SpaceX Falcon 9 historic landing thread (1st landing attempt & most recent missions)

Discussion in 'The Watering Hole' started by georgegassaway, Dec 11, 2014.

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  1. Dec 6, 2018 #3121

    OverTheTop

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    Rotational rate decreased when the legs deployed (see my earlier comment), but the angular momentum is still almost identical. That is the energy that needs dissipating. A little drag plus greater authority of the CG thrusters over the gridfins (getting less effective) got them there in the end. That's what I think. The CG thrusters should have the same moment available as long as they are fed with the same gas pressure, regardless of altitude, to a first-order approximation. Less mass due to fuel use during the landing burn probably factors into the equation somewhat also.
     
  2. Dec 6, 2018 #3122

    Ben Martin

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    Gas powered RCS thrusters have a lower ISP (efficiency) and thrust at sea level due to the gravitational force and the properties behind the thruster system. I agree with you that the reduced weight greatly helped and the video makes it evident that the landing gear had a substantial impact on the rotation. My guess is that the lowered velocity, decently efficient RCS thrusters, higher moment of inertia and more drag are what slowed the roll down and stabilized the booster for landing.
     
  3. Dec 6, 2018 #3123

    Marc_G

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    Also, as it approached landing, the amount of fuel remaining approached zero and thus lowered the mass of the booster making it easier to slow the spin.
     
  4. Dec 6, 2018 #3124

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    I said that earlier too :p.

    It will be a little dependent on how much swirl was induced in the fuel during spin, and how much internal anti-slosh baffling there is in the tank to couple the fuel rotation to the tank structure. There is likely a time delay in both directions to some extent to this effect.
     
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  5. Dec 7, 2018 #3125

    georgegassaway

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    Article on recovery efforts on the Falcon booster:
    https://www.americaspace.com/2018/1...-floating-falcon-9-rocket-off-cape-canaveral/

    some photos:
    [​IMG]

    [​IMG]

    [​IMG]

    Musk claimed yesterday that SpaceX would launch this rocket again, for SpaceX payloads. I'll believe that when I see it, but don't really expect to see it. At the least it's going to need a new interstage (black area at top, a carbon-fiber structure). Interstage is badly broken along one side, probably from when it fell over and hit the water.
    Enlargement from above photo:
    [​IMG]

    One of the legs was recovered by one of the support ships, no info on whether it broke off, or if it was purposely removed by divers today to reduce the draft so it can be towed into Port Canaveral. In the photos, you can see air bags attached to two of the legs, to help keep it from rolling over due to the mass of the leg up in the air while there's no leg to counterbalance it under the water.

    A video of the reentry burn, loss of grid fin control, and landing in the ocean, from US Launch Report. Seems like the exact same angle but shown four times at four magnification levels. This is the first clear ground-based view of how much wobbling it did once the hydraulic pump quit and the fins lost control then locked up.

     
    Last edited: Dec 7, 2018
  6. Dec 7, 2018 #3126

    manixFan

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  7. Dec 7, 2018 #3127

    Marc_G

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    Do we know yet why the pump failed, based on telemetry data?
     
  8. Dec 7, 2018 #3128

    georgegassaway

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    The pump "stalled". No info on what data lead to that conclusion. Now, some said one fin quit but all of the fins stopped wherever as the pump failed.

    But this morning it did finally occur to me how one grid fin mechanism MIGHT have led to a stall of the pump. If something mechanically failed with the grid fin bearings to cause far more friction to rotate than normal, or anything within the hydraulic actuators/lines jamming up for whatever reason. That could have made the pump try to pump far harder than it was designed to handle. Not saying that is that I think happened, just the possibility of how one grid fin problem might have led to an overall pump failure that took everything out.

    Fortunately, with the retrieval of the booster mostly intact, they'll have an easier time trying to pin that kind of thing down than if it had crashed at 300 mph into the ocean and sank.

    And it is being brought into Port Canaveral today. Apparently they are moving (or have moved) the landing barge OCISLY from its regular dock location. So they can bring the booster in to lift it with the cranes normally used for picking up boosters from OCISLY to the dock, and later to rotate horizontally onto the transport trailer.

    Photos by John Kraus
    [​IMG]

    [​IMG]
     
    Last edited: Dec 7, 2018
  9. Dec 7, 2018 #3129

    georgegassaway

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    Annnd, it's at the dock. They left OCISLY in place, tying up alongside it.

    Photo by Tom McCool

    [​IMG]
     
  10. Dec 8, 2018 #3130

    Peartree

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    From Twitter:


    Full Story here
     
  11. Dec 8, 2018 #3131

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    On December 07, 2018 while departing Port of LA on a cruise I was surprised to see this from the stateroom balcony. Falcon9OnBarge_20181207.jpg
     

    Attached Files:

  12. Dec 8, 2018 #3132

    SpaceManMat

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    Guess they used the central post that pushes the 2nd stage away to lift rather than the interstate itself.
     
  13. Dec 9, 2018 at 1:38 AM #3133

    georgegassaway

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    CRS-16 booster back on land, 3 days later than intended.
    Photos by Ken Kremer
    [​IMG]

    One engine bell got badly bent up. Scott Manley mentioned it probably got bent by the "missing" leg, when that leg came off. The leg apparently was removed on purpose (port is probably too shallow otherwise), not as a result of the water landing.

    [​IMG]

    Two EXCELLENT videos by Tim Dodd (Everyday Astronaut), and Scott Manley



     
    Last edited: Dec 9, 2018 at 1:45 AM
  14. Dec 9, 2018 at 7:31 AM #3134

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    There is a nice patina developing on those engine bells :(.

    Hopefully there is only mainly surface corrosion and they can fly the thing again. Good learning exercise anyway. Having the recalcitrant hydraulic system available for autopsy is priceless information for the future.
     
  15. Dec 9, 2018 at 7:25 PM #3135

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  16. Dec 9, 2018 at 11:42 PM #3136

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    A very impressive Photoshop....

    [​IMG]

    ..... Except that even more impressively, that is REAL.

    As told by photographer Ken Kremer:

    "2 Marvels of Technology and ships passing at sea- Floating #SpaceX#Falcon9 arriving and USS Indiana nuclear sub departing Port Canaveral & Jetty Park Pier. United States Navy. Soaring to Space and Submerging at Sea. #USSIndiana. "

    [​IMG]
     
  17. Dec 9, 2018 at 11:56 PM #3137

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  18. Dec 10, 2018 at 12:46 AM #3138

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    I met Ken Kremer earlier in the year in Titusville and purchased some pics off him. Nice guy, and a good photographer!
     
  19. Dec 10, 2018 at 6:44 PM #3139

    georgegassaway

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    Iridium-NEXT launch that had been scheduled for Dec 30th has slipped to Jan 7th.

    So, last launch scheduled for this year is USAF GPS III-1 on December 18th from Vandy (an expendable launch due to the need for maximum performance to use up fuel needed for landing. So the recent hydraulic problem for landing won't require a fix).

    That one would make it 21 launches for this year. Last fall SpaceX announced 28 for 2018. I think I said at the time I didn't expect more than 24 based on past overoptimistic launch schedules vs actual flown.

    Interesting graphic showing how many spacecraft are docked/berthed with ISS, CRS-16 the newest arrival:
    [​IMG]

    A computer 3D image:

    [​IMG]
     
    Last edited: Dec 11, 2018 at 2:52 AM

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