SpaceX debuted on the Nasdaq on Friday, opening at $135 per share with an initial valuation of nearly $1.8 trillion and closing at $160.95 after rising more than 19 percent. Elon Musk became the world's first trillionaire from his stake, and thousands of current and former employees became millionaires. A disputed claim of a $2.18 trillion market cap was contradicted by other reporting.