A turbine disc used in a turbo-pump that is exposed to a large thermal gradient across the sides of the rotor disc. The warm side of the turbine disc is covered by a cover plate that forms a sealed space between the turbine disc and the cover plate, and this space is evacuated or insulated to form a complete vacuum or as near as a complete vacuum as possible. The surfaces of the turbine disc and cover plate that form the vacuum space are also coated with a reflective coating such as with a highly polished surface of low emissivity in order to minimize the radiation heat loss through the vacuum space. The turbine disc can have a cover plate forming a vacuum space or insulated cavity on both sides of the turbine disc. Ribs are also used within the vacuum space as supports for the cover plate due to the difference in pressure from the ambient side and the vacuum.