SpaceX Crew-1 [video]
Elon Musk may or may not know it yet, but his biggest contribution to humankind will not be that the Starship will take us to Mars, or that Tesla will help us shake off the dependency on fossil fuels. His biggest contribution will be to bring the end of the MAD world. The Mutually Assured Destruction world in which the majority of the living people  were born, and never thought it will ever end.You see, in the '80s the US had a missile defense idea called Brilliant Pebbles [1]. Basically they would put about 10k to 100k small missiles in orbit and these missiles would detect ICMB launches and go and destroy them. The problem was the economics of the system. It was simply too expensive. And because of that it was very easy to counter it: it was cheaper to build a few additional ICMBs than to add the necessary "pebbles" to neutralize them.But SpaceX changed this calculus. It's now much easier to put things in LEO. And it will become cheaper still. It is very likely that in 10 years the Brilliant Pebbles will become economical. And if they do, they become obligatory. Because it will be only a matter of time until Russia (or maybe China) builds the capability of cheap space launches that will match SpaceX. And if they do, and build the Brilliant Pebbles first, then the US will find itself in a very unenviable position.So in a very near future someone from the Pentagon will approach Elon Musk with an offer he won't be able to refuse. And why would he? Being part of the thing that ends the MAD will be certain to net him a Nobel Prize for Peace. And he will definitely be worth it.[1] https://en.wikipedia.org/wiki/Brilliant_Pebbles