An update on the Falcon 9 landing attempt

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Link here.

Lots of interesting details describing the entire first stage landing attempt. Two interesting facts: 1. The barge was not seriously damaged by the landing crash and will be ready for the next attempt. 2. It appears they will try for a barge touchdown again instead of on land.



  • Cotour

    Is it me or does that little barge look much too small for that big rocket?

  • The linked article, along with a number of other articles, don’t seem to be entirely explaining what went wrong with the landing. Yes, there was a valve which was responding slowly. But it landed upright, turned off its engines, and then remained upright for a few seconds before toppling over. It wasn’t that it landed with its center of mass over the fulcrum line between two feet. Rather, it tipped exactly in the direction of the rightward foot (as seen from the deck view) and, just before exploding, we get an ever so brief view of that leg which the rocket was tipping over. That leg is no longer deployed down but has retracted back up by about half of its deployment yet its pneumatic tube is still well in place. In other words, that otherwise intact leg was not functioning right for some reason. All joints seem to be working fine. If the pneumatic tube had continued working I think that the rocket wouldn’t have fallen over or exploded. So, what was the problem with that pneumatic tube. A sticky valve indirectly? Inquiring minds want to know.

  • Gealon

    My understanding is that the sticking valve caused the computer to wait for it, slowing down the reaction time of the motors. You can see in the last second or two before touch down, the engine gimbals to one side, but remains there way too long and tips the rocket to the opposite side. Just as it’s touching down the engine swings back the other way to try and correct this but it too slow in it’s response. You can see that the rocket doe not land vertically and the reason it remains upright for as long as it did was because the computer knew the rocket was not upright and was using the nose RCS jets to try and correct even after the main engine was shut down. The RCS though did not have enough power to keep the rocket upright and it toppled off of the barge.

    Hope that helps.

  • Gealon

    And sorry to reply to myself, I neglected the point about the landing leg. I think if they di address it specifically at all, it won’t be found to be a defect in the leg, it is more likely the leg was damaged by how roughly the rocket came down as the legs are a fairly simple mechanical system. It’s retracted/semi deployed appearance is most likely due to a mechanical breakage between it and it’s drive cylinder during the landing. The vehicle leaning to that side would naturally fold the leg back up against the body as they are hinged at the bottom.

    I would go on to speculate that this was a safety feature/design simplification, as if the legs were hinged at the top they would put stress on a section of the vehicle that isn’t intended to support that kind of stress and would also require an extending mechanism so that after they unfold they would protrude further down then the engines do. The bottom hinging eliminated both of those problems by simply having the legs fold down farther then the engines. I don’t think it alarming that this mechanism failed, the rocket did crash on the deck after all. I think it is just a simple case that the landing exceeded what the leg could withstand and it broke.

  • pzatchok

    I have just watched the loopof the deck camera of the landing.

    Those three jets of smoke coming off of the top of the rocket do not look like the RTS system.

    They look more like venting valves letting off excess pressure from something.

    They look way to weak to do any good as a stabilizing system. Not at all like small rockets.

    And from what I understand the RTS system is just for stopping the rotation of the rocket during final decent. And they are on the bottom of the rocket.
    The grid fins are on the top to do pretty much the same thing but at far higher speeds. They would have no effect at slower speeds.

  • Gealon

    Here, try this one:

    You can see the RCS firing and the gimbaling motion of the main motor as the stage comes show and looks like it sweeps across the barge during landing.

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