Space-Based Solar Power: Current Programs and Technical Hurdles

Space-based solar power (SBSP) is one of the oldest concepts in space engineering. Herman Potočnik described orbital solar collectors in 1928, and Peter Glaser filed a foundational patent in 1973. The idea is elegant: a large solar array in geostationary orbit receives sunlight 24 hours a day, converts it to microwave or laser energy, and beams it to a receiving antenna (rectenna) on Earth. No weather, no night, no seasonal variation.

The question has always been whether it could be done economically. After decades on the drawing board, several serious national programs are now actively investing in SBSP, but significant technical and economic challenges remain.

Active National Programs

SBSP has moved from theoretical studies to funded demonstration programs in multiple countries:

• United Kingdom: The UK Space Energy Initiative and ARIA (Advanced Research + Invention Agency) have funded feasibility studies and are exploring a pathway to a multi-gigawatt demonstration system. The Cassiopeia concept proposes modular construction using robotics
• European Space Agency: ESA's SOLARIS initiative is studying SBSP as a potential strategic energy technology, with a decision on further development expected following member state consultations
• China: Chongqing University and the Chinese Academy of Space Technology have conducted ground-based wireless power transmission demonstrations, and China has published plans for orbital verification experiments in the 2030s
• Japan: JAXA has a long research history in SBSP and has conducted wireless power transmission ground demonstrations; Japan's 2023 space strategy includes SBSP as a long-term goal
• United States: The Naval Research Laboratory demonstrated converting solar energy to microwave power aboard a small satellite (PRAM/SSPIDR), and the Department of Energy has commissioned new feasibility studies, though no large-scale program exists

The Core Technical Challenges

Mass and Launch Cost

A gigawatt-class SBSP system in GEO would mass tens of thousands of tonnes based on current solar panel and structural technology. Launching that mass to GEO at even optimistic future launch costs represents a multi-trillion dollar launch bill, before accounting for the system itself. This is the central economic barrier: SBSP only makes sense if in-space manufacturing, in-space assembly, or dramatically reduced launch costs (on the order of Starship at scale) materialize.

Wireless Power Transmission Efficiency

Microwave power transmission from GEO involves four efficiency losses in series: DC-to-RF conversion, beam propagation losses, atmospheric absorption, and RF-to-DC rectification at the ground. End-to-end efficiency for a microwave system operating at 2.45 GHz is typically estimated at 40–60% under ideal conditions. Laser-based systems can achieve higher collection efficiency at smaller rectenna sizes but are severely degraded by cloud cover and atmospheric turbulence.

In-Space Assembly and Robotics

A practical SBSP system cannot be launched as a single unit; it requires assembly of thousands of modular components in orbit. This demands either extremely capable autonomous robotic assembly systems or a substantial in-space human workforce, neither of which exists today. Demonstrations at smaller scales are feasible, but scaling to gigawatt systems requires capabilities well beyond current in-space assembly technology.

Thermal Management

Solar cells and power electronics generate waste heat. In the vacuum of space, radiation is the only heat rejection mechanism. Maintaining electronics within operating temperature ranges on a large, high-power structure requires extensive radiator area, adding mass and complexity.

Spectrum and Regulatory Coordination

Microwave power beams at the required intensity level would need ITU frequency allocations and must be designed to be safe for aviation, wildlife, and people near the rectenna. The rectenna itself would cover several square kilometers. International coordination for a system of this kind would be a significant diplomatic and regulatory undertaking.

What Would Make It Viable

SBSP becomes economically plausible under a combination of conditions: dramatic reductions in launch cost (sub-$100/kg to LEO), mature in-space manufacturing reducing the mass of solar arrays and structural elements, and continued advancement in power electronics efficiency. None of these are impossible, but achieving all three simultaneously at the required scale is a multi-decade engineering program.

Track government space energy investments and emerging SBSP companies through SpaceNexus market intelligence and the launch database as demonstration missions begin to appear on manifests.