Faster, more affordable flights possible
This feels like a bad dream. I am now waiting in Los Angeles International Airport, after a two-hour flight from Phoenix, Arizona, USA. The next leg is the dreaded 14-hour flight across the Pacific to Shanghai. Then I have to clear customs and wait another five hours before flying to Shenzhen. Including hours spent waiting in LA and Shanghai, that's 26 hours of agonizing travel.
Does this sound familiar? It would seem impossible to have short, direct flights every hour from Phoenix to Shenzhen, but as an engineering professor, how can I realize this dream?
Flying is slow and uses a lot of energy. Fully 40 percent of airplane takeoff weight is fuel. On this round trip to China, I produced as much carbon dioxide as my yearly commute to work. Most of that fuel is used to push against air across the Pacific for 14 hours.
You fly high to reduce air drag. But we don't fly high enough — only 10 kilometers up instead of 50, where air is one thousand times thinner than at sea level. At that altitude, you skip on top of the atmosphere like a thrown pebble across a pond. You can fly 1 km per second, or three times the speed of sound. Traveling from Phoenix to Shenzhen for 10,000 km takes only 10,000 seconds. That's three hours instead of 14 for a direct flight.
Why 26 hours, then? You need large airplanes like the 747 to carry a large amount of fuel for long-distance flight. Now by skipping on the upper atmosphere, you use less than half the fuel. Large airplanes can only be flown from large airports in big cities. To fly from Phoenix to Shenzhen I must change planes twice, wasting. Instead, what about direct flights between Phoenix and Shenzhen?
But there aren't enough passengers flying every hour from the west coast of the USA to the east coast of China. If you fly high and fast, you carry only 20 percent of fuel by weight. The airplane can be made lighter, with carbon composite fuselage and 3D-printed engines. With small wings and an aerodynamic shape, the aircraft is small, carrying tens instead of hundreds of passengers.
Hypersonic air travel must be safe and cheap. To ensure the former, you must use redundant propulsion systems. Here's what's on my "wish list" for now, and the future.
I want a Vertical Take-Off and Landing system, like a helicopter. I flew on helicopters, and I can tell you lift off and landing is safer and gentler than airplanes speeding up or slowing down on runways.
I want to fly at low speeds and altitudes with turbine electric propulsion. Large bypass airflow of the turbofan can give maximum thrust and fuel efficiency.
I want to fly at high speeds and altitudes with ramjets. I want to fly in and out of the atmosphere and experience zero gravity. Virgin Galactic does that, but you must pay quarter of a million dollars. I would pay only $1,000 for a three-hour direct flight across the Pacific Ocean.
I want VTOL spacecraft. A key aspect is integrating turbine electric and ramjet propulsion. You need the triple safety of turbine-ramjet: propulsion with fixed wings, turbine electric propulsion with rotary wings, and a parachute in case all else fails.
I am revealing my hypersonic spacecraft at the Chinese Academy of Sciences on Friday, April the 13. It would take off vertically every hour and directly between pairs of cities in China and the USA. You would only have to pay an economy ticket price for a three-hour hypersonic trip. Through this technology, we could make the space between China and the USA a lot smaller.
Joseph Y. Hui is professor emeritus of Arizona State University in the USA and president and CEO of Monarch Power Corp, a renewable energy company.