• GPS launch stuttering

    From Snidely@21:1/5 to All on Sat Jul 3 02:21:44 2021
    At T+2:55 in the GPS III, the two views show a stuttering or
    stroboscopic effect.
    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>
    If just the booster camera did this, I'd guess a signal issue, but you
    can see in 2nd stage camera, below the MVac, that there's actually a
    flashing, apparently illumination of the 1st stage by the exhaust.

    I haven't seen this before. Does anyone know more about it? The MVac
    view shows the exhaust as mist before this, but the exhaust is nearly
    clear as the flashing occurs, so any stuttering of the exhaust would be
    hard to see.

    /dps

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  • From Snidely@21:1/5 to All on Sun Jul 4 16:50:47 2021
    On Saturday, Snidely yelped out that:
    At T+2:55 in the GPS III, the two views show a stuttering or stroboscopic effect.
    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>
    If just the booster camera did this, I'd guess a signal issue, but you can see in 2nd stage camera, below the MVac, that there's actually a flashing, apparently illumination of the 1st stage by the exhaust.

    I haven't seen this before. Does anyone know more about it? The MVac view shows the exhaust as mist before this, but the exhaust is nearly clear as the flashing occurs, so any stuttering of the exhaust would be hard to see.

    Okay, I'm now looking further, and for SXM-8 <URL:https://youtu.be/bgtDRR2F2wA?t=1277>
    the booster camera shows the stuttering effect,
    but the MVac has a very bright exhaust
    and the booster can't be seen from that camera.

    CRS-22 was in between ... because of the flip maneuver,
    the booster camera saw much less of the MVac startup,
    but the MVac camera showed a couple of flashes lighting up
    the top of the booster.
    <URL:https://youtu.be/QXf9mRWbXDM?t=2180>

    Transporter 2 also had a flip maneuver, but the top of the booster was
    out of sight at the edge of the MVac view. <URL:https://youtu.be/sSiuW1HcGjA?t=1032>

    Starlink (#29?) looked similar to the GPS III Vehicle 5 launch: <URL:https://youtu.be/xRu-ekesDyY?t=1119>

    /dps

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  • From JF Mezei@21:1/5 to Snidely on Sun Jul 4 20:27:54 2021
    On 2021-07-04 19:50, Snidely wrote:
    On Saturday, Snidely yelped out that:
    At T+2:55 in the GPS III, the two views show a stuttering or stroboscopic
    effect.
    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>


    1- not sure that the 2 camera s are time synchronized in the live feed. Different compression, different transmission and on gound, how they
    assemble the "broadcast" video may result in the 2 not being in phase,
    so you can't assume that a the picture on right (2nd stage) matches the
    same momet as a falsh on left (forward facing, F9).

    Having said this, at 2:46, you can see bright light get bigger on left,
    and a grey "cloud" emerge on right at same time. So the sync appears
    fairly good.

    Going frame by frame helps. (, and . ) ,,

    At 2:48, the bright light diminishes just as the grey cloud out of stage
    2 engine bell diminishes.

    But at the end of 2:48, a bright flash on Stage 1 cam (with some red),
    and no cloud from engine bell, but you can see some red inside the stage 1.

    As seen from Stage 2, the redness inside of stage 1 fluctuates and can
    be fairly bright.

    My take: exhaus from stage 2 collected into the stage 1 cavity and
    burned there with unclean burn (orange glow). The orange can be seen on
    some frames on the stage 1 camera. Once far enough away, the exchaust
    likely dispersed (less density) and more burnt so no residual flames
    inside the stage 1 cavity.
    .

    From a reusability of Stage 1 point of view, suspect they may wish to
    add some distance before firing stage II. But from an energy point of
    view, firing stage 2 that close will cause exhaust to "push" stage 1
    back and help it lose energy. Have no idea if either is a concern. Does
    any tof the stuff in the interstage/mating section get re-used. If not,
    then they don't care much of stage 2 burns it off.

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  • From JF Mezei@21:1/5 to All on Sun Jul 4 20:36:20 2021
    BTW in that video, you have good example of different synchronisation at
    Stage 1 landing where the stage 1 feed is a second or two ahead of the
    video from the ship. (was it I still love you?).

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  • From Snidely@21:1/5 to All on Mon Jul 5 14:14:38 2021
    JF Mezei is guilty of <emsEI.33017$NP.22203@fx42.iad> as of 7/4/2021
    5:27:54 PM
    On 2021-07-04 19:50, Snidely wrote:
    On Saturday, Snidely yelped out that:
    At T+2:55 in the GPS III, the two views show a stuttering or stroboscopic >>> effect.
    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>


    1- not sure that the 2 camera s are time synchronized in the live feed.
    [...]
    Having said this, at 2:46, you can see bright light get bigger on left,

    At 2:48, the bright light diminishes just as the grey cloud out of stage
    2 engine bell diminishes.

    For which video?
    [...]
    My take: exhaus from stage 2 collected into the stage 1 cavity and
    burned there with unclean burn (orange glow).

    I'm am not sure that all the samples show the orange glow being
    restricted to /inside/ the interstage. I require more convincing of
    this explanation.

    /dps

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    Well hung: curricle-hung in fact. Come sit by me and we'll test the
    springs."
    (Speculative fiction by H.Lacedaemonian.)

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  • From Snidely@21:1/5 to All on Mon Jul 5 14:18:19 2021
    Snidely speculated:
    JF Mezei is guilty of <emsEI.33017$NP.22203@fx42.iad> as of 7/4/2021 5:27:54 PM
    On 2021-07-04 19:50, Snidely wrote:
    On Saturday, Snidely yelped out that:
    At T+2:55 in the GPS III, the two views show a stuttering or stroboscopic >>>> effect.
    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>


    1- not sure that the 2 camera s are time synchronized in the live feed.
    [...]
    Having said this, at 2:46, you can see bright light get bigger on left,

    At 2:48, the bright light diminishes just as the grey cloud out of stage
    2 engine bell diminishes.

    For which video?
    [...]
    My take: exhaus from stage 2 collected into the stage 1 cavity and
    burned there with unclean burn (orange glow).

    I'm am not sure that all the samples show the orange glow being restricted to /inside/ the interstage. I require more convincing of this explanation.

    Also, you've only addressed where the glow might be, and not why it
    stutters like a pulse jet.

    /dps

    --
    "First thing in the morning, before I have coffee, I read the obits, If
    I'm not in it, I'll have breakfast." -- Carl Reiner, to CBS News in
    2015.

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  • From JF Mezei@21:1/5 to Snidely on Mon Jul 5 23:54:58 2021
    On 2021-07-05 17:14, Snidely wrote:

    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>


    I'm am not sure that all the samples show the orange glow being
    restricted to /inside/ the interstage.


    Well, the shape of the orange glow matches the area at the top of the
    Falcon 9, an area that is the forward edge of the interstage.

    There are also a couple of frames after the first very bright light
    where you see orange glow in the "metal" part on the lower portion of
    the image on left. This part is definitely near camera and definitely
    inside the interstage.

    If you look at the initial "bright light", only the inside cylinder
    lights up to fuill white, while that metal part in lower portion of
    image does not change colour.

    Then, as the second stage engine bell ceases to create itense light,
    yuou start to see orange colouring of the metal part at bottom of left
    image AS well as one small part of the piole in middle of cyclinder.
    And that point, the image from stage 1 shows stage 1 interstage is dark.

    But 2 frames later, the stage 1 view has orange that spreads quickly and brightens to white. At that point on stage 2 camera, you see the orange
    glow spread from about 2'oclose position in the falcon 9, to dark, then
    almost full orange, with, if you look carefully, the middle pole and
    "tripod" visible. (so this indicates that the glow is from behind that tripad/pole in interstage).

    Also, at that point, that lower "metal" portion on left image is mostly
    normal cllour, except for rightmost part that has bright orange glow.

    Eventually, looking at image fro stage 2, you see flashing of the
    orange glow. On the Stage 1 camera on left, this is likely affected by
    rolling shutter artifact.


    Rolling shutter: a camera's CCD doesn't campute the 12 megapixels (or
    whateer resilution) all at once. Each pixel is sensed serially. This
    takes time.

    Consider you going in a car at speed and having camera pointed to the
    side and you take picture of a tree. If the CCD goes from top to bottom,
    the tree will appear to lean forward. This is because you moved between
    the time the topmost pixels were registered and when the bottom pixels
    were done.


    In this case, the cameas scan from bottom to top (at least in the
    orientattion presented to us). My guess is that there were a succession
    of very short flashes/explosions of O2/kerosene. The camera's CCD was
    slow enough that it would capture a flahs on only a portion of image and
    by the time the CCD was finished scanning a frame, the flash had ceased
    and you could see more normally.

    For the stage 1 camera, this represents full field of vision. For stage
    2, at that point, the end of flaacon 9 from which the orange glow is
    emitted represents only a small part of its fiueld of vision, so the CCD
    scan of the part of image covering the falcon 9 takes far less time
    compared to CCD scan of the full frame.


    Also of note: initially before stage 2 ignites, you see only the loose
    wires that have just been severed. At the end, before they cut to
    another camera, the left camera also shows a wider strap flappiong about.

    So it looks to me that there was stuff from stage2 engine beel being
    thrown at the interstage area, and it ignited at first on larger bursts
    and then very short burst and then quiet.

    But it seems to me that there was "wind" in the interstage to cause the
    wires to move that way and for a flap to later show up.

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  • From Snidely@21:1/5 to All on Mon Jul 5 22:06:52 2021
    JF Mezei explained on 7/5/2021 :
    On 2021-07-05 17:14, Snidely wrote:

    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>


    I'm am not sure that all the samples show the orange glow being
    restricted to /inside/ the interstage.


    Well, the shape of the orange glow matches the area at the top of the
    Falcon 9, an area that is the forward edge of the interstage.

    There are also a couple of frames after the first very bright light
    where you see orange glow in the "metal" part on the lower portion of
    the image on left. This part is definitely near camera and definitely
    inside the interstage.

    If you look at the initial "bright light", only the inside cylinder
    lights up to fuill white, while that metal part in lower portion of
    image does not change colour.

    Then, as the second stage engine bell ceases to create itense light,
    yuou start to see orange colouring of the metal part at bottom of left
    image AS well as one small part of the piole in middle of cyclinder.
    And that point, the image from stage 1 shows stage 1 interstage is dark.

    But 2 frames later, the stage 1 view has orange that spreads quickly and brightens to white. At that point on stage 2 camera, you see the orange
    glow spread from about 2'oclose position in the falcon 9, to dark, then almost full orange, with, if you look carefully, the middle pole and
    "tripod" visible. (so this indicates that the glow is from behind that tripad/pole in interstage).

    Also, at that point, that lower "metal" portion on left image is mostly normal cllour, except for rightmost part that has bright orange glow.

    Eventually, looking at image fro stage 2, you see flashing of the
    orange glow. On the Stage 1 camera on left, this is likely affected by rolling shutter artifact.


    Rolling shutter: a camera's CCD doesn't campute the 12 megapixels (or
    whateer resilution) all at once. Each pixel is sensed serially. This
    takes time.

    Consider you going in a car at speed and having camera pointed to the
    side and you take picture of a tree. If the CCD goes from top to bottom,
    the tree will appear to lean forward. This is because you moved between
    the time the topmost pixels were registered and when the bottom pixels
    were done.


    In this case, the cameas scan from bottom to top (at least in the orientattion presented to us). My guess is that there were a succession
    of very short flashes/explosions of O2/kerosene. The camera's CCD was
    slow enough that it would capture a flahs on only a portion of image and
    by the time the CCD was finished scanning a frame, the flash had ceased
    and you could see more normally.

    For the stage 1 camera, this represents full field of vision. For stage
    2, at that point, the end of flaacon 9 from which the orange glow is
    emitted represents only a small part of its fiueld of vision, so the CCD
    scan of the part of image covering the falcon 9 takes far less time
    compared to CCD scan of the full frame.


    Also of note: initially before stage 2 ignites, you see only the loose
    wires that have just been severed. At the end, before they cut to
    another camera, the left camera also shows a wider strap flappiong about.

    So it looks to me that there was stuff from stage2 engine beel being
    thrown at the interstage area, and it ignited at first on larger bursts
    and then very short burst and then quiet.

    But it seems to me that there was "wind" in the interstage to cause the
    wires to move that way and for a flap to later show up.

    You need to specify which of the samples you are analyzing.

    You need to clarify which of the other samples support your analysis.

    /dps

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  • From Snidely@21:1/5 to All on Mon Jul 5 22:29:40 2021
    JF Mezei noted that:

    But it seems to me that there was "wind" in the interstage to cause the
    wires to move that way and for a flap to later show up.

    Since I've been watching recent EVAs, I've seen plenty of lines
    flapping outside the ISS. No wind, just an impulse imparted through an
    anchor point.

    /dps

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    Trust, but verify.

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  • From Snidely@21:1/5 to All on Thu Jul 8 01:13:41 2021
    JF Mezei noted that:

    But it seems to me that there was "wind" in the interstage to cause the
    wires to move that way and for a flap to later show up.

    Since I've been watching recent EVAs, I've seen plenty of lines
    flapping outside the ISS. No wind, just an impulse imparted through an
    anchor point.

    /dps

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    "He does very well in a suck-up, kick-down culture."
    Bill in Vancouver

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  • From Snidely@21:1/5 to All on Thu Jul 8 01:18:02 2021
    Snidely was thinking very hard :
    JF Mezei noted that:

    But it seems to me that there was "wind" in the interstage to cause the
    wires to move that way and for a flap to later show up.

    Since I've been watching recent EVAs, I've seen plenty of lines flapping outside the ISS. No wind, just an impulse imparted through an anchor point.

    Sorry for the duplication ... my noosereeder got itself into a knot.

    -d

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  • From Snidely@21:1/5 to All on Mon Nov 22 19:10:01 2021
    Snidely was thinking very hard :
    JF Mezei is guilty of <emsEI.33017$NP.22203@fx42.iad> as of 7/4/2021 5:27:54 PM
    On 2021-07-04 19:50, Snidely wrote:
    On Saturday, Snidely yelped out that:
    At T+2:55 in the GPS III, the two views show a stuttering or stroboscopic >>>> effect.
    <URL:https://youtu.be/QJXxVtp3KqI?t=1364>


    1- not sure that the 2 camera s are time synchronized in the live feed.
    [...]
    Having said this, at 2:46, you can see bright light get bigger on left,

    At 2:48, the bright light diminishes just as the grey cloud out of stage
    2 engine bell diminishes.

    For which video?
    [...]
    My take: exhaus from stage 2 collected into the stage 1 cavity and
    burned there with unclean burn (orange glow).

    I'm am not sure that all the samples show the orange glow being restricted to /inside/ the interstage. I require more convincing of this explanation.

    Heck, after some more launches to look at, including Crew 3, I guess I
    should concede.

    /dps

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    Who, me? And what lacuna?

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