The Rector of NSU, Professor Michail P. Fedoruk co-authored by other former graduates of the NSU Physics Department 鈥� Dr. Alexander M. Rubenchik (Lawrence Livermore National Lab, USA) and Prof. Sergei K. Turitsyn (Aston University, UK) 鈥� has published an article 鈥楾he effect of self-focusing on laser space-debris cleaning鈥� issued in 芦Light: Science & Applications禄 by Nature Publishing Group.
The Earth orbit (about 2K km high) has collected quite a few natural and artificial objects drifting there since the beginning of the space exploration era. They include various small meteorites, fragments of rocket stages, etc. and total in thousands tons of space debris.
The consequences of numerous satellites and orbital stations colliding with orbital debris might be quite undesirable and even disastrous. The space debris problems are being widely discussed both by scientists and Hollywood film-makers, which resulted, for example, in an Oscar-winner film 鈥楪ravity鈥�.
The Livermore National Lab Project 鈥淥rion鈥� suggests removing small dangerous objects, which comprise most of the space debris, into lower dense atmosphere under the influence of a powerful ground-based pulsed laser changing the debris trajectories.
Essentially, the article is devoted to the issue of atmosphere influence on the laser beam propagation and, thus, its ability to change the trajectories of small space objects. The dynamics depends on the atmosphere density changing with the height, which changes the nonlinear atmospheric refractive index, which, in turn, influences the propagation of the beam. The authors applied the numerical calculation method and demonstrated that the spatial structure of the beam on the target is smooth, without filaments, but the nonlinear effects noticeably decrease the peak intensity. A laser Gaussian input beam while propagating vertically (up to 1000 km) is to have the constant shape but changes the radius and laser-pulse power according to the model due to diffraction and self-focusing, even under the great initial power exceeding the critical power for self-focusing in air (on the Earth surface). 鈥楢lthough the effects considered are quite simple, we faced a number of unexpected phenomena. Surprisingly enough, such initially powerful laser beams do not result in self-focusing and filamenting the beam,鈥� explains Michail Fedoruk. 鈥業t sounds quite fantastic, but this project is taken very seriously by such a world-known institution as the Livermore National Laboratory. Of course, we did not aim at the complete description of the problem and its ultimate solution. We did our best by stimulating further, more accurate and cumbersome computations for this global problem, as the losses of valuable satellites can have bad long-term effects. How to influence distant space objects from the Earth by means of a laser beam effectively is quite a hard nut to crack. This project has a large dimension and its execution time is quite distant.鈥�
