Abstract
Apart from the looming climate change and global warming, the world is facing a disaster in her space infrastructure, if space debris continues to fill the orbit. Records from NASA shows that, over 19,000 of debris, which are more than 1 cm in size, have been tracked, but more is believed to exist that cannot be observed.
Areas of great concern to astronauts are the Lower earth orbit and the geostationary earth orbit. This calls for hastening of mitigation measures to stop their increase and remove the space debris (Remer 1).
Introduction
The modern world stands to face various challenges if manmade objects orbiting the earth are not safeguarded. It is in this spirit that space surveillance networks have been established to track space debris or junks that may cause collisions to space orbits.
The United States has been credited with space debris tracking as the world tries to elude repercussions that may be associated with the ever increasing space junks (Remer 1). The world has witnessed several cases of space collisions, for example, the collision between a privately owned U.S. satellite (iridium) and a dead Russian satellite, on the 12, February, 2009.
This collision led to destruction of both satellites and subsequent creation of more debris in the earth’s orbit. These additional junks are of great concern to astronauts as they can lead to further collisions with orbiting satellites. This research paper will explore space debris in detail, by defining it, why and where they are a problem, as well as how to track and mitigate their growth (Remer 1).
Space Debris
Space Debris, also known as Space junks are objects made by man that orbit the earth and are of no use in space. These particles usually orbit the earth and may cause concern when they meet a functioning satellite of spacecraft. The most recent estimation pieces of space debris as of 22nd March 2011, by NASA is 22000. This is quite frightening as these are the traceable space junks, and gives a clue on how much is untraceable.
Such facts show how much the world is at risk of witnessing more collisions, which would worsen the situation (David 1). Another recent occurrence was the destroyed Chinese satellite which nearly caused collision with ESA’s (European Space Agency) satellite. It is claimed by orbital debris experts that the two mentioned collisions alone increased space debris by about 50% (David 1).
Space debris refers to the various particles that get discarded in the earth’s orbits by manmade objects. They include bolts, nuts, collision discards, slag, rocket motors, paint flakes, dust and coolants from satellites, among other materials that litter the earth’s orbit. These materials orbit around the earth and pose great danger to satellites. These particles also have the propensity to erode parts of spacecrafts and satellite, leading to more fragments in pace.
Probability of collision with spacecraft tends to increase as more objects are discarded in the orbits since they overlap spacecraft trajectories. The earth’s orbit is divided into two, the high and low earth orbits. These orbits are all polluted by space debris and flight engineers are tasked with the responsibility of tracking them to avoid further collisions (Remer 1).
Why space debris is a problem
Space debris, as has been stated above consist of the fragments, and discards from objects such as satellites and spacecrafts in space. These particles can erode parts of the spacecrafts and satellites on collision and have the capability of causing damage to the body of the objects traversing space. Since these particles cannot be traced all as may be desired, let alone taking them out of the orbit.
They cause collision dangers to other satellites and spacecrafts in the orbit and have the potential of increasing debris in space, which would increase the likelihood of collision and hence affect the normal operation of space objects that are of great importance to the earth. Weather and satellite information received from space are important to science, communication, aviation and astronomy (Remer 1.
Areas of concern
Several countries are already exploring ways of removing space debris from the orbits; this is because of rise in concerns on their space infrastructure. One of the areas of great importance in space is the (GEO) geostationary orbit, which is uniquely place for satellites that can orbit at the same rate as that of the earth.
In essence the satellites tend to be stationary, relative to the earth’s rotation. This makes it unique for weather and communication satellites which are the basis of space science (Remer 1).
Another area of concern is the pollution of LEO (Low Earth Orbit). This is mainly because the universal orbits are few and it is these universal orbits that can keep spacecrafts on specific rings.
The layout of LEO satellites also make it difficult as they are place in numerous orbital planes. In addition, even though high altitudes tend to have fewer satellites, orbital decay is very slow (in millennia), and this makes it a prospective cause of concern in the future as the debris reaches their threshold (Whipple 517).
Tracking space debris
Given the high risk caused by space debris, several measures have been taken to ensure they are observable so as to help in avoiding collision. To achieve this, various technological researches have been carried out and special detectors developed for tracking purposes.
These equipments include optical and radar detectors such as lasers and transit telescopes, among others. However, the use of these devices is limited as they can on trace objects of limited sizes. Another problem facing tracking of space debris include stability of such tiny debris in the orbit, this makes determination of orbits for (re-acquisition) difficult.
Furthermore, these tracking devices cannot track debris of less than 1 cm in size, making their traceability more complicated. It is believed that the smaller debris is numerous and still remains unobserved. According to ESA Metroid, over 600,000 of objects bigger than 1 cm are in the orbit. Other ways used include measurement campaigns, done by radars (Whipple 517).
Another way used to track debris is through measurements done in space, in this method, researchers use returned debris hardware, which act as an information base regarding orbit environment. Examples of such satellites used are the EURECA satellite which was recovered by STS-57 Endeavor. Moreover, debris can be tracked using Gabbard diagrams.
When satellite breakups occur, the group fragments that break are usually studied using Gabbard diagrams. Gabbard diagrams are scatter plots which use the altitudes of debris against orbital period to ascertain the points of collision as well as the directions taken after collision. These, method have limitations, especially with smaller space debris which are unstable in the orbits and tiny (Whipple 517).
Mitigation
Various countries such as the United Kingdom, United States, Russia, France and the like’s have made several steps to counter the increasing danger caused by space debris increase. These steps include research studies on how to reduce manmade objects from the orbit, campaigns to raise awareness of the danger posed by these space junks, steps to mitigate growth of space debris, designing satellites that are capable of moving out of the orbits after use, also known as self-removal orbits.
The other method is external removal, which is currently underway in its five-year implementation plan. In external removal, several ideas are still emerging with in-depth research being conducted to come up with the best way of removing space debris from the orbit.
The current close call events tracked weekly is estimated at 13,000 and is expected to increase. According to Lewis, a researcher, the coming decade will present another 50% rise in space debris, with another estimation of four times increase by the year 2050 (Remer 1).
Mitigation of debris Growth
These research findings have made it a priority to unearth ways of mitigating space debris. In growth mitigation, a number of proposals have been studied, some of which were successful, and these include change in Delta boosters, which eliminated their debris contribution. In 2007, United Nations Committee (COPUOS) published guidelines that were voluntary to countries wishing to minimize increase in debris.
Several agencies such as ESA, NASA and ISO, among others have also implemented ways that would mitigate on debris creation. Robotic capture has also been proposed in this line, to mitigate growth (Remer 1).
Self removal
Requirements for GEO satellites to have the capability of removing themselves once they become useless have been proposed by ITU, to achieve this, adequate fuel would be required to power these satellites to their decaying orbits. Suggestions have also emerged to de-orbit satellites and tethering them for rolling after its lifetime has ended (Whipple 517).
External removal
It is in this method that there have been proposals to remove the debris from their orbits by various methods such as aerogel, unmanned space vehicles, laser booms and space shuttles among others. Most of these methods are still under studies, and their implementations are yet to take stage. Furthermore, the space shuttle accident that occurred has contributed heavily to the slowed development this process (Whipple 517).
Summary
Space debris has increasingly caused concern to most countries of the world, such as United States, European and Asian countries, among others. They have the propensity to erode body parts of spacecrafts and satellites when they collide as well as create more debris in the orbit which would increase the chances of other collisions.
These objects are usually manmade materials discarded in the orbit or dead satellites. Areas that require high alert are the LEO and GEO which have many satellites and stationed targets respectively. Flight engineers and space agencies have stationed various tracking devices like optical and radar detectors, among others, used to track space debris.
These devices are however limited to debris of sizes1cm and above, leaving several tiny debris unchecked. Various methods have been proposed to help mitigate growth of debris, as well as remove them from the orbit. Much effort still continues to be placed on space safety (Remer 1).
Conclusion
Space debris is increasingly filling the earth’s orbit, with prediction putting it at four times its present value by 2050. To avoid rampant collision, much should be done to mitigate its growth and remove the existing debris (Remer 1).
Works Cited
David, Leonard. “Space Junk Mess Getting Messier in Orbit”. Space.com. 23.02.2011. 28.04.2011. https://www.space.com/7956-space-junk-mess-messier-orbit.html
Remer, Lorraine. “Space Debris”. Earth Observatory. 12.09.2009.28.04.2011. https://earthobservatory.nasa.gov/images/40173/space-debris
Whipple, Fred. “The Theory of Micrometeorites”. Popular Astronomy, Volume 57, 1949, p. 517.