Elon Musk, founder, CEO and lead designer at SpaceX and co-founder of Tesla, speaks at the SpaceX Hyperloop Pod Competition II in Hawthorne, California, in August 2017. | REUTERS NEW YORK – SpaceX has adopted corporate governance policies that will erode typical shareholder protections in unprecedented ways, giving founder Elon Musk virtually unchecked executive authority when the rocket maker goes public later this year. Excerpts of SpaceX's IPO registration statement show the company is combining supervoting shares, mandatory arbitration, stricter rules on shareholder proposals and Texas corporate law to give Musk and other insiders broad control. At the same time, it sharply limits investors' ability to challenge management, sue in court and force votes on governance issues. And the only person who can fire Musk is Musk, who will retain majority control through supervoting shares. "It closes the voting door, the courthouse door and the proposal door simultaneously.…