Elon Musk's Next Great Idea? Electric Air Travel (bgr.com)

An anonymous reader writes with this excerpt from BGR: Elon Musk is changing the world one idea at a time. First, with Tesla, the man so many people call the real life Tony Stark has done an incredible job of bringing electric vehicles to the mainstream. Second, Musk has been doing an impressive job over at SpaceX in the realm of space travel. And third, Musk's effective rough draft of a high-speed transportation system known as the Hyperloop is being contemplated and conceptualized in a very real way by some extremely smart people. So where does Musk go from here? Why, Mars of course. Recently, Musk said that he plans to unveil SpaceX's Mars roadmap next September. But on another front, Musk has also been thinking about developing an electric airplane capable of taking off and landing vertically. While answering a few questions during a Q&A session at the SpaceX Hyperloop Pod Award Ceremony last week, Musk was asked what his 'next great idea' was. The answer? Electric-powered air travel.

Comments

Re:The technical problems with this are immense.

[brambus]

So batteries don't necessarily need to directly compete with combustion engines because electric engines could (and I stress "could") have higher efficiencies than either piston or turbine engines (both of which actually lose a fair amount of the energy in the fuel to their engine cycle as exhaust heat). At 20MJ/kg a battery would compare very well to jet fuel. A good high-bypass turbofan can get maybe 40-45% efficiency. An electrically driven fan, might go as high as 80-90%. But AFAIK Musk wanted to make these aircraft supersonic. While a fan-driven engine *theoretically* can go supersonic, in practice it's so horribly inefficient that it's unlikely to be practical. That's where the Brayton cycle comes in and we're back to the 40% efficiency range (regardless if the reaction mass heating is provided by hydrocarbon fuels or an electrically-sourced heating mechanism) and batteries in that case are dead in the water.
The kicker though, as you correctly identified, is mass loss during flight. Aircraft get a lot of efficiency from this mechanism and also significant mission flexibility (for shorter missions you can take less fuel and more cargo). An electric aircraft would pretty much have to be factory-built for max range from the factor. I highly doubt it's ever going to be practical to reconfigure an electric aircraft on the flight line for shorter haul by taking some batteries out - keep in mind how tricky even comparatively tiny electrical systems are (see Boeing 787 Li-Ion battery fires). Plus the red tape on this is would boggle the mind.
Lastly, we needn't rely on fossil fuels. The public at large always thinks "smelly fuel = dirty". Not necessarily. We can synthesize a wide range of synthetic jet fuels already. Provided that the carbon source for that fuel is "renewable" (e.g. dissolved carbonic acid in ocean water), we could keep the venerable jet engine in place and simply source the fuel in a renewable manner. Then the fuel simply becomes a liquid chemical battery with fantastic power density and deployment flexibility.

the man so many people call the real life Tony Sta

[alexhs]

Well, you see the problem: it doesn't fit in the subject line.

Next time you reference Him, I suggest you use the proper enneagrammaton for The Man Known As The Real Life Tony Stark: TMKATRLTS.

Re:Batteries just don't store enough energy...

[phayes]

Electric air planes with lithium-air batteries would weigh the same at landing as they do at takeoff whereas a 747 loses around a quarter of it's weight en-route.

Musk considering what NASA has been researching

[Geoffrey.landis]

NASA has been researching electric aircraft for quite a while. They do have some advantages, although they're not ready to commercialize yet.

http://www.nasa.gov/centers/ar...

  http://www.nasa.gov/aero/testi...

  http://aero.larc.nasa.gov/file...

  http://ntrs.nasa.gov/archive/n...

  http://ntrs.nasa.gov/archive/n...

Dumping fuel before landing

[Firethorn]

Yes, they still do that, though in developed areas it's often flying for longer to burn the fuel rather than just dumping it.