South African-American Elon Musk, inventor and entrepreneur, best known for founding PayPal has just unveiled his latest oversized project called the’ Hyperloop.’ The Hyperloop low-pressure system would transport up to 28 people from city to city via pods enclosed in metal tubes. Hyperloop would travel between Los Angeles, California, and San Francisco, California in 35 minutes.
For travel at high speeds, the greatest power requirement is normally to
overcome air resistance. Aerodynamic drag increases with the square of speed,
and thus the power requirement increases with the cube of speed. For
example, to travel twice as fast a vehicle must overcome four times the
aerodynamic resistance, and input eight times the power.
Just as aircraft climb to high altitudes to travel through less dense air,
Hyperloop encloses the capsules in a reduce pressure tube. The pressure of air
in Hyperloop is about 1/6 the pressure of the atmosphere on Mars. This is an
operating pressure of 100 Pascals, which reduces the drag force of the air by
1,000 times relative to sea level conditions and would be equivalent to flying
above 150,000 feet altitude. A hard vacuum is avoided as vacuums are
expensive and difficult to maintain compared with low pressure solutions.
Despite the low pressure, aerodynamic challenges must still be addressed.
These include managing the formation of shock waves when the speed of the
capsule approaches the speed of sound, and the air resistance increases
sharply. Close to the cities where more turns must be navigated, capsules
travel at a lower speed. This reduces the accelerations felt by the passengers,
and also reduces power requirements for the capsule. The capsules travel at
760 mph (1,220 kph, Mach 0.91 at 68 ºF or 20 ºC).
Ashlee Vance from Bloomberg wrote: The tubes would, for the most part, follow Interstate 5, the dreary but direct freeway between Los Angeles and points near San Francisco. Farmers would not have swaths of their land blocked by train tracks but could instead access their land between the columns. Musk figures the Hyperloop could be built for $6 billion with people-only pods, or for $10 billion with the larger pods capable of holding cars. So in effect, he’s proposing an alternative that’s four times as fast and 1/10 the cost of the high-speed rail.