Richard Madonna: Powering Earth from Orbit with Caltech’s Space Solar Initiative

As global energy demands continue to rise and geopolitical conflicts threaten stable energy supplies, it becomes increasingly imperative to identify clean, reliable, and renewable national energy sources to rely on. Among the most ambitious projects towards addressing this goal is Caltech's Space Solar Power Project (SSPP), led by Richard G. Madonna, with his team’s research investigating space-based solar power.  

Dr. Madonna has served as the project manager and system engineer for the Space Solar Power Initiative for nearly eight years. His extensive background - comprising a Ph.D. in theoretical physics, four years of service in the U.S. Air Force, and work with Northrop Grumman - has contributed significantly to the development of the groundbreaking ideas now being presented by his team. 

The initial concept proposed by the SSPP involved constructing a compact 10 cm by 10 cm "sandwich" module for deployment on a satellite in geosynchronous orbit (GEO). The design would utilize photovoltaic cells on one side to collect solar energy, and produce radio frequency (RF) energy on the other side for wireless power transmission. Their original concept employed concentrators that used mirrors to amplify light onto a thin strip of photovoltaic material to have, in essence, an amplification or concentration of light nearly tenfold stronger than previous designs.  

SSPP "sandwich" module, image courtesy of Caltech.

However, these mylar mirrors were extremely difficult for the team to produce, making them impractical for the mission. In addition, the mirror’s design would only allow for the model satellite to generate energy for half of its orbit if they continued on course in GEO. This inefficiency led the team to explore alternative configurations, such as collecting sunlight from both sides of the module or transmitting RF energy in multiple directions. 

After extensive research into alternative materials, the SSPP team adopted a 3:5 compound semiconductor material that is less sensitive to radiation damage than gallium arsenide, offering enhanced durability in space. This material also achieves a high power-to-mass ratio, making it suitable for orbital applications. The structural result of this design became strikingly similar to Earth-based solar panels- but optimized for space radiation.  

The current proposed module requires long strips of tiles (composed of photovoltaics on either side and an array of antenna on one side), which allows for light to be collected on both sides and energy to be omitted on one end. This brought them towards their final design with a layer of antennas atop a layer of groundplay, all laid over a flexible integrated circuit board. This final design would allow for the pop-up antennas to transmit energy gathered from the sun towards Earth.  

This team's research could provide breakthroughs in solar powering across the world, with one of these systems being able to power a small town, equivalent to replacing an entire coal plant. In addition, Dr. Madonna’s team noted the importance of the scalable capabilities of their project, allowing for more modules to be added or removed from the system at will, increasing the maximum amount of energy able to be generated by the apparatus.  

Despite these breakthroughs, the team has experienced difficulty with orbital slot allocations, finding that all GEO orbital spots are filled, stressing the need for design changes to accommodate the current saturated spatial climate. While the team was first considering Medium Earth Orbits (MEO), the design change required for such an orbit would be too drastic, rendering the plan itself obsolete. Currently, the team is investigating a tundra orbit, which is a highly elliptical orbit focused on a certain portion of land.  

In addition, the team currently has no working prototype in place due to the extremely large nature of their array systems. The phasing of an array at this scale has never been demonstrated before and would require more intensive research to complete. Alongside this issue comes problems with thermal control and radiation protection, as well as issues with orbital removal and fuel addition, since the machine would need its yaw adjusted regularly.  

SSPP Demo Design, image courtesy of Caltech

At EcoAero, we believe that sustainability should be valued above all else in space, no matter the time or cost necessary. While the future of space energy generation is still unknown, the Space Solar Power Initiative holds promising results towards greener energy creation for the modern world. This technology and drive is a heartening step towards the future of space. 

Image courtesy of Caltech.