Monday, April 24, 2017

Suddenly, Alpha Centauri is a Popular Destination

Groups small and large set their sights on our neighboring star system.

The launch of Breakthrough Starshot a year ago, backed by Russian billionaire Yuri Milner, has re-opened the idea of exploring nearby stars—first by telescope, and eventually by spacecraft. While the group is holding a second “Breakthrough Discuss” conference this week to highlight its progress so far, other groups, large and small, are getting in on the action.

Starshot proposes sending a nano-spacecraft to the nearest star system, Alpha Centauri, at 20 percent of the speed of light within 20 years. Last summer scientists reported finding a rocky planet in the habitable zone of Proxima Centauri, one of the stars in the system. Meanwhile, scientists at the Max Planck Institute in Germany were so inspired by the Starshot idea that they came up with a way to slow down the spacecraft once it reaches its destination, using stellar pressure. Such braking would be critical if the spacecraft is to take pictures or collect science data.

Now a new NASA-funded project has jumped on the bandwagon. Called “A Breakthrough Propulsion Architecture for Interstellar Precursor Missions,” the study was selected as part of the agency’s advanced concepts program. The idea is to use a laser to beam power across the solar system, which is similar to the Breakthrough Starshot concept. The architecture also includes a highly (60 to 70 percent) efficient solar photovoltaic array, and a lithium-based ion propulsion system.

“Doing a real interstellar mission is extraordinarily difficult,” says principal investigator John Brophy of NASA’s Jet Propulsion Laboratory. “It doesn’t take you very long to see that one of the keys to doing this [interstellar travel] is that you really have to get the mass of the power system off the vehicle. You try to carry that with you, it’s too massive and takes you too long.”

Brophy acknowledges that this mission is decades away from happening; his $125,000 NASA grant will go to firm up the calculations for his initial projections. And even though his architecture includes an exceedingly fast spacecraft, it’s not fast enough for interstellar flight. A tiny probe could theoretically make it as far as Pluto in just a year, but to get to Alpha Centauri, the journey would take roughly 6,800 years.

While we’re waiting for interstellar missions to take shape, Brophy says the technology could be applied to exploring the outer solar system. He says a spacecraft’s photovoltaic array could be “tuned” so that it converts the incoming laser energy to a voltage that could be used directly by the spacecraft’s ion drive.

Not every interstellar wannabe is funded by a billionaire or government agency. A project to find potentially habitable planets in the Alpha Centauri system plans a new try at Kickstarter crowdfunding, after an initial round raised just a third of the requested $1 million last year. The money would be used for preliminary design of a 50-centimeter Earth-orbiting telescope, dubbed Project Blue, and planned for launch in 2020 on a two-year mission. The primary goal is to gaze at the triple-star Alpha Centauri system, which is roughly four light-years from Earth. Project Blue is also considering sponsorships and other ways to raise funds for the project, which is expected to cost between $25 million and $50 million.

Leader John Morse says that even though $1 million is only a fraction of what his BoldlyGo Institute needs to make Project Blue viable, crowdfunding would generate excitement and investment in the project from the outset. “Crowdfunding is only one arrow in the quiver, but a crucial one as we seek to provide novel opportunities for the public to be engaged,” he says. A former NASA director of astrophysics, Morse says the institute’s goal is to raise money to augment NASA’s work in space science and flight research.