Space debris is the combination of natural(meteoroid) and artificial(man-made) particles. Natural debris orbits around the sun and artificial debris orbits around the earth. Hence they are called Orbital Debris. This can be any man-made object in the orbit moving in the earth’s orbit. Such debris includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris, and fragmentation debris.
In this article, we are going to focus on Artificial Debris, the Reason for its cause, and its prevention.
What is Artificial space debris?
Any non-functional man-made object in space is called Artificial debris.
They come from
- Satellites and spacecraft which are failed.
- Satellites whose life has ended.
- Rocket dismantle stages during the launch.
- Hardware like nuts, bolts, payload covers, etc.
- Solid propellant slag.
- Cast aways during space activities like human wastes.
- Fragments due to battery explosions, collisions, etc.
When two satellites collide they produce thousands of particles that are dangerous and can cause further destruction which makes Earth’s orbit unfit for satellite launches.
The number of satellite and rocket launches as of April 2021 is given below:
|Number of rockets launched(excluding failures) since 1957||5560|
|Number of satellites carried by rockets launched||11139|
|Number of satellites still in space||7389|
|Number of satellites still functioning||3170|
Let’s have a look at the number of satellites launched only in 2020 and 2021(April)
|Satellites launched in 2020||1283|
|Satellites launched in 2021 (April)||853(65% of 2020)|
In the year 2009, 19,000 debris over 5 cm in size were tracked.
In July 2013, more than 170 million debris smaller than 1 cm(0.4), around 670,000 debris of 1 to 10 cm in size, and approximately 29,000 larger debris were detected.
By July 2016, nearly 18,000 artificial debris were orbiting the earth.
In October 2019, nearly 20,000 artificial objects including 2,218 were tracked.
The speed with which the debris travel is more than 28,000 kph(23 times the speed of sound).
Have you heard of Kessler syndrome?
NASA scientist Donald Kessler in 1978, proposed that more launches could increase the junk around the earth which results in the chain reaction of collision of objects in space and further making the earth’s orbit unfit for satellites.
This situation would be extreme, but some experts worry that a variant of this could be a problem one day, and precautionary steps should be taken to avoid the problem.
How do they track space debris?
The USA and Russia have set up tracking networks to monitor the orbital space object population. The European Union is also starting to develop its ways to track debris.
Powerful lasers are used to measure the distance of these objects, like radar or sonar. When a laser beam hits the debris and bounces back to Earth, ground crews can measure how long it takes to figure out where they are and where they are going it alerts the ground stations in case of collisions. But usually, laser technology is used to detect the movement of satellites and if the same technique is used to detect the debris then continuous monitoring should be there since debris are found randomly in space.
India’s status on tracking debris
NETRA(Network for space Objects, Tracking, and Analysis)
Till now, ISRO was dependent on NORAD(North America Aerospace Defense Command) data,
which is available in the public domain, to keep track of space debris and monitor our active and passive satellites. However, this global data is not accurate but NORAD keeps accurate data available for those who are members of its network. Therefore, ISRO cannot access the data.
But now, ISRO has decided to set up telescopes and radars in four corners of the country to get accurate data and avoid unwanted collisions of the satellites.
In September 2019, India launched the early warning system NETRA to secure satellites and other assets in space.
Can satellites be protected from space debris?
There are two ways in which the satellites and spacecraft can be protected:
- Computer programs can search for possible collisions between large debris. This system is used in the International Space Station to detect. These operations are expensive and can disturb delicate experiments. Space tracking networks can only track objects more than 100 mm in size. Even a 10 mm object can cause big trouble this cannot be called 100% effective.
- A debris shield can be designed to provide additional protection for a spacecraft. One way is to increase the thickness of the craft but that can increase the mass of the craft/satellite. Hence, a specially designed shield called the Wipple shield was used. It was made of two thin walls separated by some space. It was observed that this wall was more resistant to debris. The outer layer absorbs a lot of debris energy so that the inner wall is not punctured.
Space debris Removal
Removing space junk, especially larger pieces before they fragment is not easy. The best way to do this is retarding the force and deorbiting the junk. When it drops in altitude less than 400 km above the earth it is burnt.
For years NASA, ESA, and other space agencies are studying debris removal technologies. Some of the ideas include the usage of nets to gather junk and robotic arm. Japanese are now developing a type of satellite that uses magnets to catch and destroy the debris. Last year, UK has successfully cast a net around a dummy satellite.
Clearspace-1 will be the first space mission to remove debris from the Earth orbit, it was planned to launch in 2025. The technology demonstration satellite was first developed by the Swiss Federal Institute of Technology in Lausanne.
Many countries are trying to invent new technologies to reduce the threat of debris. Russia invented a Self Destroying Satellite. Australian researchers are developing the Hunter-Killer satellite to neutralize space junk. Finland has developed a Wooden Satellite and planning to launch this year.
credits to the right owners of the pictures used.