How to Fly to Alpha Centauri

Feature

Friday, July 18, 2014

An artist's rendering of a conceptual design of a starship An artist's rendering of a conceptual design of a starship (Ralph McNutt of Johns Hopkins University, Advanced Physics Lab/Courtesy of the Tau Zero Foundation)

Talking about building an interstellar space ship makes you sound like a sci-fi fan who’s lost touch with the real world. Unless you’re Mae Jemison, a former astronaut — the first African-American woman in space. Then you might legitimately wonder, “How in the hell do you get to another star system?”

Jemison actually needs to answer that question; she’s the head of 100 Year Starship, an organization the home page of which boldly commands, “Let’s make human interstellar travel capabilities a reality within the next hundred years.”

“That time frame is reasonable, why?” she asks rhetorically. “If you said ten years — 'Nah, we know that’s not long enough.’ If you said 500 years, people would say, ‘I can kick back for another two to three hundred years because I don’t have to worry about it.’ One hundred years is close enough."

The problem: space is big, and our current rocket technology isn’t cutting it. “If you’re travelling with technology we can already conceive, like say the Voyager spacecraft, it’s going to take about 80,000 years to travel a distance to our nearest neighboring star," says Marc Millis, the head of the Tau Zero Foundation. “And it is going 0.00006 times the speed of light.” Nuclear-powered spacecraft might go much faster, and have their proponents, but are politically and environmentally dangerous: no one wants to risk a nuclear meltdown during liftoff. 

The heads of yet another interstellar organization, Starship Century, think they are on the right track. James Benford is president of a company that does microwave research; his identical twin brother Gregory is an astrophysicist at the University of California, Irvine. The Benfords make a strong case for a technology right out of a science fiction novel. The technology is the beam sail, and the book is Rocheworld, written by Robert Forward in 1982. “[It’s] a very solid scientific concept for a starship,” James says.

A beam sail is like a regular sail — “envision it as a giant umbrella, maybe 100 meters across,” says Gregory — pushed with microwave beams, instead of wind, to extremely high speeds. Beam sails are still in the experimental phase, and far more tests will be necessary on Earth and in space before we know if they can propel an object across the galaxy. Even Jemison admits that the hundred-year estimate is kind of a tease — it’s more about figuring out the physics than building the Enterprise.

But Gregory Benford likes to remind us of how greatly we underestimate the pace of change. “Thomas Jefferson said in 1812 that it will take 1,000 years for the republic to reach the Pacific. He never envisioned that 57 years later, a train would run all the way to San Francisco.”

Slideshow: Starship Designs

Alpha Centauri, the closest star to our solar system. Organizations like 100 Year Starship believe humans could launch a starship to Alpha Centauri in as little as a century.
Wikipedia Commons

Alpha Centauri, the closest star to our solar system. Organizations like 100 Year Starship believe humans could launch a starship to Alpha Centauri in as little as a century.

One of NASA's two identical Voyager space probes, launched in 1977. The fastest unmanned space probe that we have, Voyager would take 80,000 years to reach Alpha Centauri.
Wikipedia Commons

One of NASA's two identical Voyager space probes, launched in 1977. The fastest unmanned space probe that we have, Voyager would take 80,000 years to reach Alpha Centauri. 

Designed in the 1970s, the bulbous Daedalus was the first engineering study of an unmanned starship. In this updated computer rendering, the Daedalus dwarfs Saturn V, the largest rocket launched into
Adrian Mann/Courtesy of Icarus Interstellar

Designed in the 1970s, the bulbous Daedalus was the first engineering study of an unmanned starship. In this updated computer rendering, the Daedalus dwarfs Saturn V, the largest rocket launched into space.  

The Innovative Interstellar Explorer, a 1990s engineering study for a starship using the existing technology of the day.
Ralph McNutt of Johns Hopkins University, Advanced Physics Lab/Courtesy of the Tau Zero Foundation

The Innovative Interstellar Explorer, a 1990s engineering study for a starship using the existing technology of the day.

A 1990s rendering of a starship powered by a solar sail and nuclear fission.
Alexander Szames/Courtesy of the Tau Zero Foundation

A 1990s rendering of a starship powered by a solar sail and nuclear fission. 

A conceptual rendering of a starship powered by beam sails. Beam sails would propel a starship using microwaves beams and could be propelled at high speeds.
Rick Sternbach /Courtesy Starship Century

A conceptual rendering of a starship powered by beam sails. Beam sails would propel a starship using microwaves beams and could be propelled at high speeds. 

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Produced by:

Ann Heppermann

Comments [2]

Chet Beardman from Maryland

The technology to get to Alpha Centauri has existed since shortly after the end of World War II. The size of the ship and a place to launch it are more problematic than the basic drive. We're simply not desperate enough yet.

I submit that Project Orion presented the world with nuclear pulse propulsion. Pournelle and Niven explored its use within the Sol system in "Footfall."

Jul. 19 2014 03:07 PM
Jake Sterling from East Boston

I have been wondering for a while if anyone is going to look at balloon and parachute technology when thinking about travel in space. Mostly what we see is structures (spaceships) made of metal, with designs based on the compressive strength of metal. But in space gravity isn't the controlling force that it is on earth. What is important is relative air pressure. In other words there is an almost complete vacuum in space and us human beings require an atmospheric pressure of around 15 lbs. per square inch. The obvious way to construct a space ship is as a balloon. With the air pressure inside, the skin of this balloon would become quite rigid, though it would still retain a level of flexibility that rigid metal doesn't have. The structure would also be extremely light and could be packed into a very small space for taking off and landing on planets.

There is no reason to think that habitats in space need to be cramped when large structures can simply be inflated. The interiors could be divided into chambers with fabric walls. These walls could also serve as structural elements to control the balloon's outer shape.

I notice that in the illustration, Beam Sails are imagined as flat, rigid surfaces, sort of like sheets of plywood; but there is no reason an inflatable structure couldn't be shaped so as to also act as a sail. Imagine a huge parachute shaped structures made of fabric with an inflated "hem" (like the hem of a skirt) for habitat at the trailing edge. If Beam Sails function in ways similar to the way wind sails work on boats, a flexible, curved surface would add an element of efficiency and control that flat surfaces lack.

Jul. 19 2014 08:02 AM

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