Next week, a SpaceX Falcon Heavy rocket will launch a cluster of 24 satellites for the US Air Force in the Space Test Program-2 mission. The rocket will deposit its payloads into three different orbits. At the second stop – in a circular orbit 720km above the surface of the Earth – it will deposit the Planetary Society’s unusual spacecraft.

This spacecraft (LightSail 2) will test the ‘solar sail’ mechanism, which has not yet been trialled for a significant period of time in space. The ‘solar sail’ concept could propel a spacecraft using radiation pressure exerted by sunlight (solar pressure) on large mirrors on the surface of the craft, like a sail being blown by the wind except using the momentum of photons (tiny bundles of light) rather than of air molecules.

The concept of this spacecraft was first proposed by a group of astrophysicists which included astrophysicist, author, and Planetary Society co-founder Carl Sagan and has been under development in the decades since. The solar sail spacecraft has been entirely paid for by members of the Planetary Society.

Solar pressure is a far less powerful means of propulsion than chemical propellant. However, a spacecraft propelled by solar sailing would be extremely low cost; very light, due to requiring no propellant, and less likely to require fixing due to having few moving parts.

Bill Nye, CEO of the Planetary Society, told Ars Technica that: “We are carrying on a legacy that has been with us since the founders [of the society]. It’s just an intriguing technology because it lowers the cost of going all over the place in the Solar System.”

According to the Planetary Society, an early version of the solar sail concept was proposed in the seventeenth century by astronomer Johannes Kepler, who described ‘sailing among the stars’ on ‘heavenly breezes’.

The concept of solar sails has never caught on among national space agencies, with the Planetary Society leading most efforts. In 2005, a solar sail spacecraft was launched aboard a Volna rocket. However, the rocket failed in its first stage and the solar sail concept was never trialled in space. A second solar sail spacecraft (LightSail 1) was launched in 2015 aboard an Atlas V rocket, but experienced some technical faults and lasted just a few days. LightSail 2 is an improvement upon LightSail 1 and the Planetary Society hopes that it may remain in orbit for a year.

The LightSail 2 satellite is expected to be ejected from its carrying case into space after approximately one week. If all goes according to plan, it will unfurl into a solar sail 5.6m tall and 4m wide. The polyester film (Mylar) from which the sail is made is extremely thin, so the total weight of the satellite is just 5kg. A small wheel will be used to adjust the orientation of its sail.

According to Nye, a spacecraft using solar radiation for propulsion could be used to maintain a probe at a set point in space, or for deep-space exploration due to its continuous acceleration throughout the vacuum of space indefinitely.

Next week, a SpaceX Falcon Heavy rocket will launch a cluster of 24 satellites for the US Air Force in the Space Test Program-2 mission. The rocket will deposit its payloads into three different orbits. At the second stop – in a circular orbit 720km above the surface of the Earth – it will deposit the Planetary Society’s unusual spacecraft.

This spacecraft (LightSail 2) will test the ‘solar sail’ mechanism, which has not yet been trialled for a significant period of time in space. The ‘solar sail’ concept could propel a spacecraft using radiation pressure exerted by sunlight (solar pressure) on large mirrors on the surface of the craft, like a sail being blown by the wind except using the momentum of photons (tiny bundles of light) rather than of air molecules.

The concept of this spacecraft was first proposed by a group of astrophysicists which included astrophysicist, author, and Planetary Society co-founder Carl Sagan and has been under development in the decades since. The solar sail spacecraft has been entirely paid for by members of the Planetary Society.

Solar pressure is a far less powerful means of propulsion than chemical propellant. However, a spacecraft propelled by solar sailing would be extremely low cost; very light, due to requiring no propellant, and less likely to require fixing due to having few moving parts.

Bill Nye, CEO of the Planetary Society, told Ars Technica that: “We are carrying on a legacy that has been with us since the founders [of the society]. It’s just an intriguing technology because it lowers the cost of going all over the place in the Solar System.”

According to the Planetary Society, an early version of the solar sail concept was proposed in the seventeenth century by astronomer Johannes Kepler, who described ‘sailing among the stars’ on ‘heavenly breezes’.

The concept of solar sails has never caught on among national space agencies, with the Planetary Society leading most efforts. In 2005, a solar sail spacecraft was launched aboard a Volna rocket. However, the rocket failed in its first stage and the solar sail concept was never trialled in space. A second solar sail spacecraft (LightSail 1) was launched in 2015 aboard an Atlas V rocket, but experienced some technical faults and lasted just a few days. LightSail 2 is an improvement upon LightSail 1 and the Planetary Society hopes that it may remain in orbit for a year.

The LightSail 2 satellite is expected to be ejected from its carrying case into space after approximately one week. If all goes according to plan, it will unfurl into a solar sail 5.6m tall and 4m wide. The polyester film (Mylar) from which the sail is made is extremely thin, so the total weight of the satellite is just 5kg. A small wheel will be used to adjust the orientation of its sail.

According to Nye, a spacecraft using solar radiation for propulsion could be used to maintain a probe at a set point in space, or for deep-space exploration due to its continuous acceleration throughout the vacuum of space indefinitely.