The Flotilla was a fleet of two kilometre long, re-purposed in-system freighters launched from Mercury in 2083, as humanity's first manned interstellar colonization effort. The fleet's final destination was the 61 Cygni A system; a planet they named Journey's End. When first launched it comprised the Santiago, Palestine, Brazilia, Islamabad, and Baghdad.
Their main engines were powered by a lithium/antilithium reaction, with the reactant antimatter stored in two massive reservoirs -- one for initial acceleration and one for final deceleration -- as they lacked the technical knowledge to stop the flow of antimatter once a reaction had been initiated (the latter tank contained slightly less antilithium to compensate for inevitable loss of mass during the journey).
Each vessel originally possessed nine-hundred and sixty passengers in reefersleep caskets, and a crew of one-hundred and fifty. Its crew size was predetermined for maximum internal harmony and general well-being; large enough to allow individuals to move in different social cycles, but small enough to prevent deep internal schisms.
Unfortunately, due to external sabotage and internal political scheming, only three of the five flotilla ships reached their destination. Once there, the fractious atmosphere cultivated by the crews would be transmitted to the passengers, and global conflict soon erupted between the northern and southern settlements.