Oxidizer

Oxidizer
Density		5 kg/l
Transferable		Yes
Tweakable		Yes
Drainable		Yes
Flow mode		Adjacent
Cost		0.18 /l
		0.04 /kg
Since version		0.18

Oxidizer is a resource that fuels liquid fuelled rocket engines. A liquid fuel engine burns 11 parts oxidizer for every 9 parts liquid fuel. It was added with version 0.18, prohibiting rocket engines being fuelled by jet fuselages alone.

It is stored in liquid fuel tanks together with the usually correct amount of liquid fuel. Tweakables introduced in version 0.23 allow for altering during construction the amount of oxidizer or liquid fuel in a tank independently of each other. Oxidizer can also be transferred between tanks independently of transferring liquid fuel, so ratios can be throw off if not done carefully.

Planes using jet engines don't need and cannot use oxidizer as they are made to use intake air instead. Note, only Kerbin and Laythe have oxygenated atmospheres necessary to function as true “air”.