Dennis Tito is planning an ambitious private flyby of Mars for 2018 that will carry all kinds of logistical challenges during its proposed 501-day span, not the least of which is shielding the crew from radiation without consuming valuable resources. The team's solution is a clever one, if not especially pretty: human waste. While the walls of the Inspiration Mars spacecraft will initially be lined with water-filled bags to guard against cosmic rays, their contents will be gradually replaced with er, byproduct
