"A satellite is a benevolent angel when alive and a precarious devil when dead."
– Anon



Space debris around earth

The Biggest Engineering Challenge of the 21st Century

   Where there is traffic, there is pollution and there are accidents, be it on earth or in space surrounding the earth. They are increasing in direct proportion with the human curiosity to explore and conquer space which, in turn, is reflected by the ever-growing space missions over the last few years. It is easy to clear the trash following accidents if they take place here on the earth's surface, but what about those which eventualize in space orbits? Space debris belongs to nobody, so who is going to take up the responsibility to delimitate them and hinder its future growth in the wake of the ever-increasing competition? As for the debris which has already accumulated in tons, who is going to eliminate them? Scientists have not yet found answers to these questions till date. Since the threats posed by space junk to spacecraft and the environment has reached a critical point, it has become the biggest engineering challenge of the 21st century to develop a technology capable of removing it.

Causes of Space Debris


• Old dysfunctional satellites
• Old dysfunctional space stations
• Parts of the spent and failed rockets and drifted satellites
• Fragments caused by smash-ups between various space objects
• Explosions of propulsion bodies
• Frozen coolant balls, space-suites, cameras and other electronic junk

Proposed Solutions and Challenges


• Built-in Propulsion Systems for Satellites: This is a great solution that tries to conceive a propulsion system that could be activated once the satellite is dead. But this solution carries a potential of explosion due to the pressurized fuel in the propulsion system.

• Enforcing a 25-year Timeline Rule: International Governments have set a threshold of max 25 years for LEO (Lower Earth Orbit) satellites so that it could be deorbited within the specified timeline and thus prevent adding to the thickness of the orbital debris. But this does not solve the problem of dead satellites which are already present in the thermosphere. At the moment, there are around 1100 functional satellites while more than 2200 are dead which are revolving in the thermosphere along with operational satellites as an aftermath of 5000 launches made after the start of the space age.

• Auto Cleanup During Solar Maximum: Every 11 years, thermosphere heats and expands to the maximum, thus dragging the space debris from adjacent belt into the atmosphere. This auto cleanup process in space is being increasingly threatened as thermosphere refuses to heat up due to the continuously rising levels of CO2 in the atmosphere following the greenhouse effect.

• Taking Satellites Down by Firing Missiles: This technique has been tried by the U.S., China and Russia. Although it gave prompt results, it added to the mass of already present space junk and moreover, the falling parts of satellites emitted toxic fumes. It also gave an implicit indication to the superpowers to flex their muscles against each other, thus implying a boost to carry out more dangerous maneuvers out in the space.

• There are some solutions in experimental stages like:

a. Focusing sunrays to vaporize small junk
b. Firing laser rays into space to destroy the garbage
c. Using photon pressure to avoid possible predicted collisions
d. Trying to implement massive fishing nets to catch debris (!)



FATE OF LOW EARTH ORBIT (LEO) SATELLITES



     wear and tear of a satellite
     satellite grows old
  ↓
     satellite runs out of propellant
  ↓
     Impact of atmospheric drag and solar flares
   ↓
     satellite slows down
   ↓
     satellite lowers down progressively
   ↓
     satellite enters mesosphere and
     is burned down by atmospheric friction




FATE OF A GEOSTATIONARY SATELLITE



    Geostationary satellites operate at a level above 42,000 km above the equator and they have almost zero possibility to enter the atmosphere. After they become non-operational, they are propelled further away into the orbit, named Graveyard Orbit, a few hundred kilometres above the GEO belt.

The Incomprehensible Scale of Orbital Waste


   Space is big but the human desire to explore space is even bigger. NASA scientist Don Kessler states that more junk causes more collisions and more collisions create more junk thus creating a self-sustaining collision chain reaction. The implications of such an activity are considerably threatening as far as orbiting satellites are concerned. Owing to their enormous speed (28160 km/hr), each of the junk objects carries a potential to damage a satellite. The impact of a one-cm-sized object on the spacecraft is equivalent to the energy released by an exploding hand grenade. 

    The following numbers speak for themselves about the potential of possible space accidents:


   i. The tennis ball sized or bigger junk objects in space count more      than 30 thousand. These can be tracked by Air Force Space Junk Surveillance.
   ii. The number of objects with a size between that of a grape and a tennis ball amounts to more than 500 thousand. These can be tracked by the Space Fence Radar System.
   iii. The objects, the size of which fall between a grape and a pomegranate grain, outnumber 1 lakh thousand. These can be detected by ground-based radars.
   iv. The objects smaller than 1 mm are countless. Their existence can be assessed by examining the surface of returning spacecraft which has borne their impact.

   The total mass of this debris is 6300 tons and most orbital debris is within 2000 km of the earth's surface.



"We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special."
– Stephen Hawking

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