The Bristol GyroWheel is an innovative attitude control system device that provides both an angular momentum bias and control torques about three axes while at the same time measuring the spacecraft angular rates about two axes. The principles of operation of this device are explained and the flight model design is described that is targeted at small satellite applications which is currently under development. A fully functional prototype of the GyroWheel has been developed that has demonstrated the actuator and rate sensing capabilities and some of the test results are given. One of the key advantages of the GyroWheel is that, for earth pointing applications, it can be used with a single 2-axis earth sensor to provide fine pointing control in all three axes. This allows for reducing the mass, power above all cost of this class of ACS system. A GyroWheel based ACS design is developed for an example case consisting of a small earth pointing microsat mission. Performance simulations are given that show that the pointing control can be maintained within 0.1 degrees in all axes. The GyroWheel promises to fulfill the need for low cost, low mass, high reliability and high accuracy attitude control systems for applications such as communications, remote sensing, and space science.