A spherical tank for storing liquid oxygen on the space shuttle is to be made from stainless steel of 0.80 m outer diameter and 5 mm wall thickness. The boiling point and latent heat of vaporization of liquid oxygen are 90 K and 213 kJ/kg, respectively. The tank is to be installed in a large compartment whose temperature is to be maintained at 240 K. Specify an appropriate insulation material and thickness of this material that will maintain oxygen losses due to boiling below 1kg/day assuming a combined convective and radiation heat transfer coefficient of 10 W/m2K.