Implementations are described for maintaining helium/air mixture within a tube in an evacuated tube transportation system. A first implementation includes a set of helium tanks uniformly fitted along the tube length, where helium is injected with controlled valves that open or close to maintain the desired level of helium. An operations control center (OCC) receives helium concentration levels in the tube and instructs a controller in the tube to release helium into the tube when detected levels of helium is lower than the desired level of helium. Another implementation is described where a capsule traversing the tube may have a source of helium gas that can be released into the tube. A hybrid approach is also described where helium can be released from a source within the tube and from another source within the capsule.