THE INTERPRETER: Mars One (and done?) | MIT News : “The ISS is based on the idea that if something breaks, you can call home and get a new part quickly,” says Owens. “If you want a spare part on Mars, you have to send it when a launch window is open, every 26 months, and then wait 180 days for it to get there. If you could make spares in-situ, that would be a massive savings.”