Half of the atmosphere from a Ringworld is a stupendous amount of gas. 100 years is basically nothing on the timescales you need to think about when building a

Half of the atmosphere from a Ringworld is a stupendous amount of gas. 100 years is basically nothing on the timescales you need to think about when building a Ringworld. You might be able to slow down the loss of gas by putting lips on the tops of the walls and maybe even air jets blowing downward though. Or leave it mostly closed except for a few openings for spacecraft to enter or leave. Also, working out the practical considerations for a Ringworld is an exercise in futility anyway. You are already well beyond practical when you start building one.