Elon Musk, Tesla and SpaceX CEO, continues to give more details about his "Hyperloop" idea, which is a new take on high-speed travel. Elon Musk says that Hyperloop is a "fifth mode" of transportation, distinct from planes, trains, automobiles and boats. The Hyperloop could potentially take passengers from San Francisco to Los Angeles in just 30 minutes.

"Pulled all nighter working on Hyperloop (as did others)." Musk, who heads the SpaceX rocket venture as well as the Tesla electric-car company, wrote in a Twitter update on Monday, NBC News reports. "Hopefully not too many mistakes. Will publish link at 1:30 PDT [4:30 p.m. ET Monday].

Musk must have been preparing some big ideas, because he told Tesla investors last week that he is too busy to carry out his own invention.

"I think I kinda shot myself in the foot by ever mentioning the Hyperloop, because I'm too strung out," he said. "Obviously I have to focus on core Tesla business, and SpaceX business, and that's more than enough."

Musk has also hinted about the capabilities of the Hyperloop.

"It would work better than a high-speed rail, or a plane, between the right city pairs, like San Francisco and L.A., or New York-Boston," he told CNBC.

Musk guessed that the system could be built for a tenth of the cost-per-mile associated with California's proposed $68 billion high-speed rail system, which won't be nearly as high speed as Japan's, NBC News reports.

Musk noted that in order to get from San Francisco to Los Angeles in a half-hour, the average speed would have to be about 700 mph (1,127 kilometers per hour), thus traveling "effectively faster than the speed of sound," Musk said.

During May's D11 Conference, he said the Hyperloop would be a "cross between a Concorde, a rail gun and an air hockey table."

Musk dropped some additional hints last Thursday during a Google+ Hangout, and said the Hyperloop concept "does involve a tube, but not a vacuum tube ... not frictionless, but very low friction."