Richard Branson has touted Virgin Galactics space flights as an adventure unlike any other. 

"In the silent tranquility of space," he intones during a soaring promotional video, "you will experience weightlessness and views of our beautiful planet that will change your perception of life." While safety is mentioned, specific risks are not.

A fatal crash on Friday of Virgin Galactics SpaceShipTwo will move safety concerns into the discussion about space tourism. 

The accident raises new questions about the oversight US regulators exert in the nascent field, in which at least three major companies hope to make space tourism commercially viable. 

Elon Musks SpaceX seeks to make space travel routine -- and to become a key player in the colonization of Mars -- while Amazon founder Jeff Bezoss Blue Origin is researching technologies to make private space travel more affordable. Hotel titan Robert Bigelow is aiming to develop large living modules for space tourism and research.