For nearly a decade, champions of space tourism and other commercial ventures seeking to get beyond the atmosphere have predicted the rapid emergence of a new industry.

But a pair of launch failures last week, including Friday’s high-profile crash of a Virgin Galactic LLC rocket ship that broke apart miles above the earth killing one pilot and seriously injuring another, are prompting further questions about the future trajectory of such company-funded endeavors.

Already, proponents as well as critics of commercializing space travel are rethinking the likely pace of progress. Some predict difficulties obtaining additional private-equity funding for startup ventures, while others working in the industry worry about nagging propulsion problems and ways to restore public confidence.

(Further reading:Safety board cites improper pilot command in Virgin Galactic crash).

“Recent events bring home the reality that we’re in a very dangerous phase” of pursuing myriad space activities relying on the private sector, said Howard McCurdy, a space history expert who teaches at American University. Launching rockets and vehicles “is always a very risky business,” he added, and no amount of ground tests “can duplicate the aerodynamic stresses and other conditions” of actual space flight.