Staff Editor
One of mankind’s dreams has been to sail the vast reaches of interstellar space, as we happily sailed the waves of vast oceans. Designs are paving the way for exploration by humans beyond our solar system, using miniaturized robot modules to solve the challenges of design.
Rugged sail design
A sail isn’t as flimsy an idea for interstellar propulsion as one might imagine, provided it’s designed properly. The human race is once again getting serious about space exploration, so missions are on the drawing board for a fleet of space stations, observation posts, robot factories and colony habitats. They’re planned to stretch from low Earth orbit, to Luna, Mars and beyond.
The first way station of interstellar space is our nearest neighbor, a trinary star system we call Proxima Centauri. Only 4 light years away, it might as well be on the other side of the universe because our rockets would take until 82022 to make the trip, one way.
The seemingly low tech sail idea has advantages, as theoretically one can be accelerated up to 20 percent light speed. That would make the journey to Proxima Centauri in a manageable (for robots) 20 years. Sunlight alone won’t accelerate a craft enough, so lasers are employed.
That’s the tricky part. We don’t have enough laser power yet. It also limits the size of what can be sent cruising off into space to a module the size of a bedside digital clock.
There is a possibility of a planet in the habitable zone of the Proxima system, making it something we seriously want to explore. Someday, humans may be sailing around space in luxury capsules but if that’s ever going to happen, we first need to get that clock sized module from here to there.
Light might not seem to be something that packs a punch but the physicists say, if the sail isn’t designed just right, the photons will rip right through.
Microchip size probes
Back in 2016, astrophysicist Stephen Hawking and investor Yuri Milner challenged the scientific and engineering community with Breakthrough Starshot. Their initiative calls for microchip-size space probes to sail toward Proxima Centauri at 20% the speed of light.
The basic design “centers on a lightsail that harnesses the power of photons, aka light particles, beamed from an Earth-based laser, instead of wind like a traditional sail.” The idea, experts say, “gained so much popularity that researchers everywhere began studying how to bring the contraption to fruition.”
One team at the University of Pennsylvania is working on the sail itself. They published a pair of papers recently suggesting “a way to ensure these innovative spacecraft don’t tear from intense laser pulses during the two-decade-long interstellar voyage.”
After crunching all the numbers, they say a spacecraft needs to have a similarly designed sail as a boat. It “has to ‘billow’ in space’s void like standard boat sails wave amid Earth’s winds.”
According to associate professor Igor Bargatin, “when the photons hit our lightsail, they get reflected and they also create pressure.” The light pressure on the sail is more than you might expect.
“Designed pressures on our lightsails are not huge,” Bargatin said. “They’re about the same as having a penny on your hand.” Still, that “requires a significant amount of laser power” which means ultra harsh laser pulses can damage the sail material unless they’re designed to billow out.
