The extraordinary success of SpaceX’s initial public offering on Wall Street—which saw the company end up with a valuation of $2.1 trillion at the end of its first day of trading—is a sign of investor faith in the future of the space economy. SpaceX promoter Elon Musk’s talk about building artificial intelligence data centers in space and colonizing Mars might look fanciful. His ideas about using SpaceX “to build the systems and technologies necessary to make life multiplanetary … and to extend