Recap: While drinking whiskey and smoking pot with Joe Rogan, Elon Musk let slip his idea for an electric airplane design. He said it would be a VTOL capable of supersonic speeds at high altitude. However, he's not planning on building it at the moment. There are more important things demanding his attention.

Joe Rogan had an engaging conversation with Elon Musk on his YouTube podcast Thursday night. The "Joe Rogan Experience,” as the show is called, is more stream consciousness conversation with guests and less traditional talk show.

As Joe and Elon sat in the studio sipping whiskey and smoking weed (Musk only had one puff and didn't even inhale at 2:10:00), they wandered from topic to topic ranging from Musk’s business pursuits to his personal life. At one point Rogan asks him if he had ever thought about planes.

“Yeah. I have a design for a plane,” said Musk almost as if it was a trivial matter.

When pressed further the SpaceX boss seemed reluctant to spill any details. He had evidently only told his girlfriend and a few other friends about it.

“I’m your friend,” said Rogan.

Under pressure from the host, Musk described his idea for a vertical take-off and landing (VTOL) supersonic electric airplane. Rogan made the mistake of asking him how it would work and Musk lost him in the details and technical aspects.

“I’ve thought about this quite a lot, quite a lot. The interesting thing about an electric plane is that you want to go as high as possible, but you need a certain energy density in the battery pack because you have to overcome gravitational potential energy. Once you’ve overcome gravitational potential energy and you’re at a high altitude, the energy you use in cruise is very low, and then you can recapture a large part of your gravitational potential energy on the way down. So you really don’t need any kind of reserve fuel.”

“I’m too stupid for this conversation,” Rogan whispered into his microphone.

Even though Musk has put much thought into this plane design, he admits that it is not a priority. He has a lot of other things on his plate right now and thinks electric planes are not "necessary" at this time. His priorities lie with electric cars and sustainable storable energy solutions.

“The electric airplane isn’t necessary right now,” said the Tesla CEO. “Electric cars are important, solar energy is important, stationary storage of energy is important. These things are much more important than creating electric supersonic VTOL.”

While the electric plane may not be a priority for Musk at the moment, now that the proverbial cat is out of the bag, he might have to shift his attention to it before someone else steals his idea.