The US Army has developed a new way to enable soldiers to carry less water. They have created rehydratable food rations that come in a wrapping that is actually a sophisticated semi-permeable membrane. So to rehydrate the food, soldiers can simply pee on it, or even pour dirty water on it if that’s all that is around. The membrane filters out 99% of the bad stuff so that only clean water gets into the food. Sounds appetizing.