and lower the risk for an early stage SPS demonstrator.
For wireless power transmission (WPT), the SOS will use the 5.8 GHz radio frequency as this is becoming the standard for most Space Solar Power system concepts. The higher frequency of 5.8 GHz allows for a significant reduction in the size of both the transmitting antenna on the satellite and the receiving rectenna on Earth. If other SPS demonstrators using ELEO all follow an agreed standard, they will achieve win-win synergy: each new satellite adding additional microwave power supply for all existing rectennas, and each new rectenna adding additional customers for all existing satellites. The maximum rectenna size for receiving the beamed power from the SOS would be 2 kilometres in diameter. However, a smaller rectenna with a diameter of one kilometre would be practically sufficient for a successful demonstration and substantially less expensive for the participating countries.
SOS Geopolitical Mission:
The proposed SOS in ELEO would be an ’operational demonstrator’ with the potential to deliver electricity to Malaysia, Indonesia, Papua New Guinea and Singapore in Asia, Brazil, Colombia, Ecuador, and Peru in South America, and to Gabon, Kenya, Rwanda, Sao Tome, Somalia, Tanzania, Uganda and the Congo nations in Africa. Not all of these countries are developing countries, yet all have a need for plentiful clean energy. To be successful, large-scale Space Solar Power will most likely be the result of international collaboration.
According to the United Nations Sustainable Development Goal 7 (SDG 7) which focuses on ensuring access to affordable, reliable, sustainable and modern energy for all – with its targets of universal access, energy efficiency and renewable energy will open a new world of opportunity for billions of people. It will lay the foundation for the eradication of poverty, for climate action and for a sustainable world. Simply put, without progress on SDG 7, it will be impossible to achieve the 2030 Agenda for Sustainable Development and the Paris Agreement on climate change.
Link: https://sdgs.un.org/goals/goal7
Today, about a 700 million people currently live without electricity, which greatly limits their development opportunities. More than 3 billion people rely on wood, charcoal, animal and crop waste or other solid fuels to cook their food and heat their homes. Each year, close to 4 million people die prematurely from illnesses attributable to household air pollution from inefficient cooking practices. As such, the development of Space Solar Power as a potentially new electrical power system could first benefit developing countries where millions of people still live without adequate electricity supply, and yet, would be highly accessible from an equatorial orbit. This makes the proposed SOS in ELEO particularly important to the early deployment and eventual success of Space Solar Power.
Countries along the Equator
Key findings by the UN Conference on Trade and Development (UNCTAD) in partnership with the UN Department of Economic and Social Affairs (UNDESA) and the United Nations Development Programme (UNDP) indicate that achieving the energy transition in the developing countries is projected to cost about $5.8 trillion annually from 2023 to 2030 for the 48 developing economies studied, equal to 19% of their GDP. Per person, the annual cost comes to $1,271 to achieve goals like providing universal access to electricity and improving access to clean energy, including clean cooking solutions.
Link: https://unctad.org/sdg-costing/energy-transition
SOS Economic Mission:
The SOS in ELEO will deliver power to equatorial rectennas which will use battery storage at the rectenna to provide continuous electricity supply to the local neighbourhood. Although, as an early demonstrator, this project is not specifically designed to be commercially viable, however it would initiate commercial relations between terrestrial electricity supply companies and SPS operators. Electricity supply companies in the equatorial countries would build and operate the rectennas and will contract with SPS companies for delivery of microwave power to agreed specifications.
Once operational, such a project would be very flexible in enabling growth by different countries and teams adding more equatorial satellites and/or rectennas to the system. Later, larger more powerful SPS systems could be deployed and the rectennas expanded to accept more power. Indeed, other SPS designs from other companies could be deployed in ELEO to test and demonstrate their systems to the installed rectennas. With each additional SPS added to the system, more power would be received at the rectennas.
The SOS in ELEO could become the first commercial Space Solar Power project of the proposed Private-Public Partnership (PPP) Greater Earth Energy Organisation (GEEO). All participating space companies, organisations and investors would become Strategic Partners of the private entity.
Link: https://astrostrom.ch/the-greater-earth-energy-organisation/
SOS in ELEO
SOS Mass Calculations:
Mass of SOS
Mass of icosahedron framework 57 kg
Mass of Photovoltaics: 9,400 kg
Mass of Transmitter. 2,400 kg
Mass of Satellite Deployment Bus: 1,000 kg
Total mass 12,857 kg
Total mass of SOS: 12.9 tonnes
SOS Power Calculation
Estimated Surface Area of solar isolation hitting the icosahedron: 7,854 m2
Monograin layer MGL Photovoltaic:
Efficiency 12.06% = 164.62 W/m2
Power Output at Rectenna: 0.72 MW
Perovskite Photovoltaic:
Efficiency 20% = 273.00 W/m2
Power Output at Rectenna: 1.2 MW
Both types of photovoltaics could be incorporated into the demonstrator mission.
Average power output: 0.96 MW providing an average of 177,852 kWh/year
Estimated Cost of the SOS Mission:
Total cost of SOS spacecraft: € 57 million (CHF 54 million)
Cost of Ariane 64 launch: € 90 million (CHF 85 million)
Rectenna:
2. km2 rectenna located in Labaun, Malaysia
Cost of one rectenna: € 2.7 million – € 10.7 million (CHF 2.5 – 10 million)
3-6 rectennas will be placed in cooperating countries located on or near the equator.
1,000m diameter (Surface Area: 785,398 m2): € 2,670,353
2,000m diameter (Surface Area: 3,141,593 m2): € 10,681,41
Ariane 64 Launch System:
The heavy Ariane 64 consists of two liquid stages and four solid rocket boosters. Its gross weight is 870 tons, it can launch up to 21.6 tons of cargo to LEO and up to 11.5 tons to geo transfer orbit. The payload volume the 20-meter fairing is 140 cubic meters. Ariane rockets launch from the Guiana Space Centre also called Europe’s spaceport located north of Kourou in French Guiana. Kourou is located approximately 500 kilometres north of the equator at a latitude of 5°.
Ariane 64 Payload Fairing
Chemically Rigidized Expandable Structures (CRES):
https://spaceoptionstar.space/chemically_rigidized_expandable_structures_mcbc.php
Inflatable Technologies for Space Solar Power:
https://www.youtube.com/watch?v=t3nRfGUwHs4
Monograin Layer (MGL) Thin-Film Photovoltaics:
For collecting sunlight and generating electricity the SOS will use Monograin Layer (MGL) solar cells with an efficiency of approximately 12%. Further development of this technology is expected to reach a power conversion efficiency of +/- 25%. MGL technology is completely different from traditional crystalline or thin film solar cell technologies and represents an entirely new type of flexible photovoltaic technology. The patented technology combines the advantages of high efficiency single-crystalline materials and low-cost roll-to-roll production. The technology is based on decades of research at Philips semiconductor in the 1960s and is commercially available from the company crystalsol GmbH in Vienna, Austria.
The core innovation is the light absorbing layer made of a patented new crystalline semiconductor powder. The light absorbing active layer of the film is made of crystalline semiconductor particles with a typical diameter of 40 μm arranged as a single layer fixed by a polymer film. This gives it an area density of 0.4 kg/m2. New ultra-thin polymer sealants could reduce the area density by up to 50%.
MGL schematic diagram (Image courtesy crystalsol GmbH, Vienna)
https://crystalsol.com/
The semiconductor particles contain the abundant and low-cost elements copper, zinc, tin, sulphur, and selenium (CZTS). Every semiconductor particle is coated with an extremely thin buffer layer to create the p/n junction. Before the crystalline powder enters the module production it is already a finished working solar cell. The module production process is based on roll-to-roll technology ensuring high throughput and yield, similar to the printing industry. The size and distribution of the microcrystals should make MGL solar cells radiation resistant in the space environment. Furthermore, MGL solar cell crystalline material can be recycled and reused when their end-of-life has been reached.
Scientists at Estonia’s Tallinn University of Technology (TalTech) are developing a MGL solar cell based on pyrite (FeS₂) which could be obtained from lunar regolith to eventually produce solar power satellite photovoltaics on the Moon. Astrostrom and TalTech are collaborating in the SOS project to demonstrate the viability of MGL solar cells for use in the space environment.
Cu2ZnSnS4 monograin layer solar cells for flexible photovoltaic applications (12.06% efficiency)
https://pubs.rsc.org/en/content/articlehtml/2023/ta/d3ta04541b
Related SPS Demonstration Developments:
Caltech SSPD-1:
In 2023, the California Institute of Technology (Caltech) sent a spacecraft called Space Solar Power Demonstrator (SSPD-1) into space to test three new solar power technologies.
- Testing how to send power wirelessly in space
- Checking the efficiency of different solar cells
- Trying out a lightweight structure to carry and support the solar cells and power transmitters.
Led by professors Harry Atwater, Ali Hajimiri, and Sergio Pellegrino, the project gained international attention for its advancements. Wireless power transfer was demonstrated on March 3,2023 by MAPLE, one of three key technologies being tested by the Space Solar Power Demonstrator (SSPD-1), the first space-borne prototype from Caltech’s Space Solar Power Project (SSPP).
Japan OHISAMA:
In 2025, Japan plans to launch a small power satellite into orbit which it should transmit generated solar energy back to Earth. The project named Ohisama – Japanese for ‘sun’ – is expected to take off in 2025. Advisor Koichi Ijichi of the Japan Space Systems research institute shared details of the mission at the ESA/UK International Conference on Energy from Space 2024.
OHISAMA is a satellite that will transmit the solar energy generated to Earth wirelessly, where it will hover in relatively close orbit. “It will be a small satellite of about 180 kilograms. It will transmit about 1 kilowatt of energy from an altitude of 400 kilometers,” according to Ijichi. This is clearly a first, tentative step as 1 kilowatt is not much power. The battery aboard the satellite will be charged by means of a 2 square-metre photovoltaic cell. Then the collected energy will then be converted into microwaves and sent to a receiving antennas on Earth.
Virtus Solis and Orbital Composites:
Virtus and Orbital composites announced a proposed 2027 mission designed to showcase critical power-generation technologies including in-space assembly of solar panels and transmission of more than one kilowatt of power to Earth. Virtus Solis intends to deploy 1.65-meter solar tiles in a medium-Earth Molniya orbit. Through robotic assembly, Virtus Solis intends to build expansive solar arrays. Their concept was presented at the ESA/UK International Conference on Energy from Space 2024 in London.
Space Solar and Iceland:
Space Solar UK, in collaboration with Transition Labs in Iceland, have announced an agreement to provide Reykjavik Energy with electricity from a Space-based Solar Power (SBSP) plant. This experimental solar power plant in orbit is designed to deliver 30 MW of power to the Earth. Including the solar arrays, this will be a 400-meter-wide Solar Power Satellite (SPS) that will be robotically assembled in space and placed in a 3-hour High Elliptical Orbit (HEO) covering rectenna sites north or south of 30 degrees latitude. The SPS will weigh approximately 64 metric tonnes (MT) and circle the planet in a near-space region at altitudes between 2,000 and 36,000 kilometres. Four satellites are planned in this initial mission and Space Solar believes it can have the £600 million (CHF 676 million) system orbiting and providing clean power to Earth by 2030. In addition to Iceland, receiving stations could be located in Canada and northern Japan.
ASTROSTROM is seeking strategic partners and investors to implement the Space Option Star.
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