24 humans have reached moon. Our spacecrafts have crossed the solar system. But within all such milestones, we have left our garbage out there in open space. Just like unclean roads become nastier over passage of time similarly space is getting nastier with these junks and also becoming dangerous.
Space debris (also called space junk, space pollution, space waste, space trash, or space garbage) are man-made objects floating in space which are of no use. When something doesn’t work at home or something which is of no use now is usually discarded in the garbage bin. But there is no such garbage bin in space so the unfunctional or dysfunctional things are left out as they are.
These include bigger objects like dead spacecraft, lost equipment, boosters, weapons and can even constitute of paint flecks, bolts etc. Now it is easy to think of about how the bigger objects might have been left out, but how such small objects come into this category, can be observed in the case of an American Astronaut Ed White who lost a glove while performing space walk in Gemini 4 flight in 1965.
In 2009, two satellites collided at speed of around 22,300 mph. This was caused by the inactive Russian satellite Cosmos 2251 which destroyed the active U.S.-based communication satellite Iridium 33. This is just one of the many accidents that took place because of space debris. If we want to know the seriousness of the problem then here is another incident. Astronaut Tim Peake showed a picture of a 7mm chip which might have been caused by a paint flake or small metal fragment no bigger than a few thousandths of a millimeter across. Anything above 1 cm could penetrate the shields of the Station’s crew modules, and anything larger than 10 cm could shatter a satellite or spacecraft into pieces. An object of 1 cm or lesser can hamper the instrumentation of satellites.
Keeping future space expeditions in eyes, we need to eradicate this major issue else the day will be no farther when we will see astronauts being hit by debris.
So what is the solution then? Let’s first focus on large debris that is satellites which bear the real threat. There are three techniques of reducing junks. They are-
1. Preventing the debris from accumulation
2. Capturing the debris
3. Removing the debris
·Destroying the debris
·Deviating the path of the debris
Prevention involves three ways. First one is the entry to the atmosphere once the satellite is dead. Earth’s atmosphere produces enough friction to burn anything falling through it and if the object is small enough then only ash reaches the ground which is quite harmless. Making satellites orbit in low lying orbits makes this step easier. Second is deviation of the satellite from its orbit to a storage orbit. Storage orbits are graveyard / junk / disposal orbit which is an orbit that lies away from common operational orbits. The third way is bringing the satellite or any such space vehicle directly to the earth for further use.
Capturing method involves a lot of techniques. Capturing can be contactless (like using electric charges, gravity) which means that the machine which will remove debris will not have direct contact with the debris. Rather it will attract the debris towards a certain part of itself or in any other direction by using its gravity, or magnetic property or by producing difference in charges etc. Capturing can also involve having direct contact with the debris which includes many ways like using robotic arm, net, rope, harpoon, sticky materials etc.
Removal of debris involves two possible solutions. Destroying the debris by exploding contain a risk of a debris getting converted to smaller pieces. Again these small pieces have the potential to damage other satellites because of their high speed in space. In general a paint flake or small metal piece can travel at a speed more than 8 times that of a bullet and can cause cracks in satellites. This may lead to loss of millions of rupees. But at least smaller debris is better than a larger one. Also during explosion, some part of the debris might come into the earth’s atmosphere there by reducing the density of debris accumulation.
Deviating seems the safest compared to other option. In this method debris is deviated from its path so that they head towards earth and get burnt up in the atmosphere or fall in the ocean. In such systems the high energy lasers, ion beams or any such similar techniques are used to decrease the speed of satellite so that it can reenter the earth or directly push the satellite towards earth in order to remove it from space.
There are still numerous projects and innovations being done in this path. Even you could be the next one to solve this. So keep up learning and keep up trying.
Barnali Das, IISER, Kolkata
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