And then there was the grand finale, the discussion about actually sending a spacecraft to a planet around another star. This project, called Breakthrough Starshot, was announced in April 2016 to considerable fanfare. Using a giant laser on Earth, a small chip with a massive sail would be accelerated to one-fifth the speed of light, reaching Proxima Centauri – and thus Proxima b – in just 20 years.
Breakthrough Discuss, however, highlighted just how difficult such a proposal might be. One attendee told IFLScience that they thought the project was now less likely to happen that it was a year prior, based on the huge number of challenges that have become apparent.
One is actually firing the laser at the spacecraft in the first place, laid bare by Zac Manchester from Harvard University in a fascinating talk titled “How to ride a laser beam”. He pointed out that the force of the laser hitting a flat sail could send it spiraling off course, so it may be necessary to use a spherical sail to stay on track for Proxima. This itself presents new challenges that have yet to be solved, such as how to spread the force of the laser over the whole sail.
Even if the spacecraft gets there, sending data back is also a huge issue. The chip at its center will be barely a gram in weight, with the sail mere atoms thick. Thus there will be no room for an antenna to transmit data – including images of the planet – back to our planet. Some novel ideas include using the sail itself as a giant antenna, although we don’t yet know if this is possible.
Will Starshot get off the ground? Breakthrough Initiatives
And even if we get there, the flyby will be extremely brief. René Heller from the Max Planck Institute for Solar System Research in Germany said in a talk how, after 20 years of travel, the flyby would last just a matter of seconds. He instead proposed using Proxima’s companion stars, Alpha Centauri A and B, to slow down the spacecraft and enter orbit around Proxima b, something that would return much more data at the cost of a much longer mission. We’ve covered this interstellar roundtrip idea before if you want some more information.