Extending the Internet off-Earth

Tracy Caldwell Dyson in Cupola ISS

Self portrait of Tracy Caldwell Dyson in the Cupola module of the International Space Station observing the Earth below during Expedition 24.
photo: NASA/Dyson
Providing Worldwide Web access to the International Space Station is one thing.

Providing the ability to browse the web from Mars and beyond will be quite another.

Today, the crew aboard the International Space Station (ISS) can browse the web about as easily as you or I can. It’s relatively easy to provide web access, because the ISS orbits at an altitude of less than 300 miles, so packets traverse the radio link quickly and then they travel on terrestrial fiber. [Description of NASA’s Disruption Tolerant Networking for Space Operations (DTN)]

In the future, browsing the web across millions of miles will be tough, because of network latency, which is the transit time required for a packet to travel from sender to receiver, and good old multi-path RF (radio frequency) signal problems familiar to mobile radio users. Doppler shift may also cause trouble.

When we earthlings browse the web, our computer converses with at least two servers: our DNS (domain name system) server, and the desired web server. These conversations take place at nearly the speed of light — 186,000 miles per second. Typical latency across a few hundreds or thousands of miles is so small that we’re barely aware of these conversations.

Once we leave the realm of Earth, though, long distance radio links will cause long network latencies. The distance to Mars varies, but if we assume a minimum of 40 million miles, network latency will approach 4 minutes. (Our mechanical hero, Explorer 1, is 11 billion miles away. Radio signals from it require 14 hours to reach us.) Because of relative movement between transmitter and receiver, there’s bound to be transmission errors, and if just one garbled packet must be resent, it will require 8 minutes.

Some form of FEC (forward error correction) will help, but impose its own overhead. I suppose that frequency diversity may help the multi-path problem, but it will impose a complexity and power-consumption cost. I’ve never tried to use a web browser on such a sluggish network, but I’m sure that it’s frustrating, if not impossible. To some extent, the users could be helped by installing local DNS and caching proxy servers on Mars, but this would work only for frequently visited static pages.

RF signal latency will either halt exploration or force colonization

The Landing of Columbus at San Salvador, October 12, 1492.

Space explorers will eventually need to create their own little colonies far removed from Earth — sort of what the colonists did in the new world. Not only will their new colonies include their own local networks, but quite likely their own dialects, and eventually their own languages. As mankind explores the solar system and beyond, it’s likely that the explorers and colonists will develop their own amenities and technologies. Will their bodies evolve to adapt to their new environments? If so, at what point does it make sense to define them as something other than Homo Sapiens?

The next question is, Are we descendants of colonists from a distant planet?

Visit my website: http://russbellew.com
© Russ Bellew · Fort Lauderdale, Florida, USA · phone 954 873-4695

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