A high-temperature, steady-state, in-pile experiment was developed to simulate prototypical nuclear thermal propulsion conditions. The experimental development of the resistively heated test apparatus involved spatially scaling the device to a larger heated region from a previous smaller out-of-pile prototype. A series of tests and investigations were conducted to replicate the smaller out-of-pile system’s success of achieving 2500 K. However, limitations within the larger assembly were identified; specifically, the heater filament design does not scale well. The larger assembly can reliably generate usable temperature levels from room temperature up to those exceeding 1300 K for hours. It can briefly sustain a usable 1800 K. The larger system is achieving temperatures over 2500 K, but these are localized and unable to be monitored in the current design. The achieved temperature levels remain suitable for testing various components considered for a nuclear thermal rocket. However, due to the limitations of the current heater filament, it is recommended that the apparatus be redesigned to utilize a rigid heating element similar to that used during the Radioisotope Propulsion Technology Program (Project POODLE) in the 1960s.