The ML-X5 is a prototype Mun rocket capable of landing and returning a kerbal from the Mun. The rocket was designed to be very compact, so it only has as much fuel as it needs for its mission. The first stage of the ML-X5 is a group of 6 solid rocket boosters to get you in the air. Once you eject the SRBs, the main engine ignites and will carry your rocket to an orbital altitude. The third stage is designed to circularize your orbit, perform the Munar transfer, and circularize a low orbit around the Mun. The fourth and final stage will take you to the surface and is capable of returning you to Kerbin. Be warned, the low amount of fuel on the lander means that you have to be very careful with your flight profile, or else you won\'t have enough fuel to return.