With the end of the Mar500 simulated mission this coming Friday, the Russians are now proposing an eighteen month simulated Mars mission on board the International Space Station.

The Russians have been pushing to do this on ISS for years. Unfortunately, NASA has always resisted.

Yet, as I wrote in Leaving Earth, we will never be able to send humans to any other planets until we have flown at least one simulated mission, in zero gravity in Earth orbit, beforehand. Wernher von Braun pointed out this reality out back in the 1950s, and that reality has not changed in the ensuing half century. Not only will such a mission tell us a great deal about the medical issues of living in weightlessness for years at a time — issues that are far from trivial — it will give us the opportunity to find out the engineering problems of building a vessel capable of keeping humans alive during interplanetary flight, far from Earth.

You see, to do this simulation right you can’t just send up a crew and have them live on ISS for eighteen months. You also have to insist that they get no physical aid from Earth. A true simulation would stock ISS sufficiently for the full eighteen months prior to the start of the mission, and then provide no further supplies until the mission ends.

Furthermore, the crew should be required to maintain and repair the station on their own during the simulation, with as little help from the ground as possible. Should a piece of equipment fail, the flight crew should fix it themselves. Only if the problem is life threatening should the ground intervene.

This will be the reality on an actual flight to Mars: Should something fail when a spacecraft is in orbit around Mars, there will be little that ground controllers on Earth could do to help. Instead, we need build our interplanetary vessel so that is capable of making the journey reliably, and if not, build it so that the crew will have the ability to make repairs on their own. A simulated flight in Earth orbit would be the way to uncover these engineering issues.

Unfortunately, ISS is not a very good vessel for making this test, as it was not designed to be independent of Earth. Much of its operation is run from the ground. And on the American half, the equipment is often not designed for simplicity, making it difficult if not impossible for the crew to take it apart and make their own repairs.

Still, ISS is what we have, and we could learn a great deal about building our first interplanetary space ship by flying a simulated mission to Mars on the station. The Russians have the right idea. Let’s hope that NASA finally agrees and okays the mission.