Why fly out of the earth at the speed of the first universe?
Newton published the law of gravitation in "Philosophical Principles of Natural Science" published by 1687, which revealed the interaction of celestial bodies in the universe and the free falling motion of objects on the earth. This is actually a truth!
The attraction between celestial bodies is directly proportional to their mass and inversely proportional to the square of the distance.
In the free falling motion on the earth's surface, the gravity of the falling body is the same as that of the earth. When an object falls, in fact, the earth is closer to the object.
After Newton discovered gravity, he also thought about leaving the earth, but in fact, he never thought that he could really leave the earth like this in the future! So what is the method?
Newton's method of leaving the earth in the scientific principle of natural philosophy
It looks simple, too. Isn't the earth a super sphere? When we travel on the ground, we are actually circling a circle with a radius of about 6370 kilometers. But so far, only a few navigators have sailed around the world, and most of them have only circled part of this circle of about 40 thousand kilometers!
The simple understanding is? Centrifugal force? Just equal to gravity, this speed is about 7.9 km/s on the surface and 7.8 km/s in low-earth orbit, which will change with the height.
Various ways to get off the ground
Although Newton found a way to leave the earth, he didn't achieve his goal for a long time, even flying, until 1783 when the Mongols invented the hot air balloon! Maybe you will have a different opinion. We in China have long invented the Kongming Lantern with rising heat, but unfortunately we have never used it to carry people!
Sky Lantern
How high can a hot air balloon rise?
The principle of hot air balloon is simple. A large balloon that can be controlled to open and close will generate static buoyancy in the atmosphere when the fuel at the bottom is heated and the expansion density of hot air decreases. When the static buoyancy is greater than its own mass, it can overcome the gravity rise!
The earliest hot air balloon
1862 meteorologist James? Grescher and hot air balloon driver Amelia? Rennes, without oxygen, rose to 9 144 meters, which was the limit level at that time. It's not that the hot air balloon doesn't work, but the human body's tolerance to the hypoxic environment. Above 3000 meters, the oxygen content drops to about 18%, and people begin to feel uncomfortable, reaching 12% at 5000 meters.
Balloons (helium balloons) in modern practical pressure-resistant cabins can generally reach about 40 kilometers. For example, on April 4, 20 12, 10, Felix successfully parachuted at an altitude of 39,045 meters above the ground, which is about five times the height of a civil airliner!
But neither hot air balloon nor helium balloon can break through the atmosphere, because they need the atmosphere as a medium! Like a hot air balloon, an airplane can't leave the atmosphere, because its wings need air to give it lift, and it is difficult to move without the atmosphere! And the limit of the plane is not as good as the balloon!
SR7 1 of double triple, Mach 3, 30,000 meters.
A rocket that easily breaks through the constraints of the earth
Like hot air balloons, the principle of rockets has long been discovered by humans. This is the Chinese nation that invented black powder, and we use it to make firecrackers, which is also commonly known as kicking! But it is obviously difficult to send objects into space, but Robert? Goddard's state changed rapidly after the successful test flight of the first liquid rocket on March 26th 1926!
Robert? Goddard and the first liquid rocket
As early as 19 19, tsiolkovsky published a paper on multistage rockets, Space Rocket Train, which initiated the cooperation of concepts, theories and tools of multistage rockets. It was modified by the Soviets with P-7 intercontinental missiles at the Baikonur launch site on June 4th. 1957? Satellite? The world's first artificial earth satellite was launched by a launch vehicle? Putnik 1? The key to putting Chang 'e-1 into orbit!
Why accelerate the rocket to the first cosmic speed and climb out slowly?
Tsiolkovsky's multi-stage rocket theory is the key to understand it, because the earth has a thick atmosphere (the standard of space is at least 100 km from the ground), and there is great resistance when flying inside, so it must be this speed when hovering!
Then there is a very critical requirement, that is, the rocket must climb to the clear height above 100 km as soon as possible after taking off. Vertical penetration is obviously the shortest, but there is a problem. Rocket fuel is limited. When it climbed vertically to 100 km, the fuel had already burned out. At this time, there is no horizontal speed, so the rocket will still fall back to earth after a period of inertia rise!
The only way is to fly vertically out of the lower atmosphere and quickly turn to the direction of the earth's rotation. At this time, the speed of the rocket can be added to the speed of the earth's rotation (460 m/s in the equatorial region), which can save a lot of fuel! When the rocket climbs above 100 km, the horizontal speed may already be 4 km per second. At this time, abandon the self-weight of the first-stage rocket, then start the second-stage rocket and accelerate to the vicinity of the first cosmic speed. After the relay, you can hover in low orbit! If this orbit is not the desired altitude, we can abandon the second stage and start the third stage rocket to climb to the desired orbit.
How high can I climb slowly to get rid of the gravity of the earth?
If you are in the equatorial region, you must climb vertically to the geostationary orbit above the equator, because it is produced when the angular velocity of the earth's rotation reaches 42 164.438+069 km (from the center of the earth)? Centrifugal force? To compete with the gravity of the earth here! This height is about 35786 kilometers from the ground. At this time, the linear speed of 465 meters per second on the equator will be enlarged to 3.07 kilometers per second, which is enough for this object to stay in geostationary orbit for millions of years!
Various orbital data
None of our rockets can be so sick. For example, the specific impulse limit of solid rockets is 285S, and the specific impulse of liquid rockets of hydrogen and oxygen can reach more than 450S, but these rockets are far from reaching the geostationary orbit directly. The specific impulse of ion thruster is above 3000s, which can meet the requirements, but the thrust is extremely small. So far, it has only been used for satellite orbit change. In the future, the Hall thruster may be able to achieve interstellar flight, but it can only be relied on.
GOCE's satellite ion engine
Future space plane
Above we said that the aircraft needs the atmosphere as a source of lift, but this premise is that the engine does not give force, and the early propellers push the atmosphere as a support for progress. Later, jet engines needed to inhale a lot of oxygen to maintain combustion, but now they are changing rapidly, because series engines will be realized in the future!
When taking off on the ground, use turbojet engine instead of turbofan engine, because turbojet has low bypass ratio and is suitable for high speed. Then bypass the turbojet engine after the supersonic speed of Mach 5-6, start the ramjet engine, and then start the rocket engine until it reaches high altitude and flies out of the atmosphere! This combination mode can save a lot of space to carry oxidant, because the rocket comes with oxidant and fuel, and it consumes oxidant from the beginning, which is really a waste!
Therefore, the most promising model in the future is the space plane, because it is a technology that human beings can learn with a little effort, and I believe it will be realized in the near future!
Really slowly climb out of the space elevator.
Its principle is simple. Make a rope about100000 kilometers, one end is tied to a certain point on the equator, and the other end is equipped with a counterweight to make it stay on the equator. Centrifugal force? Under the pulling force, then you can make an electric-driven elevator, slowly rising from this rope to a height of about 36,000 kilometers, and then you can get rid of the elevator and become an aircraft that flies around the earth and will not fall down in a short time!
Elevator port group
foundation
This way you can really climb out slowly, no matter how slow! However, this technology has encountered a very big problem, that is, this ultra-high strength material has never been found. Even ultra-high strength steel will break due to its own weight after more than ten kilometers. Carbon nano-materials may far exceed steel, but we still can't make them on a large scale! In theory, this technology is the most ideal, because that kind of elevator can use electricity, and even can use solar cells installed on the top of the elevator to supply power, and use solar energy to climb out of the earth. It is exciting to think about it!