Musk's Hyperloop Plan Draws Praise, SkepticismAn illustration shows the Hyperloop transport concept, which entrepeneur Elon Musk says could allow passengers to make the trip between San Francisco and Los Angeles in half an hour.Serial entrepreneur Elon Musk on Monday unveiled his long-awaited plans for a potentially revolutionary "fifth mode" of transportation. Dubbed the Hyperloop, the new mode of transport would complement planes, trains, cars, and boats as a means of travel.

Hyperloop involves shooting a solar-powered, aluminium pod that floats on a cushion of air through an elevated tube at near-supersonic speeds. The entire system resembles the pneumatic tubes that are used to shuttle paper between different parts of old buildings. (See related pictures: "Amazing Transportation Inventions.")

In a 57-page white paper released Monday, Musk estimates Hyperloop could traverse the 400-mile (640-kilometer) distance between Los Angeles and San Francisco in about half an hour while traveling at speeds of nearly 800 miles per hour (1,287 kilometers per hour).