Former NASA Flight Director Gene Kranz is best known for his prominent role in bringing the crew of Apollo 13 safely back to Earth—and the now-famous saying "Failure is not an option." But as NASA and the United States prepare to embark on human missions back into deep space, Kranz warned this week that the country can't be too timid as it does so. It must embrace some risk if it wishes to go back to the Moon and beyond.

During a panel discussion with other Apollo flight directors in Houston, Kranz was asked how NASA accomplished so much so quickly in the 1960s and early 1970s but hasn't been back to deep space since then. By some accounts, in the decades following the Moon landings, NASA has succumbed to a "mind-numbing" bureaucracy and a "paralyzing" cultural requirement for perfection, especially after two space shuttle accidents. Kranz said NASA benefited from a different culture in the 1960s.

"It was an environment in which we were more capable of accepting risk as a nation," Kranz replied. "Space involves risk, and I think that's the one thing about Elon Musk and all the various space entrepreneurs: they're willing to risk their future in order to accomplish the objective that they have decided on. I think we as a nation have to learn that, as an important part of this, to step forward and accept risk."

Another Apollo flight director, Milton Windler, also offered praise for SpaceX's accomplishments during the discussion. "I think it's incredible that we have a company that can fly a rocket, land it, and then refurbish it, and send it up and fly it again," he said. "That's pretty impressive to me personally."

The panel discussion was held at Space Center Houston on Tuesday evening to promote the documentary movie Mission Control, which will be released in select theaters on Friday. Ars will have a full review of the movie later this week.