The latest experiment to explore the concept of “solar sailing” — space travel propelled by particles of quantum light that radiate from our sun — will take place next week as scientists test a technology that could one day be used to propel cargo to Mars and visit new star systems.
Called LightSail 2, the solar sail will be tucked inside Prox-1, a suitcase-sized carrier spacecraft, until it reaches its drop-off point about one hour and 20 minutes after launch.
Prox-1 will spend its first week circling Earth quietly, allowing time for the other spacecraft launched into the same orbit to drift away so that each can be identified individually. Seven days after its release from the Falcon Heavy, the front door of Prox-1’s CubeSat dispenser will swing open and allow a large spring to nudge LightSail 2 gently out into space.
Its destination isn’t a neighboring star system, though. This mission is more of a test drive, and an Earth orbit is the goal. “The goal is to raise LightSail 2’s orbit by a measurable amount, showing that solar sailing is a viable means of propulsion,” according to The Planetary Society.
Bill Nye, CEO of The Planetary Society, described the project this week as a little “romantic,” but also notes that the technology could help send cargo to Mars.
“LightSail 2 could be up for about a year, depending on solar activity,” Nye says. “It’s really a romantic notion that has tremendous practical applications. Solar sails are an idea people have speculated on, using them as cargo ships to take material to Mars and so on, but what we’re doing is advancing space, science, and exploration, and LightSail 2 is a big part of that.”
The launch is set for this coming Monday night, when a SpaceX Falcon Heavy rocket will launch from Kennedy Space Center, carrying a cluster of 24 satellites, mostly for the Air Force. Known as the Space Test Program-2 mission, the rocket will deposit its payloads into three different orbits.
To do this, the Falcon Heavy’s upper stage will have to complete long coast periods and four upper-stage burns. The complexity of the flight plan has prompted SpaceX to call it “among the most challenging launches in SpaceX history.”
Scheduled to exit at the second stop, some 447 miles above the Earth’s surface, is The Planetary Society’s LightSail 2 spacecraft, which is no bigger than a loaf of bread.
Once the LightSail 2 is nudged into space, it will boot up, deploy its antenna, and begin sending out health and status information beacons. The team will spend several days conducting health checks, uploading orbital information, and taking test images from two wide-angle cameras mounted on the spacecraft’s solar panels.
About five days after initial deployment, the solar panels are engaged, swinging outward, revealing the four storage compartments that hold the spacecraft’s triangular solar sail sections, and roughly a day after that, the team will command the spacecraft’s solar sail to deploy.
After the sails are out, LightSail will use its momentum wheel to adjust the orientation, tacking like a sailboat as it flies into and away from the current of photons streaming from the sun.
When flying toward the sun, the sail orients itself edge-on, effectively turning off its thrust. When flying away from the sun, the sail turns broadside to the photons, getting a slight push. And we do mean slight.
“The Weight of a House Fly”
“That the total force on the sail is approximately equal to the weight of a house fly on your hand on Earth gives you an idea of how small it is. But again, the key is that it’s constant. It’s always there,” says Dr. Bruce Betts, The Planetary Society’s chief scientist and program manager for LightSail 2.
"The key for solar sailing is that the source is always there."
“In terms of the amount of force that solar pressure is going to exert on us, it’s in the micronewton level. It’s very tiny compared to chemical propulsion, or very small even compared to a electric propulsion — but the key for solar sailing is that the source is always there. So even though you were at the micronewton level of force, that level of force is always there, and you’re able to use it to accelerate the spacecraft and go where you want to,” says David Spencer, project manager for LightSail 2.
If successful — and there’s really no reason why it shouldn’t be — this experiment will demonstrate proof of concept for solar sailing, an idea that legendary scientist Carl Sagan, founder and first president of The Planetary Society, first proposed in the ‘70s. Theoretically, this could represent one way that mankind could eventually travel to the stars.
As if this wasn’t already enough to blow your mind, this whole endeavor has been crowdfunded, says Jennifer Vaughn, COO of The Planetary Society.
“This is maybe a new way of pursuing space flight projects,” Vaughn says. “This $7 million project has been 100 percent funded by individuals. These are people who are passionate about space, people who want to do something to advance space exploration and were willing to put their own personal dollars behind a project. Not just at one time, too; it was over 10 years. So these are people that understand the complexity and the patience that you have to have to produce a space mission.”
"Space brings out the best in us. It’s where we solve problems we’ve never addressed before."
“We think that this is just the beginning. Since we were able to get to this point, this is quite the accomplishment to say that we were able to complete this project using all crowdfunding. Now that we’ve gotten here, we’re looking to the next horizon,” says Vaughn.
“As I so often say, space brings out the best in us. It’s where we solve problems we’ve never addressed before. It just really appeals to people of all political orientations and nationalities. It’s exciting. This is a big step. LightSail 2 is going to be a game-changer,” Nye says.
The launch is set for 11:30 p.m. Eastern on Monday — weather permitting, naturally.