Let us look at the odds. Elon Musk succeed with Zip2 (sold for a miserly $300M), PayPal (sold for a measely $1.5B). Now he has SpaceX running, and doing well with $1.6B in government contracts for 12 launches; this is the 3rd launch today and looks successful so far. Rocket biz is very technical and they built most of the components in house. Entire sovereign countries spend $Bs and decades to achieve similar goals.
Tesla is risky on the long side, no doubt. However, the short side looks much worse considering the risk/reward and the hi short interest. With all the pessimism, Tesla is actually doing ok. It built a facility that can produce 20,000 cars/year. The Model S that I test drove was impressive. Very hi tech with impressive display, nice and smooth ride. Incredible acceleration. Range is ok for 95% of the time. SC will resolve the long distance travel issue. The company now needs to optimize operations. Not exactly as difficult as rocket science!