Electric cars and and commercial spaceflight are clearly not enough. Tesla and SpaceX CEO Elon Musk said he’s mulling how to provide super-convenient, electric-powered air travel. When asked to reveal his “next great idea” during a brief Q&A session this week, Musk answered: “Well I have been thinking about the vertical takeoff and landing electric jet a bit more. I mean, I think I have something that might close. I’m quite tempted to do something…