What is a light sail?

What is a light sail?

• A. A device that stores solar energy in batteries
• B. A large sheet of reflective material that can catch sunlight and be pushed by it (no fuel needed)
• C. A type of solar panel
• D. A navigation reference in space

Answer: (B)

Light sails propel a spacecraft by using momentum carried by light. A light sail is a very thin, large sheet of highly reflective material that sits in sunlight or in a focused beam of light. When photons hit the sail and reflect, they transfer momentum to the sail, producing a push. Because there’s no fuel or onboard engines, the sail can keep accelerating as long as it’s exposed to light, allowing potentially significant speeds over time. The key is having a lightweight, expansive, highly reflective surface to maximize the tiny force from light. This differs from a solar panel, which converts light into electricity, and it isn’t a navigation reference or a device for storing energy. Concepts like beaming powerful light from Earth or the Sun to drive tiny sails illustrate how this propulsion idea could work.

Light sails propel a spacecraft by using momentum carried by light. A light sail is a very thin, large sheet of highly reflective material that sits in sunlight or in a focused beam of light. When photons hit the sail and reflect, they transfer momentum to the sail, producing a push. Because there’s no fuel or onboard engines, the sail can keep accelerating as long as it’s exposed to light, allowing potentially significant speeds over time. The key is having a lightweight, expansive, highly reflective surface to maximize the tiny force from light. This differs from a solar panel, which converts light into electricity, and it isn’t a navigation reference or a device for storing energy. Concepts like beaming powerful light from Earth or the Sun to drive tiny sails illustrate how this propulsion idea could work.