SPACE WASTE Children

What is space junk? Why is it a serious problem?

This file photo taken on April 29, 2021 shows a Long March 5B rocket, carrying China's Tianhe space station core module, lifting off from the Wenchang Space Launch Center in southern China's Hainan province.   | Photo Credit: AFP

A core segment of China’s biggest rocket re-entered Earth’s atmosphere above the Maldives in the Indian Ocean and most of it burned up early Sunday, according to the country’s space agency.

The Long March 5B rocket carried the main module of China’s first permanent space station — Tianhe, or Heavenly Harmony — into orbit on April 29.

Usually, discarded rocket stages re-enter the atmosphere soon after liftoff, normally over water, and don’t go into orbit. However, the roughly 100-foot long rocket stage did not fall soon after discharging its payload. China's space program hasn’t said why it put the main component of the rocket into space rather than allowing it to fall back to earth, as is usual in such operations. It is to be noted that China plans 10 more launches to carry additional parts of the space station into orbit.

Uncontrolled de-orbits are not unheard of. One of the largest ever was NASA's 77-ton Skylab de-orbit which occurred in 1979. NASA was not able to prevent it from sinking out of orbit, and it eventually came down over the Indian Ocean but also over populated areas of Western Australia.

What is the solution?
  • The solution involves steps to clean up the mess, mitigate damage, and avoid future debris. There are systems in place to track the debris and avert disasters. Various space organisations have been working on reducing the amount of trash by adopting better designs of rockets and other objects. For example, making rockets reusable could vastly cut down waste.
  • The UK’s TechDemoSat-1 (TDS-1), launched in 2014, was designed in such a way that once its mission is over, a system, like a parachute, would drag the satellite to re-enter the atmosphere and burn up. Some satellites at the end of their lifecyle are made to fall out of orbit and burn up in the atmosphere, provided they still have fuel left in them for the descent. Some satellites are sent even farther away from Earth.
  • Technologies to remove space junk are also being developed. Cleaning the debris that already exists comes at a high cost, because it will take multiple trips to remove objects from space. Other proposals include the use of a laser to remove debris by changing their course and making them fall towards the atmosphere of Earth and later burn up.
  • In December 2019, the European Space Agency awarded the first contract to clean up space debris. ClearSpace-1 is slated to launch in 2025. It aims to remove a 100-kg VEga Secondary Payload Adapter left by the rocket Vega flight VV02 in an 800-km orbit in 2013. A "chaser" will grab the junk with four robotic arms and drag it down to Earth's atmosphere where both will burn up.

A number of satellites and space probes are launched every year, but not everything returns. Thousands of non-functional ones end up in the orbit of the Earth contributing to what is called – space debris or space junk. While some of them, such as rocket parts fall back to Earth, many of them, their parts and random objects like an astronaut’s gloves are still up there as space junk. This shows that we are not just polluting the Earth but also the space! And they come with potential risk.

What are the risks?

In-orbit risks: Objects in Low Earth Orbit travel at speeds up to 10km/second, fast enough to cause significant damage to satellite, spacecraft, or spacewalking astronauts. The rising number of space debris increases the potential danger to all space vehicles, especially to ones with humans aboard, the International Space Station (ISS), for instance.

A number of space shuttle windows have been replaced because of damage caused by paint flecks.

The density of the junk may become so great that it could hinder our ability to use weather satellites, and hence to monitor weather changes.

Debris that re-enters Earth

A helmet, believed to be from the space shuttle Columbia, in Nacogdoches, Texas, Saturday, Feb. 1, 2003, is seen in this image made from television. Space shuttle Columbia disintegrated 39 miles over Texas on Saturday in a meteoric streak that rained smoking debris over hundreds of miles of countryside. All seven astronauts were lost.

A helmet, believed to be from the space shuttle Columbia, in Nacogdoches, Texas, Saturday, Feb. 1, 2003, is seen in this image made from television. Space shuttle Columbia disintegrated 39 miles over Texas on Saturday in a meteoric streak that rained smoking debris over hundreds of miles of countryside. All seven astronauts were lost.   | Photo Credit: AP

Space trash is often attracted by Earth’s gravitational pull. It is pulled lower and lower until it finally reaches Earth’s atmosphere. Most objects burn up when they enter Earth’s atmosphere due to the compression of atmospheric gases, but larger objects can reach the Earth intact. But most of them fall into the ocean, simply because Earth is mostly covered by water. According to NASA website, an average of one catalogued piece of debris has fallen back to Earth each day over the last 50 years. But there have not been any significant damage. People on Earth should avoid contact with the fallen debris, such as rocket parts, because of the possible presence of hazardous chemicals in them.


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Printable version | Jun 14, 2021 6:59:09 PM | https://www.thehindu.com/children/what-is-space-junk-why-is-it-a-serious-problem/article34532546.ece

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