Interplanetary Net

This Antarctic Selfie Is Helping Build the Interplanetary Internet

Delay Tolerant Networking is the future of getting online in space.

Daniel Oberhaus

Daniel Oberhaus

The selfie above is remarkable for a number of reasons. In the first place, it features three NASA engineers at the National Science Foundation’s McMurdo Station, the largest research base in Antarctica. There’s also the picture inside the picture featuring Vint Cerf, best known as the “father of the internet” for his role in creating the protocols that determine how information is sent on the web.

However the most remarkable thing about this photo is what’s not pictured: the interplanetary internet it is helping to create.

After taking this photo on November 20, the NASA engineers sent it from McMurdo to the International Space Station. Although many of us trade selfies on a daily basis, sending a snapshot between two of the most remote human habitats in existence requires more than just opening up your photo app of choice. In this case, these NASA researchers were reliant on an experimental way of routing data called Delay (or Disruption) Tolerant Networking, and it’s the future of the internet in interplanetary space.

The terrestrial internet you’re using to read this article relies on a number of different protocols to route data between the servers hosting the websites you visit and your phone or computer. The two most fundamental protocols in this respect are the Transmission Control Protocol (TCP) and Internet Protocol (IP), which control how data is packaged and routed through the internet, respectively.

TCP is basically responsible for dividing data into packets of certain sizes and ensuring that they are correctly labeled so that they will arrive at their intended destination, and then the IP actually routes this packet through the internet. In the analog world, TCP would be a person sorting documents into addressed envelopes, and IP would be the mail service delivering these packages to their intended destinations.

The TCP/IP suite works great for most internet applications, but the terrestrial internet has a major weakness: it requires constant connectivity. This is because the TCP layer basically engages in a series of confirmations when sending or receiving data on the internet. If the TCP layer doesn’t receive a confirmation that the data package it sent has been received at the correct address, it will timeout and try again. If the connection between these two points, say your local laptop and a web server, is not connected, you can’t visit that site.

NASA realized access the internet on the Mars will be crucial for both research and personal reasons when the first boots start kicking up Martian dust, but surfing the net in space comes with a host of difficulties not found on Earth.

With all the fiber optic cable crisscrossing the Earth’s surface, the constant connectivity needed for the internet isn’t a big deal. But things get more difficult in space, where large voids sit between objects in constant motion. You can’t exactly use 30 million miles of fiber optic cable to connect satellites in orbit around Mars and Earth. You also can’t depend on a constant wireless link between two satellites in orbit, which may be on opposite sides of their planetary bodies and unable to maintain a connection.

Enter the Bundle Protocol (BP), the core technology at the heart of Delay Tolerant Networking. Its development began in 1998 when NASA’s Jet Propulsion Laboratory invited Vint Cerf to help the agency create a new type of internet that could function in the difficult space environment. Cerf had already created the protocols that defined the way we internetwork on Earth, and with the Bundle Protocol he helped define the way we’ll network in space as well.

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Simply put, the Bundle Protocol is a way of storing and forwarding information between network nodes that are not always connected. It packages data in self-contained bundles that are routed from node to node when connectivity is possible. If connectivity is impossible, that data bundle is stored at the node until another node becomes available and the data can continue to its destination.

In this sense, Antarctica represents a good space analog. The continent lacks a dedicated cable connection to the global internet, which means the only way of getting online is using satellite internet. In the case of the selfie sent to the ISS last week, the NASA engineers first used the Bundle Protocol to package the data (in this case the selfie taken on a normal smart phone) and send it to a Tracking and Data Relay Satellite, which routes data from the agency’s satellites to ground stations on Earth.

The Tracking and Data Relay Satellite relayed the data bundle to the White Sands Complex in New Mexico, where it was forwarded to NASA’s Marshall Space Flight Center in Alabama through a series of terrestrial DTN nodes. Marshall then sent the bundles back up to a Tracking and Data Relay Satellite, which forwarded the bundles to a DTN node on the ISS once a connection was available. On the ISS, the receipt of the selfie looks like this:

This wasn’t the first time DTN was used to send information to the space station, but it was the first time it was possible using a normal cell phone. In 2012, astronauts on the ISS were able to use DTN to successfully commandeer a rover made of Legos on Earth. In 2015, astronauts at the European Space Agency repeated the experiment using a 2,000 pound rover at one of their labs.

Although this may seem like an absurd amount of work just to send a selfie, the experiment shows how DTN can also find applications on Earth by connecting remote research stations like McMurdo to satellites and other ground stations. More importantly, however, it is another demonstration that DTN can be trusted as the core of an interplanetary internet.