Question: would you sign up for a one-way trip to Mars? Followup question for those who answered "No": what if you had an internet connection? Obviously, a lifetime on Mars would be a lot more enjoyable with a steady diet of cat videos. But would it be possible?
The concept of an Interplanetary Internet first came into being in 1998, about a year after the quarter-century anniversary of the design of the Internet. At the time, a man named Vint Cerf was ruminating on the future of the Internet, and with good reason; Cerf co-developed the Internet protocol suite, a set of rules (commonly known as TCP/IP) that helps orchestrate the transfer of data throughout the network of devices we call the Internet.
"In 1997, I asked myself what should I be doing that will be needed 25 years from then," Cerf recounts in a recent interview with Wired. "And, after consultation with colleagues at the Jet Propulsion Laboratory, we concluded that we needed much richer networking than was then available to NASA and other space faring agencies."
And by "richer," what Cerf really means is "functional." If you want to communicate between planets, you're going to need networking protocols that accommodate for vast distances, long communication times, and lots and lots of interrupted signals. Communication between Earth and Mars, for instance, takes anywhere from four to twenty minutes, depending on the position of each planet in its respective orbit. And remember, that's the time it takes to send information in one direction. One of many reasons this is a problem: connecting to a website here on Earth relies on looking up an IP address that is constantly changing. Trying to nail down a website's IP address with an 8-minute data transfer delay between Earth and Mars just isn't going to happen.
Then there's the issue of connectivity. Disconnections and breaks in communication are among the biggest impediments to efficient interplanetary networking, which can be disrupted by everything ranging from the spin of a planet about its axis (something that can be predicted and scheduled for) to solar storms (which can't). When combined with the vast distances these communications need to travel, it's easy to see why delays, errors, and disconnections must be accounted for, something TCP/IP simply cannot do.
So Cerf helped develop a platform that does account for delays and disconnections: Disruption Tolerant Networking (DTN).
At the heart of DTN is something called the Bundle Protocol (BP), which is similar to IP. The crucial difference is where IP relies on an uninterrupted stream of information between one device and the next, BP allows information to be stored in packets when communications are severed, and forwarded when communication is re-established. This "store and forward" technique, as NASA calls it, allows space-based networks to compensate for intermittent connectivity.
Last year, NASA and the European Space Agency tested DTN and BP by having International Space Station Commander Sunita Williams pilot a LEGO robot in Germany all the way from low-Earth orbit.
The experiment was successful, but it's just the first step. Remember: DTN was designed to accommodate long delays, and unanticipated interruptions. Communicating to the surface of the Earth from orbit with a high quality connection is relatively straightforward, but it's an important proof of concept. "The demonstration showed the feasibility of using a new communications infrastructure to send commands to a surface robot from an orbiting spacecraft and receive images and data back from the robot," said Badri Younes, deputy associate administrator for space communications and navigation at NASA Headquarters in Washington. "The experimental DTN we've tested from the space station may one day be used by humans on a spacecraft in orbit around Mars to operate robots on the surface, or from Earth using orbiting satellites as relay stations."
By improving data timeliness, says the Agency, "we are reducing risk, reducing cost, increasing crew safety, improving operational awareness… improving science return." And, of course, improving the load-time of cat videos.