The Junk “above” us!
Yes, most of you are correct. This blog is basically about trash. Yes, someone (that is me) has spared their time and efforts in writing about junk. But don’t worry, you can be rest assured that, what you are about to read is not junk, even if it’s ABOUT junk. Not just any junk, mind you, important junk! Junk that stays ‘above’ us! (yes, pun totally intended). This junk is so hard to clean; it is possibly an issue equivalent to global warming! In the age where we are aspiring to expand our reach and become an interplanetary species; what if I tell you that, this junk, if not dealt with quickly, can eventually stop us from launching even small missions to orbit our own planet! How? Well, read on to find out more...
Humans have always worked towards improving their lifestyle. Various choices made by our ancestors are a clear reflection of how our species has always strived to make life more comfortable. Almost all the major paradigm shifts that have occurred throughout our evolution have been at least fuelled by a desire to make living easier, if not ignited. Right from ancient paradigm shifts like moving from being hunter-gatherers to farmers, the invention of the wheel, the discovery of ways to control fire and moving from stone-age to bronze-age; to even fairly recent ones like the industrial revolution, all happened as a direct result of the innate human yearning for a comfortable life.
However, the age we live in can be considered to be somewhat unique, somewhat special. This is because, for the first time in recorded human history, we have become capable of altering and disrupting the whole planet's ecosystems in a bid to secure our comfort. And this, I’m afraid, is not a very conducive state of affairs for the progress of civilization; in fact, it is almost akin to plotting our own downfall by our own hands!
Global warming and ozone layer depletion are 2 of the most popular examples of the negative impact caused by our technological advancements. From the rise in average global temperatures and sea levels all around the world, to the enormous amounts of glacial ice melting, everything is a direct cause of global warming. The worrying part is that we needed almost 2 centuries just to acknowledge them as a serious global issue, and several years after that to actually take corrective measures!
This clearly indicates how big of a problem, just a "lack of incentive" can be.
For the growth and survival of many large industries like electricity generation, transport etc., causing air pollution and global warming has become a necessity. Since these sectors are global powers, both financially and politically, there is little incentive to stop the current unsustainable and harmful practices followed by them.
Fortunately, the world is slowly but surely regaining its conscience, and starting to take significant measures in mitigating the ill - effects of these events. The refilling of the ozone layer hole formed above Antarctica can be viewed as a substantial achievement on this recovery path.
But as we slowly stumble out our way through these threats, another grave danger looms over mankind; Space - junk.
Space-junk, or space debris, comprises of any piece of machinery in orbit around the Earth, which no longer serves a useful purpose. It comes in numerous sizes and masses. It can include all kinds of objects, from smaller ones like lost astronaut gloves, cameras, thermal blankets; to even larger ones like dead satellites and the discarded upper stages of rocket boosters! According to Erik Gregerson of the Encyclopaedia Britannica, "This material can be as large as a discarded rocket stage or as small as a microscopic chip of paint."
Okay, so we now do have a basic idea of what space-junk comprises of, and where it exists. If we ponder a little over its location, then most of us will suddenly realise and panic over a certain question! Well, so here goes...
1) How does the ISS (International Space Station) keep clear of the space debris and function properly?
The simplistic answer to this question is, IT DOESN’T. It has been hit by fast moving debris on numerous occasions in the past, but fortunately no significant damage was caused. The ISS division of NASA keeps track of around 23000 catalogued space debris objects (the exact number is unclear, as it keeps fluctuating) for potential collisions with the ISS. It is equipped with “whipple shielding” to protect itself against the small debris. The ISS also performs “debris avoidance manoeuvres” for all objects with probability of collision greater than 1/10,000. According to NASA officials, “The International Space Station has conducted 29 debris avoidance manoeuvres since 1999, including three in 2020."
Okay, so that’s settled (phew!). Now, let’s get to business and talk numbers...
2) How to quantify the seriousness of the hazard?
A very large percentage of this debris is microscopic, or a few millimeters in diameter. But the hazard of space debris is usually quantified by its total Kinetic Energy, i.e. it is dependent on BOTH, the mass in orbit as well as its velocity. So even if the mass of an average space junk particle is not very high, its velocity is. According to the Orbital Debris division of NASA, the average IMPACT velocity of a Space junk object is close to 10 km/s, while the orbital velocity is around 7-8 km/s. We can easily compute the total kinetic energy of artificial objects in earth's orbit as follows - (These are very rudimentary calculations and meant to give just a rough idea to the reader)
- Total mass of space debris- 9400 tonnes (ESA)
- Average Orbital velocity of an object - 7.5 km/s
- On applying Kinetic Energy = 0.5*m*v² to this data, we get,
- The total Kinetic Energy in orbit = 264,375,000,000,000J or roughly 2.6 x 10¹⁴ Joules!
This is equivalent to almost 63000 tonnes of TNT or almost a 1 megaton hydrogen bomb!
A few other factors influencing this figure can be:-
- Percentage of colliding mass in unit time with reference to total mass in orbit (I mean not ALL the objects will collide with each other)
- The avg. cross sectional area exposed, of an object in orbit
- The rate of naturally burning up extremely small debris in the Earth’s atmosphere due to loss in velocity and subsequent de-orbiting, thus, causing a small but consistent decrease in the mass in orbit.
- The rate at which new launches are made into the Earth’s orbit, which provides a somewhat counter-rate of increasing the mass in orbit.
- The variation in the average orbital velocities and masses of space debris objects in different Earth orbits (Low Earth, Geosynchronous, Medium Earth, Polar etc.)
I have ignored these and more such factors in my calculations for simplicity purposes.
Okay, so now we have answers to 2 of the major questions that arise. We have talked numbers, calculated and quantified the threat (at a very basic level). This means we have achieved a major milestone for any scientific research i.e. quantifying and boiling down abstract ideas and questions to actual numbers that we can work with. Kudos to you on making it this far! You can give yourself a pat on the back!
“But the work is NOT done! It will always NOT be!” A lot of other aspects of this problem have to be looked at. We have to see how this threat varies across different orbits of the Earth, situated at varying heights from the surface. We also have to explore a little more on how much space debris is costing us for every mission currently, and whether it is likely to increase or decrease in the near future. Finally, the most important part; SOLUTIONS! No constructive probe into any problem can be complete without suggesting solutions to the problem. So, take a short rest, and come back for part 2 to know the solutions!