Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Calculating distance, object speed, etc - RE:Falcon9

  1. Sep 4, 2016 #1
    This deals with photography more than anything so I wasn't entirely sure which forum it's best suited for, hopefully Astronomy is semi-suited.

    September 1st saw the static test fire of the Falcon9 rocket. Wherein, a reported anomaly in the upper stage o2 tank caused a catastrophic failure, explosion of the vehicle, which destroyed its payload, the AMOS6 Satellite.

    Original Footage (best/closest view of explosion)

    Official updates from Space-X


    If you look at the footage of the explosion and freeze frame it just as it happens, you will notice an unidentified object above the space vehicle. It enters from the right side of the screen, and exits shortly after, the explosion happens just as reaches vertical positioning over the rocket.

    There are a flurry of accusations and hypotheses floating around, about whether or not the object is related to the incident. I was hoping someone might be willing to calculate the size and speed of the object, as it would provide valued insight into the incident. Calculating the size/speed/etc will most likely falsify/validate some ideas floating around.

    Because of an obvious lack of data, it's very hard to make many conclusions on the video, and the object itself. One idea is that not only did it pass by the rocket, but made a 180 and returned up behind the explosion.

    Highlighted here in this GIF: https://gfycat.com/MeatyFrigidGalah

    I was hoping someone can help calculate the size and the speed of the object. A rough calculation of the sound delay, puts it at 4 Kilometres away. Though it might not be very accurate.

    The launch was at SLC-40 (they are currently modifying 39a to continue operations)


    I've been trying to locate the exact position of the http://www.uslaunchreport.com camera, but Im not entirely sure of the accuracy. Here are two different screen caps of the surrounding area, one with Google Earth laying out a 4-5 KM radius. I'm not entirely sure what is/isn't off limits, because the group that films it are veterans, they might have access to areas others don't.



    Any help would be greatly appreciated. To note Im not looking for any opinions on the validity of the hypothesis, or debunking, or arguing its validity or anything like that. Simply looking for some math to deduce exactly what the object may or may not be, to find out its speed, size etc.

    Thank you in advance for any help.
  2. jcsd
  3. Sep 4, 2016 #2


    User Avatar
    2017 Award

    Staff: Mentor

    I'll discuss where to put this thread with other mentors.

    You cannot calculate the speed without knowing the distance to the camera.
    What about a fly close to the camera?
  4. Sep 4, 2016 #3
    A fly would not be seen. Just like you don't see dust on your eye.... it's more than 2 miles away (this can be judged by the sound travel delay), so by default it's a telephoto lens (my guess is 200mm+ waiting on a reply from the channel) -- with the field of view so distant, and focus set to infinity, you'd see no flies or bugs. In fact, you can see what appears to be that (in comparison to a wide-angle lens for instance), but those are likely birds, in close range.

    The object does not appear like the previous "bugs" (see: birds) and it cannot be a bug, since if it was, we'd all be walking around blind as bats (no pun intended). Basics of field of view, depth of field, explain this. As for calculating it all, Im just bad at math.
  5. Sep 4, 2016 #4


    User Avatar

    Staff: Mentor

  6. Sep 4, 2016 #5


    User Avatar

    Staff: Mentor

    Seeing the slow-mo, it looks to me like a bird that is somewhere between the camera and launch pad.
  7. Sep 4, 2016 #6


    User Avatar
    2017 Award

    Staff: Mentor

    Fly, bird, same thing: much closer to the camera than the rocket. It doesn't look very focused, which is additional evidence that it is smaller and close to the camera.
  8. Sep 4, 2016 #7


    User Avatar
    Science Advisor
    Gold Member

    No it doesn't. It happens earlier, as can be readily seen if you play with freeze-frame carefully:
    This is silly, but I'm going to play along.
    Judging from the sound delay, the camera is about 4.5 km away. Using the rocket as measuring stick, the scene is approx 150m across.

    Now, taking all the silly talk at a face value, and assuming the 'object' is passing just by the rocket (i.e., same distance from the camera), and seeing how it takes the 'object' approx. 1/2 of a second to cross the screen, we would have to deduce it's moving at almost 1 Mach (even though it's not flying straight, almost as if it was... flapping its wings?).

    However, it then makes a sudden turn, in what looks like about 0.1 seconds, and flies in the opposite direction, again crossing the width of the screen in about 1/2 of a second. So, if we are to keep our assumption about it being roughly collocated with the rocket, we also need to conclude that the UFO can make turns with acceleration on the order of 6000g.

    On the other hand, if we were to assume it's, oh I don't know, a butterfly maybe - with its typical flight speed on the order of 3 m/s, it would have to be flying around at a distance of 45 metres in front of the camera, where the field of vision spans approx 1.5 metres from side to side.

    Or, maybe it's a sparrow? At 9m/s, it'd be flying 'round 150m mark.

    You'll have to show some calculations for that. For example, using this handy calculator here:
    and the default settings for the camera, I get DoF in front of the rocket to extend to a little over two metres from the camera. I.e., only objects closer than that would be unfocused, which is nowhere near as far as either of the distances calculated for a bird or a bug.

    Anyway, there's plenty of identical looking UFOs in the video, and they all look like flying animals.
  9. Sep 5, 2016 #8


    User Avatar

    Staff: Mentor

    I think we're done here.

    Thread closed.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook