Guessing the causes of the accident Falcon 9



    As you probably already heard, on Sunday, in the third minute of the flight, the Falcon 9 launch vehicle crashed with the Dragon cargo ship. The hope that the cause of the accident will be quickly found, it seems, did not materialize - despite the abundance of telemetry, video recording of the flight from the ground and cameras mounted on the rocket itself, Twitter Elon Mask on June 29 reported that after several thousand man-hours of work, the reason still unknown, and has not been updated since. The investigation seems to drag out. Therefore, you can do an exciting thing - try to guess the cause of the accident from the available public information.

    Facts


    Those who watched the broadcast saw this:



    At 2:19 flight time, a white cloud appeared in the head of the rocket. The size of the cloud spoke of a very serious accident, obviously, rocket fuel components - liquid oxygen and kerosene - flowed out. Three seconds later, in the video you can see the cone of the ship, ripped off by an unknown process and flying sideways. The first stage engines ran for another ten seconds, illuminating the cloud. And only at 2:29 a.m. the first step is lost sight of, and small fragments fly out of the formed even larger cloud.

    Here's the gif of the accident:



    Obviously, something very serious happened at the top of the launch vehicle. But the exact location is hardly possible. It is not even clear that the accident began at the second stage or on the ship itself.

    A rather fast video appeared from a different angle:



    GIF directly of the accident:



    Static picture:



    Unfortunately, additional information did not clarify the picture.

    There was still hope that the reason would be shown by the cameras on the rocket itself, but one turned off almost immediately, and the other showed a useless picture from a ripped and spinning ship (monitors from right to top):



    Enthusiasts quickly made a slow motion video:



    And the network even appeared frames from an infrared camera:



    Alas, little is visible on them, and the flash at 2:27 is already the final destruction.

    What other facts do we know? You can watch the press conference of June 28:



    And read the Mask Twitter. Curious details are mentioned there:



    Overpressure was observed in the oxidizer tank of the second stage. Data suggests an illogical reason


    Comment: From what is written, it is not clear when the overpressure appeared, and how long it lasted. With “counterintuitive” everything is very bad, it is “unexpected”, “illogical” and even “contrary to common sense”.



    After several thousand man-hours of engineering analysis, the cause is still unknown. With the help of the HEX editor, attempts are being made to extract data on the last milliseconds of flight


    Comment: If you are trying to extract data from the last milliseconds, then, obviously, the accident process went very quickly.

    Also, we made an interesting animation by placing a photo of the rocket on the visible cloud:



    Materiel




    A double trace in the region of 1:20 is a completely normal Prandtl-Glauert effect, which in this case means the rocket is approaching the speed of sound. The comment “vehicle supersonic” a few seconds later confirms the transition of the speed of sound. Two areas of visible fog are created by two solar fairings. This picture looks completely normal.



    The upper part of the second stage and the ship.



    The second stage in the assembly and test building. Photo from an older satellite launch.

    Versions


    The destruction of the oxidizer tank of the second stage due to insufficient strength . Due to a design error, a violation of production technology or careless handling in preparation for the start, the oxidizer tank of the second stage was less durable than it was necessary. In the third minute, the rocket has already passed the area of ​​maximum speed pressure, but the first stage has almost worked out, the rocket accelerated very actively. The tank could not stand it and collapsed. The version is attractive in that the destruction may not manifest itself in any way on telemetry. But a crack or hole can be detected by the rate of pressure loss.
    The destruction of the cylinder pressurization of the oxidizer tank of the second stage. It can also happen very quickly - the balloon balloon is under very high pressure and can actually explode. The fragments cut the walls of the tank and the telemetry wiring, so the accident does not have time to get into the telemetry data.
    Failure of pressurization / drainage systems . A control system error or a failed valve creates too much pressure that the second stage oxidizer tank cannot withstand. The problem is that pressure must increase extremely quickly.
    The destruction of the ship . The Dragon service module could not withstand heavier loads and break. The ship hits the top of the stage, it is destroyed. The problem is that telemetry must have time to fix it.
    Failure of the docking unit mounting system. A feature of this mission was a rather heavy docking unit in the cargo compartment of the Dragon. If it was poorly fixed, he could come off and hit the second step.
    Destruction of the adapter from the ship to the second stage . The scenario “ship destruction” repeats, only in this case the ship is not destroyed, but its fastening to the second stage.

    Conclusion


    As sources of information were used:


    On the tag "space accidents" various space disasters, accidents and incidents.

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    What do you think is the cause of the accident?

    • 21.7% Structural - they made a mistake at the design stage, for example, they incorrectly calculated the strength of the node 129
    • 33.3% Production - were mistaken at the production stage, for example, poorly made weld 198
    • 21.2% Operational - were mistaken in preparation for the start, for example, they were hit during transportation 126
    • 23.7% Other - aliens, special services, sabotage, eccentric birthday present Mask - all come here 141

    Which version do you like more?

    • 33.9% Second stage oxidizer tank failure due to insufficient strength 154
    • 18% destruction of the cylinder pressurization of the tank oxidizer of the second stage 82
    • 8.3% Failure of boost / drain systems 38
    • 8.8% Ship Destruction 40
    • 12.7% Failure of the docking unit mounting system 58
    • 11% Destruction of the adapter from the ship to the second stage 50
    • 7% Other (in comments) 32

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