From Saudi Aramco to Facebook, these are the biggest IPOs in history and why SpaceX could dwarf them all.

Before SpaceX's upcoming IPO sets an expected record, Alibaba, Facebook and Visa raised historic sums in the U.S.

NEW YORK: Elon Musk's SpaceX rocketed toward Wall Street on Wednesday (May 20), filing plans for what could become the largest initial public offering in history as the company…