Mars Science Laboratory Will Launch on an Atlas V 541
When mission planners are considering different launch vehicles, what they take into consideration is how much mass each launch vehicle can lift into space.
Details on the Launch Vehicle
Atlas V rockets are expendable launch vehicles (ELVs), which means they are only used once.
The thee numbers in the 541 designation signify a payload fairing, or nose cone, that is approximately 5 meters (16.4 feet) in diameter; four solid-rocket boosters fastened alongside the central common core booster; and a one-engine Centaur upper stage.