Max burn time / sufficient fuel indicator is wrong for LH2/O engines #7
Description
The max burn time calculation is wrong, and hence the Est. Burn (~) insufficient fuel indicator too, for engines which consume fuel mixtures of unequal density, because BetterBurnTime doesn't take fuel density into account.
This bug doesn't manifest for the stock LF/O engines only because LF and O happen to have the same density (5 kg/l) so ignoring it "works". But for engines which use an LH2/O mixture (e.g. @ChrisAdderley's CryoEngines) or any other fuel mixtures of non-homogeneous density, BetterBurnTime miscalculates the max burn time, always indicating insufficient fuel when there will actually be plenty.