How do you use the Ion Engine?

@Jetspeed1001 @Bmcclory @LiamW @Mostly @tsampoy Yea i figured it out, I was just missing Xenon.

You need to put Xenon gas and Battery.
I made the same mistake too.

You use it in space

@Jetspeed1001 @LiamW @Bmcclory .............oooooooohhhhhhhhhhh. ok. That makes sense. thank you

Ion engines use electrical power to push negatively charged particles really, really fast out the back of it. Everything has to obey conservation of mass and momentum so you need xenon as expendable fuel. Since it requires electrical power, you'll need batteries to store power as well as solar panels to produce power. You should be able to see an option on fuel tanks to change their fuel type to xenon, monopropellant, battery or RP1. You'll need one battery and one xenon tank at a minimum.

you need xenon fuel