LONDON -- Elon Musk is a busy man. With Tesla he is spearheading the adoption of electric cars. At SpaceX he is pushing the boundaries of space exploration. With Hyperloop he has designed a next generation, high-speed mass transportation system.

That doesn’t leave him with much time for anything else -- including building a supersonic, vertical takeoff, electric jet. Musk has spoken about the possibility of an electric jet previously, but the inventor and entrepreneur has now revealed for the first time that he has a design in mind for the jet, but he simply doesn’t have the time to develop it.

In an interview with Marketplace’s Corner Office, Musk was asked what he would be doing if he wasn’t running Tesla. “I do like the idea of an electric aircraft company. I do think one could do a pretty cool supersonic, vertical takeoff and landing electric jet. That would be really fun,” he said.

When asked by host Kai Ryssdal if he was just making things up, Musk responded: “No, I have a design in mind for that, but I have too many things on my plate to do, and then of course there is the Hyperloop.”

Photo: Hyperloop Transportation Technologies

Hyperloop is the high-speed transportation system Musk has designed and which is currently being developed by two competing companies. Last year, speaking at MIT’s Aeronautics and Astronautics Centennial Symposium, Musk said he was “toying” with the idea of developing an electric aircraft adding: “I would love to do it, but I think my mind would explode.”

In the MIT interview, Musk also mentions some aspects of the design anyone developing an electric jet would need to look at, including the removal of “unnecessary” parts like tails, rudders and elevators.

Musk told Marketplace that electric motors are, without a doubt, the future of transportation, but there is one area it won’t impact: “[With] rockets, you can’t go electric unfortunately, but aircraft, ships, and all other forms of transport will go fully electric, not half electric, fully electric, no question.”

Musk added: “Electric is fundamentally more efficient than any kind of combustion engine vehicle because in a combustion engine vehicle most of that energy is going into heat.” As well as the environmental impact, a typically gasoline car engine is only about 20 percent efficient, Musk said, while an electric motor is about 90 percent efficient at turning energy into motion.

When asked about handing over the day-to-day running of Tesla or SpaceX to someone else to give himself some more time, Musk said: “In the long term I won’t be running either company because I will be retired or dead [but] I expect to be with SpaceX and Tesla for as long of the future as I can imagine.”