When buying a part, before placing it, if upgrading it until we have almost no money or red cristal left, and then accepting the placement (or deplacing), we can reach negative money or red cristals. If reaching negative money, it wont let us quit the hangar, but we can get to negative red cristals and leaving. http://prntscr.com/jcrc90

When opening the hangar, if placing a part that was in our storage and then upgrading or repairing it and puting it back in the storage, leaving the hangar will actually make us pay for the changes without asking confirmation.