I may have another way...Akari's ears are used to hearing small things - the engine noise of a ship at long range, for example - so when they take off, and are on the shakedown cruise, she could say that the ship 'sounds' wrong, or something like that.<br/><br/>The atmosphere idea is good...but it requires airtight doors between sections of the ship that can be pressurized and such.  Just my 0.02 on the matter.