Elon Musk: 'Hyperloop' design revealed Aug 12

Billionaire futurist entrepreneur Elon Musk teased a big reveal of his "Hyperloop" plans, tweeting somewhat mysteriously that "Critical feedback for improvements would be much appreciated."

Musk, the co-founder of Pay Pal, Tesla Motors, and SpaceX, first introduced his Hyperloop concept last July calling it a "fifth mode" of transportation, completely different from planes, trains, automobiles and boats.

Musk claims the first iteration of the Hyperloop would connect Los Angeles to San Francisco. He claims people would be able to travel between cities in less than 30 minutes.

He also claims it would cost just $6 billion to build, or about 10 percent of the current estimated cost of building a high-speed rail along the nearly 350 miles of that route.

So far there have been no details about the technology behind the system, other than a few scattered clues.

Musk has said it will be a cross between a Concorde, a rail gun and an air hockey table. He has also explicitly stated it is not a vacuum tube. He has said transport pods will be available on demand, and there would be no possibility of pods crashing, and the system would be unaffected by weather. Musk also raised the possibility of solar self-powering.

Is it feasible? Travelling between downtown L.A. and downtown San Francisco in 30 minutes gives a speed of about Mach 0.91, just subsonic, which is what Musk has described as the "totally possible" goal.

If a railgun uses electromagnetic forces to move objects at high speeds, and an air hockey table reduces friction, the Hyperloop could be a pneumatic transport system (PTS), with a closed loop in which both the transport capsule and the air stream are traveling through the loop at subsonic speeds, over 600 miles per hour.

Once concern would be keeping g-loads small enough, comparable to a commercial plane, which can generate about 1g.

Musk plans to push the Hyperloop as a low-cost, high-efficiency alternative to bullet trains and high-speed rail projects. Once the internet gives him the necessary "critical feedback," he says he will release the Hyperloop Alpha design on August 12 and launch the project with open source.