Soyuz-TM spacecraft motion control system
In my hubs, I want to tell you about the management of manned spacecraft. Basically about the ships "Soyuz" and "Space Shuttle". For 15 years of studying these ships, I have gathered a sufficient amount of information about them, as well as the knowledge that I want to share with you.
On Habré, I want to tell you about the mode of bringing the Soyuz spacecraft closer to the International Space Station (ISS). Since abbreviations are used in space in 70% of cases, I will have to use them as well, but I will try to decipher and explain the most complex and incomprehensible values.
In order to talk about this mode, we need to describe the dynamics of the ship and the station, as well as describe the basic principles of the control of the ship.
When approaching under space conditions, the dynamics of the transport ship (TK) and the international space station (ISS) can be represented in the form of two independent movements:
')
Therefore, management includes:
In practice, in the process of convergence, the ISS moves along a known orbit and maintains a predetermined orientation (to the TC, which was set in advance for ease of docking), therefore the ISS is called a passive ship (PC). The transport ship, which is an active ship (AK), is assigned the task of maneuvering, that is, controlling the rotation and movement relative to the center of mass relative to the ISS. Therefore, in order to realize the approach of the TC to the ISS, the approach control system (TAS) of the TK is provided for in the TK system.
What problems solves the convergence mode?
So, the proximity system, like any other control system, must meet the following requirements:
In addition, I want to note that in order to control the progress of the approach mode and operational intervention of the MCC in the management of the TC in case of emergency situations (NSHC) at critical stages of approach (fly-around, hang-up, docking, docking) it is desirable that these operations be performed in the light during sessions communications, that is, in the visibility zones of ground measuring points. But communication sessions are possible only at certain time intervals, due to the geographical location of ground measuring points and the precession of the orbit due to the daily rotation of the Earth. Therefore, it is necessary to create such control of the transport ship in the approach mode to bring it to the ISS area (relative distance less than 1 km) to a given point in time, ensuring reliable and long-lasting communication with the MCC and favorable cut-off conditions at the fly-around, docking and docking stages.
The purpose of the system, its requirements and time limits, taking into account the light and shade situation, determine the principles of control of the transport vehicle and the principles
the construction of the COURT TC in the mode of convergence.
Now let's analyze with you the principle of TC control in the SAT mode.
Since the requirements for the approach control system are contradictory, it is impossible to fully satisfy them, because it is impossible to choose such a method of targeting the target to control a transport ship that would ensure the simultaneous fulfillment of all system requirements. Therefore, in practice, the whole process of convergence is divided into two sections:
Free path guidance
The method of free trajectories takes into account the orbital motion of the spacecraft in the field of the Earth. It allows the transfer of the transport ship from the waiting orbit to the vicinity of the ISS with the help of a multipulse maneuver, which consists of sections of ballistic (free) motion of the spacecraft in the field and controlled (with the propulsion system on) movement of the spacecraft. The direction, magnitude and moments of the issuance of these corrective pulses are calculated from the condition of hitting ultimately in the vicinity of the ISS. It should be noted that the time for issuing corrective pulses is very short compared with the time of free movement of the TC. Thus, the approach path consists of sections of free movement of the TC, at the interface points of which corrective impulses are issued. Hence the name of the method of guidance. For TK, aiming at a target using the free trajectory method provides the following approximation schemes with the ISS:
Of course, there are other schemes, but in this article we will consider only these.
1. In the case of a two-pulse scheme, the approach path is built using a 2-pulse maneuver, where
ΔV1 is designed to build the interception orbit, which ensures that TK gets into the vicinity of OK at a given time Tzad;
ΔV2 is designed to align the orbital velocities of TC and OK.
2. In the case of a three-pulse scheme, the approach path represents a bi-elliptical transition realized by three corrective pulses ΔV1, ΔV2, ΔV3 .
In this case, ΔV1 is applied in the waiting orbit to transfer the TC to the internal
elliptical transition orbit,
ΔV2 - designed to make the transition of the TC in the vicinity of the ISS to the specified
time tzad
ΔV3 - is required to align the orbital velocities of the TC and the ISS.
In the following articles, we will examine the guidance along the line of sight, parallel guidance, etc.
On Habré, I want to tell you about the mode of bringing the Soyuz spacecraft closer to the International Space Station (ISS). Since abbreviations are used in space in 70% of cases, I will have to use them as well, but I will try to decipher and explain the most complex and incomprehensible values.
In order to talk about this mode, we need to describe the dynamics of the ship and the station, as well as describe the basic principles of the control of the ship.
When approaching under space conditions, the dynamics of the transport ship (TK) and the international space station (ISS) can be represented in the form of two independent movements:
')
- rotation of each of the spacecraft around its center of mass (setting the angular velocity);
- the relative movement of the centers of mass of the TC and the ISS (set the linear velocity).
Therefore, management includes:
- motion control of each spacecraft around its center of mass ( orientation control or control of the mutual angular position )
- control of the relative motion of the centers of mass of spacecraft (control of the relative trajectory of convergence).
In practice, in the process of convergence, the ISS moves along a known orbit and maintains a predetermined orientation (to the TC, which was set in advance for ease of docking), therefore the ISS is called a passive ship (PC). The transport ship, which is an active ship (AK), is assigned the task of maneuvering, that is, controlling the rotation and movement relative to the center of mass relative to the ISS. Therefore, in order to realize the approach of the TC to the ISS, the approach control system (TAS) of the TK is provided for in the TK system.
What problems solves the convergence mode?
- selection of the optimal approach path (TSS) of the TC with the ISS, based on the minimum fuel consumption for its implementation;
- the organization of TC control along the chosen trajectory of convergence;
- provision of automatic (discrete) or manual (analog) flight to the specified docking station of the ISS, hanging in front of it, mooring with relative motion parameters, ensuring the normal operation of the docking mechanism;
- provision of automatic monitoring of the traffic control system
- TC in convergence mode. When a failure occurs automatically
- switching to serviceable devices;
- issuing information to the crew about the passage of the convergence mode, parameters
- relative motion and failures of the COURT of TC;
- provision of automatic or manual removal of TC from the ISS in the presence of danger
- collisions.
So, the proximity system, like any other control system, must meet the following requirements:
- minimum fuel consumption for convergence;
- high precision control TC;
- simplicity of software and instrumentation;
- minimum weight, dimensions and power consumption of the system;
- high system reliability;
- security convergence process.
In addition, I want to note that in order to control the progress of the approach mode and operational intervention of the MCC in the management of the TC in case of emergency situations (NSHC) at critical stages of approach (fly-around, hang-up, docking, docking) it is desirable that these operations be performed in the light during sessions communications, that is, in the visibility zones of ground measuring points. But communication sessions are possible only at certain time intervals, due to the geographical location of ground measuring points and the precession of the orbit due to the daily rotation of the Earth. Therefore, it is necessary to create such control of the transport ship in the approach mode to bring it to the ISS area (relative distance less than 1 km) to a given point in time, ensuring reliable and long-lasting communication with the MCC and favorable cut-off conditions at the fly-around, docking and docking stages.
The purpose of the system, its requirements and time limits, taking into account the light and shade situation, determine the principles of control of the transport vehicle and the principles
the construction of the COURT TC in the mode of convergence.
Now let's analyze with you the principle of TC control in the SAT mode.
Since the requirements for the approach control system are contradictory, it is impossible to fully satisfy them, because it is impossible to choose such a method of targeting the target to control a transport ship that would ensure the simultaneous fulfillment of all system requirements. Therefore, in practice, the whole process of convergence is divided into two sections:
- a distant section (DM), the task of which is to bring the TC to the area where the ISS is located along the optimal approach path, that is, with minimal fuel consumption;
- - near section (CU), whose task is to provide control with a given accuracy by the orientation and movement of the center of mass of the TC to the selected docking station and soft contact when docked. Based on the above considerations, for the transport vehicle, the proximity approach is implemented using the free path method, and the BU using the modified pointing method along the line of sight (here, a line connecting the centers of mass of the approaching objects is taken under the line of sight (LW)).
Free path guidance
The method of free trajectories takes into account the orbital motion of the spacecraft in the field of the Earth. It allows the transfer of the transport ship from the waiting orbit to the vicinity of the ISS with the help of a multipulse maneuver, which consists of sections of ballistic (free) motion of the spacecraft in the field and controlled (with the propulsion system on) movement of the spacecraft. The direction, magnitude and moments of the issuance of these corrective pulses are calculated from the condition of hitting ultimately in the vicinity of the ISS. It should be noted that the time for issuing corrective pulses is very short compared with the time of free movement of the TC. Thus, the approach path consists of sections of free movement of the TC, at the interface points of which corrective impulses are issued. Hence the name of the method of guidance. For TK, aiming at a target using the free trajectory method provides the following approximation schemes with the ISS:
- two-pulse;
- three pulse.
Of course, there are other schemes, but in this article we will consider only these.
1. In the case of a two-pulse scheme, the approach path is built using a 2-pulse maneuver, where
ΔV1 is designed to build the interception orbit, which ensures that TK gets into the vicinity of OK at a given time Tzad;
ΔV2 is designed to align the orbital velocities of TC and OK.
2. In the case of a three-pulse scheme, the approach path represents a bi-elliptical transition realized by three corrective pulses ΔV1, ΔV2, ΔV3 .
In this case, ΔV1 is applied in the waiting orbit to transfer the TC to the internal
elliptical transition orbit,
ΔV2 - designed to make the transition of the TC in the vicinity of the ISS to the specified
time tzad
ΔV3 - is required to align the orbital velocities of the TC and the ISS.
In the following articles, we will examine the guidance along the line of sight, parallel guidance, etc.
Source: https://habr.com/ru/post/457842/
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