Earth does not exactly look like what we saw in the images taken from space; actually, it’s slightly different. It is surrounded or (say) littered by small objects that constantly orbit the Earth, known as Space debris/junk /trash/pollution, etc.
Space debris is non-functioning artificial objects in space; most space debris orbit around the Earth. They mainly include derelict spacecraft -non functional spacecraft and abandoned launch vehicle stages -mission-related debris, fragmentation debris from the breakup of limp rocket bodies and spacecraft. In addition to these, space debris also includes tiny pieces from erosion, collisions, or even paint dots, and solid liquified propellant expelled from rockets and spacecraft.
According to a report by ESA (European Space Agency), there are 36500 objects whose sizes are more significant than 10cm, 1 million objects whose sizes are between 1cm to 10cm, and 130 million objects whose size is between 1mm to 1cm
Table of Contents
History of Space Debris:
Even before artificial objects were launched into space, there was an assumption that Earth might be surrounded with undetectable small chunks of natural debris that might obstruct spaceflights. The first satellite launched by the Soviet Union, SPUTNIK 1, didn’t start the accumulation of debris. The core stage of its launch rocket remained in orbit only for two months.
The satellite burned while re-entering into the Earth’s atmosphere a month later. However, the problem started when Us launched its second satellite, VANGUARD-1, in 1958, which stopped radio transmission six years later. It is expected to remain in orbit for another 200 years. Also, during the 1960- 1980 space race between the US and Soviet Union, none of them paid any attention to this problem.
Sources of Space Debris:
There are many sources of space debris that seen around the Earth, some of which are:
Dead satellite:
As of now, 3000 dead satellites are orbiting the Earth-like KOSMOS 1300, INSAT-1A, etc., a collision between US communication satellite IRIDIUM 33 and RUSSIAN spy satellite KOSMOS 2251, which produces more than 3000 tiny fragments.
Lost Items during spacewalk:
There had many incidents where during a spacewalk, astronauts lost some equipment, like Ed White lost a glove on the first American spacewalk, Michael Collins lost a camera, Sunita Williams lost a camera, etc.
Boosters:
Most of the debris was due to the rocket’s upper stage, which ended up in orbit and broke up due to the decomposition of Unvented unburned fuel.
Anti-satellite missile (ASTS):
After World War 2, as the space race started, countries started looking to strengthen their defense by sending spy satellites into orbit and trying to destroy other countries’ satellites in case of war. The use of ASTSs generates space debris which may collide with other satellites and produce more space debris.
Problems of Space Debris:
Kessler Syndrome:
A term coined by NASA Scientist Donald J Kessler in 1978. It is a scenario in which the amount of space junk in low earth orbit (LEO) reaches a critical point where it will create more and more debris by colliding with other active satellites or debris. This concept was shown in the movie GRAVITY in 2013.
Spacecraft and Satellite:
Fragment debris revolving around Earth at high speed may cause catastrophic damage to satellites in Low Earth Orbit. Satellites are believed to be destroyed by micrometeorites and orbital debris (MMOD). In 1996 French microsatellite Cerise was hit by the upper stage booster of Ariane-1-H, which exploded in 1986. Many such incidents were observed.
International Space Station:
By 2019, over 1400 meteoroid and orbital debris had been recorded on the ISS. ISS uses the Whipple shielding to protect itself from such collision. Astronauts on ISS have to perform a maneuver to protect it from debris. There have been many instances when debris hit ISS; in June 2021, a piece of debris made a hole in one of its robotic arms. Since 1999, ISS has changed its path about 25 times to avoid a collision.
On Earth:
Though most of the debris that enters Earth’s orbit naturally gets destroyed because of frictional heat, sometimes large pieces crashes on Earth. Despite their size, there has been no significant damage to property.
Tracking of Space Debris:
More than 27000 pieces of space debris around the Earth are tracked by the Department of Defense’s global space surveillance network (SSN) sensors. Usually, debris size greater than 10 cm is tracked. DOD’s Space Surveillance Network can track objects as small as 5cm in Low Earth Orbit(LEO) and about 1 meter in geosynchronous orbit. The US Strategic command keeps known orbital objects to help ISS and satellites. Its 2009 edition listed around 19000 objects.
Also, returned space hardware is one of the most important sources of debris distribution and its orbital path. The LDEF satellite EURECA satellite, which mission STS-32 Columbia retrieved and STS-57 Endeavour used for debris study. LDEF satellite spent 5years and eight months in orbit to generate debris data. Solar arrays of Hubble Telescope returned by STS-61 Endeavour were used to study the impact of debris.
How to clean those Debris?
Deorbiting the space junk:
Here, deorbiting means to push space junk out of low earth orbit (LEO) either to Earth’s atmosphere so that it can be destroyed by frictional heat or moving up to a designated “graveyard orbit” where they can’t posses any threat.
Huffing and Puffing:
This method ( called Space Debris Elimination or Spade) would push satellites into lower orbit by using air bursts within the atmosphere.
Giant Lasers:
This method is called Laser Orbit Debris Removal (LODR). Shooting space debris by using a high-powered pulse laser based on the ground to slow them and get them to re-enter and burn in the atmosphere.
Capturing the derelict satellite:
RemoveDEBRIS:
It is a satellite research project aimed at performing active debris removal(ADR) technology tests in search of the best ways to clean space junk. It was launched on` 2 april,2018.
ClearSpace-1:- This is the successor of e.Deorbit, (ESA shut down e.Deorbit mission in 2018). It will target the Vega Secondary Payload Adapter from the 2013 Vega flight VV02. It will be launched in 2015.
Nets:
The idea is pretty simple: fire a net, trap a piece of space debris, and drag it to the Earth’s atmosphere. The RemoveDEBRIS satellite had demonstrated this method in 2018 in space, in which it captured a nearby target probe released by satellite a few seconds earlier.
All the methods mentioned above are only for large-sized debris, though most of them are in development, and it is nearly impossible to capture small size debris.
Frequently Asked Questions:
- Which technique is used by spacecraft to protect themselves from space debris?
Ans: – Whipple shield - Which is the oldest artificial object in orbit?
Ans: – Vanguard-1(American satellite launched in 1958). - Which organization keeps an eye on the orbit of space debris?
Ans: – US Space Surveillance network - What is the main source of space debris?
Ans: – Explosion of the upper stage of the launch vehicle. - How much debris is currently in orbit?
Ans: – 36500 objects of size >10cm,
1 million objects in between 1cm to 10 cm,
135 million objects of size <1cm - Is space debris uniformly distributed?
Ans: – No, concentration is high between 500-1000 km. - How long can orbital debris remain in Earth orbit?
Ans: – Higher the altitude, the longer the debris will remain in orbit. - What is the average speed of orbital debris?
Ans: – 8-10 Km/sec. - When was the RemoveDEBRIS satellite launched?
Ans: – 2018 - What is Kessler syndrome?
Ans: – It is a chain reaction like the concept, in which debris will collide with other debris or active satellites and keep on producing more debris.
Conclusion:
When we look up at the night sky, we can’t see collisions, explosions, and fragments of debris; if we are lucky and conditions are right, we might see one white dot drifting across the sky, a tiny testimony of humankind’s high ambitions. But that dot is at risk, along with all it represents. If we don’t address this invisible problem, one of humankind’s greatest inventions will be at risk because Kessler syndrome isn’t waiting.
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