Traveling 4.37 light years at 20 percent the speed of light (i.e. really fast) for two decades seems like a difficult journey. It's the trip that Stephen Hawking and Russian billionaire and space enthusiast Yuri Milner want to send a tiny (think postage stamp size) spacecraft on. This project, named Breakthrough Starshot, aims to get this 'nanocraft' to Proxima b, an Earth-like planet in the nearby solar system Alpha Centauri.
One of the main issues with this far-out plan, however, is the ability of this spacecraft to "put the brakes on" in order to stop. Because this little craft would be hurling through space at 13,800 km (8,574.9 miles) per second, figuring out how to slow down is obviously necessary, but fairly tricky. If the braking mechanisms aren't correct, the spacecraft could overshoot the entire solar system and completely miss the opportunity to collect information.
One of the proposed methods to solve this problem is what is called a solar sail. This would be a sail that deploys close to the craft's target, and uses the gravitational pull and radiation of nearby stars to swing into orbit and decelerate. To make this happen, initial plans must be deviated from. Originally the size of a postage stamp, the craft would be enlarged to about the size and weight of a bar of soap (less than 100 grams). Additionally, this sail — a massive, lightweight structure — would be attached in order to help the craft to both accelerate and decelerate.
To speed up the craft, the sail would absorb photons from the Sun, and to slow down, it could absorb radiation nearing its target. The radiation would also, hopefully, allow the probe to be steered towards the Earth-like planet. Getting into the exact solar system is tricky enough, but navigating to Proxima b will add much more difficulty to this journey. This sail-craft concept would be slower than the original Breakthrough Starshot design, but this team is hopeful that the sail can be improved upon even more.
Scouring the Universe
The original Breakthrough Starship plan suggested that instead of just landing on the Earth-like planet Proxima b, a fleet of these 'nanocrafts' could be deployed to survey larger interstellar areas. While this possibility seems promising in theory, there is only so much information to be gathered while hurling through space at blinding speeds. The essential purpose of this fleet would be a blanket survey — searching for information and possible signs of life — as there is only so much information be gathered via this method.
While it might not be deployed with many others in a fleet, a slightly larger craft able to land on the promising Proxima b could potentially gather much more in-depth and useful information. It would also travel a great distance and could survey from afar, but would have the additional advantage of up-close and — most importantly — long-term data collection. Instead of a fraction of second to collect data, the probe would have as much time as it required — at least until it breaks.
While there is still so much for these scientists and engineers to consider and evaluate before finalizing a model to launch, it is important not to forget the purpose of the mission: to learn. Regardless of the type of craft deployed, it will be a momentous and historic moment. Even if it takes more time, it is vital that the craft is designed in a way that allows it to collect as much information as possible. The opportunity to travel to another solar system doesn't come along very often, so we better make sure that we are putting out best tiny spacecraft forward.