Organized and funded by entrepreneur Jared Isaacman, the Inspiration4 mission touts itself as "the first all-civilian mission to orbit" and represents a new type of space tourism.

The four crew members will not be the first space tourists this year.

While there are similarities between those launches and Inspiration4 — the mission is being paid for by one billionaire and is using a rocket built by another, Elon Musk — the differences are noteworthy.

From my perspective as a space policy expert, the mission's emphasis on public involvement and the fact that Inspiration4 will send regular people into orbit for three days make it a milestone in space tourism.

Related: SpaceX's Inspiration4 private all-civilian orbital mission: Live updates.

SpaceX's Falcon 9 rocket and Crew Dragon vehicle, however, are powerful enough to take the Inspiration4 crew all the way into orbit, where they will circle the Earth for three days.

While the rocket and crew capsule are both fully automated — no one on board will need to control any part of the launch or landing — the four members still needed to go through much more training than the people on the suborbital flights.

While Bezos' and Branson's flights brought on criticism of billionaire playboys in space, Inspiration4 has tried — with mixed results — to make space tourism more relatable.

Sending a crew of amateur astronauts into orbit is a significant step in the development of space tourism.

However, despite the more inclusive feel of the mission, there are still serious barriers to overcome before average people can go to space.

Finally, space remains a dangerous place, and there will never be a way to fully remove the danger of launching people — whether untrained civilians or seasoned professional astronauts — into space.

Despite these limitations, orbital space tourism is coming.

Even as space remains out of reach for most on Earth, Inspiration4 is an example of how billionaire space barons' efforts to include more people on their journeys can give an otherwise exclusive activity a wider public appeal.