Atlantis may have taken off on the last ever space shuttle mission last week but that doesn't mean it has finished racking up firsts. Along with ferrying its last batch of supplies to the International Space Station (ISS), Atlantis is also carrying a urine recycling system that is designed to convert astronaut's urine into a sports drink. The Forward Osmosis Bag (FOB) system will reportedly be tested by one of the four-man crew towards the end of the shuttle's 12-day mission.
Although the ISS already has a urine-recycling machine that produces clean reclaimed water from urine using a distillation process to remove impurities, the system consumes valuable power from the station's limited supply. In contrast, the FOB system doesn't rely on any direct energy input as it relies on osmotic pressure to draw solution from a lower concentration to a solution with higher concentration. It uses a semi-permeable membrane that allows small molecules such as water to pass through while blocking larger molecules like salts, sugars, starches, proteins, viruses, bacteria and parasites.
Forward osmosis systems have already been used on Earth by soldiers but the final space shuttle mission will be the first time such a system has been tested in the zero gravity environment of space. Its performance will be compared to that of similar systems used on the ground, which produce around a liter of drinkable fluid in around four to six hours.
Although the system is designed to work with urine and sweat - or just about any dirty water - the Atlantis crew won't be using their own urine but will instead be testing it using an experimental fluid. After the fluid passes through the semi-permeable membrane it will be combined with a sugary solution to produce a sports drink-like fluid.
The applications for such technology in space include incorporating a small forward osmosis device into EVA suits to recycle sweat and urine and provide drinkable fluids on extended space walks. It could also be used to extend the non-potable resources on the ISS in the event that a resupply vehicle is delayed, or as a space- and weight-saving method of providing returning crews with fluids using seawater after a splashdown.