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Researchers of Samara University has developed the technology intended for performing the mission of efficiently and safely removing space orbital debris. The technology is described in detail in the book “Attitude Dynamics and Control of Space Debris During Ion Beam Transportation” (1), published in November in the Elsevier Publishing House, one of the four largest scientific publishing houses in the world. The authors of the monograph are Professor Vladimir Aslanov and Associate Professor Aleksandr Ledkov. The technology presented by the scientists is the improved technique for cleaning the orbit using the plasma torch, i.e. the ion beam created by the electric engine of the “janitor” spacecraft. This method of cleaning the orbit is as follows: the plasma “broom” of the space “janitor” sweeps away space debris in the needed direction by the ion beam, sending it into the Earth’s atmosphere for subsequent combustion in its dense layers, or moving it to the special orbit for the debris disposal — the spoil disposal orbit.
“Cleaning the orbit from old non-functioning satellites or spent rocket stages that remained in orbit after putting there the payload is the multifaceted and complex scientific and technical problem. To solve it, many schemes and methods have already been proposed in the world, including the use of ion beams, but no space debris cleanup missions have been conducted yet. Our monograph presents in detail the method of contactless debris collection in orbit by using the automatic cleaning spacecraft equipped with ion engines, such engines are widely used in modern cosmonautics. Approaching the selected debris object at the distance of about ten meters, the “janitor” spacecraft will direct the ion jet of the engine, the so-called plasma torch, onto it. Colliding with the space garbage surface, the ion jet particles generate the force that will be used to move the debris object in the needed direction,” said one of the authors of the book, Aleksandr Ledkov, Associate Professor of the Department of Theoretical Mechanics at the Institute of Space Rocket Engineering of Samara University.
As the scientist noted, most of developed in the world methods for cleaning space debris involve direct contact — docking or capturing the transported object with the harpoon, the net, the rope or the robotic manipulator. However, all these methods are quite complex and dangerous, they can cause emergency collision and appearance of a large amount of small space debris. The contactless method is safer: the “janitor” spacecraft does not need direct mechanical contact with space debris, which reduces the probability of their collision. Moreover, this method is suitable for transporting rapidly rotating objects that are very difficult to be captured with a robotic manipulator or a space net.
The published book provides the broad overview of studies in the field of contactless cleaning of space debris. Scientists show how to independently develop mathematical models and conduct computer modeling of the transportation system, demonstrate the features of space debris fluctuations inside the ion beam, and propose various laws and schemes of controlling over the space “janitor”, for the purpose of the most efficiently moving the objects selected. Despite the fact that designing the construction of the cleaning device was not included in the tasks and plans of the authors of the monograph, the book describes the methods for selecting the design parameters of the spacecraft.
“Of course, the spacecraft should be automatic. Time delays will not allow the operator from the Earth to properly respond to changes in the situation. For generating the ion beam, the spacecraft should be equipped with an electrodynamic ion thruster, for example, it can be the commercial NEXT-C engine. In the most common scheme, two such engines are needed to be installed, so that the thrust of the ion-generating engine could be compensated by the oppositely directed engine. Otherwise, the active spacecraft will fly away from the space debris object,” noted Aleksandr Ledkov. “We have invented various ion beam control schemes to improve efficiency of the transportation system, which ultimately results in reduction in time and fuel consumption. For implement the most promising scheme, the ion engine needs to be installed on the rotary platform, for the purpose of slightly changing the ion beam focus.”
According to the developers, this method of cleaning by applying the ion beam is primarily suitable for elimination of large debris objects.
“All space debris traditionally is divided into three groups: small (less than a centimeter), medium (less than 10 cm) and large (more than 10 cm). We mean cleaning large objects: old rocket stages and non-functioning satellites. Theoretically, the ion beam can remove small debris too, but this will be extremely inefficient, since most of the ion beam particles will miss the blown object, and only those particles to have collided with the object surface and transmitted part of their momentum to it do useful work. All other particles will be wasted,” stressed the scientist.
According to experts, about 130 million space debris objects less than 1 cm in size, about 1 million — up to 10 cm and over 30 thousand objects with their size of more than 10 cm can currently be in various orbits. Because of their high-speed movement, even the most microscopic fragments of the debris can pose a danger to astronauts and spacecrafts. What kind of space debris should be cleaned first? In 2021, the joint paper was published by 19 scientists from 13 universities, among the co-authors of this publication was Professor Vladimir Aslanov. Scientists from different countries compared results of their studies and compiled the list of top 50 most dangerous objects of space debris. It included rocket stages and satellites weighing from 1.1 to 9 metric tons. You can safely take any object from this list, and develop the mission on its removing from the orbit, with the help of Samara scientists’ monograph.
“For succeeding in removing debris, the object must be “brought” to the border of the Earth’s atmosphere or to the spoil disposal orbit (2). Then you can go to the next object. Choosing the optimal sequence for removing space debris objects from the orbit is a separate difficult task. By the way, the “janitor” spacecraft itself should not become space debris, no doubt about it. It will need to be taken out of the orbit together with the last object planned for removing,” told us Aleksandr Ledkov.
According to the scientists, such a space “janitor” with ion engines will be useful not only in course of the orbital “subbotnik”, but also as a kind of satellite rescuer: for example, it will be able to adjust with its ion beam the orbit of a long-running spacecraft, to increase its service life. Or to solve the problem of orbit raising, when the satellite turns out to be put into the non-target orbit, the “rescuer” will help the device that has strayed from the right path to get to the target orbit.
About the book
The monograph “Attitude Dynamics and Control of Space Debris During Ion Beam Transportation” is based on the research conducted by Vladimir Aslanov and Aleksandr Ledkov at the Department of Theoretical Mechanics at the Institute of Aviation and Space-Rocket Engineering of Samara University. This is not the first experience of the authors’ working together. In 2012, the book about tethered systems was published in the same publishing house (V. S. Aslanov, A. S. Ledkov “Dynamics of Tethered Satellite Systems”), which, due to its great reader demand, was republished in Chinese in 2015.
Transportation of space debris by the ion beam is the relatively new area. The idea of such a system was independently formulated by several research groups from Spain, Japan and France in 2011. In 2016, scientists of the Department of Theoretical Mechanics headed by Vladimir Aslanov began to research this area, and in 2017, the first article on this issue was published.
For five years, the researchers of the Department have published a series of articles in high-rank scientific journals on this topic, and have been recognized as leaders in this field at the international level. After that, this monograph was prepared and published in 2022.
Currently, scientists of the Department of Theoretical Mechanics actively develop this area within the framework of the grant from the Russian Science Foundation (Project No. 22-19-00160). It is planned to carry out new research on the dynamics of space debris movement in the ion beam. The Doctoral dissertation and the Candidate dissertation in this area has been prepared and will be submitted for defense in the near future.
For reference
1) V. Aslanov, A. Ledkov “Attitude Dynamics and Control of Space Debris During Ion Beam Transportation”
2) According to recommendations of the Inter-Agency Space Debris Coordination Committee, there are two protected regions crucially important for practical use: low Earth orbit (anything below 2,000 km) and geostationary orbit (35,793 +/- 200 km). Space debris from the low Earth orbit is usually lowered to the Earth, but it is very expensive to bring garbage from the geostationary orbit to the Earth, so it is thrown higher, into the so-called spoil disposal orbit: this is the orbit, from which the object should not return to the protected region in the next 100 years.
