Arc heater facilities have been developed to simulate entry environments for nosetip and heat shield materials. Discussed in this paper is a recent advancement for testing 1 in. diameter models at pressures to 156 atm by using a cold gas shroud to confine the hot core to the boundary layer of the model, thereby minimizing the power requirement. Results of large and small model tests are presented. Also included are results of heat shield materials tested at heating rates from 500 to 5000 Btu/ft2s showing comparable performance using two different arc heaters and two model sizes.