Elon Musk has built the Tesla Gigafactory in the midst of the Nevada desert. But even the deep pockets of the greenminded billionaire could be challenged by the investment needed to create mass-market cars that are electric and driverless, writes Jon Gertner.

Tesla Motors has previewed its Model 3 sedan, saying more than 130,000 people had ordered the car even though it is more than a year away from production.