Space debris or junk is the collection of defunct and unusable man-made objects in space. These includes old satellites, spent rocket stages and fragments, some of them formed as result of a collision with other space debris, while others as a result of slow erosion and disintegration of other space-based objects. These space debris objects travel and spin at a very high velocity of up to 28,000 km/hr. A collision of any space-based object with space debris traveling at such speeds can be fatal.
Even tiny paint flecks can damage a spacecraft when traveling at these velocities. In fact a number of space shuttle windows have been replaced because of damage caused by material that was analyzed and shown to be paint flecks. : NASA
According to ESA, as of January 2017, there were 5250 rocket launches with 7500 satellites launched into orbit. Of these 4300 satellites are still in space while only 1200 of them are functioning, the rest are just space junk. US Space Surveillance Network tracks and manages a catalog of about 23,000 objects. Most of the debris object can’t be tracked due to their small size. But being small does not mean that they are less dangerous. According to NASA, “Even tiny paint flecks can damage a spacecraft when traveling at these velocities. In fact a number of space shuttle windows have been replaced because of damage caused by material that was analyzed and shown to be paint flecks”. Below is a table of relation between Number of Space Debris Objects and their Size.
|Greater than 10cm||1cm to 10cm||1mm to 1cm|
|Number of Space Debris Objects||29,000||750,000||166 million|
As space debris increases, potential collision risks also increases, which will require more planning and use of expensive shielding equipment, resulting in increase in costs.
Companies like SpaceX are working on reducing the cost of space missions, making it cheaper to send objects in orbits around the earth. This is good in a way because, it will enable organizations and countries with small budgets to send payloads into orbit but, at the same time it increases the probability that payloads which don’t need to be up in the space ending up there due to reduced costs. These will further contribute to increase in space debris. As space debris increases, potential collision risks also increases, which will require more planning and use of expensive shielding equipment, resulting in an increase in costs. This is an irony as the companies trying to reduce costs will be the cause of increase in costs in future, if proper planning is not done.
On 22 May 2013, two satellites of Argentina and Ecuador collided with other space debris present in orbit due to which the Ecuadorian satellite suffered physical damage and loss of altitude. The satellite remained in orbit, but due to the damage, its antenna could not point correctly towards the earth station. This is not a lone case, and there have been several space-based collisions in the past also. These collisions create more debris which can be a source of more collisions in the future. There is a comprehensive list of space-based collisions here.
According to NASA and ESA, there are many procedures for avoiding space-based collisions but, there is not a single concrete work in progress on how to reduce the existing debris that is already there. The next article in this series will discuss methods employed by organizations to avoid collisions and potential methods for removing the already existing space debris.
If you are interested in Space travel then, check out our article on how SpaceX is planning to send people around Moon Orbit. Below is a short film by ESA (European Space Agency) about Space debris.