OK, so just to clarify: it is the amount of air STORED in the intakes, you need them closed when in space And also to clarify: you do not have to get INTO space on jets, what was attached to the radial decouplers were SRB's to get it into space, this is purely to see who Gets the longest flame duration in space, considering you would have to have a stupid amount of intakes to run it longer, and a even more silly launching mechanism.