A billionaire adventurer returns to space, this time on a riskier mission [Video]

Three years ago, a billionaire entrepreneur named Jared Isaacman made a groundbreaking trip to space. That space flight, which Isaacman called Inspiration4, was the first to orbit Earth without a professional astronaut aboard.

This week, Isaacman, founder and CEO of Shift4, a payment processing company, is scheduled to head into space again. This time the itinerary is longer, more daring and riskier, and includes a spacewalk, the first by private astronauts.

The mission, named Polaris Dawn, hearkens back to the earliest era of spaceflight, the 1960s, …