The process of space exploration, which practically 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, already after the launch of the first satellite, a completely different negative process began in parallel, associated with the clogging of near-Earth orbits. Man-made debris in space poses a host of threats to both spacecraft and Earth.
Sources of space debris
Garbage in this case refers to derivatives of a man-made nature, which are very diverse, but are associated with direct human activity. For example, naturally occurring meteoroids do not pose a threat, unlike man-made waste, which poses threats due to its long stay in Earth orbit.
So, where does the dangerous debris come from in space? Most of it isgenerated during satellite launches and launches of other vehicles into orbit. In such processes, accompanying manned or automatic ships are necessarily involved, 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 unmanaged equipment and structural parts of aircraft remain in space. By themselves, the fragments after the crashes of equipment or in the process of the planned release of waste do not pose a serious threat in a single number. However, with long-term accumulation, large objects are formed, often with a high radioactive potential, which makes it difficult to destroy them.
A significant role in the processes of formation of hazardous debris is played by the effect of the "age" degradation of debris from space objects in an aggressive environment. The same accumulations of debris are negatively affected by cosmic dust, radiation, temperature extremes, oxygen oxidation, etc. Thus, one has to deal not just with physical elements that pose a threat of collision, but with uncontrolled and explosive materials that increase the risk of disasters.
Monitoring space debris
The existing dangers associated with the presence of space debris also necessitate constant research into near-Earth orbits. Special devices scan man-made 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 conventionally covers a distance from 100 to 2000 km. Radio engineering, radar, optical, optoelectronic, laser and other devices for observing space debris operate in this spectrum. At the same time, special algorithms are being developed to analyze the information received on these devices. To combine a set of fragmented data, complex mathematical computational models are used, which give a relatively complete picture of what is happening in a particular area of observation.
Despite the use of high-tech monitoring methods, there are still problems tracking small particles as small as a few millimeters. Such fragments can only be partially studied by onboard sensors, but this is not enough to obtain comprehensive information, for example, about the chemical composition of the object. One of the directions for monitoring such particles is the so-called passive measurement. At one time, according to this principle, the components of the Mir space station returned to Earth were studied. The essence of this technology is to register the impacts of the studied particles on the surface of the apparatus in open space. In laboratories, various types of damage were analyzed, which made it possible to obtain additional information about space debris. Today, teams of cosmonauts are working along this path of research directly in orbit, inspecting the surfaces of operating spacecraft.
Distribution of debris in near-Earth space
Monitoring of outer space indicates an uneven distribution of debris of different types in orbits. The largest clusters are observed in the low-orbit region - in particular, compared with high orbits, the difference in density can be a thousandfold. At the same time, there is a relationship between the density of clusters and particle sizes. The spatial density of medium-sized debris is usually lower in high orbits than in low orbits in a smaller proportion compared to coarse-grained elements.
The characteristics of the distribution of space debris around the Earth are influenced by a number of factors, among which are the features of origin. For example, small fragments formed as a result of the destruction of parts of the station or satellites have unstable velocity vectors. As for large debris, due to its high dynamics it is able to reach high altitudes up to 20,000 km, and also spread in the geostationary ring. At the 2000 km level, there is an uneven distribution with points of density increase at 1000 and 1500 km in particular. By the way, the geostationary orbit is the most clogged, and in its own region a high tendency of debris to drift is recorded.
Space debris development trends
Space scientists are more concerned about potential rather than current threatsdebris in Earth orbits. At the moment, studies suggest an increase in the rate of pollution by 4-5% per year. Moreover, the role of spacecraft launches has not yet been reliably assessed in terms of the growth of the population of foreign bodies in different orbits. Large objects are amenable to forecasting, but, as already noted, the limited information on small debris even in near space does not allow us to speak with a high degree of objectivity about the characteristics of mass debris. Despite this, scientists make two unambiguous conclusions about small debris:
- The volume of small particles that are formed as a result of destruction steadily increases along with the increase in the number of collisions. Both in laboratory conditions and in theoretical studies, it was shown that small fragments make up a significant proportion of elements that are separated from 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 debris is exposed to aggressive conditions for a long time reduces the likelihood of a reliable assessment of the future of such accumulations.
Obviously, the problems of finding debris in space will only get worse, which requires appropriate measures to be taken. But even with a complete shutdown of space-related projects, 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 100years.
Types of effects of space pollution
The most dangerous negative consequences from the impact of space debris include the following:
- Ecological damage to the Earth. In itself, the presence of technogenic debris within the near-Earth orbit entails a change in the ecological background and violates the original purity of the environment. According to astronomers-observers, the process of reducing the transparency of near-Earth space is already progressing, which also explains the presence of interference with 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.
- Debris falling to Earth. Even without a radioactive effect, the fall of man-made waste from near space can lead to catastrophic consequences. To date, the largest landed objects had a mass of no more than 100 tons, but this did not pose a serious threat to the planet. On the other hand, as the intensity of the obstruction of the Earth's orbit increases, this scenario will become increasingly bleak.
- Space collision danger. Do not underestimate the harm of space debris for the equipment used in flight support. The same impacts of large and small particles can lead to significant disruptions in the operation of devices, and large accidents jeopardize the prospects for the implementation of expensive ambitious projects.
Crash damage assessment systemsrubbish
First of all, the already established practice of analyzing the effects on the surface of spacecraft is applied by external examination by the cosmonauts themselves. As mentioned above, the results of such studies can be further used to determine the characteristics of garbage. However, the most accurate analytical information is provided only by laboratory tests in which the target materials are artificially affected. An imitation of a collision of equipment with debris in space is realized through ultra-high-speed impacts. Further, by means of computer and digital modeling, the obtained data are processed with an analysis of the characteristics of the damage and the mechanics of the impact on the target object. Among the main indicators are such properties as strength, preservation of functionality, survivability of individual components, the degree of fragmentation, etc.
Determining the threat level of space debris
Even at the design stages of orbital stations and space complexes, the possibility of collision with various types of debris is taken into account. To calculate the optimal design reliability, data about the specific environment where the device will be used is used. At the same time, the inaccuracy of experimental and analytical methods for assessing threats is still a significant problem. Debris in space can only be examined to a certain degree of assumptions, making it difficult for designers to properly prepare vehicles for high speed collisions. ForFor an approximate threat assessment, the concept of general flows of space debris is used, which can potentially be encountered on the path of the spacecraft. Further data are displayed on the flux density, speed, angles of attack and the number of expected impacts.
Ways to reduce threats from debris in space
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 man-made waste in outer space. Today, two directions are being considered to solve this problem. Firstly, this is a general reduction in flights, as well as the minimization of technological processes that lead to clogging of orbits at different levels. Secondly, we can talk about the structural optimization of vehicles with the reduction of parts that could potentially become space debris. Special attention in space control 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 the fight against debris in the near space
Active work towards the regulation of space activities at the global level gives grounds for optimism in assessing the development of the situation in the future. Careful attitude to the cleanliness of orbital environments is included in the concepts of strategic programs of the largest states, which contributethe greatest contribution to the fight against debris in space. Cleaning and removal of small and large particles to polygon orbits is one of the key areas in the cleansing of space from man-made pollution, but there are no effective methods for implementing this concept yet. This is a technologically difficult task, so the main emphasis at the moment is still on ways to optimize human activities in space.
Conclusion
One of the radical ways to solve space debris problems is to completely stop launching orbital stations and satellites until new and more affordable means of cleaning the near-Earth environment appear. But this direction is also 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 several decades, you can notice fundamental changes in the attitude of the person himself to this problem. So, if during the operation of the Mir space station, the usual practice was the direct release of the crew's waste products, then today this is impossible to imagine. More and more stringent rules are being introduced to regulate the processes of being in outer space. This is also evidenced by international conventions, according to which countries participating in space activities are obliged to adhere to the principles of reducing the negative impact on the ecological situation in the near-Earth environment.
