Manned spacecraft landing

    All the good times of the day saturated with us turned out to be the last month. First, the launch of the Soyuz TMA-11M spacecraft, then the launch of the Soyuz TMA-09M spacecraft, and for dessert, the launch of the Progress M-21M spacecraft according to the 4-day connection scheme with the ISS approaching on the 2nd day of flight on a very short distance. Since my main work is to ensure the descent of spacecraft, in this article I will talk about the features of organizing the completion of manned programs using the example of an emergency landing (the “Olympic” Union TMA-09M).


    It’s worth mentioning right away that the organization of a manned flight is quite different from unmanned missions, but in any case, all work on conducting dynamic operations in space can be divided into two stages: design and operational, only in the case of manned missions, these stages, as a rule, take significantly more time. In this article, I will mainly touch upon the operational part, since the ballistic design work for the descent is ongoing and includes various studies to optimize all kinds of factors that affect the safety and comfort of the crew during landing. So, let's begin.

    For 40 days

    The first approximate descent calculations are carried out in order to determine the landing areas. Why is this done? Currently, full-time controlled descent of Russian ships can be carried out only in 13 fixed landing areas located in the Republic of Kazakhstan. This fact imposes a lot of restrictions related primarily to the need for prior coordination with all our foreign partners of all dynamic operations. The main difficulties arise when planting in autumn and spring - this is due to agricultural work in the planting areas. This fact must be taken into account, because in addition to ensuring the safety of the crew, it is also necessary to ensure the safety of the local population and the search and rescue service (MSS). In addition to the regular landing areas, there are also landing areas upon failure to ballistic descent,

    For 10 days

    The preliminary calculations on the descent trajectories are being specified, taking into account the latest data on the current orbit of the ISS and the characteristics of the docked spacecraft. The fact is that a fairly long period of time elapses from the start to the descent, and the mass-centering characteristics of the spacecraft change, in addition, the great contribution is made by the fact that, together with the astronauts, payloads return from the station to Earth, which can significantly change the position center of mass of the descent vehicle. Here it is necessary to explain why this is important: the shape of the Soyuz spacecraft resembles a headlight, i.e. he has no aerodynamic controls, but to obtain the necessary landing accuracy, it is necessary to control the trajectory in the atmosphere. For this, the Soyuz provides a gas-dynamic control system, but it is not able to compensate for all deviations from the nominal trajectory, therefore, an extra balancing weight is artificially added to the apparatus design, the purpose of which is to shift the center of pressure from the center of mass, which will allow you to control the descent trajectory by turning over the roll. Updated data on the primary and backup schemes are sent toPSS . According to these data, all settlement points are circled and a conclusion is made about the possibility of landing in these areas.

    For 1 day

    The descent trajectory is finally being specified taking into account the latest measurements of the ISS position, as well as the forecast of the wind situation in the main and reserve landing areas. This must be done due to the fact that at an altitude of the order of 10 km the parachute system opens. At this point in time, the descent control system has already done its work and cannot correct the trajectory in any way. In fact, only wind drift acts on the device, which cannot be ignored. The figure below shows one of the options for modeling wind drift. As you can see, after entering the parachute, the trajectory changes greatly. Wind drift can sometimes be up to 80% of the permissible radius of the dispersion circle, so the accuracy of the weather forecast is very important.

    On the day of launch:
    In addition to the ballistic and search and rescue services, many more units are involved in ensuring the launch of the spacecraft to the ground such as:
    • transport ship management service;
    • ISS Management Service;
    • crew health service;
    • telemetry and team services, etc.

    Only after a report on the readiness of all services, flight managers can decide to carry out the descent according to the intended program.
    After this, the passageway closes and the ship is undocked from the station. A separate service is responsible for undocking. Here it is necessary to calculate in advance the direction of undocking, as well as the impulse that must be applied to the device in order to prevent a collision with the station. When calculating the descent trajectory, the undocking scheme is also taken into account. After undocking the ship, there is still some time before turning on the brake engine. At this time, all equipment is checked, trajectory measurements are made, and the landing point is specified. This is the last moment when something else can be clarified. Then the brake motor is turned on. This is one of the most important stages of the descent, so it is constantly monitored. Such measures are necessary in order to understand, in the event of an emergency, under which scenario to move on. With a regular pulse test, after some time, the compartments of the ship separate (the descent vehicle is separated from the household and instrument-aggregate compartments, which then burn out in the atmosphere). If, when entering the atmosphere, the descent control system decides that it is not able to provide a landing for the descent vehicle at the point with the required coordinates, then the ship “breaks down” into the ballistic descent. Since this all happens already in the plasma (there is no radio connection), it is possible to establish which path the device is moving only after the radio connection is resumed. If there was a breakdown on the ballistic descent, you must quickly clarify the proposed landing point and transfer it to the search and rescue service. In the case of a full-time controlled descent, specialists begin to “lead” the ship in flightPSS and we can see live the descent of the device by parachute and even, with luck, the operation of soft landing engines (as in the picture).

    After that, you can already congratulate everyone, shout cheers, open champagne, hug , etc. Officially, ballistic work is completed only after receiving the GPS coordinates of the landing point. This is necessary for the post-flight miss assessment, which can be used to evaluate the quality of our work.
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