MIT is developing an Earth-based hopper prototype for autonomous planetary exploration. This paper describes the initial development of the hopper prototype and its application as a testbed for lunar hopper technologies. The prototype hopper consists of a gravity-canceling system, composed of battery-powered electric ducted fans, and an integrated lunar hopper system, which operates using cold gas propulsion. The gravity-canceling system is designed to allow the lunar hopper system to operate in an environment which is dynamically similar to the surface of the Moon, although it also allows for recovery and safe touchdown if the cold gas system experiences a failure. The environment provided by the electric ducted fans applies the fan thrust against Earth's gravity to obtain a desired upward acceleration, allowing the cold gas jets to operate as if they were in a fractional-gravity environment. The key design features of the integrated gravity-canceling and lunar hopping systems are presented in this paper.