Quora Question: How Do Different Countries Share the International Space Station

Scott Kelly Space Photography
The lights of Perth, Australia, top, and the stars in the Milky Way are seen in this picture by NASA astronaut Scott Kelly taken from the International Space Station August 20. NASA/Scott Kelly/Handout/Reuters

Quora Questions are part of a partnership between Newsweek and Quora, through which we'll be posting relevant and interesting answers from Quora contributors throughout the week. Read more about the partnership here.

Answer from Robert Frost, Instructor and Flight Controller at NASA

It isn't that the vehicle is divided into different sections for different countries. It is that individual space agencies contributed modules and those agencies are the experts on those modules and are responsible for operating those modules.

It works out that every module aft of Node 1 (Unity) is the responsibility of the Russian Space Agency and is referred to as the Russian Segment and everything from Node 1 forward is referred to as the USOS (U.S. segment). The Russian and American segments are designed to be fairly independent from each other. The U.S. segment does provide the Russian Segment with most of its electrical power and the GNC computers on the Russian and American segments do control the vehicle attitude together, but other than that the two segments can operate individually.

The U.S. segment includes the European and Japanese modules. Those modules are not capable of functioning independently. They are reliant on the U.S. for cooling, power, and data connectivity. They therefore are not considered separate segments.

The biggest pro is it simplifies the responsibilities of the crew and flight controllers. For example, the American flight controller responsible for the electrical power system is called SPARTAN. SPARTAN has to have a very intricate understanding of how the electrical system on the U.S. segment works. There are dozens of boxes and a multitude of connectivity paths that they have to master, across the U.S. segment. But, they don't have to master the Russian segment power system. They need to understand the American box that sends American power to the Russian segment and they need to understand the Russian box that accepts that power, but they don't need an intimate understanding of what happens after the power passes through those boxes and they don't have to monitor the power after it has passed through those boxes.

The crew's responsibilities are similarly simplified. We have various levels of training certification for the crew for each system. They can be a User, an Operator, or a Specialist for each individual system on the vehicle. We develop a matrix for each crew so that we have the right combination of expertise. We don't need to have all six people be a specialist in every system. There might be two specialists, two operators, and two users for a system. Over the years, to reduce training time and expenses, the astronauts have become less responsible for activities on the Russian segment and the cosmonauts have become less responsible for activities on the U.S. segment. Astronauts are usually users on Russian systems and cosmonauts are usually users on American systems.

If a Russian box fails, a Russian flight controller will analyze the telemetry and determine what needs to be done. They will then direct the Russian cosmonauts to do whatever needs to be done. If an American box fails, an American flight controller will analyze the telemetry and determine what actions the U.S. astronauts need to do.

I'm having difficulty thinking of a con.

"What are the pros and cons of the ISS being divided into different sections for different countries?" originally appeared on Quora: The best answer to any question. Ask a question, get a great answer. Learn from experts and access insider knowledge. You can follow Quora on Twitter, Facebook and Google+. More questions:

Quora Question: How Do Different Countries Share the International Space Station | Tech & Science