Video of Long March 2C grid fins used in July


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China Central Television has released a very short video showing the grid fins used during the July 26 launch of China’s Long March 2C rocket in order to better control the descent of that rocket’s expendable first stage.

I have embedded the video below the fold. It shows the four grid fins unfolding, but not much else. It also reveals that the Chinese very clearly were inspired by SpaceX’s Falcon 9 grid fin design.

The video also gives me the impression that the Long March 2C first stage does not have any thrusters, which were SpaceX’s primary mode for controlling its first stages, the grid fins added later when they understood better the engineering required. Thus I suspect that the fins were not very successful in controlling that stage’s flight.

Nonetheless, the Chinese are doing these tests during operations, which means they are only a first step on a path to success.

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6 comments

  • Max

    Wow! After watching the video, Mr. Zimmerman’s comments were extremely kind to what we are witnessing. Grid fins that do not move or guide the ship, their only function is to simply fold out. I actually laughed out loud at what I saw and was embarrassed for the Chinese.
    The most surprising thing, that I haven’t seen used in 60 years, is exposed rivets! Very sloppy workmanship, not modern at all. Further illustrated later in the video of the rivets popping as the skin bubbles. These stages will not be able to land if they come apart during reentry. A massive redesign is necessary if they want to reuse the Rockets.
    No engineering has been performed for this purpose, only to put the payload into space without any concern of where the booster falls or recovery. Designed to be disposable.

    I love the comparison to SpaceX in the video, smooth skin with responsive thrusters and guidance system engineered for pinpoint landings.
    Then the Chinese grid fins, that seem to be for the only purpose of propaganda. A fake mock up installed as an afterthought. Ridiculous.
    I can’t help but notice the “ram” material on the skin (radar absorption material) that was used on early stealth craft. The orange peel skin has a long known ability to make water and aircraft have less friction. (The shark is the fastest swimmer in the ocean and has rough skin, and the divots in a golf ball work for the same reason)

  • Max: I am quite sure that they plan no reuse of these stages. They are simply trying to control where they land so that they will no longer threaten inhabited regions.

  • Chris Lopes

    In any case, it’s a start. Also keep on mind that people were mocking Soviet technology and workmanship right up until Sputnik. Just because they don’t do it like we do, that doesn’t mean they are “backward”. After all, they can put people in orbit, a capability NASA does not currently possess.

  • MDN

    I was struck by the riveted construction too. I thought I was looking at a tower on the Golden Gate bridge.

    That said, simple is not necessarily bad and as a state run enterprise they don’t need to be especially efficient, just successful. And for the purpose of not crashing into populated villages it will likely suffice. I wonder how much this stuff reduces their payload capacity though? Given the construction technology I suspect the system isn’t particularly light, and the exposed rivets and unshrouded grid fins must impose some pretty serious aerodynamic drag.

  • Edward

    From the video: “We didn’t designate a land area when we designed the test. … The distance of the landing site from the theoretical site (was) in a range of two to three kilometers.

    This tells me that they did not intend (design) the test to guide the spent stage to a specific place, but that they had a general idea of where it should fall. I suspect that this test was only to determine whether the fins would deploy and were controllable, as well as to determine their effect on the rocket’s performance, which is probably much more than the effect of the aerodynamic drag of the rivets. Clearly, they did not attempt to guide the stage to a specific location.

    It is similar to SpaceX’s first Falcon 9 reentry test. SpaceX did not attempt to land it on anything but only attempted to relight an engine or three to see if they could get the rocket to zero velocity as it reached the ocean’s surface. They learned quite a bit about what happens during reentry, including the unexpected spin-up of the vehicle and the resulting starvation of the engine as propellant moved up the side of the bottom of the tanks due to centrifugal action. It was this test that informed them that the grid fins were necessary for control (and perhaps for guidance) in the atmosphere.
    https://en.wikipedia.org/wiki/Falcon_9_first-stage_landing_tests#Flight_6

  • Dick Eagleson

    Watch the video again, Max. The grid fins are functional. One of them is briefly shown rotating and the video repeats this bit of footage several times.

    As for concerns about aerodynamic drag of rivets and the grid fins themselves, as an object approaches Mach 3 the boundary layer expands quite a bit – well beyond the height of rivet heads and probably even of the grid fins in their stowed position. In their extended position, of course, the grid fins extend beyond even the hypersonic boundary layer or they couldn’t do their jobs.

    The late sci-fi author Jerry Pournelle used to tell the story about how Boeing lost the XB-70 contract to North American because the Boeing entry in the competition used an expensive flush riveting system to make the exterior of its design as smooth as possible. The North American design was rougher and even had some external antennas. North American knew about the expansion of the boundary layer at high speeds and took advantage of it. NA knew this because it had built the X-15. Boeing had never built or flown a heavily-instrumented hypersonic testbed before. I think the only supersonic project Boeing had ever done, up to that point, was the Bomarc long-range anti-aircraft missile and it flew at Mach 2.5.

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