SpaceX Moon Mission Won't Be Rich People's Joyride, Says Space Travel Vet

SpaceX's plan to fly 2 non-astronauts around the moon next year is insanity -- if they're sending 2 flight newbies up there ... this according to another private citizen who went to space.

Richard Garriott is a video gaming mogul who spent 12 days on the International Space Station in 2008 ... all on his own dime -- $30 mil to be exact. But he also underwent intense training, and says the so-called "space tourists" paying for the SpaceX better be ready for the worst ... or they won't survive.

Garriott says even a mere passenger on such a mission will have to know how to operate multiple systems onboard the Dragon 2 spacecraft Elon Musk says will fly to the moon.

SpaceX hasn't named the 2 private citizens, but says they've paid a hefty deposit. Garriott's point is ... it's gonna take way more than their money to make it to the moon and back ... alive.