University of Pennsylvania Innovates Solar Sail Control with Kirigami

Researchers at the University of Pennsylvania have developed a novel technique for controlling solar sails, a promising technology for spacecraft propulsion that does not rely on traditional propellant. This innovative method, detailed in a pre-print paper available on arXiv, employs an ancient Japanese art form known as kirigami to enable precise adjustments in the sail’s angle, thereby enhancing its maneuverability in space.

Solar sails harness the momentum of sunlight, but turning them presents a unique challenge. Traditional sailing techniques, which involve adjusting the sail’s angle, are not applicable in the vacuum of space. Existing methods for turning solar sails often depend on heavy equipment such as reaction wheels, tip vanes, or Reflectivity Control Devices (RCDs). Each of these options has significant drawbacks, including weight, complexity, and energy consumption.

The technique introduced by Gulzhan Aldan and Igor Bargatin involves creating intentional cuts in the sail material, specifically in the aluminized polyimide film. These cuts allow the material to buckle when tension is applied, transforming the sail into a 3D surface. Each segment of the sail can reflect light at different angles, effectively turning the sail in the opposite direction of the reflected light due to the conservation of momentum.

While some power is required to create the necessary buckling, this is achieved using servo motors, which are notably more energy-efficient compared to the systems used in past solar sail missions. Unlike RCDs, which drain batteries even when not in operation, the kirigami method only consumes power while actively adjusting the sail.

To validate their approach, Aldan and Bargatin conducted both simulations and physical experiments. Using COMSOL, a well-established physics simulation software, they performed ray tracing experiments to measure the forces generated on the sail under varying conditions. Although the measured force was small—approximately 1 nN per Watt of sunlight—the cumulative effect is sufficient to maneuver a small solar sail and its payload over time.

In practical tests, the researchers cut sections of film and placed them in a test chamber. By illuminating the film with a laser while stretching it, they observed that the laser’s position on the chamber wall aligned closely with their simulations. This confirms the effectiveness of their kirigami design in achieving the desired angles of incidence under different strains.

The potential implications of this technology for the future of solar sailing are significant, particularly in reducing both energy and propellant costs associated with maneuvering. Yet, the competitive landscape remains challenging, with various technologies vying for dominance and a lack of extensive experimental missions to assess their viability.

As the field of solar sailing continues to evolve, the implementation of kirigami techniques could revolutionize how future spacecraft navigate the cosmos. Although it may take some time before this innovation is deployed in space missions, the prospect of a solar sail leveraging this technique promises to be visually and technically impressive.