Hi, After watching and listening to a lot of talks about colonizing Mars it seems like a good idea to make passenger sections removable to leave behind. Basically you go in your cabin you keep that cabin. Less strain for fuel to return to Earth and more resources for Mars. Plus each passengers waste materials, as these can have some use on Mars. And each passenger should take with them about their own body weight in seeds of food they eat on Earth. Will help keep them healthy to eat the food and liquids their body has become accustomed to. And each cabin have about 1 inch of water circulating around these removable cabins. Helps absorb radiation and reusable for drinking and recycle from washing and toilet. You even leave the ultra steel section behind. Metal would be major commodity or even be part of one of your burrowing tunnellers. Which could lead to a future hyperlink to the poles.