If you are a fan of the science fiction horror film “Alien: Covenant” directed by Ridley Scott, you would be familiar with the spacecraft Covenant, which transports crew members to a new planet for human colonization.
The Covenant utilizes solar panel technology for propulsion in space. As early as 1976, the renowned astronomer Carl Sagan shared about a spacecraft engine called the solar sail. Four decades later, The Planetary Society, based in the United States, officially proved the feasibility of this technology.
After 10 years and a cost of $7 million, the non-profit spacecraft LightSail 2 became the first spacecraft to utilize sunlight as propulsion in space.
Devices that use solar energy on Earth to generate thrust, such as propellers, require a surrounding medium (air or water) and are therefore useless in space. The traditional approach in spacecraft technology has been to use fuel combustion to produce thrust.
“We are excited to announce the successful mission of LightSail 2,” said Bruce Betts, project manager.
“We wanted to demonstrate that solar sails could be used in CubeSats. We changed the spacecraft’s orbit solely using the pressure from sunlight, something that had never been done before,” (CubeSats are an international program that allows universities, colleges, and private companies to launch small, amateur satellites into space at a low cost).
A significant step from past achievements, the LightSail 2 spacecraft has been in orbit for over a month, with its sail deployed for the first time last week. Over a span of more than 8 days, the spacecraft raised its orbit by 1.7 km, utilizing the thrust from solar photons.
Following Japan’s IKAROS solar sail project launched in 2010, LightSail 2 is the second successful endeavor in deploying light-based propulsion technology in space. However, unlike IKAROS, LightSail 2 can use its sail to actively change its orbit.
According to project director Dave Spencer, LightSail 2 is autonomously controlled by an onboard algorithm. Every 50 minutes, the spacecraft rotates 90 degrees, whereas IKAROS could only rotate about four or five degrees.
This algorithm is continuously updated and refined. One of the significant challenges to date has been fine-tuning the spacecraft’s momentum, controlled by a momentum wheel.
The momentum wheel is used to adjust the spacecraft’s rotation angle. When the solar sail generates excessive thrust, a counteracting force is required to slow down the rotation speed. This is achieved by utilizing electromagnetic torque rods, which orient the spacecraft using Earth’s magnetic field.
“We have learned a great deal from controlling LightSail 2,” said Bill Nye, CEO of The Planetary Society. “Even though the mission has been successful, we are still learning how to control the spacecraft more effectively in the future.”
The boundless applications of new technology
It is difficult to accurately predict how far a spacecraft can elevate its orbit solely using sunlight. In reality, LightSail 2 increased its orbital altitude by approximately 900 meters in just one day. However, scientists are still pushing the spacecraft as far as possible to explore the limits of this new technology.
LightSail 2 in space. Image: Planetary.
The applications for solar sail technology are limitless. Scientists have proposed using it in the search for extraterrestrial life, monitoring solar weather, and equipping systems to warn of approaching asteroids that may collide with Earth. Furthermore, if a material capable of withstanding extreme temperatures and radiation can be developed, a solar-powered spacecraft could approach the Sun to receive tremendous thrust from the radiation, enabling it to travel even farther and at higher speeds.
“This technology allows us to go farther, beyond the Solar System, even indefinitely,” Nye said. “Because you don’t have to worry about fuel. Fuel management systems are not necessary, the spacecraft will be lighter, and refueling stations will no longer be needed for interplanetary journeys.”
NASA’s Near-Earth Asteroid Scout mission, scheduled for launch in the mid-2020s, may incorporate this technology. This mission could serve as a foundation for future manned spacecraft equipped with solar sails.
The idea of solar sails has been present in science fiction, as massive sails are required to generate enough thrust. However, it is the tiny spacecraft that have ultimately pioneered the feasibility of solar sails. Science and technology have transformed science fiction into reality so rapidly that we can hardly keep up with the advancements.