Nov 192015
 

From Epic World-Ship Journeys to Spamming Our Galactic Neighbors

Illustration by Adrian Mann

Artist’s rendition of a WaferSat propelled to the stars by laser. (Illustration by Adrian Mann)

In Science Fiction, there are three ways to reach the stars: fly fast, fly slow, or fly tricky, or so an old saying goes.

In science, mostly there are the same three ways, but none of the options can be reached through a creative, technobabble paragraph. Some current theoretical approaches will likely turn out impossible despite research that suggests there could be ways around the speed limit set by light. There are always costs to breaking the speed limit.

The potential means to reach the stars, and the possible sociological impact the journey would have on their crews and the people left on Earth, drew vigorous discussions at this year’s 100-Year Starship Symposium in Silicon Valley during Halloween weekend. Charged with fostering research on the technology and planning systems needed to build a starship, and started by a seed grant from DARPA and NASA, the 100-YSS still has 96 years to reach its stellar goals.

The variations discussed this year were to fly big, fly long and the most innovative, to fly really small. Discussion on flying tricky, however, such as research on the Alcubierre warp drive, occurred only in hallway discussions as there were no formal presentations on faster-than-light concepts.

The Next Generation, and the Next, and the …

For the slow track, there’s an old concept, the generations ship – though often described with a newer name, the “world ship.” It would carry thousands of colonists and their offspring on a one way epic journey to the latest New World surrounding a distant star.

The world ship has the advantage of not needing a star drive that violates what we know about physics. It would be a huge ship, however, requiring advances in our current technology to not only propel the ship up to perhaps 20 percent of light speed, or .2c, but to incorporate a life-support system that will maintain its mini society of 10,000 to 100,000 people alive for, well, generations.

It takes a lot of engineering and money to send thousands of people to one star system. A variation of the plan sends a convoy of ships comprising one lead ship or mother ship, smaller robotic ships to mine resources along the way, and landers or “seed ships” to deposit colonists on suitable planets in several star systems. The mother ship, however would never stop. Letting the main, and most massive ship continue to star after star saves tremendous energy since the star-farers wouldn’t have to expend half the energy they brought with them to bring the giant ship to a halt.

Bruce Mackenzie, a founder of the Mars Foundation, developed the convoy plan, but Peter Swan, President of the International Space Elevator Consortium, subbed for him when Mackenzie couldn’t make it. Swan emphasized that a key part of the plan is not requiring all the resources needed for the journey to be sent with the world ship.

“I think we need resources along the way,” Swan said. “The idea of having a closed environment, I believe personally, is wrong.”

He expects the colonists and crew would continue to refurbish and upgrade the mother ship and mining ships as the convoy drops off only a portion of the colonists on each suitable planet it encounters. The rest of the colonists and potentially succeeding generations, would travel deeper into the galaxy, settling more planets along the way. Of course, the people on the ship may have their own ideas about continuing the journey, and could even decide one planet is enough. But the plan gives the opportunity for expanding humanity far into the galaxy.

(I’ll write more about Swan and his efforts for building a space elevator in a later blog.)

Spamming Our Stellar Neighborhood

A mix of a new concept with a well-studied propulsion idea would send a kind of human offspring, a multitude of tiny AI probes, on a fast track to our galactic neighbors. Each miniaturized probe on a 4-inch wafer would be propelled by a short laser burst to send then on their way to the stars at 25 percent of the speed of light. It could be a dramatic step for space exploration, or a giant leap for galactic spam.

Philip Lubin, Professor at University of California Santa Barbara.

Philip Lubin, Professor at University of California Santa Barbara. (Photo Credit: Sonia Fernandez, UCSB)

Once we launch one, we can launch the next one, and the next one, 140 per day if you want, or 40,000 per year.

Philip Lubin, Professor physics at the University of California Santa Barbara, presented the idea of propelling these mini explorers by a 100 gigawatt laser array in orbit. The laser, aimed at a square-meter star sail on each of the wafer-mounted probes, could accelerate the “WaferSat” to .25c in 10 minutes. At these speeds, the WaferSats could reach Alpha Centauri in about 16 years. By comparison, the Voyager spacecraft has been traveling for nearly 40 years but only recently left our solar system. The incredible acceleration would be possible because of the light mass of the wafer-mounted probes, weighing possibly no more than a gram on Earth. Yet these tiny probes could withstand the 10,000 g’s during the acceleration, a stress already endured by instrumentation on some military weapons.

Despite the small size, the wafer could carry miniaturized sensors including a camera that makes them viable probes to star systems  within our cosmic neighborhood. Lubin emphasized that mass producing the probes allows the system to launch numerous WaferSats at one system, and even more toward other stars.

“Once we launch one, we can launch the next one, and the next one,” Lubin said, “140 per day if you want, or 40,000 per year.” He didn’t offer any speculation what any sentient life in nearby star systems might think of such mass cosmic mailings.

Lubin emphasized that what he was describing was a roadmap to a launch system that could be used for many purposes, including larger probes to the stars at slower speeds, cargo and crewed craft on interplanetary trips that could reduce the time to Mars from months to days, and the laser array could even be used for planetary defense by redirecting asteroids on a collision path with Earth. Such multiple uses would more readily amortize the cost of the laser array, and Lubin emphasized there’s no need to build everything at once.

“You can do this. You can build your 100-year starship. It just won’t carry humans. There’s no reason why you can’t do this. It’s a roadmap. It’s completely scalable and modular. It has many other applications.”

Yet Lubin admitted, “It’s hard, it’s really hard to do … But it’s not impossible.”

Related

Roadmap to the Stars

The Atlantic: What happens When Intelligent Life is Discovered?