Orbital solar power satellites represent a transformative approach to sustainable energy generation in space, particularly for hydrogen production via electrolysis. These systems leverage the uninterrupted solar flux available in space, free from atmospheric absorption or day-night cycles, to generate electricity at a scale and efficiency unattainable on Earth. When combined with space-based electrolysis facilities and in-situ resource utilization from lunar or asteroid mining, this architecture could enable a self-sustaining off-world hydrogen economy.

The foundation of this system lies in the design of orbital solar arrays. Unlike terrestrial solar panels, space-based photovoltaic systems must operate in extreme conditions, including high radiation levels, micrometeoroid impacts, and thermal cycling between intense sunlight and deep shadow. Advanced multi-junction solar cells, with efficiencies exceeding 40%, are the preferred technology due to their high energy conversion rates and radiation resistance. These cells are typically arranged in large, lightweight structures, often using deployable designs to minimize launch volume. Concentrator systems, incorporating mirrors or lenses to focus sunlight onto smaller photovoltaic surfaces, further enhance power density. The arrays must be actively cooled to prevent efficiency losses from overheating, employing heat radiators to dissipate excess energy into space.

Power transmission from orbital solar satellites to electrolysis facilities is achieved through wireless energy transfer, most commonly via microwave or laser beams. Microwave power transmission operates at frequencies between 2.45 GHz and 5.8 GHz, chosen for their balance between atmospheric penetration and antenna size efficiency. The transmitting antenna, or phased array, directs a coherent beam toward a rectenna (rectifying antenna) at the receiving site. Laser-based transmission offers higher energy density and smaller receiver footprints but faces challenges with beam dispersion and atmospheric interference if used in planetary applications. For space-based electrolysis, microwave transmission is often favored due to its maturity and scalability. The rectenna converts the microwave energy back into direct current electricity, which powers the electrolysis process.

Electrolysis in space presents unique challenges compared to terrestrial systems. Water, the primary feedstock, must be sourced from extraterrestrial reserves, such as lunar ice deposits or hydrated minerals on asteroids. Proton exchange membrane (PEM) electrolyzers are well-suited for space applications due to their compact design, high efficiency, and ability to operate in microgravity. Solid oxide electrolysis cells (SOECs) offer higher efficiency at elevated temperatures but require robust thermal management in the vacuum of space. The produced hydrogen and oxygen can be stored cryogenically or as compressed gas, with careful consideration given to boil-off losses and material compatibility in space environments.

Integration with lunar or asteroid mining operations is critical for scalability. Lunar polar ice, detected by missions such as NASA's Lunar Reconnaissance Orbiter, contains water concentrations exceeding 5% by weight in some regions. Robotic mining systems could extract and process this ice into purified water for electrolysis. Asteroid mining targets carbonaceous chondrites, which contain hydrated minerals and organic compounds. Water extraction from these materials involves heating to release bound water, followed by condensation and purification. The hydrogen produced can fuel spacecraft, support life support systems, or serve as a reducing agent in metallurgical processes for construction materials.

A key advantage of space-based hydrogen production is the elimination of Earth's gravity well for hydrogen storage and transport. Hydrogen produced in orbit or on the Moon can be transported more efficiently to other space-based facilities, such as fuel depots in Lagrange points or Mars-bound missions. This reduces the need for costly launches of hydrogen from Earth, where escape velocity imposes significant energy penalties. Additionally, oxygen, a byproduct of electrolysis, is valuable as an oxidizer for rocket propulsion or life support.

The system's energy balance must account for all inputs and outputs. Solar power satellites must generate sufficient electricity not only for electrolysis but also for mining, water extraction, and transportation operations. Studies indicate that a single square kilometer of orbital solar arrays could produce several gigawatt-hours of electricity annually, enough to support large-scale hydrogen production. However, the energy return on investment (EROI) must be carefully evaluated, factoring in the energy costs of manufacturing, launching, and maintaining the infrastructure.

Material sourcing for construction presents another challenge. While some components may be launched from Earth, in-situ resource utilization (ISRU) can reduce dependency on terrestrial supply chains. Lunar regolith contains metals such as iron, aluminum, and titanium, which can be refined and used for structural components. Silicon, abundant in lunar soil, is essential for photovoltaic cells. Advances in additive manufacturing and autonomous robotics could enable on-site fabrication of solar panels and other critical infrastructure.

Radiation hardening and longevity are crucial for system durability. Solar arrays and electronics must withstand prolonged exposure to cosmic rays and solar particle events. Redundancy and modular design ensure continued operation despite component failures. Self-repairing materials and autonomous maintenance robots could further extend operational lifetimes.

Economic viability hinges on reducing launch costs and scaling production. Reusable launch vehicles, such as SpaceX's Starship, aim to lower payload costs to under $100 per kilogram, making space-based infrastructure more feasible. Once established, the system can leverage economies of scale, with modular solar arrays and electrolysis units being mass-produced in orbit or on the Moon.

Regulatory and international cooperation frameworks will be necessary to govern space-based energy and resource utilization. Issues such as spectrum allocation for power transmission, mining rights, and environmental impact assessments must be addressed to prevent conflicts and ensure equitable access.

The potential applications extend beyond hydrogen production. Excess energy from solar power satellites could support other space industries, such as manufacturing, research stations, or deep-space exploration missions. Hydrogen fuel depots in low Earth orbit or cislunar space could revolutionize space logistics, enabling longer-duration missions and reducing reliance on Earth-based supply chains.

In summary, orbital solar power satellites coupled with space-based electrolysis and mining operations offer a pathway to a sustainable off-world hydrogen economy. The technology leverages high-efficiency photovoltaics, wireless power transmission, and in-situ resource utilization to overcome the limitations of terrestrial energy systems. While significant challenges remain in engineering, logistics, and governance, the long-term benefits for space exploration and industry are substantial. This integrated approach not only supports human expansion into the solar system but also establishes a foundation for a resilient and scalable energy infrastructure beyond Earth.