First Solar Energy Beamed from Space: Lights on Caltech’s SSPD-1

Launched into orbit by the SpaceX Trasnporter-6 mission in January 2023, the Space Solar Power Demonstrator (SSPD-1) completed two significant tasks, proving that the technology can work in space. The California Institute of Technology (Caltech) announced that on March 03, 2023, the orbiting test bed was able to transmit wirelessly power in space, and on May 22, 2023, it successfully beamed detectable energy back to the ground.

Caltech’s Space Solar Power Program has demonstrated that power can be beamed wirelessly from orbit to Earth: https://t.co/8CPtuw2sNm
— Caltech (@Caltech) June 1, 2023

SSPD-1, not just some academic experiment

Since its first engineering description in 1968, Space Solar Power (SPP), or Space-Based Solar Power (SBSP), has been a never-ending promise. Different technologies have been considered over the years, some of them capable of functioning on the Earth, but until now, no one had been tested in space.

1970s vision of solar-power satellite construction. Credits: ESA

Caltech’s SSPD-1 is the prototype of its Space Solar Power Project (SSPP), financed by Donald and Brigitte Bren, two members of the Caltech Board of Trustees. The aim of the project proposed by Mr. Bren was “to harvest solar power in space and transmit it to the Earth’s surface” since he was intrigued by SPP potential.

After years of studies and tests in the laboratory, the first release of the SPP testbed, SSPD-1, was finally realized, consisting of three devices integrated into a Momentus’ Vigoride spacecraft:

DOLCE (Deployable on-Orbit ultraLight Composite Experiment) is the unfolding modular structure that proves the architecture and the deployment mechanisms for the future solar power station
ALBA is a set of 32 different photovoltaic cells to find the most suited to the space environment
MAPLE (Microwave Array for Power-transfer Low-orbit Experiment) is an array of microwave power transmitters to test the wireless power transmission in space and to Earth.

DOLCE device is being lowered onto the Momentus’ Vigoride spacecraft. Credits: Caltech, SSP

SSPP’s first steps are achieved. What’s next?

As announced, MAPLE demonstrated its ability to transmit power in space, turning on two LEDS on the other side of the spacecraft. Exploiting the constructive and destructive interference between individual transmitters, it was also able to direct the energy beam to the Caltech roof, where it was collected by a microwave receiver, called a rectenna.

Detecting power from MAPLE on the roof of Moore Laboratory. Credits: Ali Hajimiri, Caltech

Once SSPD-1 has finished its mission, the SPP Project will have enough information to continue the improvement of the prototype. This will finally lead to build the ultra-lightweight, cheap, and flexible units that will form an SPP system, capable of being economically competitive with ground-based power plants.

“The hard work and dedication of the brilliant scientists at Caltech have advanced our dream of providing the world with abundant, reliable, and affordable power for the benefit of all humankind” – Donald Bren, SSPP funder