Date of Award


Document Type


Degree Name

Master of Science in Astronautical Engineering


Department of Aeronautics and Astronautics

First Advisor

Milton E. Franke, PhD


Presented in this work are the results of an investigation of alternative means for powering spacecraft and launch vehicles with energy sources other than chemical combustion. Nuclear thermal propulsion and the energy release of a nuclear spin isomer present potential for increased rocket performance with compact, high-energy fuel sources replacing the combustion engines of the Delta IV-H 1st and 2nd stage vehicles. Analysis of historical fission designs along with the isomer hafnium-178-m2 in a particle bed configuration was conducted. Energy storage levels of 1.3 GJ/g are possible with this material, though the successful triggering and maintenance of a chain reaction in this material are still debated topics within the scientific community. The best application for either technology is as an upper stage vehicle with the shielding requirements reduced to that of just a shadow shield between the core and the spacecraft's upper structure. The fission designs are capable of specific impulse values between 800 and 1,000 s leading to mass savings in the range of 7,000 to nearly 10,000 kg once the engine masses and shielding have been included. An isomer core in the configuration of a 19-element PBR may be able to achieve a specific impulse on the order of 880 s with the isomer in metallic form, and specific impulse values as high as 1,090 s if the isomer is in the form of hafnium carbide. This translates to somewhere between a 5,000 and 9,000 kg depending on the material makeup of the core and heat efficiency. Payload mass increases by a factor of two or greater velocity changes are the payoffs of these systems.

AFIT Designator


DTIC Accession Number