It wasn't a fact anyone really liked to think about, but in the pursuit of galactic surveying/colonialism the few ships made and sent out to search out for new planets people died. This event is always a shock to everyone in the Federation who has the best medicine and science to keep everyone at tip top shape and reverse aging if necessary, but going into parts unknown was dangerous and you could easily get killed if you made a small mistake. If it were merely one person out of a few dozen or hundred it wouldn't be the worst loss, but usually these ships had only a handful of people. Sometimes a minimum of 3 for the smallest of ships, and if anyone of those were to have been lost permanently ...
Well thanks to the federation there were cloning bays, and thanks to the wireless connections and nanomachines in people you could just clone someone who had just died with their consciousness in the new clone... At least that's what the scientists said, and only the paranoid nutcases said you'd just be dead and a clone who was virtually indistinguishable from yourself would take your place... and your nut a paranoid nutcase right? Most people said out loud they believed in the scientists but... no need to test and try it out.
A ship to explore the great unknown has just been manned, and was shipped off but this time for some reason the cloning bay was going to malfunction. Not so bad that the cloning process wouldn't happen or you'd be trapped in some abomination, but the clone may not exactly be a clone.