What would happen if you jumped from space with a parachute? Would you be able to land safely?

It depends on how you define "space".

The general consensus of the scientific community is that the entire space outside the atmosphere is called outer space. The atmosphere is generally divided into five layers. From sea level, the troposphere is about 10km below the sea level, the stratosphere is 10km~40km, the mesosphere is 40km~80km, the thermosphere is 80km~370km, and the ionosphere (exosphere) is above 370km.

75% of the mass of the Earth's atmosphere exists in the troposphere, and 97% of the mass is below the stratosphere. There is still air at 16,000 km, and there are air particles at an altitude of 100,000 km. The latest research shows that there are still Earth atmospheric particles at a distance of 600,000 km from the Earth. Therefore, there is no obvious boundary of the Earth's atmosphere. Where is outside this atmosphere?

However, the International Aeronautical Federation defines a "Kármán line", which is an altitude of 100 km (kilometers) above the Earth's sea level. People generally regard this altitude as the lowest altitude of "space", where the air density is only 1/300,000 of that at sea level, and below this altitude it cannot be called "space". Artificial satellites and other spacecraft generally operate at their lowest altitude above the thermosphere, where the air density is less than 1/100 billion of that at sea level. According to this definition, so far, no human has dared to parachute in the so-called "space".

Basic conditions for skydiving

Skydiving is a sport in which one jumps from a certain height, including from an airplane, balloon or other aircraft, or from a cliff on a mountain top, a high-rise building, etc., and uses air resistance to open a parachute, completes various technical moves before and after opening the parachute, and finally uses the parachute to cushion the speed and land on the ground.

From the basic process and requirements of this sport, it mainly relies on gravity and air. Gravity comes from the gravitational force of the earth's center, which pulls the skydiver and makes him fall faster and faster; the role of air is to increase the resistance of the skydiver, and the increased resistance after the parachute is opened, and finally a balance between gravity and resistance is achieved, allowing the skydiver to land safely.

In space, the air is already very thin, and the air resistance is almost non-existent or very weak. Therefore, if you jump in space, you will lose the air resistance and will not be able to open the parachute. Objects can only fall in free fall, and there is no way to carry out skydiving.

Some so-called "space parachuting" nowadays is actually not in the space above the Karman line, but in the troposphere, at most in the stratosphere. Therefore, strictly speaking, this kind of parachuting activity cannot be called "space" parachuting, but can only be called high-altitude parachuting.

World record for skydiving

People call some of the world's highest altitude skydiving records "skydiving at the edge of space." This is only a game for the brave. It is impossible to attempt without solid skills and strong psychological support.

In 1960, U.S. Air Force Colonel Joe Kittinger set a skydiving record from an altitude of 31,300 meters and was hailed as the "father of stratospheric skydiving." In 2012, Austrian extreme athlete Felix Baumgartner set a skydiving record from an altitude of 39,045 meters. This time, the highest descent speed reached 377.12 m/s, breaking the speed of sound of 340 m/s. In 2014, former Google vice president Alan Eustace jumped from an altitude of 41,400 meters, once again breaking the world record for skydiving height.

Skydiving at this altitude is totally different from the conventional skydiving we imagine, because at this altitude, the air density is only 1~3% of that at sea level, the air pressure is only one thousandth of that at sea level, and the perceived temperature is as low as -50℃. If the skydiver does not have protection or ordinary protection during conventional skydiving, the death is certain.

First, the air density at such a high altitude is not enough to provide resistance for opening a parachute, so you can only fall in free fall at an extremely fast speed, which will cause the body to overload. Secondly, there is no air and you cannot breathe. Thirdly, the extremely low air pressure will cause the gas in the body to expand and the body fluids to boil. Thirdly, you will be frozen to death by the low temperature.

Therefore, when jumping from this height, the above challengers must wear space suits that keep heat, maintain pressure and supply oxygen, and their bodies must be able to withstand extremely high acceleration overloads.

Airplanes cannot fly to such a high altitude, so these skydivers all went up in helium balloons. The helium balloon that Eustace rode did not have a space capsule with a life support system like the previous two times, but he directly hung his body on the hot air balloon and ascended into the sky. However, he wore a special space suit with a life support system. When the balloon rose to the predetermined height, he cut the rope hanging on him and fell down in free fall.

Eustace maintained a free fall at high altitude for 4 and a half minutes, during which time his maximum speed reached 357.64m/s, which exceeded the speed of sound, but did not seem to exceed Felix's record. However, ground observers observed a small sonic boom from him.

The consequences of a real space jump

If you really want to realize space parachuting, you must go above the Karman line, that is, reach an altitude of more than 100km above the ground. The first problem is what kind of aircraft to take to get up there.

Helium balloons use the principle that helium is lighter than air and rely on the buoyancy of air to rise continuously. When the altitude is above 40km, the air becomes thinner and thinner, and there is almost no buoyancy of air, so helium balloons cannot rise. Airplanes rely on aerodynamics to rise, and cannot fly without air. Then we can only rely on rockets or spacecraft.

A spacecraft must reach an orbital speed of 7.9 km/s, the first cosmic speed, to be able to orbit the Earth without being pulled down by the Earth's gravity. In space, when flying at an altitude of about 400 km, the orbital speed needs to be about 7.6 km/s, where the air resistance is very small, so a lot of fuel is not needed, and inertia is mainly used to maintain its orbit.

If you jump from this height, even if you are wearing a space suit, you will definitely die, because at this height, there is almost no air resistance, and after jumping out of the spacecraft (or space station), the skydiver will continue to fly around the earth at the same speed as the spacecraft, unless his space suit has enough power to use reverse thrust to actively slow himself down.

Of course, even without active deceleration, there would be passive deceleration, because there is still a little air resistance at that altitude. It is likely that after orbiting the earth for several years, the skydiver would gradually lower his orbit and eventually fall into the atmosphere. No space suit can sustain life for such a long time, so the unfortunate skydiver would have suffocated and starved to death before the parachute was opened.

Before the body reaches the Karman line altitude, the parachute is completely useless and the body can only fall freely, maintaining a speed of more than 7km/s.

As the density of the atmosphere gradually increased, the temperature of the air friction shock wave exceeded 1500℃, and the unlucky skydiver was burned to ashes before he entered the Karman line. The speed overload and cold here had no meaning to the dead skydiver. Therefore, the so-called space parachuting is not feasible, and jumping from real space can only be called death.

Of course, there are many descriptions of space travel in science fiction works, such as Superman, Iron Man, Bee Man, and Ant Man. However, these are all entertainment and do not have much scientific core.

If you have the opportunity to skydive from the edge of space, would you be willing to try it? Welcome to discuss, thank you for reading.

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