Farewell to the "Palace of Heaven"

We, people, are subject to cognitive distortions, and a vivid picture of a large space station, uncontrollably falling to Earth, seems much more terrible than a rational assessment of the probabilities and dangers of this same event. Therefore, it is not surprising that much attention has been riveted on the fall of the Chinese station Tyangun-1. At the time of writing these lines, she literally had a few hours left, a great time to remember the station itself, to recall similar events from the history of astronautics and to allay irrational fears.

Radar image "Tyangun-1", a snapshot of the Institute of High Frequency Physics Fraunhofer

The horrors of cognitive distortion

Almost the entire territory of Russia "Tyangun-1" can not threaten purely physically. The fact is that the station's orbit inclination is 42.7 °, and over the regions north of 43 ° north latitude and south of 43 ° south latitude, the Tyangun-1 does not fly and cannot fall there. In Russia, south of 43 ° are only the south of Dagestan, the southernmost parts of Chechnya, Ingushetia and North Ossetia, and a small area south of Vladivostok, with low population density and without major cities.

In the rest of the world, according to the latest data, there are about 40 cities with a population of over a million people not far from the station's trajectory, but just look at the map to notice that most of the track passes over the seas and oceans, and a significant part of the land is uninhabited.

The last turns of the station, the source

Population density and probability distribution of the fall depending on the latitude, the scheme of the European Space Agency

The calculations of the European Space Agency show that if you live inside the fall strip, the probability that the Palace of Heaven falls on your head is 1 in 300 trillion, which is 10 million times less dangerous than lightning. But these numbers look pale compared to two factors that make the situation seem more dangerous than it actually is. First, the feeling of lack of control increases the apparent risks - a classic example is that people are more afraid of flying on airplanes than traveling by car, despite the fact that statistics is clearly not in favor of the latter. Secondly, the sense of risk is increased by uncertainty. Alas, the fall of “Tyangun-1” happens uncontrollably and will happen at an unknown moment (the best predictions now give an estimate of ± 2 hours).

Dive into the story

The Chinese station is not the largest man-made object that fell uncontrollably on our planet. The weight of the Tyangun-1 is approximately 8 tons (according to various estimates, from 7.5 to 8.5 tons). In 2003, a controlled landing of the Columbia shuttle at an altitude of approximately 60 kilometers turned into uncontrollable destruction, and a ship weighing 106 tons spilled debris throughout the territories of the states of Texas and Louisiana.

Colombian wreckage on meteorological radar, photo by US National Meteorological Service

In the old news stories you can find how people found debris on their doorstep, but there were no victims on the ground, not to mention victims.

The earth's atmosphere copes quite well with the destruction of unprotected objects at high speed. The case of Columbia can be called special, because the shuttle braked for quite a long time and completely “honest” could be called the fall of Skylab station, weighing about 77 tons, completely “honest”. The huge station, for the removal of which used super-heavy rocket "Saturn-V", safely collapsed and burned in the atmosphere. Relatively small fragments that fell in the sparsely populated areas of Australia flew to the surface. This tank was the largest discovered (the man and the car show a great scale).

Photo of the Esperance Museum in Australia where the Skylab fragments are stored

In general, it is worth noting that objects that were inside the structure and are distinguished by high strength and low density often reach the surface. These criteria are well met by various tanks, which are indeed quite often found in places where spacecraft have fallen. Other debris are usually relatively small.

The wreckage of Skylab in the museum, space.com

Also uncontrollably fell "Salyut-7" weighing in the region of 39 tons. Its debris landed in Argentina, and there were no casualties.

Fragment "Salyut-7" in the Argentine Museum, photo by Carloszelayeta / Wikimedia Commons

And Cosmos-557, which due to the accident did not receive the name Salyut-3, collapsed completely unnoticed. Nobody saw the fall of the station, and the debris reached the surface not in the Indian Ocean, or in the Bolivian region.

In general, it is worth noting that "Tyangun-1" is a very light station. Even the sad memory of Phobos-Grunt, fully charged, weighed about 5 tons more. Incidentally, he, too, fell without witnesses somewhere in the region of South America.

Nice work

Launch of "Tiangun-1"

Station "Tyangun-1" (translated as "Heavenly Palace") was launched September 29, 2011. It became the first Chinese orbital station and a test stand for testing docking and other technologies. The station had a working volume of about 15 cubic meters, androgynous docking unit and was structurally divided into two compartments - habitable and service. After launch, the station produced two orbital maneuvers to test docking technologies. In November 2011, the station docked twice with an unmanned spacecraft "Shenzhou-8". In June 2012, a manned ship "Shenzhou-9" with a crew of three people, including the first female cosmonaut in China, launched and successfully docked to the "Tiangun-1". Taykonavty (cosmonaut Chinese designation) spent six days at the station, then undocked and docked again in manual mode. After another four days, the crew undocked a second time and successfully returned to Earth.

Station interior

In the summer of 2013, the station took the second expedition from three people who arrived on the ship "Shenzhou-10". Taykonavty spent at the station for 12 days, during which they conducted scientific experiments, station maintenance, and also gave a lecture from orbit. More manned expeditions on the "Tyangun-1" was not planned. The station was put into sleep mode, extended the regular two-year service life and began to study issues of degradation of equipment in space. It was originally planned that the “Palace of Heaven” would be controlled to be derailed from orbit, but in 2016 it seemed to have broken - an official message says that the station “stopped functioning”.

Reducing the height of the station orbit, illustration heavens-above.com

Latest data and reaction

The less time left before the fall of the station, the more accurate the predictions are to make. But, in any case, the specific place and time of the fall cannot be calculated with an accuracy greater than a few turns and hours. Last week, the Sun was calm, so there were few atmospheric molecules slowing the station in a low orbit, and the forecast for a fall in the April 1 region eventually slid off onto the night of April 1-2. According to the latest calculations, the station finally closes into the atmosphere on April 2 at 1 UTC ± 2 hours. So if you read these lines after 6 am Moscow time, the station, most likely, has already fallen.

Estimated time window of the fall of the station, illustration of the European Space Agency

Track last orbits, source

In the meantime, the station did not fall, observers are trying to look at it at last. Here is a three-dimensional radar image of the station, made by the Fraunhofer Institute for High Frequency Physics:

But the last turns in the optical range

Conclusion

Increased attention and understandable anxiety sometimes give rise to a paradoxical, but very positive reaction. When people were expecting the fall of Skylab, some jokers hung targets on their homes.

Also sold "protective helmets" from the station.

Today's astronomers turned out to be connoisseurs of old jokes, having added to the helmet a foil protecting Nibiru from radiation.

Astrophysicist Jonathan McDowell Helmet

And such a helmet looks even too serious, because it really protects against small debris.

Dr. Marco Langbroek Helmet

So far, the center of the calculated fall is in the middle of the Atlantic Ocean, there is a considerable chance that no one will notice the fall, but in any case it is worth following the news.