Just how dangerous is it to travel at 20 percent the speed of light?


#Speed #DangerousJust how dangerous is it to travel at 20 percent the speed of light? : Breakthrough Starshot is one of the more exciting scientific ideas that has popped up in the past decade, with its promise to deliver hardware to the nearest star in time for many people currently alive to see it.

While the idea would work on paper as an extrapolation of existing technology, there are a lot of details that need to be thoroughly checked out, because it’s possible that one of them could present a show-stopper.

There’s a bit of good news there: Breakthrough Starshot is apparently funding the needed research to give its concept a thorough vetting. A recent posting to the arXiv describes a careful look at the odds of a spacecraft surviving an extended journey at the speeds planned for the trip.

Overall, things look good, but a bit of shielding will be needed, and there’s the potential for a catastrophic collision with a speck of dust. The work, done by a team of four astronomers, focuses on one of the most basic issues: spacecraft survival.

The goal of Breakthrough Starshot is to accelerate its craft to about 20 percent the speed of light. At that speed, even individual atoms can damage the vehicle, and a collision with a bit of dust could be catastrophic. So the team set out to quantify just how risky these collisions could be.

The space between here and the nearest star isn’t completely empty. Earlier generations of stars have left a sparse collection of tiny dust particles, and various processes have left individual atoms scattered through the interstellar space. These particles pose very distinct risks, and the team worked through each separately.

The main problem with running into an atom isn’t the physical collision but rather the energy deposited in the spacecraft by the impact, which can cause local heating that damages the craft in two ways.

When high enough, the heating causes the material the craft is made of to evaporate into space. Below that threshold, it can cause local melting, leading to a change in material properties as the area resolidifies.

Using information on the bombardment of quartz (silicon dioxide) and measurements of the interstellar gas concentration, the authors performed some calculations to describe the damage that will occur during flight.

They found that while hydrogen and helium are the most common atoms the spacecraft will encounter, heavier atoms-specifically oxygen, magnesium, and iron-will do the vast majority of the damage.