How difficult is it to maintain the ISS?
-- John T. (Team Explorer)

MAGNUS: The actual work is not that difficult, mainly because when the ISS was designed a lot of thought went into how you would fix things in orbit. You have to think about access to the various parts, for example, along with what to do with loose bolts and screws. Here on the Earth, they drop to the ground and you can find them. In orbit, if they get loose, they pretty much float away and disappear. So the engineers designed the bolts and screws to be captive so that you can unscrew them and release them but they stay put in their holes and do not float off. You cannot just go to the hardware store to buy what you need when something breaks, or to get a replacement part. People have to do analysis and lots of thinking ahead of time to figure out what kind of parts and equipment to send and store on the ISS so that if/when something breaks it is possible to replace it. This means that as the equipment is designed you have to figure out how long the various parts will last and where the probable failures are, so you can plan for that and send those parts early to the ISS. Another aspect to consider is whether you design a piece of equipment to be completely replaced or design it such that it can be fixed by taking it apart and replacing the small parts. It gets very complicated, but it is a very interesting engineering problem.