In the first part, I began to tell you about the work of the Movement Control System (DMS) at the stage of convergence. We stopped at the method of free paths and I promised to tell you about the method of guidance along the line of sight and parallel guidance. The post will be small, but interesting.

Guidance on the line of sight (LV)

Line of sight (LV) is a line connecting the centers of mass of objects.

This method has a big minus. Since this method does not take into account the laws of the orbital motion of spacecraft (SC), therefore, when approaching using this method, it is impossible to predict the relative motion of the spacecraft and the station, and to predict the consequences of control actions quite accurately even at relatively short time intervals. In this regard, certain restrictions are imposed on the trajectory of convergence.


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The vector of the relative velocity of approach Vot should be directed strictly along the LV:
V _Rel = V _TK -V _ok , where

V _tk -vector orbital velocity TC,
V _ok -vector orbital speed OK.

In this case, the angular velocity of the line of sight must be maintained equal to zero:
ω = V _bok / ρ , where

ω - vector of angular velocity of LV,
V _side - the vector of lateral velocity of approach,
ρ is the relative distance.

If this condition is met, the line of sight in inertial space moves parallel to itself. The control of the ship, in which ω = 0 is supported, is called parallel-guidance control. Practically to implement this method in its pure form is difficult. There is always a residual angular velocity of approach, which means that the approach comes with some slip. The magnitude of this miss is proportional to the distance and the magnitude of the angular velocity. The task of implementing the method of parallel guidance, both in manual and automatic modes, is the sequential damping of the angular velocity of the line of sight, thereby reducing the miss and keeping the radial velocity of approach within the specified limits.



The method of inertial parallel guidance is preferable in practical terms due to the fact that it is simple to implement, does not require complex computing technology. The disadvantage of the method is that it is applicable only at a relatively short range and the approach time should be minimal. This reduces the effect of the difference
gravitational accelerations acting on the ship and the station. The method of parallel guidance is used both in the final section of the automatic approach of the TC (from a distance of 200–100 m in the mooring mode), and in the case of manual control in the standby modes of approach.

In the next article I will try to talk about the principles of building a spacecraft motion control system in rendezvous mode, describe all the coordinate systems used in the Soyuz COURT of the Soyuz system, and also write a checkmate. models of the movement of the ship and the station, which are implemented in the Soyuz ship.