space

SpaceTalk : Orbital Debris !

We have a garbage problem! Every year we dump more than 2 billion tons of waste. Our precious forests are up in flames and our oceans are burdened with inappropriately high quantities of plastic. But let’s talk about that some other time. Today, I want to talk about space junk ! Yes … sadly, the human epidemic is spreading.

Space debris is defined as all non-functional, human-made objects, including fragments and elements thereof, in Earth orbit or re-entering into Earth’s atmosphere.

The first artificial satellite, Sputnik-1, was launched by the Soviet Union on 4th October 1957. In the last 62 years, mankind has sent around 9000 satellites to space. Currently there are about 5000 satellites orbiting Earth and a handful orbiting other celestial bodies. Only about 40 percent of these (less than 2000) are presently operational i.e. they are being used for various applications like remote sensing, communication, navigation etc.

According to ESA , as of January 2019, more than 128 million bits of debris smaller than 1 cm, about 900,000 pieces of debris 1–10 cm, and around 34,000 of pieces larger than 10 cm were estimated to be in orbit around the Earth. Concerned agencies around the world maintain detailed catalogs and regularly monitor these objects as they pose a threat of collision and irreversible damage to operational satellites.

Space debris is created due to seemingly harmless reasons like the upper stage of a rocket, or end-of-life of a satellite, or out-of-the-blue accidental collisions, or finally, and also recklessly, due to intentional anti-satellite technology demonstrations. Then there’s also stuff which astronauts mistakenly ‘drop’ while spacewalking at the International Space Station including items like a glove, a camera, a tool bag etc. There’s a variety of space junk discarded up there, from tiny toothbrushes to deserted space stations. Some of the debris disintegrates, as it re-enters into Earth’s atmosphere. But the orbital decay is a slow process and natural atmospheric re-entry may take up to decades or sometimes even centuries.

Collision with a golf ball sized debris, or maybe an even smaller object, in low earth orbit, could be catastrophic for a satellite. You may recall from high school level physics, that momentum is mass times velocity. Even though these objects may seem harmless, given their small size, its the massive speeds with which they’re whizzing about in orbit (about 7 kilometers per second), that make them nothing less than ticking time bombs. A head on collision could occur at speeds of up to 16 kilometers per second and can damage solar panels, equipment, payloads, or maybe even lead to an entire satellite breaking into bits and pieces and further aggravating the space debris problem.

The already complex problem of sending satellites to space and maintaining them in orbit (After all, it is rocket science 😉 !!) to serve useful applications, is further complicated due to space debris. Earlier space agencies resorted to relatively simple tactics like delaying launches, or carrying out special orbit maneuvers for changing the course of their satellites (which, nowadays are becoming more common than ever before) in order to mitigate the risk of collision with orbital debris. But with the amount of debris steadily increasing year-by-year, they’ve had to come up with more innovative solutions. The present focus is not only towards generating less debris in the future, but also towards active debris removal techniques like docked de-orbiters, tethers, nets, harpoons and so on to literally ‘catch’ orbital debris and deliberately make them disintegrate on atmospheric re-entry or bring them to a graveyard orbit (found the topic for my next post !!).

Satellites have provided us with the best vantage point to observe our home planet. They have helped us in gathering monumental information about the Earth and have enabled us to understand it in a much better way. But that gives us no right to mindlessly pollute space. Just as we are obliged to leave a habitable Earth for our future generations (I believe we are terribly failing at this 🙁 !!), we must also leave them a clean and useful outer space to ensure their journey towards newer horizons.

The skies up there are super crowded !
Illustration Courtesy: ESA

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