"The most beautiful sight in orbit…is a urine dump at sunset"*
Um. Awkard. So, could you explain yourself please Russel?
Russel wasn't available for comment but I can regurgitate what others have said for you. Space shuttles don't have much space on board for the little extras, like bodily waste, so they regularly have to release them to lighten their load. When urine is released from the exit nozzle it freezes immediately and 'instantly flashes into 10 million little ice crystals which go out almost in a hemisphere…a spray of sparklers, almost' (say Scientific American anyway). And it gets better, once those little droplets are crystals, the sun then hits them and transforms them into water vapour to create a kind of mesmerizing cloud of human bodily fluids.
The urine dump that Russel was talking about was a particularly big one (about 68 kilos of urine and water) because the shuttle couldn't unload during it's 10-day stay at the international Space Station. Nice.