In 1964, the first simulation showing that Pluto is in a mean-motion resonance with Neptune was published: https://articles.adsabs.harvard.edu/pdf/1965Obs....85...43C
They ran a 120,000 year simulation that showed libration of the resonant angle for the first time. This must have been terrifyingly hard to do. Punch cards, vacuum tubes, FORTRAN? I don't even know how they did this, but it was run on the Naval Ordnance Research Calculator
This was the first time Pluto's orbital stability was explained.
@sundogplanets
In 1966 #LarryNiven a SciFi author in #WorldOfPtavvs had #Pluto a moon of Neptune, long previously hit by a spaceship at relativistic speed aimed at #Neptune An artifact protected by a plot device remained on it.
He would have been aware of that work I think.
Good story, although the usual elements wouldn't do this century.