A goal for recycling is to achieve Closure, where all waste products are converted back to useful states and the only external input is energy. We expect this to be a theoretical limit similar to conversion efficiency in electrical transformers and motors. Those devices can reach 98% efficiency but not 100%. Similarly, practical recycling is expected to reach a high percentage, but not 100%. To the extent your percent closure CL% approaches 100, the amount of new raw materials required is reduced to 100-CL% of an open system with no recycling. So a high percent closure can have a dramatic effect on the need for new raw material processing or replacement items brought from elsewhere.
Some items by their nature are not amenable to recycling. A prominent example is reaction mass expelled outside a gravity well by a propulsion method. You are deliberately throwing that mass away in order to get thrust, and outside a gravity well there is no practical way to recover it to use it again. Within a gravity well, such as launching from Earth using a chemical rocket, all the reaction mass is sub-orbital - ranging from about -1/2 orbital velocity to +1/2 orbital velocity depending on the vehicle velocity. Therefore it all ends up back on Earth and can be used again. While some reaction mass cannot be recovered, you can deliberately choose high efficiency methods that lose less mass this way, and use methods such as gravity assist that do not lose propellant mass.
A goal for recycling is to achieve Closure, where all waste products are converted back to useful states and the only external input is energy. We expect this to be a theoretical limit similar to conversion efficiency in electrical transformers and motors. Those devices can reach 98% efficiency but not 100%. Similarly, practical recycling is expected to reach a high percentage, but not 100%. To the extent your percent closure CL% approaches 100, the amount of new raw materials required is reduced to 100-CL% of an open system with no recycling. So a high percent closure can have a dramatic effect on the need for new raw material processing or replacement items brought from elsewhere.
Some items by their nature are not amenable to recycling. A prominent example is reaction mass expelled outside a gravity well by a propulsion method. You are deliberately throwing that mass away in order to get thrust, and outside a gravity well there is no practical way to recover it to use it again. Within a gravity well, such as launching from Earth using a chemical rocket, all the reaction mass is sub-orbital - ranging from about -1/2 orbital velocity to +1/2 orbital velocity depending on the vehicle velocity. Therefore it all ends up back on Earth and can be used again. While some reaction mass cannot be recovered, you can deliberately choose high efficiency methods that lose less mass this way, and use methods such as gravity assist that do not lose propellant mass.
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