The results of the investigation of the accident "Union MS-10"

    On Thursday, a press conference of the emergency commission for journalists was held, at which they named the cause of the accident "Union MS-10". Rumors about the valve that did not open turned out to be true, but it did not open due to the fact that the sensor was damaged when the rocket was assembled, which normally forms a command for this discovery.

    Shot from video of Roskosmos

    Press conference video

    We were shown a video of the accident recorded by the onboard recorder.

    What is this sensor, and where is it located?


    Start from the Kourou cosmodrome, video of the European Space Agency

    In a very abbreviated and simplified form, the separation of the side units (first stage) occurs in several stages:

    1. Side block motors are converted to low thrust mode.
    2. The lower links are broken, the tail part of the side blocks moves to the side
    3. Side block motors shut down
    4. Side blocks retract, retract from power mounts
    5. The waste is fixed by a mechanical sensor, at the command of which the oxidizer tank drain valves open
    6. Under the pressure of oxygen and gas pressurization tanks are twisted

    In the case of the Union MS-10, the problem manifested itself in step 5 - the sensor bent, and only 6 ° 45 'was enough for it not to work and “tell” the side unit that it was time to open the oxidizer tank valve.

    Bent sensor, a frame from the press conference

    The sensor is located on top of the "ball", which is located at the very top of the side unit. According to the information from the Astronautics News magazine, this is a simple mechanical sensor with a spring, which normally has to come out and give an electrical command to open the valve of the oxidizer tank.

    Sensor under the red cap on the top right, the valve is closed with a round red cap to the left and below, photo by the CEC of the USSR

    There is no independent telemetry system on the side unit, and the mechanical sensor does not write logs, so the investigation commission had to analyze the hypotheses that the sensor was bent when the top of the step was steaming the central unit or it was damaged when the step fell to the ground.

    Acting Director of RCC Progress Dmitry Baranov shows the location of the sensor to Dmitry Rogozin during his visit to Samara on October 17, photo of Roskosmos.

    Thus, the accident repeats the scenario of thirty-two years ago.
    03/26/1986 - Soyuz-U - Baikonur - Non-standard separation of the side block G of the first step from the central block A of the second step of the PH due to the non-retraction of the upper part of the side block G due to the failure of the command to enter the keypad BU302-0M opening the cover B4300-845M of the jet nozzle oxidizer tank due to non-output of the B4411-0A contact probe stem as a result of its jamming in the housing due to the deformation of the stem during assembly of the “package” at the cosmodrome caused by the joining of the side block G with random deviation from the requirements of technical documentation on the mutual position of the blocks at the time of docking and putting the spherical support in the thrust bearing

    A couple of words about SED

    After the press conference, Roskosmos published a chronology of the emergency rescue system. When the side unit destroyed the central one, the rocket spun heavily (we managed to notice it in the video from the ship’s cabin), and the SAS that had triggered the ship to the side.

    Roscosmos scheme


    It is curious that the assembly process of this particular emergency rocket is on the Roscosmos TV video. And it seems that the fatal mistake was made just then.

    I am against the defamation of these people. We love the phrase “every mistake has a last name, a first name and a middle name” and begin to dream of the strictest punishments possible, but the imperfection of our world is such that the one who does nothing is not mistaken. And it is more correct, in my opinion, to improve the processes so that the inevitable errors are trapped by subsequent checks and do not cause any harm. So most importantly, what was said at the press conference about the change in assembly operations. After 32 years, the Soyuz launch vehicles may well fly, but it is precisely this mistake that should no longer manifest itself. Also, the incident showed at least two very good things:

    • Emergency control algorithms for the descent of the Soyuz spacecraft worked correctly, despite the fact that they needed to be developed for each new onboard computer (Argon-16 appeared on Soyuz-T, TsVM-101 on TMA-M) . Soviet cosmonauts on the Soyuz-18-1 in 1975 were saved by a completely different control system.
    • The search and rescue service was also at the height despite the fact that the last time they searched for a ship that had landed in a planned area was 10 years ago when the Soyuz TMA-11 crashed into a ballistic descent upon returning from orbit.

    So in the end, with all the troubles from the accident, she showed excellent work of equipment and people, which is doubly valuable, because this work is not very noticeable in normal flight, and for decades without accidents, it is difficult to maintain readiness.

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