An Internet That Works in Space
We already mentioned the idea of connecting spacecraft and probes in a vast network across space, so that scientists could connect to them the way that they do to a Web site on the Internet. But as some critics point out, this approach might not be the best because the Internet's basic design wouldn't work very well in space. The Internet protocol that we use on Earth relies upon breaking up everything we transmit -- whether we're talking about text, voice or streaming video -- into little pieces of data, which is then reassembled at the other end so someone else can look at or listen to it. That's a pretty good way to do things, as long as all that information moves along at high speed with few delays or lost packets of data, which isn't that tough to do on Earth.
Once you get into space -- where the distances are enormous, celestial objects sometimes get in the way, and there's a lot of electromagnetic radiation all over the place to mess with the signal -- delays and interruptions of the data flow are inevitable. That's why some scientists are working to develop a modified version of the Internet, which uses a new sort of protocol called disruption-tolerant networking (DTN). Unlike the protocol used on Earth, DTN doesn't assume a continuous end-to-end connection will exist, and it hangs onto data packets that it can't immediately send, until the connection is re-established. To explain how that works, NASA uses a basketball analogy, in which a player just holds onto the ball patiently until another player is open under the basket, rather than panicking and tossing up a wild shot or throwing the ball away. In 2008, NASA ran its first test of DTN, using it to transmit dozens of images from a spacecraft located about 20 million miles (32.187 million kilometers) from Earth [source: NASA].