They are presently working on cells that you fill with alcohol and run. The prime market for this is your laptop, never run out. But with this technology it won't be long before we refuel and fly till the alcohol runs out, ie you'll need to have an on off switch. Electric control line is already here, just not widly known. It will be the norm in the future, but it will be a while. Many of us will always love the sound of the engines.