"Space Internet" to Link Worlds by 2011?

Brian Handwerk
for National Geographic News
July 9, 2009
For all its might, the World Wide Web is still limited to, well, our world.

But that's quickly changing with the advent of an "interplanetary internet" that planners say will revolutionize space communication.

The Disruption Tolerant Networking (DTN) system, which entered another phase of testing this week, will allow astronauts to Google from the moon or tweet their observations from space.

But DTN provides far more than a connection to check your email. It's also essential for simplifying space command and control functions—such as power production or life-support systems—crucial for future space initiatives.

(Related: "'Rocket NASCAR,' Moon Base Part of 50-Year Space Vision.")

"You need an automated communications technology … to sustain planetary exploration on the scale that NASA and others want to perform over the next decade," said Kevin Gifford, a senior research associate at BioServe Space Technologies at the University of Colorado, Boulder.

"DTN enables the transition from a simple point-to-point network, like a walkie-talkie, to a true multimode network like the Internet."

After a decade of development DTN has advanced quickly over the past year, and NASA missions are planning to adopt the network by 2011. In November 2008 NASA test-drove the network by sending space images to and from the EPOXI spacecraft, some 20 million miles (32 million kilometers) from Earth.

DTN protocols were also installed on the International Space Station in May, and summer testing began the first week of July.

Houston, We're Fixing a Problem

Though tweeting astronauts have gotten a lot of press, "the reality is that they [don't really] tweet or have browsing capability on the International Space Station," explained Gifford, who is part of a large, cooperative DTN effort that has also included NASA and Internet veterans.

"Right now they actually voice down a simple blurb, and the tweet is operated manually from Houston," he said. In fact most current space communication involves humans manually scheduling each and every link, sometimes weeks or even months in advance for distant spacecraft, and dictating exactly which data are sent and when.

(See photos: "Humans in Space in 2057.")

Adrian Hooke, a veteran of the Apollo 11 mission launch team, manages the new space DTN project.

"Typically spacecraft go off and do their thing, gather up data, and then on some schedule they connect to the ground and [we] pull down the results of what it has been doing and send up instructions for the next time period," Hooke said.

Such manual operations are inefficient and expensive. But simply extending Earth's Internet into space won't work.

The Web uses Transmission-Control Protocol/Internet Protocol (TCP/IP), a type of communication language in which hosts and computers must be constantly connected.

This rarely happens in space, where intermittent connections are the norm because of the vast distances involved and the tendency of orbiting moons, rotating planets, and drifting satellites to temporarily disrupt wireless lines of communication.

Communications Leap

Typical space delays, even those caused by solar storms, are handled in stride by DTN, Hooke said.

Each node in the network—whether it's the International Space Station or a small orbiting robot—stores all the data it receives until a clear opportunity arises to pass its "bundle" along to the others in the network. DTN nodes do not discard data when a destination path can't be identified.

Hooke likens this "store and forward" process to a basketball team systematically passing the ball downcourt to players closer to the hoop.

The result, he explained, will be a communications leap akin to that between the post office and the telephone.

"A letter is a pretty self-contained story, it says do this or order that, and you mail it off and wait for a response."

But the new DTN system will open a more consistent line of back-and-forth communication.

(Read about how humans are exploring the cosmos.)

Edge of the Solar System

DTN is already used for earthbound projects.

Scientists, for instance, are using the system to tag and track wildlife with a data-delivery capacity far more reliable than past satellite-based networks.

DTN can also bring broadband Web to remote areas with few communication structures, connecting remote humans such as the Arctic's Sami people via satellite with far shorter time lags.

The U.S. military has also embraced the technology to help keep lines of communication open in remote areas—or when other infrastructure is destroyed.

So far, DTN doesn't seem to have a catch, experts say.

"There are no physical limits on where the protocols would stop working," Hooke said.

"We could use it to [send messages to] the edges of the solar system—the question is, how long will you wait for a response?"

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