A series of programs has been conducted to develop erosion-resistant nosetip ERN concepts to provide an all-weather flight capability for high- performance reentry vehicles. In a previous effort, two ERN designs utilizing monolithic solid tungsten subtips were designed for flight tests on Advanced Nosetip Test A.N.T. vehicles. In the present program, ground tests were conducted in a rocket motor test facility to evaluate the thermal and structural performance of full-scale models of these flight designs. The results of these tests indicated a low probability of survival for monolithic tungsten subtips in ICBM flight environments. Therefore, additional studies were performed to develop an improved subtip concept that would be more resistant to thermal stress failures. These studies resulted in a segmented construction approach that will reduce the applied thermal stresses to acceptable levels and provide a high probability of survival in flight. Two segmented and two monolithic tungsten subtips were then designed, fabricated, and tested on HEARTS and FLAME flight test vehicles. All four nosetips survived to impact with no evidence of thermostructural failure and with no development of vehicle trim angles-of- attack at low altitudes. Additional tests at more severe conditions are required to verify the improvement in thermal stress performance provided by the segmented construction technique.