The process of space exploration, which almost began in the middle of the 20th century, is usually presented on the positive side as a new stage in the development of scientific and technological knowledge. However, after the launch of the first satellite, a completely different negative process began in parallel, associated with the clogging of near-Earth orbits. Artificial debris in space poses a lot of threats to both spacecraft and the Earth.
Space debris sources
In this case, garbage is understood as derivatives of anthropogenic nature, which are very diverse, but related to direct human activities. For example, meteoroids of natural origin are not dangerous, unlike man-made waste, which creates threats due to its long-term presence in Earth orbit.
So, where is the danger from space in space? Most of it is formed during the launch of satellites and the launch of other vehicles into orbit. Such processes necessarily involve the accompanying manned or automatic ships, which leave behind technical objects and consumables. The most dangerous source of pollution of this kind is the destruction of satellites and ships in orbit, as a result of which uncontrollable equipment and structural parts of aircraft remain in space. Fragments per se after equipment crashes or during a planned waste disposal do not pose a serious threat in a single number. However, with long-term accumulation, large objects are formed, often having a high radioactive potential, which makes their destruction difficult.
The effect of “age-related” degradation of the debris of space objects under the influence of an aggressive environment plays a significant role in the processes of formation of hazardous debris. Cosmic dust, radiation, temperature changes, oxygen oxidation, etc., negatively affect the same accumulations of garbage. Thus, one has to deal not only with physical elements that pose a threat of collision, but with uncontrollable and explosive materials that increase the risk of disasters.
Space debris monitoring
The existing dangers associated with the presence of space debris also necessitate the constant study of near-Earth orbits. Special devices scan technological waste according to several characteristics, including size, mass, shape, speed, trajectory, composition, etc. Depending on the distance from the Earth, certain equipment is used. For example, the low Earth orbit of the LEO system conditionally covers a distance of 100 to 2000 km. In this spectrum there are radio engineering, radar, optical, optoelectronic, laser and other devices for observing space debris. At the same time, special algorithms are developed for analyzing the information received on these devices. To combine the set of fragmented data, complex mathematical computational models are used that give a relatively complete picture of what is happening at a particular observation site.
Despite the use of high-tech monitoring methods, there still remain problems in tracking small particles several millimeters in size. Such fragments lend themselves only to a partial study by airborne sensors, but this is not enough to obtain complex information, for example, about the chemical composition of an object. One of the directions of monitoring such particles is the so-called passive measurement. At one time, the components of the Mir space station returned to Earth were studied using this principle. The essence of this technology is to record the impacts of the investigated particles on the surface of the apparatus in open space. Different types of damage were analyzed in the laboratories, which made it possible to obtain additional information about space debris. Today, astronaut crews work directly in orbits along this path of research, inspecting the surfaces of existing ships.
Near-Earth space debris distribution
Outer space monitoring indicates the uneven distribution of various types of garbage in orbits. The largest clusters are observed in the low orbit region - in particular, in comparison with high orbits, the difference in density indices can be a thousandfold. At the same time, there is a correlation between the density of clusters and particle sizes. The spatial density of medium-sized debris is usually lower in high orbits than in low ones in a smaller proportion compared to coarse-grained elements.
The characteristics of the distribution of space debris around the Earth are affected by a number of factors, including the characteristics of origin. For example, small fragments resulting from the destruction of parts of a station or satellites have unstable velocity vectors. As for large debris, thanks to its high dynamics, it is able to reach large heights of up to 20,000 km, and also spread in the geostationary ring. At the level of 2000 km, an uneven distribution is observed with points of increasing density at altitudes of 1000 and 1500 km, in particular. By the way, the geostationary orbit is the most clogged, with a high tendency of the garbage to drift in its area.
Space debris development trends
Specialists involved in space exploration are more concerned not with current threats, but with the potential for contamination of near-Earth orbits. At the moment, studies suggest an increase in pollution rates by 4-5% per year. Moreover, the role of spacecraft launches has not yet been reliably evaluated in terms of the growth of a foreign body population in different orbits. Large objects can be predicted, but, as already noted, the limited information on small garbage even in near space does not allow us to speak about the characteristics of mass clogging with a high degree of objectivity. Despite this, scientists make two unambiguous conclusions about small garbage:
- The volume of small particles that are formed as a result of the destruction is steadily increasing with an increase in the number of collisions. Both in laboratory conditions and in theoretical studies it was shown that small fragments constitute a significant proportion of the elements that separate from the objects of destruction.
- Very small particles in the form of the same collision products are more susceptible to the negative effects of external forces. The effect of degradation when the garbage is in aggressive conditions for a long time reduces the likelihood of a reliable estimate regarding the future of such clusters.
Obviously, the problems of finding debris in space will only be exacerbated, which requires the adoption of appropriate measures. But even if the projects related to space activities are completely stopped, the near-Earth orbit will continue to become clogged as a result of the collision of existing pollution elements with natural particles. By inertia, this process will continue for at least another 100 years.
Types of space clogging effects
The most dangerous negative consequences from the influence of space debris include the following:
- Environmental damage to the Earth. The mere presence of man-made debris within the near-earth orbit entails a change in the ecological background and violates the pristine purity of the environment. According to observer astronomers, the process of lowering near-Earth space transparency is already progressing, which also explains the presence of interference for the operation of radio equipment. Directly for the Earth, one can note the danger of falling components with fuel materials that ensure the operation of jet engines.
- The fall of garbage to Earth. Even without a radioactive effect, the fall of man-made waste from near space can lead to disastrous consequences. Today, the largest landing objects had a mass of not more than 100 tons, but this did not pose serious threats to the planet. On the other hand, as the intensity of the near-Earth orbit clogging increases, this scenario will become increasingly gloomy.
- The danger of space collisions. Do not underestimate the harm of space debris to equipment used in flight support. The same impacts of large and small particles can lead to significant disruptions in the operation of the devices, and large accidents jeopardize the prospects for the implementation of expensive ambitious projects.
Collision Damage Assessment Systems
First of all, the already established practice of analyzing the effects on the surface of spacecraft is applied by external inspection by the astronauts themselves. As mentioned above, the results of such studies can be further used to determine the characteristics of garbage. However, only laboratory tests provide the most accurate analytical information in which the target materials are artificially impacted. Simulation of a collision of equipment with debris in space is realized through ultra-high-speed impacts. Then, through computer and digital modeling, the obtained data is processed with analysis of the characteristics of damage and the mechanics of exposure to the target object. Among the main indicators, such properties as strength, the preservation of functionality, the survivability of individual components, the degree of formation of fragments, etc. are highlighted.
Determining the level of space debris threat
Even at the design stages of orbital stations and space systems, the possibility of collision with debris of various types is taken into account. To calculate the optimal structural reliability, data on the specific environment where the device will be used are used. At the same time, the inaccuracy of experimental and analytical methods for assessing threats is still a significant problem. Debris in space can be investigated only with a certain degree of assumptions, which complicates the tasks of designers who must properly prepare equipment for a collision at high speeds. For an approximate threat assessment, the concept of common streams of space debris, which could potentially be encountered along the path of the vehicle’s movement, is used. In the future, data on flux density, speed, angle of attack and the number of expected hits are displayed.
Ways to reduce space debris threats
The relatively low level of monitoring and characterization of space debris with its prediction is only part of the problem. At the present stage, specialists are faced with a number of issues related to reducing the risks of the negative impact of industrial waste in outer space. Today, two directions for solving this problem are considered. Firstly, this is a general reduction in flights, as well as minimization of technological processes that entail clogging of orbits at different levels. Secondly, we can talk about the structural optimization of the apparatus with the reduction of parts that could potentially become space debris. Special attention in space monitoring systems today is devoted to contamination with radioactive substances. This concerns the minimization of engine exhaust products up to the transition to fundamentally new fuel resources.
Prospects for dealing with debris in near space
Active work in the direction of regulation of space activities at the global level provides grounds for optimism in assessing the development of the situation in the future. A careful attitude to the cleanliness of orbital environments is included in the concept of strategic programs of the largest states that make the greatest contribution to the fight against debris in space. The cleaning and removal of small and large particles into orbits-polygons is one of the key areas in cleansing space from technogenic pollution, but there are as yet no effective methods for implementing this concept. This is a technologically difficult task, so the main emphasis at the moment is still on ways to optimize human activity in space.
Conclusion
One of the radical ways in solving the problems of space debris is the complete cessation of launches of orbital stations and satellites until new and more affordable means of cleaning the near-Earth medium appear. But this direction is utopian due to a number of economic and technological reasons. Nevertheless, there are prerequisites for changing the situation for the better. Even if you look back a few decades, you can see the fundamental changes in the attitude of the person to this problem. So, while during the operation of the Mir space station, direct release of the crew’s vital products was common practice, today it’s impossible to imagine such a thing. Introducing more and more stringent rules governing the processes of being in outer space. This is evidenced by international conventions, according to which the countries involved in space activities are required to adhere to the principles of reducing the negative impact on the environmental situation in the near-Earth environment.