Elon Musk took to Twitter Sunday to refute the idea that SpaceX could be using electric rockets, as The Simpsons implied in a recent episode.

"For a man who likes electric cars, he sure burns a lot of rocket fuel," Lisa says in an episode featuring Musk while he's jetting away.

Musk learned of this and tweeted that if anyone saw the episode and wonders why SpaceX doesn't use electric rockets, that's because "that is impossible."

If u saw @TheSimpsons and wonder why @SpaceX doesn't use an electric rocket to reach orbit, it is cuz that is impossible— Elon Musk (@elonmusk) January 26, 2015

Musk claims that Newton's Third Law says you can't push against anything in a vacuum, and you need the "ejected mass" you get with a traditional space rocket. He says Ion thrusters are "great" but can't produce enough force to lift a rocket off the ground and into orbit.

And pls don't ask me about space elevators until someone at least builds a carbon nanotube structure longer than a footbridge— Elon Musk (@elonmusk) January 26, 2015