Seven Steps to the Moon: Overview of Significant Heights and Orbits

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Seven Steps to the Moon: Overview of Significant Heights and Orbits
Seven Steps to the Moon: Overview of Significant Heights and Orbits
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From the Earth to the Moon - 384 467 kilometers, and at this distance there are many interesting things. Naked Science invites you to come up and watch.

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Baumgartner height - 39 kilometers

On October 14, 2012, the Austrian extreme and parachutist Felix Baumgartner ascended into the stratosphere at a height of 38,969 meters above sea level and made a parachute jump. It was not an ordinary jump at all, and neither was the place from which it was made.

A sealed fiberglass capsule, attached to a balloon filled with helium, lifted Baumgartner to a height above which airplanes cannot fly (up to 20 km) and clouds practically do not rise. Even the ozone layer (and it is at an altitude of 20 to 30 km above the Earth) remained under it.

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Already at an altitude of 19 kilometers, water boils at the temperature of the human body, and from 35 kilometers at 0 ° C. Above, water can no longer be in a liquid state. Breathing is impossible without special equipment, and you can navigate by bright stars even during the day. This is the stratosphere.

Almost space. Although for someone already. The American company World View Enterprises plans to send tourists to the stratosphere in the near future. Such near-space travel is considered as a budget alternative to tourist space flights.

Of course, they conquered the stratosphere before Baumgartner. The previous record, which lasted almost 50 years, was set by the Soviet parachutist Yevgeny Andreev on November 1, 1962. He then jumped from a height of 25.5 kilometers.

And already 2 years after the Baumgartner jump, on October 24, 2014, the vice president of Google Alan Eustace climbed to an even greater height - 41, 42 km and made a jump with a stabilizing parachute. True, unlike Baumgartner's jump, which was watched live on YouTube by more than 8 million people, his jump did not receive as much attention, since it was not so publicized.

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Karman Line - 100 kilometers

Space begins where aviation becomes impossible. Guided by this principle, the International Aviation Federation established a conditional boundary between the atmosphere and space at an altitude of 100 kilometers above sea level.

Starting from this height, it makes no sense to use wings for flight. In order to create lift and fly, it is necessary to develop a speed exceeding the first space speed, which is 7, 9 km / s. But having reached this speed, any object enters a near-earth orbit and turns into a satellite of the Earth. For the first time this height was determined by the American scientist Theodor von Karman. She was named after him. Strictly speaking, the Earth's atmosphere continues above the Karman line, but then it is extremely rarefied and consists mainly of hydrogen atoms.

Flights to the Karmana line and above are not available to ordinary aviation. On July 19, 1963, NASA test pilot Joseph Walker reached an altitude of 106 km on a North American X-15 hypersonic rocket plane. And a month later - 108 km.

For the second time in history, a hypersonic aircraft crossed the boundary between atmosphere and space in 2004. In the period from June 21 to October 4, 2004, the SpaceShipOne crew, who fought for the Ansari X Prize, made 3 such flights, the maximum altitude of the last of which was 112 km.

At an altitude of 120 kilometers, the orbits of spy satellites are already beginning. Low orbit is convenient for aerial reconnaissance when intelligence is collected using surface photography. But the lifespan of satellites in such low orbits, due to the proximity of the atmosphere, ranges from several months to several years.

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"Inhabited belt" - 200-500 km

The orbital altitude of the International Space Station is 413-418 km, the Mir station is 354-374 km. The world's first manned orbital station Salyut-1 was launched on April 19, 1971 into an orbit of 200-222 km.

All orbits are within 200-500 km. This choice is not accidental. It is impossible to raise a manned orbital station higher, as it is dangerous for astronauts. From an altitude of 500 kilometers, the radiation level rises.

Below is also impossible. The space station will "cling" to the atmosphere, which, although rarefied, still provides aerodynamic resistance to spacecraft in low orbits.

Every day, the orbital altitude of the ISS, due to the resistance of the atmosphere and under the influence of the Earth's gravity, decreases by 150-200 meters. It is no coincidence that every time manned and cargo ships visit the station, its orbit is raised higher.

In addition, higher orbits would be disadvantageous for economic reasons, since the delivery of goods in this case would be more expensive.

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The lower border of the radiation belt - 500 km

Beginning from an altitude of 500 km, the intensity of radiation from the radiation belts that hold the electrons and protons of the solar wind captured by the magnetic field of our planet increases.

Predicted by Nikola Tesla, they were discovered with the beginning of the first space flights.

Radiation belts protect our planet, including orbital stations located in low orbits, from cosmic radiation. But at the same time they are a serious obstacle on our way into space. Cosmonauts flying through the radiation belts are exposed to radiation, and if the passage of the belts occurs during solar flares, they may die.

Proponents of the lunar conspiracy theory call the insurmountability of radiation belts without harm to the health of astronauts one of the reasons for the impossibility of American flights to the moon.

It was always believed that there are two belts. The first, at an average altitude of 4,000 km above the Earth, consists mainly of protons.

The second one is located higher - approximately at an altitude of 17,000 km - and consists mainly of electrons. There is a gap between the first and the second, located in the interval from 2 to 3 Earth radii. In addition, the lower boundary of the inner radiation belt is located at different heights above the planet's surface. Over the Atlantic, the belt can go down to an altitude of 500 km, and over Indonesia - up to 1300 km.

Not so long ago, NASA announced the discovery of the third radiation belt. It is located between the two already discovered and has, apparently, a temporary character. The belt was discovered by twin probes Van Allen Probes, launched in August 2012.

The spacecraft are named after James Van Allen, a scientist considered to be the discoverer of the radiation belt. In the English-speaking world, the belts are named after him: the Van Allen belts.

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Orbit "Iridium" - 780 kilometers

Seeing a bright flash in the night sky, somewhat similar to the trail of a shooting star, someone will rush to make a wish, but many already know: this is not a star at all. Thousands of people around the world take to the streets at certain times to see what is called the Iridium outbreak.

The orbital constellation of satellite telephony spacecraft "Iridium" began to be created in the 90s of the last century. Initially, it was planned to launch 77 satellites into orbit, and since this number corresponds to the atomic number of the chemical element iridium, it was decided to call the campaign "Iridium".

Currently, 66 satellites of the constellation are located in an orbit with an altitude of 780 kilometers. Several more spare satellites (the so-called orbital reserve) are placed in an orbit of 650 km and are raised to a higher orbit in case of failure of one of the main ones.

The bright flares observed from Earth are due to the reflection of sunlight from the smooth surfaces of the satellite antennas. It looks like a smooth rise and subsequent decay of the brightest star moving across the night sky. The flash lasts less than 10 seconds. But during this time, the brightness of the flashed "star" reaches minus eighth magnitude. For comparison, the magnitude of Venus is minus 4, 6.

It is noteworthy that the satellites of the Iridium system are also known in connection with the first collision of two spacecraft. On February 10, 2009, the decommissioned Russian military satellite Kosmos-2251 did not share its orbit with the operating satellite Iridium 33. As a result of the collision, which occurred at an altitude of 788.6 kilometers above the Taimyr Peninsula, both spacecraft collapsed. The resulting debris, which is about 600 fragments more than five centimeters in size, although they remained in the same orbit, will likely decrease subsequently, which poses a threat to spacecraft in lower orbits, including the ISS.

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Navigation satellite orbits - 19,400 - 23,222 km

Now life is hard to imagine without satellite navigation. Especially if you are driving a car. Originally intended for military purposes, satellite navigation has permeated civilian life everywhere. How high are the navigation satellites above us?

The spacecraft of the Russian navigation system GLONASS (Global Navigation Satellite System) occupy the lowest orbit among other navigation systems. Its height is 19,400 km.

A little higher are the satellites of the American global positioning system GPS (Global Positioning System) - 20,200 km.

The European Space Agency is launching its spacecraft to an altitude of 23,222 km.

Other countries are also trying to keep up. After all, the presence of such a system is a matter of national security. So, China is building its Beidou navigation system. It is planned to place 27 satellites at an altitude of 21,528 km - this is the so-called middle earth orbit. Just between the orbits of the American and European satellites. Three more satellites are in geosynchronous orbit, and five are in geostationary orbit.

Global, covering the entire surface of the planet, navigation systems are not affordable for all countries. Therefore, some are building their own regional satellite navigation systems.

The Japanese QZSS (Quasi-Zenith Satellite System) is only available in that country. But on the other hand, only three satellites launched into a high elliptical orbit are enough for its construction. It is called quasi-Zenith because the orbit allows the satellite to stay high in the sky for more than 12 hours a day, that is, almost at the zenith. The height at its apogee is 42,164 km.

India, which launched another satellite of the Indian Regional Navigation Satellite System (IRNSS) in April this year, is building a system of seven satellites in a geosynchronous orbit with an altitude of 35,786 km, three of which will be geostationary.

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Geostationar - 35 786 kilometers

At an altitude of 35,786 km above the Earth's equator, an orbit is located, which is of irreplaceable practical value for us - geostationary. The satellite, being in this orbit, revolves around the Earth with an angular velocity equal to the angular velocity of our planet's rotation around its axis. It actually hovers over one point on the surface.

For an observer from Earth, a spacecraft in a geostationary orbit is at one point all the time. Please note that antennas for receiving satellite television, the so-called "dishes", are always directed to an invisible arc in the sky - geostationary orbit. And antennas of one operator to one point.

In this orbit there are satellites that carry out direct television and radio broadcasting, complementing navigation systems, communication satellites and others. This is the only orbit, the use of which is regulated by international rules, since the number of places, positions where a satellite can be placed so that it does not interfere with other spacecraft is limited.

Since the geostationary orbit is "not rubber", the satellites that have worked out their time, using the fuel still remaining in them, are lifted into a higher orbit.This orbit, located 200-300 km above the geostationary one, is called the burial orbit, where these satellites can be up to 2000 years, until we figure out what to do with them next.

An interesting idea related to geostationary orbit is the concept of building a space elevator. Delivering cargo to Earth orbit is still expensive. An elevator to space is more attractive in this respect as compared to disposable and even reusable rockets.

The basis of the elevator is a cable (or tape, depending on the project) stretched from the surface of the planet to an orbital station located in geostationary orbit. The lift with the load will move along this cable.

It will be possible to ascend into geostationary orbit on such an elevator in a week, but it will be relatively inexpensive. But the material is light and strong enough to create such a cable has not yet been created.

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Moon. Distance to Earth - 384 467 km

Now let's compare all these orbits with the distance to the Moon. The average distance to our only natural satellite is 384 467 km. This is about 30 Earth diameters, almost 10 geostationary orbits, or 925 ISS orbits.

But this distance is comparable to the highest point of the orbit of the Russian space telescope "Radioastron" (aka "Spektr-R"). At the time of launch, the height of the telescope's elliptical orbit apogee was 333,455 km. In this case, the perigee of the orbit was 600 km. That, for example, is comparable to the altitude of the low Earth orbit of the American Hubble Space Telescope (569 km).

But the telescope's orbit is not constant. It is influenced by the gravity of our satellite. It is assumed that in 5 years the attraction of the Moon will raise the telescope's orbit apogee to an altitude of 390,000 km.

The orbit of the Moon is not constant either. Our satellite is moving away from the Earth by 4 centimeters per year. This allows some scientists to assume that the Moon will sooner or later leave the Earth's orbit and turn into an independent planet.

But until this happens, we hope that humanity still flies to the Moon again, having ascended the cherished 384 467 km.

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