From Beijing to New York, only 1 hour?

Expert of this article: Lin Wenjie, engineer, senior researcher of Chuando Think Tank

When traveling long distances, which mode of transportation would you choose?

I believe that many friends, especially business people, would answer: airplane.

Although airplanes are fast and convenient, they still take a long time for international travel. For example, it takes 12 hours to travel from Beijing to New York.

But have you ever imagined that one day this time could be shortened to just one hour?

Recently, foreign media reported that a Chinese commercial aerospace company released a "suborbital travel" promotional video, claiming that it is developing a vehicle that can reach a speed of 7,000 miles per hour and can fly from Beijing to New York in one hour. This aircraft is a "winged rocket" type hypersonic aircraft.

The report has attracted widespread attention at home and abroad. Many people are beginning to wonder, does it really only take one hour to get from Beijing to New York? Wouldn't it be possible to travel around the world in one day in the future? How powerful are hypersonic aircraft? Let's figure this out first...

01

From Beijing to New York in just one hour?

Suborbital travel is a hot topic in the aerospace industry and is also a trend in the future of aviation development. The characteristic of suborbital flight is its high speed. If this type of flight is used between cities, the time can be greatly shortened.

To achieve suborbital travel, a hypersonic aircraft is needed, which is an aircraft used for point-to-point high-speed travel. It can reach a flight speed of 5 to 15 Mach, greatly shortening the time of aviation flight.

The distance from Beijing to New York is more than 10,000 kilometers, and the current flight time is about 12 hours. If the speed is increased to above Mach 5, the flight time can be shortened to 1 to 2 hours.

However, there is no suborbital hypersonic flight technology verification aircraft in the world, and powerful countries in the world are still in the design stage in this regard. According to the current status of the civil aviation industry and the speed of development, it will take at least 15 years for the relevant technology to mature in order to use suborbital flights for civil flights.

02

How to achieve suborbital hypersonic flight?

In order to carry out suborbital hypersonic flight, it is necessary to build a new type of aircraft that can fly in the suborbital space with thin air.

The suborbital altitude ranges from 30 kilometers to 100 kilometers, which is an undeveloped altitude in the current aviation field. The cruising altitude of traditional civil flights is 10 kilometers, and only some special aircraft used for military purposes can fly at this altitude.

Suborbital altitudes have the characteristic of thin air, which can greatly reduce the flight resistance of aircraft, so the speed of aircraft is increased, reaching more than Mach 5. But problems also come with it. The thin air cannot support the current aircraft engines, so we can only develop a power system specifically for suborbital altitude flights.

One of the power sources is called an air-breathing scramjet engine, where the air velocity of the inlet gas exceeds the speed of sound, so it can reach a higher flight speed. According to relevant research results, scramjet engines can produce net thrust and are more efficient than traditional subsonic combustion ramjet engines at Mach numbers of 6 to 8.

The development of scramjet engines will face various extreme technical challenges, such as wind tunnel facilities, materials, technical bottlenecks, etc. If a rocket engine is used to fly in a suborbital space, a high Mach number can theoretically be achieved, but more fuel needs to be carried, while an air-breathing engine can support combustion using thin air and does not need to carry an oxidizer.

Therefore, the air-breathing scramjet engine is one of the core power sources for long-distance suborbital flight, and requires more manpower and material resources for research and development.

The general direction of current civil airliner design has been determined, namely, a flight altitude of 10,000 meters and high subsonic cruising, which determines that the time between intercontinental flights cannot become shorter.

Britain and France once developed and put into service the Concorde, which has a flight speed of Mach 2.2 and is used for transatlantic flights. Over the same distance, the flight time is half that of a high subsonic cruise passenger aircraft, but there are also prominent problems, such as high operating costs. Every 12,000 hours of flight requires a 10-month overhaul, and each overhaul costs $10 million. In addition, the profitability is lower than that of a subsonic passenger aircraft.

If a suborbital hypersonic passenger aircraft is to be developed, the issue of operating costs must also be considered.

03

When will it enter the lives of ordinary people?

In the foreseeable future, suborbital hypersonic aircraft will be mainly used in the fields of aviation technology verification, military, scientific research, etc. It will take a long time for them to truly enter the daily travel of ordinary people. It may take until the middle of this century for large-scale manned flights to be carried out.

From the perspective of technical risks, the power system for suborbital flight at Mach 5 to 15 is far from mature, and the aerodynamic design is still at the theoretical stage, and there is still a long way to go before manned aircraft can be put into use. Even if an engineering prototype is manufactured, profitability needs to be considered, and it is obviously impossible for it to enter the lives of ordinary people so quickly.

In civil aviation, the next stage of change will not be suborbital hypersonic vehicles, but quieter supersonic passenger aircraft.

NASA and other institutions are working to solve the sonic boom problem caused by supersonic flight, and have developed the X-59 Quiet Supersonic Technology Aircraft for testing. If the sonic boom problem can be solved, supersonic passenger aircraft will be able to fly over land and take off and land at more airports around the world, which is a far more attractive prospect than suborbital hypersonic aircraft.

Suborbital travel is an imaginative vision. Whether it can be realized in decades depends on whether other modes of transportation mature.

In the foreseeable future, supersonic passenger aircraft are more realistic. Whether in terms of technological maturity or cost control, they are far closer to our lives than suborbital flight.

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