SPINDLE is designed for a 1.5 km to 4 km penetration through a terrestrial ice sheet and the HAUV has been designed for exploration up to one kilometer radius from the cryobot. The cryobot is bi-directional and vertically controllable both in an ice sheet as well as following breakthrough into a subglacial water cavity or ocean. The vehicle is designed for subsequent return to the surface at a much later date or subsequent season. The required power plant must be very powerful, so the engineers are working on preliminary designs of a compact fission power plant that would be used for actual ocean planet missions.