It might be SpaceX’s most ambitious launch yet. Shares of Elon Musk’s rocket company are poised to begin trading publicly on Friday, raising $75 billion for the company in what will be the largest initial public offering (IPO) ever. Musk, SpaceX’s chairman, CEO and controlling shareholder, rang the Nasdaq’s opening bell from the company’s headquarters in Starbase, Texas, alongside hundreds of employees. Other executives, employees and investors simultaneously joined the celebration on the floor