SpaceX is set this week to launch as a publicly traded company, giving ordinary investors a chance to participate in what is expected to be the biggest  initial public offering  of all time.  While SpaceX will be held primarily by CEO Elon Musk, company employees and private investors, the Texas-based company will set aside a sizable chunk of stock to retail investors, which experts say is unusual. Earlier this year, Reuters  reported  that as much as 30% of the shares of the rocket and AI