Why you should care
Because this ancient idea is the next big thing in space.
Dave Spencer was in bed, at age 11, when the first Viking orbiters and landers went to Mars. He could hear his parents in the other room: “Do you think that we need to get Dave out of bed for this?” They did. Twenty years later, as the Mars Pathfinder arrived on the red planet, Spencer was in the control room.
Today Spencer is at the helm of a project that relies not on rockets but sails — and it’s designed to take us far farther than Mars. Called LightSail2, the craft built by the nonprofit Planetary Society has been orbiting the Earth since July.
Imagined by scientists for centuries but only now a reality, solar sailing has all the romance of a clipper ship sailing through the water. “The thought of using similar technology in space is such an elegant thing,” says Spencer, 54, who grew up in a sailing family in Indianapolis. Just as in water, solar sailing is “propulsion without the propellant,” says Planetary Society founder and former executive director Louis Friedman. “It’s the only technology that can take us to the stars.”
The craft doesn’t rely on chemical or electrical propellants, as rockets need. LightSail instead uses the sun’s photons to boost its boxing-ring-sized Mylar sail, creating thrust. At first, the sail orbits slowly, then speeds up, moving 10 times faster than the space shuttle. It deploys from a bread-loaf-sized satellite called a CubeSat, origami-folded within the sail.
In the future, astrophysicists see the solar sail exploring interplanetary space, monitoring for solar geomagnetic storms, asteroids or space debris. Small and agile, the project has a crowdfunded budget of just $7.5 million.
In search of someone with the tenacity and experience to lead it, Friedman turned to Spencer, a former colleague from NASA’s Jet Propulsion Laboratory (JPL) and Georgia Tech. At JPL, Spencer had been the deputy project manager for the Phoenix Mars Lander, mission manager for the Deep Impact and Mars Odyssey projects, as well as the mission designer for Mars Pathfinder. Before joining the LightSail team, Spencer was leading a Georgia Tech small satellite program, Prox-1, that deployed a space sail. Now he runs a satellite program at Purdue University.
“He has spacecraft experience, systems engineering experience, plus he’s easy to work with,” says current LightSail program director Bruce Betts, “which is important when you’re in the throes of early operations and sitting in a room for 16 hours a day with each other.”
Space is really unforgiving.
Outside the lab, Spencer golfs, plays tennis and recently read Winston Churchill’s six-volume tome on World War II. Before becoming an aero engineer, he toyed with being a writer or a journalist. The sheer poetry and beauty of the sail is what excites him. That’s why the design phase of the mission is one of his favorite parts. His love for nature balances his work and is something he shares with his wife, Sallie, an established landscape artist.
Still Spencer is no pushover. “Space is really unforgiving,” he says, and “if there are any weaknesses in design or even in the team, outer space will find them.” So, when he joined LightSail1 and after 17 years with JPL, he knew that he had to be in control of the mission details, or he wasn’t going to take the job. His tenacity and love of problem-solving comes from his mother, though it hasn’t always won him friends. Sometimes his dry humor and joke delivery save him.
Spencer joined the project in 2009, ahead of the launch of LightSail1. It was fun, he says, but “things were kinda cobbled together when it got to the launchpad,” he says. Minimal on-ground testing made the spacecraft difficult, says Spencer, and it faced problems with sail orientation and communication when the craft was in Earth’s shadow. Still, LightSail1 launched into a 200-400-mile orbit above Earth and the sail deployed correctly.
In the next phase, the orbit time would be longer. So Spencer’s LightSail2 team tested, simulated, failed and tested again to avoid the pitfalls of the first generation — including making sure the sail was correctly oriented to the sun and fixing the momentum wheel that rotates the spacecraft. “From the time my head left the pillow in the morning until I went to bed at night, that’s all I thought about,” Spencer says. “It was so much fun.”
Then came the big day: On July 23, LightSail2 deployed and reached orbit using nothing but sunlight. The Planetary Society declared the mission a success on Twitter, and it was named as one of Time magazine’s best inventions of 2019.
But Harvard astrophysicist Jonathan McDowell publicly questioned whether the sailing was controlled and whether the craft was tumbling rather than achieving orbit. The Planetary Society tweaked how it described the orbit on its website but maintains the orbit is a success. (McDowell now says he’ll take their word for it.)
This summer, LightSail2 will burn up and be destroyed as it reenters Earth’s atmosphere. And work will accelerate as Spencer’s team collaborates with NASA on its own solar sail mission, Near-Earth Asteroid Scout, that will fly by an asteroid. That mission, launching in 2021, will be the first time solar sailing has a scientific application, rather than just proving it works.
But as usual, Spencer is thinking bigger. This spring his team will launch an even larger solar sail that will be 18 square meters. Destination? Outer space.
OZY’s Five Questions with Dave Spencer
- What’s the last book you finished? John le Carré’s new novel, Agent Running in the Field.
- What do you worry about? I worry that we have an entire generation in this information age that is growing up and not involved in nature or getting outdoor time like I did when I was a kid.
- Who’s your hero? My grandfather was my hero. He had such a love for life. He was an outdoorsman and a lot of fun.
- What’s your one must-have tool? I need something like a book or an article or an intellectually stimulating problem to chew on and drive my thinking.
- What’s one item on your bucket list? I want to travel the world, spending time getting to know the local vibe. My top place to go would be the Greek Isles.
Correction: An earlier version of this story misstated Spencer’s role with the Mars Pathfinder. He was mission designer, not mission director. He was in the control room for the Mars landing, but did not lead the mission.