A cryogenic tank for a space launcher, comprising a partition and delimiting top and bottom volumes communicating via at least one free central opening formed in the partition, so as, on the one hand, to allow for the flow of liquid by gravity from the top volume to the bottom volume via the central opening or openings and, on the other hand, to prevent the rising of the fluid from the bottom volume to the top volume via the central opening or openings under the action of acceleration forces, the tank also comprising at least one vent forming separate from the central opening or openings and providing fluid communication between the top and bottom volumes, the vent being configured to favor the migration of vapor from the bottom volume to the top volume and to prevent the rising of liquid from the bottom volume to the top volume.