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.”

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