Space debris: a latent danger over our heads, by Tomás Unger

In August, we covered the constellations of satellites that billionaires like Elon Musk and Jeff Bezos are launching into the space. This is an alternative to offer Internet in remote places where fiber optic cables are too expensive.

On that occasion, we mentioned one of the problems presented by these networks with thousands of small satellites in orbit: their contribution to the growing space junk that circulates around our planet.

Everything that goes up…

With the exception of those satellites that are placed in a fixed orbit, suspended 35,785 kilometers above the equator (called geostationary, because they do not move with respect to a point on the surface), . Fortunately, the speed and resistance of the wind heat them up so much that combustion vaporizes them.

Some large objects, such as some rocket motors, . This is why launch trajectories are often calculated so that these components fall over the ocean, away from busy shipping lanes.

“Several capsules and shuttles have returned to earth showing damage caused by space debris.”

The capsules with astronauts, space shuttles and other objects that return to earth have a coating of materials resistant to high temperatures.

The other smaller objects they usually burn up before they reach the height at which airplanes fly.

The problem is the trash which continues to orbit. Each satellite has a different orbit, and they usually continue to orbit many years beyond their useful life.

quantities and speeds

Space may seem large, but most orbits are elliptical and therefore constantly change height and position relative to the surface, zipping through space at great speed. Of those, 7,840 are still in orbit, but only 5,100 are still operational; 2,740 are trash.

To this must be added pieces and minor objects that are detached from every launch; when separated, many enter the same orbits but without any control. In addition, there are fragments that have been scattered after collisions between satellites, meteor impacts, internal explosions or other mishaps.

In 1996 a French satellite collided with the remains of a rocket, also French, launched 10 years earlier. In 2009, a defunct Russian satellite collided with an American satellite, resulting in more than 2,000 visible fragments and countless others.

We must also add the intentional destruction of some satellites. . The war demonstration disintegrated a disused satellite, resulting in the dispersion of thousands of fragments at a height where satellites and rockets pass. In the face of global backlash, that was the latest US test. Unfortunately, China and Russia have also tested destroying satellites; the most recent, from Russia in November 2021, produced more than 1,500 identifiable fragments.

“The current count includes more than 30,000 objects large enough to be tracked and catalogued.”

The current count includes, in addition to the satellites mentioned, more than 30,000 objects large enough to be tracked and cataloged (greater than 10 cm). Based on radar, sensors and estimates, it is estimated that there are between 500,000 and 1 million objects of 1 to 10 cm in orbit, and between 100 and 130 million fragments larger than 1 mm.

The size of these objects might seem harmless, but at that speed, a nut can do serious damage to satellites or a spacesuit.

Protection and pick up

The amount of space junk it continues to grow, occupying orbits used by satellites, the International Space Station (ISS) and the China Tiangong space station. To reduce the risk of hits, launch paths are calculated to avoid the trajectories of known objects.

Likewise, space stations and satellites that still have propulsion are moved when they are on a collision course. , and are built with redundancies and isolated components to prevent damage from jeopardizing the entire ship. Several capsules and shuttles have returned to land showing damage caused by space junk.

In the case of space stations, the sections are compartmentalized and sealed in case one loses pressure, and there is always a capsule anchored as a life preserver. When it is not feasible to move the station, the astronauts take refuge and wait in a capsule until the moments of greatest risk are over. Last December, two ISS astronauts had to cancel their outer activity indefinitely due to the risk.

A few weeks ago, China successfully tested a prototype. Japan, the US, Russia and Europe are working on various concepts, including ground-based lasers to alter orbits.

Two promising techniques would use magnetic mechanisms or thrusters for future satellites, which would activate at the end of their useful lives to cause rapid descent. This would be the safest and cheapest option, but it cannot be applied to objects already in orbit.

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