Nuclear Thermal Rockets or NTR's have been suggested as a propulsion system option for vehicles traveling to the moon or Mars. These engines are capable of providing high thrust at specific impulses at least twice that of today's best chemical engines. The performance constraints on these engines are mainly the result of temperature limitations on the fuel coupled with a limited ability of the fuel to withstand chemical attack by the hot hydrogen propellant. Fuel testing in a relevant nuclear environment is expensive and time consuming and not always necessary, especially in the early stages of fuel evaluation. An alternative to full up nuclear testing is non-nuclear testing in a simulator which mimics the environmental conditions (minus the radiation) projected to exist in an actual nuclear engine. Within such a simulator, the fission heating process is often approximately reproduced by using induction heating.
Such a nuclear rocket environmental simulator is currently being constructed at the NASA Marshal l Space Flight Center. QuickField software is being used to model the detailed the power distributions within the fuel elements resulting from the induction heating. In particular, the code is used by researchers to determine exactly how the power distributions vary as a function of the frequency of the induction heater. An induction heater test frequency is determined from the calculations which most accurately replicates the power distribution which would be expected from nuclear fission. The code also allows researchers to predict the temperature and stress distributions within the fuel element so as to provide an indication of the expected performance of the fuel element under conditions similar to those it would experience during testing or operation.
Preliminary details on the operation of the NTR environmental simulator were presented at the AIAA Joint Propulsion Conference, 9 - 12 July 2006, Sacramento, California.