How Fast is the ISS's Internet? (and Other Space Questions Answered)

By Will Smith

The International Space Station has a surprisingly speed connection to the Internet, although the ping probably isn't too hot.

I learn something new and fascinating every time I visit the Ask Science sub-Reddit. This thread, which started as a question about the ISS's Internet connection, is fascinating. The Internet connection uses the Ku-band, which delivers throughput around 10Mbit/sec down and 3Mbit/sec up from the station--roughly equivalent to a home Internet connection. The latency will undoubtedly be worse though, as the signal has to make a couple of round trips to geosynchronous orbit and back.

The thread also had information about the computers used by the crew and ground control on the station. NASA currently uses slightly modified Lenovo T61p laptops running Windows 2000 on the ISS. The modifications aren't to hardened the laptops against cosmic radiation, they have to do with cooling. You see, passive coolers rely on air convection, which doesn't exist in microgravity. On earth, when air around a radiator is warmed, it becomes lighter than the cool air around it, and rises away. This makes room for a supply of fresh cool air to replace it.

Photo Credit: NASA

In the ISS's microgravity environment, there's no up or down, so the air around a radiator just keeps getting hotter and hotter--it doesn't rise away. Adding fans to move air across passive coolers solves the problem. If the laptops use heat-pipes to move heat inside the machine, I'd assume they'd have to be replaced as well. Heat pipes use convection, along with a coolant liquid that boils at a low temperature, to efficiently transfer heat from hot components (CPUs and GPUs usually) to a single radiator and fan setup.

Those are just a couple of highlights. The entire thread is really worth a read, if for no other reason than to learn about the theoretically possible sea-level microgravity lab: could (at least in principle, never mind the inordinate expense) build an evacuated tube that encircles the earth, and orbit a lab at sea level within it. That lab would experience microgravity, despite not being in space.