Overview
The first stage of Falcon 5 was to be powered by five Merlin engines and the upper stage by one Merlin engine, both burning RP-1 with a liquid oxygen oxidizer. Along with the Falcon 9, it would have been the world's only launch vehicle with all stages designed for reuse.
The Falcon 5 would have been the first American rocket since the Saturn V to have full engine out capability, meaning that with the loss of one engine, it can still meet mission requirements by burning the other four engines longer to achieve the correct orbit. In comparison, the Space Shuttle only had partial engine out capability, meaning it may not be able to achieve proper orbit by burning the remaining engines longer.
Read more about this topic: Falcon 5