Why do we care about space debris?
The figure on the top of this page shows the debris (red) and intact satellites (white) currently in orbit around the Earth. This data set isn't complete as positions of many objects aren't made publicly available - data for only approx. 65% of all man-made objects in Space can be freely accessed on-line. Moreover we cannot track objects that are smaller than approximately 10 cm in diameter, which makes the presented dataset even more incomplete.
Still, the number of debris in the figure is comparable to the number of intact satellites. There have been collisions in orbit and we do expect many of those to happen in the future. Collisions between 10 cm objects may not seem to be a problem at all. But a collision between two 0.5 kg objects travelling at velocities of 7 km/s, which is a very usual velocity in orbits with altitude below approx. 1000 km, generates a similar amount of energy as a collision between two medium-sized cars travelling at approx. 100 km/h. And most spacecraft have masses as large as several tons, therefore the collision energies and numbers of new debris originating from those could be huge.
Any collision between an average satellite and even a very small object (in fact smaller than what we can currently track) could generate enough energy to obliterate the entire spacecraft creating many new debris. And more debris means higher likelihood of further collisions. This could lead to a chain reaction, which is more commonly known as the Kessler syndrome.
Ultimately, this "cascade" behaviour might render Space unusable. Given how reliant on Space our civilisation has become in less than 60 years of space-flight, this is clearly not desirable. We use satellites for weather forecasting, navigation, disaster monitoring and communications. If this isn't enough, have a look at how significant the Space Industry has become - quite obviously it's an important branch of today's World economy.
So the questions we should answer now are:
Still, the number of debris in the figure is comparable to the number of intact satellites. There have been collisions in orbit and we do expect many of those to happen in the future. Collisions between 10 cm objects may not seem to be a problem at all. But a collision between two 0.5 kg objects travelling at velocities of 7 km/s, which is a very usual velocity in orbits with altitude below approx. 1000 km, generates a similar amount of energy as a collision between two medium-sized cars travelling at approx. 100 km/h. And most spacecraft have masses as large as several tons, therefore the collision energies and numbers of new debris originating from those could be huge.
Any collision between an average satellite and even a very small object (in fact smaller than what we can currently track) could generate enough energy to obliterate the entire spacecraft creating many new debris. And more debris means higher likelihood of further collisions. This could lead to a chain reaction, which is more commonly known as the Kessler syndrome.
Ultimately, this "cascade" behaviour might render Space unusable. Given how reliant on Space our civilisation has become in less than 60 years of space-flight, this is clearly not desirable. We use satellites for weather forecasting, navigation, disaster monitoring and communications. If this isn't enough, have a look at how significant the Space Industry has become - quite obviously it's an important branch of today's World economy.
So the questions we should answer now are:
- Is this avalanche of collisions going to happen?
- What can we do to make sure it doesn't, so that we can retain access to Space?
What can we do to maintain access to Space?
In fact it is arguable whether we actually need to do anything - our prognoses for the future are not reliable enough yet to make a definitive statement about this. But certainly not producing new debris, i.e. debris mitigation, is a good practice - not unlike cleaning up after oneself.
But what about all the uncontrolled objects already in orbit that will stay there for millennia? Most likely the only way to prevent collisions involving those, be it to tame the growth of the debris population or to protect active spacecraft, is to perform Active Debris Removal (ADR). ADR is a broad term that describes launching spacecraft that will get rid of some of the debris by putting them on a trajectory that will result in the debris eventually burning up in the atmosphere.
This is a very complicated operation, to say the least. It also poses the risk that we will, in fact, make the debris environment even worse that it is, e.g. when some of the ADR missions fail. But perhaps there are alternatives. What I did in my PhD thesis was to quantify if we could predict the likely collisions and prevent those, thous preventing the "collision cascade".
But what about all the uncontrolled objects already in orbit that will stay there for millennia? Most likely the only way to prevent collisions involving those, be it to tame the growth of the debris population or to protect active spacecraft, is to perform Active Debris Removal (ADR). ADR is a broad term that describes launching spacecraft that will get rid of some of the debris by putting them on a trajectory that will result in the debris eventually burning up in the atmosphere.
This is a very complicated operation, to say the least. It also poses the risk that we will, in fact, make the debris environment even worse that it is, e.g. when some of the ADR missions fail. But perhaps there are alternatives. What I did in my PhD thesis was to quantify if we could predict the likely collisions and prevent those, thous preventing the "collision cascade".
Additional motivation
I care about sustainability. Period. And so the field of space debris was an obvious area for me to conduct research in. Besides, I used and improved my programming, astrodynamics, and data analysis skills while working towards making humankind more sustainable. Win-win.
You can find a more motivation for space debris and other areas of research aimed at making space-flight sustainable at the ESA's Clean Space Initiative website. The sole fact that the Initiative was formed just now is more than a sufficient reason for me to work in the area of space debris remediation as it clearly is at the very forefront of current space research.
There's also plenty of articles about space debris on-line, I particularly recommend this one as it gives good overview of the problem and points towards some rather interesting reference.
You can find a more motivation for space debris and other areas of research aimed at making space-flight sustainable at the ESA's Clean Space Initiative website. The sole fact that the Initiative was formed just now is more than a sufficient reason for me to work in the area of space debris remediation as it clearly is at the very forefront of current space research.
There's also plenty of articles about space debris on-line, I particularly recommend this one as it gives good overview of the problem and points towards some rather interesting reference.
Disclaimer: all the content of this website represents the opinions of a single individual. It does not, in any way, reflect the attitude or official policy of any associated institution or person.
