The fascination of exploring space and universe is one of the magnificent achievements of mankind that has helped us in reaching new goals in our science and technology. Exploration of space has always been a unique and mystical experience for mankind and the results we got are extraordinary too. We have come quite ahead in terms of our technology development over the last few decades and that’s why this period is known and will be known as the period of technology in our evolution for the coming generations.
But as Newton said every action has an equal and opposite reaction, is also very much applicable to us in this aspect too. When we talk about the work we have done in the department of space technology, from exploring the Moon to Mars, from sending objects to sending humans in space, our journey has been nothing less of a miracle and the achievements have been very remarkable and astonishing. But with these achievements we are also creating a snag in the form of space debris or space junk.
Space junk or debris is formed by both natural and artificial orbital debris. Meteoroids are an example of natural space debris, whereas artificial debris, also known as orbital debris, is the debris created by the dead satellites from all the rockets we have launched over the years. It also includes non functional spacecraft, abandoned launch vehicle stages, mission related debris and fragmentation debris. As of December 2020, it has been estimated that there are approximately 34,000 pieces of orbital debris, larger than a softball, present in the orbit of the Earth. They are travelling at a speed of 29,000km/hr or 8km/sec, fast enough to damage a functional satellite or a spacecraft. There are approximately 9,00,000 pieces of debris that measure 1cm -10cm; or approximately 128 million pieces of debris that measure approximately 1cm – 1mm and even smaller micrometer sized debris is also present.
Though any debris can damage a spacecraft because of the velocity they possess. But the most potent destroyers are the mm sized debris and they are ones who form the highest mission ending risk to most of the spacecraft operating in Earth orbit. In 1996, a French satellite was hit and damaged by the debris from a French rocket that had exploded a decade earlier. In 2007, China’s anti-satellite test, added 3500 pieces of large debris and many smaller debris into space. In 2009, a dysfunctional Russian spacecraft collided with and destroyed a functioning U.S Iridium commercial spacecraft. This collision added approximately 2300 pieces of large , traceable debris and many more smaller sized debris.
Tracking Debris :
Radar and optical detectors (e.g. lidar) are the main tools for tracking the space debris. In 1979, NASA founded the Orbital Debris Program in the Space Sciences Branch at the Johnson Space Centre in Houston, Texas to research ways of creating less orbital debris and design equipment to track and remove the existing space debris. The LDEF (Long Duration Exposure Facility) satellite deployed by the mission STS-41-C challenger and retrieved by STS-32 Columbia spent 68 months in the earth’s orbit to gather debris data. Similarly, STS-46 Atlantis in 1992 and retrieved by STS-57 Endeavour in 1993 was also used. NASA and DoD (Department of Defence) co-operate shares the responsibility for tracking and characterizing the satellite environment. DoD’s space surveillance network tracks objects as small as 2 inches to about 1meter(1 yard). Whereas NASA determines the population of the debris measuring under 4inches/10cms.
Dangerous effects of Space debris:
According to NASA, debris in orbits 60 kms or less from Earth will return to the planet within several years. But debris above 1000kms is expected to continue orbiting for a century or more. As we know that every manned mission, satellite and space probe can add to the load of already existing space debris and this further leads to intensification of the debris thus creating a viscous loop or cascading effect. This cascading effect is known as The Kessler Syndrome or Collisional Cascading. The low orbit of the Earth (LEO) is most affected as this orbit houses the maximum space vehicles. In addition to being a threat to space, it also increases the cost of the satellite mission. In a study conducted the cost of a mission was increased by 5-10% just in dealing with protection from debris and creation of debris. Some steps are recommended as mitigation guidelines by the UN Committee On The Peaceful Uses Of Outer Space includes:
- § limit debris release during normal operations.
- § Minimise the potential for break ups duri operational phases.
- § Minimise the potential for post break ups resulting from stored energy , like explosion of fuel tanks or batteries.
- § Limit the time period of a space vehicle or craft in the low orbit of earth.
At present all space agencies are seriously working and looking for solutions which can help them not only in reducing space debris but also reusing it. We all dream about reaching the stars and moon , as they fascinate us and there are no two ways about it that we have reached them literally, but we have to remember we are co-existing with other species and galaxies. So any turmoil can cause irreversible damage to us too. Success creating potholes for the future are more dangerous. Pollution in any form and of any space is detrimental.