Nasa unfurls solar sail for the first time as it prepares for space mission

Nasa has cleared a “key milestone” in developing solar sail technology that could allow manmade spacecraft to explore deep space.

The agency and industry partners used two 30-metre lightweight composite booms to stretch out a 400-square-metre prototype solar sail quadrant for the first time.

Solar sails are able to propel spacecraft using radiation pressure exerted by sunlight on large surfaces. A number of spaceflight missions to test solar propulsion and navigation have been proposed since the 1980s, but the first spacecraft to make use of the technology was IKAROS, launched in 2010.

Compared with chemical rockets, solar sail craft offer the possibility of low-cost operations combined with high speeds and long operating lifetimes. Since they have few moving parts and use no propellant, they can potentially be used numerous times for the delivery of payloads.

While Nasa unfurled just one-quarter of the sail in its latest test, the complete sail will measure 1651 square metres when fully deployed, with the thickness less than a human hair at 2.5 microns. The sail, developed by Redwire Space, is made of a polymer material coated with aluminium. 

Nasa recently increased funding to solar sail technology in order to reach a level of readiness so it can be flown on science missions.

“This was a major last step on the ground before it’s ready to be proposed for space missions,” said Nasa technologist Les Johnson. “What’s next is for scientists to propose the use of solar sails in their missions. We’ve met our goal and demonstrated that we’re ready to be flown.

“Once you get away from Earth’s gravity and into space, what is important is efficiency and enough thrust to travel from one position to another.”

Some of the missions of interest using solar sail technology include studying space weather and its effects on the Earth, or for advanced studies of the north and south poles of the Sun. 

The latter has been limited because the propulsion required to get a spacecraft into a polar orbit around the Sun is very high and simply not feasible using most of the propulsion systems available. 

Solar sail propulsion could also enhance future missions to Venus or Mercury, given their proximity to the Sun and the enhanced thrust a solar sail would achieve in the more intense sunlight there.

Johnson described it as “the ultimate green propulsion system” as it will continue to have propulsion as long as the Sun is shining. 

Where sunlight is diminished, he envisions a future in which lasers could be used to accelerate the solar sails to high speeds, pushing them outside the solar system and beyond, perhaps even to another star.

“In the future, we might place big lasers in space that shine their beams on the sails as they depart the solar system, accelerating them to higher and higher speeds, until eventually they are going fast enough to reach another star in a reasonable amount of time,” he added.