NASA Technical Reports Server (NASA) · 1994 · 24 citations · 0 references
Open access
EngineeringAerospace EngineeringNuclear EngineeringNuclear ChemistryNuclear MaterialsPropulsionEnergy ConversionNuclear Fuel MaterialsNuclear PropulsionPropulsion EfficiencyPropulsion System PerformanceRocket PropulsionChemical Rocket PropulsionEngine Thrust PerformanceExploration MissionsNuclear Rocket PropulsionNuclear Thermal PropulsionSpace Nuclear PropulsionSpecific ImpulseThrust-to-weight Ratio
The solid‑core nuclear thermal rocket offers a high‑specific‑impulse (≈850–1000 s) and favorable thrust‑to‑weight (≈4–20) that make it a promising propulsion technology for an efficient lunar space transportation system supporting both crewed and cargo missions. This paper evaluates an NTR‑based lunar transport system by summarizing NASA’s lunar outpost scenario, comparing performance of different LTS concepts, and discussing key operational issues such as reusability and engine disposal. The authors analyze two NTR options—the graphite‑moderated Rover/NERVA reactor and the Particle Bed Reactor—assessing their suitability for lunar missions and comparing their performance characteristics. NASA Lewis research indicates that an all‑propulsive, fully reusable NTR LTS can deliver a fully‑fueled, cargo‑laden lunar excursion vehicle to the Moon and return it to low Earth orbit with less initial mass than an aerobraked chemical system, achieving a return payload mass fraction of about 23 %, roughly twice that of the partially reusable chemical alternative.
The solid core nuclear thermal rocket (NTR) represents the next major evolutionary step in propulsion technology. With its attractive operating characteristics, which include high specific impulse (approximately 850-1000 s) and engine thrust-to-weight (approximately 4-20), the NTR can form the basis for an efficient lunar space transportation system (LTS) capable of supporting both piloted and cargo missions. Studies conducted at the NASA Lewis Research Center indicate that an NTR-based LTS could transport a fully-fueled, cargo-laden, lunar excursion vehicle to the Moon, and return it to low Earth orbit (LEO) after mission completion, for less initial mass in LEO than an aerobraked chemical system of the type studied by NASA during its '90-Day Study.' The all-propulsive NTR-powered LTS would also be 'fully reusable' and would have a 'return payload' mass fraction of approximately 23 percent--twice that of the 'partially reusable' aerobraked chemical system. Two NTR technology options are examined--one derived from the graphite-moderated reactor concept developed by NASA and the AEC under the Rover/NERVA (Nuclear Engine for Rocket Vehicle Application) programs, and a second concept, the Particle Bed Reactor (PBR). The paper also summarizes NASA's lunar outpost scenario, compares relative performance provided by different LTS concepts, and discusses important operational issues (e.g., reusability, engine 'end-of life' disposal, etc.) associated with using this important propulsion technology.