CBS

Elon Musk has made no secret of his worries about the possible destructive power of artificial intelligence.

The billionaire chief executive of SpaceX and Tesla Motors may be a techno-optimist when it comes to solar power, space exploration and electric cars, but he continues to express his concerns that superintelligent machines might one day pose a threat to human existence.

During an onstage conversation Wednesday at Vanity Fair's New Establishment Summit in San Francisco, Musk voiced concern that people did not recognize how fast AI is progressing and its potential destructive effect.

"I don't think anyone realizes how quickly artificial intelligence is advancing. Particularly if [the machine is] involved in recursive self-improvement...and its utility function is something that's detrimental to humanity, then it will have a very bad effect," Musk told Walter Isaacson, CEO of the Apsen Institute.

"If its [function] is just something like getting rid of e-mail spam and it determines the best way of getting rid of spam is getting rid of humans..." Musk trailed off to chuckles from the crowd.

Though many futurists envision a more human-beneficial application of AI, Musk has voiced his apprehensions on several occasions. In June, Musk told CNBC that he worries that -- unrestrained -- AI could breed an uncontrollable threat to humans like that depicted in the 1984 movie "The Terminator."

In August, Musk reiterated those concerns in a tweet recommending an upcoming book that addresses the dangers of a future filled with AI.

"We need to be super careful with AI. Potentially more dangerous than nukes," he tweeted.