Abstract
Space junk is a real problem today, what with million useless pieces of junk orbiting our planet. We do not see that junk does not mean it is not there or cannot be a problem. The technology we use today is innately tied to space as our modern life relies on functioning satellites. The paper looks into the presence of space junk and the issues related.
Introduction
Space junk is the collection of all the debris orbiting the earth. This orbital debris has been classified into two forms – natural and man-made. The natural debris consists mainly of fragments of meteoroids and other celestial dust orbiting a few hundreds of kilometers above the earth's atmosphere. The man-made space junk consists of defunct satellites, spent rockets, abandoned aircrafts, and debris fragmented away from satellites due to collision with other space junk. Since the dawn of space age, aeronautical organizations from all around the world have conducted innumerable space operations. Many of these space operations were meant to end, or prematurely terminated, in the space. Hence, the footprint of the dysfunctional satellites orbiting the earth has only increased ever since. The cost of fuel required to move dysfunctional satellites out of the orbit of the earth is very large in comparison to moving the satellite to the orbit radius which is at a safe distance from earth. As of now, there are around 500,000 debris pieces being tracked. These pieces move at very large speeds of 17,500 mph. Today, out of all the man-made objects tracked in the orbital space, 95% objects are space debris (Space Debris and Human Spacecraft, 2013). Before deploying a spacecraft around the earth, several calculations are made in order to determine the trajectory of the spacecraft that is deemed safe for its mission lifetime. Several adjustments are also made to the trajectory of spacecraft’s in real time so that they can avoid any unnecessary collision.
Why is Space Junk a Concern?
The very existence of space debris circling around the earth, at enormous speeds, poses a threat to the functional satellites orbiting the earth, and the spacecrafts entering or exiting the earth's orbit. The use of these satellites is not limited to the space organizations, but the majority of these satellites also provide commercial use such as GPS navigation, cellular communication, radio communication and Internet facilities. Collision of the space debris with these satellites can result in enormous losses, both functionally and economically. Kessler Syndrome dictates that the collision between space debris and satellites increase the amount of space debris by an exponential amount. In 2007, China destructed their dysfunctional weather satellite, dispersing nearly 3000 pieces of debris in the space (Hubaux et al, 2012). However, the greatest threat is posed by the millions of small debris pieces which cannot be tracked.
Classification of Space Junk
Space debris is basically classified into three categories based on their size diameter. The first group includes debris of size 10 cm and above. This debris is easy to track and collision with such debris can be catastrophic. However, scientists are able to perform collision avoidance maneuvers on space crafts and stations to avoid any contact with such large debris. The next category contains debris of size 1-10 cm. It is challenging to keep a track of such debris due to their size. Unfortunately, collision with such space junk can cause significant damage to aircrafts and even hamper space missions. Major collision threats are posed by debris falling under this category. The last category of debris falls under the size smaller than 1 cm. It is nearly impossible to track the movement of such small-sized debris. However, collision with such debris does not cause significant damage, and spacecrafts can withstand damage due to them. Prolonged duration of collisions with these small sized debris may degrade the structure of the spacecraft over time though.
Known Collision Incidents
As of now, the amount of man-made debris moving in the low earth orbit, i.e. sub-2000 km radius, has significantly exceeded the natural debris in the same region. This has left the functional satellites in a state of great risk of collision with the space debris. The Iridium Satellite aircraft was a casualty in one such incident where it collided with a spent Russian satellite and got destroyed in 2009 (Iannotta & Malik, 2009). Surprisingly, this has been the first incident where two aircrafts collided inside the earth's orbit. However, the small debris have known to collide with the space crafts on numeral occasions, sometimes causing damages which require manual repair operations.
Efforts to Reduce Space Debris and avoid Collisions
In 2008 only, the trajectory of 5 functional space crafts was modified in order to prevent collisions with space junk. Such maneuvers are themselves costly on a large scale. The Inter-Agency Space Debris Coordination Committee has tried to lay down some code and guidelines related to space debris for nations proactive in space operations (The Threat of Orbital Debris and Protecting NASA Space, 2009). Many of the guidelines aim at preventing actions such as the misfortunate Chinese satellite destruction of 2007, and intentional destruction of enemy satellites which in turn leads to the Kessler Syndrome. The Department of Defense's surveillance system tracks objects as small as 2 inches in size in the low Earth orbit, and objects as small as 1 meter in the further geosynchronous orbit. NASA tracks a safe zone around its stations, and orders necessary debris avoidance maneuvers to keep debris out of this safe zone. At times when avoiding debris is impossible due to inaccurate tracking of debris, any human on-board is instructed to move into the transport spacecrafts so that they can safely eject from the main station in case of severe collisions.
Conclusion
With so much money being spent in tracking the movement of space junk, it is clear that the issue of collision with them is not to be taken lightly. It takes time and financial investment to build spacecrafts, and even one significant collision with space debris can result in a monumental loss of a space mission. The space agencies around the world realize the importance of reducing the space debris around earth, and various international committees are working to ensure that every country follows safe guidelines under their debris disposal methods. The probability of collision will only increase with every passing time, hence a constant check on the trajectories of functional spacecrafts as well as space junk needs to be maintained, in order to avoid the Kessler Syndrome.
References
Iannotta, B., & Malik, T. (2009). .S. Satellite Destroyed in Space Collision. Retrieved from http://www.space.com/5542-satellite-destroyed-space-collision.html
Space Debris and Human Spacecraft. (2013, September 1). Retrieved from http://www.nasa.gov/mission_pages/station/news/orbital_debris.html#.VHp7jdKUdkU
The Threat of Orbital Debris and Protecting NASA Space Assets from Satellite Collisions. (2009). Ational Aeronautics and Space Administratio.
