Bell built several versions of the rocket POGO under contract with the NASA as a possible civil and military transport, because it was intended to be used as a means of transportation on the moon during the Apollo missions as well as a army transport over things like ravines; however NASA decided not to use the POGO because of the risk of a crash, and decided to send the Rover car instead of the POGO. Bell had demonstrated that all the versions of the POGO flew in Earth atmosphere.