Teddy bear travels 10,000 meters in the sky! Looks high? But it’s not in space!

In recent days, a video of several college students using a hydrogen balloon to send a teddy bear to an altitude of 28,000 meters has gone viral on the Internet. Many netizens not only lamented that this was "the elegance and romance of science and engineering students." While praising the students' space dreams, some netizens have raised some questions, such as: Did the teddy bear enter space? Will it affect the flight routes and normal flights of passenger planes?

The teddy bear was sent to an altitude of 28,000 meters (Source: Video screenshot)

Is it possible that the teddy bear's ascent could affect the passenger plane's route and normal flight?

Several college students said that all rules and regulations were followed and the altitude was only in the stratosphere, not space.

From the surface upward, the atmosphere can be roughly divided into the troposphere, stratosphere, mesosphere, thermosphere (also known as the thermosphere) and exosphere (also known as the exosphere). The stratosphere is about 10 to 50 kilometers from the ground. Therefore, if the teddy bear flies to an altitude of 28 kilometers (28,000 meters) , it has indeed reached the stratosphere .

Due to weather and air flow changes in the troposphere, civil airliners generally cruise at an altitude of around 10 km, roughly at the bottom of the stratosphere , for the purpose of safety and fuel saving.

Theoretically, the teddy bear reached and exceeded the cruising altitude of the civil airliner during its ascent, which could affect the normal flight of the airliner. The cruising speed of the airliner can reach more than 800km per hour. If it hit the fuselage or engine, it would cause great damage and affect flight safety.

The "Regulations on the Management of Clearance Protection of Transport Airports" promulgated by my country in 2022 stipulates that it is prohibited to release unmanned free balloons, tethered balloons and other objects that affect flight safety in the clearance protection area within 55 kilometers around the airport.

However, with the vigorous development of my country's general aviation industry, the airspace, especially the low-altitude airspace below 1,000 meters, has been gradually liberalized, and the relevant approval procedures have been simplified. It will be more convenient to carry out flight activities in airspace that does not affect aviation flight safety.

In addition, the student's school has issued a statement: it has consulted the local meteorological department, aviation administration and other relevant agencies, and has professional guidance. The school has fulfilled its obligation to pay attention and remind students, so please do not imitate them at will.

Careful friends will find that the students emphasized that the teddy bear did not enter the space. So, have you ever thought about where the definition of space begins, as you have been familiar with the word "space" since childhood?

At what height does space begin? Is there a clear dividing line?

Space is the abbreviation of outer space, that is, outer space (or cosmic space). For the earth, it mainly refers to the empty area outside the earth's atmosphere . The matter in this area is mainly plasma hydrogen , with extremely low density .

Since the transition from the atmosphere to outer space is gradual, and the definition of the atmosphere and outer space involves the airspace and sovereignty of various countries, there is currently no unified definition internationally, and there is no clear dividing line to distinguish the atmosphere from outer space.

3D rendering of sunrise over a distant planet system in space (Source: Tuchong Creative)

The Kármán lines are a relatively widely accepted method of defining the atmosphere and outer space .

The Karman line is about 100 km from the surface of the earth. It is named after von Karman, the mentor of Mr. Qian Xuesen, a famous Chinese scientist. Karman calculated that above 100 km from the surface of the earth, the atmosphere is too thin to effectively provide the lift required for aircraft flight. In other words, the Karman line can be regarded as the upper limit of aviation flight, and also the lower limit of space flight .

The location of the atmosphere and the Karman line. The altitude data in the figure is an approximation and varies at different latitudes (Source: Wikipedia)

Can flying objects break through the "Kármán Line"? Are there any corresponding rules?

All space flights are above the Karman line. For example, the orbital altitude of my country's space station is above 400km, far exceeding the Karman line.

Below the Karman line is aviation, but current aircraft flight altitudes are generally below 20km (some solar aircraft can exceed 20km ), and will not cross the stratosphere, which is far below the Karman line .

From a technical point of view, it is no longer a problem for aircraft to break through the boundary between the atmosphere and outer space. However, since the demarcation of this boundary involves sovereignty issues (outer space is generally considered not to belong to the scope of airspace), countries have different opinions.

Space junk orbiting the Earth in 2005 (Source: Wikipedia)

The United Nations Committee on the Peaceful Uses of Outer Space once promulgated the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (also known as the Outer Space Treaty). This treaty came into force in 1967 and is the basic framework of international space law. It provides basic principles for the peaceful use of outer space. China joined the treaty in 1983. The treaty stipulates that the exploration and use of outer space must be based on the interests of all countries, and no country may claim the moon or other celestial bodies as its own or declare sovereignty .

Author: Zhu Lei, PhD in Aerospace Propulsion Theory and Engineering, Nanjing University of Aeronautics and Astronautics

Reviewer: Deng Xiaotao, Senior Engineer, AECC Hunan Power Machinery Research Institute

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.