"It's difficult to come up with a faux urine, explained NASA's Jim Lewis, the systems manager overseeing development of Orion's potty. 'That's why we depend on collections.'" They can tell my sex, blood type, color of my eyes and hair, my favorite brand of cigarettes and my probability of being obese from a drop of my blood but they can't synthesize urine? Where there heck did things go so wrong?
Actually I'm quite sure they could synthesize it. However, why build a cow when you can get the milk for free? They could spent a ton of money developing synthetic urine, but even then there is no guarantee its going to behave exactly the same. Why not just use the real thing?