Examples include ion thrusters or nuclear propulsion. Propulsion is provided by three Azipods, ABB's brand of electric azimuth thrusters. There are 16 small thrusters and two large S5.79 thrusters for propulsion. Its propulsion system features a cluster of five thrusters, built by Frontier Aerospace. Maneuvering is accomplished using four thrusters and one main propeller. Attitude control was achieved using the hydrazine thrusters and four reaction wheels. Sixteen hydrazine MR-103 thrusters on the mission module provide attitude control. MRO has twenty rocket engine thrusters on board. It also caused the loss of the submersible's starboard thrusters. Gridded electrostatic ion thrusters commonly utilize xenon gas. The cruise speed is achieved using only the aft thrusters. The guidance system was inertial with radio control of the vernier thrusters. They are used to orient thrusters on rockets. It too has a thrust-vectoring nozzle, assisted by the nitrogen thrusters for roll. Docking is assisted by four transverse bow thrusters.