Billionaire Elon Musk-led space exploration startup SpaceX has raised $350 million at a valuation of $21.2 billion, making it one of the most valuable startups in the world. Less than ten venture-backed companies around the world are valued at $20 billion or more. Founded in 2002, SpaceX is backed by investors like Google, Fidelity Investments and Draper Fisher Jurvetson.