Project Lyra: Catching 1I/'Oumuamua-Using Nuclear Thermal Rockets

摘要

The first definite interstellar object observed in our solar system was discovered in October of 2017 and was subsequently designated 1I/'Oumuamua. In addition to its extrasolar origin, observations and analysis of this object indicate some unusual features which can only be explained by in-situ exploration. For this purpose, various spacecraft intercept missions have been proposed. Their propulsion schemes have been chemical, exploiting a Jupiter and Solar Oberth Maneuver (mission duration of 22 years) and also using Earth-based lasers to propel laser sails (1-2 years), both with launch dates in 2030. For the former, mission durations are quite prolonged and for the latter, the necessary laser infrastructure may not be in place by 2030. In this study Nuclear Thermal Propulsion (NTP) is examined for chasing interstellar objects after they have left the inner solar system, taking 1I/'Oumuamua as an example. NTP has yet to materialise as far as real missions are concerned, but due to its research and development in the US government sponsored Rover/NERVA programs, actually has a higher Technology Readiness Level (TRL) than laser propulsion. Various solid reactor core options are studied, using either engines directly derived from these programs, or more advanced options, like a proposed particle bed nuclear thermal rocket (NTR). With specific impulses at least twice those of chemical rockets, NTP opens the opportunity for much higher Delta V budgets, allowing simpler and more direct, time-saving trajectories to be exploited. For example a spacecraft with an upgraded NERVA/Pewee-class NTR travelling along an Earth-Jupiter-1I trajectory, would reach 1I/'Oumuamua within 14 years of a launch in 2031. The payload mass to 1I/'Oumuamua would be around 2.5 tonnes, but even larger masses and shorter mission durations can be achieved with some of the more advanced NTR options studied. In all 4 different proposed NTRs and 5 different trajectory scenarios are examined. It is concluded that NTP has the potential to increase payload size by an order of magnitude and trip durations reduced to 15 years compared to 20 years for chemical propulsion.