I did a four-month tour at the NASA-funded HI-SEAS—that's Hawaii Space Exploration Analog and Simulation—in 2013, and a new 8-month mission is scheduled to start in October. It's a long time to be cooped up, "so the psychological impacts are extremely important," habitat designer Vincent Paul Ponthieux says. The key to keeping everybody sane? A sense of airiness. Yep—even on Mars, you're going to need more space.
Power System | Solar panels supply power and charge the batteries for the habitat. If juice levels fall below 5 percent, a hydrogen fuel cell kicks in.
Workshop & Airlock | Crew can use the 3-D printer to make hair clips, replacement parts, and anything else they forgot back on Earth. This area is also the door to the surface; they simulate depressurization and pressurization before and after sorties.
Composting Toilets | Repurposed poop (sans pathogens) from one mission might be plant food for the next one.