A billionaire’s private SpaceX flight filled its last two seats. A scientist-teacher and a data engineer will be on board. They join the billionaire Jared Isaacman. Also aboard will be previously selected passenger Hayley Arceneaux.

The newest passengers are Sian Proctor and Chris Sembroski. Ms. Proctor is a community college educator in Tempe, Arizona. She nabbed a seat on the flight reserved for a customer of Mr. Isaacman’s credit card-processing company. Ms. Proctor plans to teach from space. She will create art up there too.

Mr. Sembroski is a former Air Force missileman from Everett, Washington. He tried to win a seat on the flight but wasn’t picked. So how did he end up on the crew? A college friend won Mr. Sembroski’s spot on the spacecraft for him. It was a gift! “Just finding out that I’m going to space was an incredible, strange, surreal event,” he says.

Mr. Isaacman is a 38-year-old pilot. He will be the mission’s spacecraft commander. Ms. Arceneaux will serve as medical officer. The 29-year-old works at St. Jude Children’s Research Hospital. She was also treated there for bone cancer when she was a child.

All four passengers gathered at the National Aeronautics and Space Administration’s Kennedy Space Center this week. Mr. Isaacman gave details about the mission. It is called Inspiration4. The billionaire is paying all the costs. Inspiration4 will be SpaceX’s first private flight. Mr. Isaacman is using the mission to raise money for St. Jude Children’s Research Hospital in Memphis, Tennessee. He is donating $100 million to the hospital. Others have contributed $13 million when they entered the drawing for seats on the flight. 

The four-person crew will launch in the SpaceX Dragon capsule in early fall. The goal is to hit an altitude of 335 miles. That’s 75 miles higher than the International Space Station. It’s the same distance from Earth as the Hubble Space Telescope.