Solar sail as big as an apartment and brighter than the brightest star in the sky: ‘New way to explore the cosmos’

At 80 square meters, the sun sail is as large as an apartment when unfolded, while the supporting structure – the boom, in sailing jargon – still fits in a human hand when rolled up. The Advanced Composite Solar Sail System (ACS3), as the new supporting structure is called in full, should make it easier to launch and use solar sails for future space missions.

ACS3 does this because the supporting structure is smaller and weighs less than previous designs. Important, because the payload volume and maximum weight allowed in a rocket are limited. The satellites and probes that use such a solar sail are also becoming smaller for the same reason.

‘Wind’ of light

A solar sail is similar to traditional sails on a boat. Where a sailing ship on the ocean is propelled by wind, in fact nothing more than particles in the air that collide with that sail, a solar sail does the same with light particles, photons, that bounce off the reflective surface.

Although the force this produces is considerably less than the force of the wind, you can still give a spaceship with a large solar sail a considerable amount of speed in the near-vacuum of the cosmos, partly because a ship experiences virtually no friction there. NASA is considering the technology, among other things, for future research missions to distant asteroids in the solar system.

2,000 square meters

Although the space agency talks about “a new way to explore the cosmos” in its promotional videos for the solar sail, the flight of NASA’s ACS3 is not the first time a spaceship with a solar sail has zoomed through the cosmos. The Japanese Ikaros mission and the Planetary Society’s Lightsail 2, among others, preceded the new sail. ACS3 must become the next step in the development of this still relatively new technology.

During the mission, NASA examines above all whether the sail works properly. For example, after launch, once it has arrived at a thousand kilometers above the Earth’s surface, it must first unfold without (literal) cracks. The spaceship must also be able to make some course corrections with the help of the sail.

On paper, the new construction is strong enough to hang much larger solar sails in the future, up to about 500 square meters. With the same technology and a slightly different setup, NASA says it will eventually even be possible to support sails of 2,000 square meters.

When unfolded, the new solar sail should be clearly visible from Earth in the night sky. NASA expects the colossus to shine even brighter than Sirius, the brightest star in the sky.