Technology Summary and Outlook
The open-cycle gas-core rocket has many unique design attributes that make it a serious challenger to other proposed propulsion for interplanetary missions. Due to the necessity of having a transparent wall inside the reactor for a closed cycle concept, the benefit of moving to a gas core from a solid core are nearly negated. The high specific impulse and large thrust possible for the OCGCR correspond to shorter mission times and higher payload fractions. However, the technical challenges and unknowns inherent in its design are many. Additionally, any test of the system performed on earth would be under a gravity field of 1 g, which would bring buoyancy effects into play inside the gaseous core.
Due to the inability to perform live testing on earth, research is focused primarily on computational modeling of such a system. It was previously mentioned that the specific impulse could be as high as or higher than 3000 s. However, results of computational modeling point towards this number being somewhat optimistic. When thermal hydraulics were modeled more completely for a typical base injection stabilized recirculation bubble gas core rocket by D. Poston, the specific impulse dropped from >3000 s to <1500 s. In the base injection stabilized recirculation bubble gas core rocket concept, it is thought that some additional method of fuel confinement will be beneficial. As mentioned earlier, relying completely on magnetic containment of the fuel bubble is not yet practical. However, a magnetic field may be able to assist in containment or help suppress turbulence that would lead to fuel-propellant mixing.
The primary areas of future research for such an OCGCR would therefore be centered on keeping the fuel and propellant from mixing as much as possible. Although this article has focused on enriched uranium for the fuel and hydrogen for the propellant, this may not be the optimal choice for either. Other fuels, such as plutonium, and other propellants, including helium or even helium-3, have also been considered and in certain situations provide advantages.
Read more about this topic: Gas Core Reactor Rocket
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