Business, Space, Technology and Society

The “Hard Landing” On The Ship

34 Comments

Elon has been tweeting some video grabs.

[Update a while later]

Here’s the video.

34 thoughts on “The “Hard Landing” On The Ship”

  2. “Residual fuel and oxygen combine ”

    That’s never a good thing when it happens outside the combustion chamber. Very bad things happen very quickly.

    My company made the grid fins for SpaceX. I don’t know about the hydraulic system controlling the fins but I don’t think we did that.

    1. They hydraulic system was fine. The problem was that the company that made the hydraulic fluid didn’t make quite enough.

    1. Is that the first rocket stage to be launched twice? Because that explosion sure propelled it over the side in a hurry.

  5. Rand, perhaps you can answer the question of exactly how the control is done. I’ve heard the term ‘control vane’ tossed about, and to me that is a thrust vectoring system like the V-2 used. Others like above are talking about fins, but at low speeds fins have no control authority.

    2. Remember that the recovery of a spent first stage will look nothing like the gentle flights of the Grasshopper and F9R out at McGregor. Those test vehicles were ballasted with excess fuel, but a nearly empty first stage cannot come even close to hovering as it weighs less than half the thrust of a single throttled-down engine, making such a landing that much more difficult. It’s as if you are hurtling down hill, coasting toward a brick wall in a car with an engine that can only be throttled between 70% and full power, and you somehow manage to slip your transmission into reverse, and have to decide the precise moment to pop the clutch to start burning rubber and then control your engine to bring your car to a stop with the bumper barely touching the wall. (And that’s only considering the z component. They also need to be on target and level.)

      The point is that they decelerate at over 2G from when they first start the landing burn until the moment they touch down, so there will be a good amount of airflow over the fins until the last couple of seconds.

  6. That video was awesome. It did hit the deck but it wasn’t vertical nor was the speed low enough. Shame.

    Maybe next time.

  7. I’m confused:

    They say they ran out of hydraulic fluid to control the waffle vanes…..

    But my impression is that those vanes matter only in fast flight.

    How are the “……engines fights to restore, …”?

    Differential engine power?
    gimbaling but no hydraulic fluid to point the engines?

    1. Musk’s tweet says fins go hard over. That will have an effect even at slow speeds, the engine (singular) gimballed to compensate but it ran out of altitude. And trying to right the rocket would require a strong horizontal vector when a strong vertical vector was needed to brake for touchdown, thus the hard landing.

      1. Eric, thanks for the explanation.

        Are the engine gimbals powered hydraulically with the same fluid as the waffle fins?

        Or something else?

        1. Something else. A portion of the pressurized RP-1 fuel out of a Merlin engine’s turbopump powers its hydraulics, with the spent fluid routed back to the low pressure inlet of the pump.

  8. That video was more than awesome, it was like a sequence from an action movie!

    What I took away from it is that the rocket made it to the ship, and while it came in fast it was close. I think next time has a high chance of being a proper landing.

  9. I was struck by how stable the ship was. If practicing for land, that’s a good thing, but it’s not taking full advantage of what a ship gives you… movement. The rocket was not coming in too fast to be caught by a moving ship with the proper netting. Then they would not need to be either perfectly vertical or perfectly stationary.

    They’ll figure it out without my observations. A great success!

  10. OK, so I saw that video of the thing “coming in” on the network TV news.

    It didn’t exactly crash, but it was more than a crump. A crump is when one of those Harrier jets sets up a hover, ingests exhaust gas and loses power, and then stops hovering and pancakes in, collapsing the landing gear. “Chief! I crumped your Harrier jet!”

    This thing made it to the barge, but it was tilted from vertical and translating sideways until, dunno, it contacted the barge, resulting in what they call “mixing of the residual fuel and oxidizer.”

    I am getting to wondering a little bit here given the cautious-but-successful test flights of the DC-X, that is, until they turned it over to NASA who crumped it.

    Yes, with enough practice they may get this right, but I am kind of wondering about the Soviet N-1 moon rocket — what did they run, like four launch attempts before they blew up the pad and the Politburo pulled the plug on the whole thing?

    I will give them a failed initial attempt, and Corona-Discoverer failed at various things, attempt-after-attempt with President Eisenhower offering, “Trust me, this thing is important, keep at it and don’t give up.” But do they have good telemetry, and do they have good people that they are not going to have rocket stages careening across the landing barge, time after time.

    Do they know what they are doing? Do they have a test stand or a test range to test this capability incrementaly?

    1. This is how they test it.

      They’ve made numerous low-speed, low-altitude flights where the Falcon takes off, hovers, and lands. They now need to test the full flight envelope, and the easiest and cheapest way to do that is to… test it with real commercial flights.

      I didn’t even expect them to reach the barge on the first attempt. That they got so close to a successful landing is quite amazing, and it looks like they would have been successful if they could have controlled the fins all the way down.

      1. I come to your fine site for much of my news, especially about aerospace. I don’t always agree 100% with your opinions, but I respect the effort and resources you put into this.

        Why am I scolded?

  11. So, I am not being scolded, instead, I am in effect being called ignorant and a liar because that describes people who speak based on incomplete along with false knowledge?

    And I am being called all of this not for making any assertions, but simply for asking questions, asking for you and your informed readers to share with me views on where SpaceX lies on the continuum of “launch and pray if we weren’t Communist atheists” of Korolev’s N-1 program and the perhaps too cautious-careful DC-X program?

    So a person cannot ask honestly posed not-intended-for-snark questions around here without being criticized for showing ignorance?

    1. Paul, I cannot imagine how you can think that I or anyone called you a “liar.” I guess I don’t even understand your questions. I’m not even sure there is such a continuum.

    2. Paul, I don’t think anyone here wants to insult you or make you feel unwelcome. You have read alot into people’s comments that is not there. I had the same reaction to your post as Rand, and a few others as well. When it is suggested you haven’t been paying attention, it is based from the perspective of many people here who have been watching SpaceX closely for over a decade. Spacex has talked a big talk over the years , and to a large degree, they have walked the walk. (not as fast, or per their own schedule , as many would have liked). They have been very open of there plans for reuseability, and that has been a stated goal of their ambitious CEO. Most posters here are aware of SpaceX’s test facilities for rocket development, as well as their admirable methodology of learning from flying. SpaceX does indeed test and model their spacecraft, but they have a much lower threshold to decide when it time to cut metal and put their machines into the sky. That is where most of us give them our admiration. When you come off as unknowing of there history, business practices, and goals, you haven’t been paying attention enough to comment as you did to this audience.

    3. Paul, the important thing to realize about these tests is that the marginal cost is rather low. The rockets are going up anyway to launch satellites. That means it’s ok that they fail (after staging), since each test only need to lead to a little learning to pay its way.

      The Soviet N-1 example, on the other hand, had tremendous cost per attempt. There was nothing else paying for each launch.

  12. After all the videos of the grasshopper flight tests in Texas and the couple of Falcon flights where the stage hovered briefly above the water before engine shut off what exactly do you propose that SpaceX does inthe way of incremental testing that they aren’t already doing, Paul?

  13. Hey! SpaceX deliberately chose not to have a “show” before each launch any more. They can’t then be upset that people have no idea wtf is going on. If you’re going to forsake educating the public, don’t be surprised when the public is uneducated.

    1. Whether there’s a show before a launch or not, their test-flight program could, and has garnered plenty of publicity. Including the loss of their test vehicle last summer.

  14. They certainly are getting coverage these days. I watched an interview with Elon Musk, about 20 minutes before the launch, while I was having breakfast in London Heathrow.

  15. And btw, I have since talked to other people and the flight profile makes sense given the maximum efficiency approach they are using, high deceleration at the last moment to minimize gravity losses. That makes the aerodynamic control vanes effective unil very near the end.

  16. I’m wondering how close they came to totalling the drone ship. The stage kind of “skipped” on the deck, didn’t plow right in. How much does one of those cost, anyhow? And can they replace it by the next launch a month later if need be?

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