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ISS

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Comments

  • #62
    jogdish
    Registered Users Posts: 1,458 ✭✭✭jogdish


    Probably well known but the 'Heavens Above' app is fantastic for ISS times, can give an alert on the phone etc, well worth the small price to get the pro (no ad) version too, but otherwise is free. Also does all the other satellites to help tag something you may have seen.


  • #63
    Bsal
    Registered Users Posts: 1,766 ✭✭✭Bsal


    Got a shot of the ISS crossing the moon tonight at 1923

    51071116188_c94a172719_h.jpg


  • #64
    iLikeWaffles
    Registered Users Posts: 4,325 ✭✭✭iLikeWaffles


    Bsal wrote: »
    Got a shot of the ISS crossing the moon tonight at 1923

    51071116188_c94a172719_h.jpg

    Very nice! Tried myself but hadn't got the shutter speed low enough on a Video capture. had it at 20ms should have been 2ms.


  • #65
    Bsal
    Registered Users Posts: 1,766 ✭✭✭Bsal


    Short video I got of the ISS passing the moon

    https://www.youtube.com/watch?v=nBe89dIiIRU


  • #66
    fryup
    Registered Users Posts: 18,069 ✭✭✭✭fryup


    just show's you how fast its travelling, but of course they wouldn't feel that up there would they?


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  • #67
    jogdish
    Registered Users Posts: 1,458 ✭✭✭jogdish


    fryup wrote: »
    just show's you how fast its travelling, but of course they wouldn't feel that up there would they?
    So they are constantly accelerating, by virtue of the orbit. You feel the push back in a car when you accelerate and so do the astronauts except that push back is in exactly the opposite direction to the earths gravity (think about going around the roundabout) hence the zero g (they have two one +g and one -g =0g's).
    The other component of the velocity is constant, so no feeling of acceleration there.


    So no is the answer, assuming you don't count the zero g as feeling it.


  • #68
    iLikeWaffles
    Registered Users Posts: 4,325 ✭✭✭iLikeWaffles


    fryup wrote: »
    just show's you how fast its travelling, but of course they wouldn't feel that up there would they?

    ~28k km/hr

    7.66 km/s = 459.6km/m = 27,576 km/hr

    Need gravity to feel G force, of course.


  • #69
    jogdish
    Registered Users Posts: 1,458 ✭✭✭jogdish


    iLikeWaffles wrote: »
    ~28k km/hr

    7.66 km/s = 459.6km/m = 27,576 km/hr

    Need gravity to feel G force, of course.
    No you don't, any acceleration is the same as gravity. A rocket accelerating at 9.8ms^-1 in empty space free of gravity will feel it


  • #70
    iLikeWaffles
    Registered Users Posts: 4,325 ✭✭✭iLikeWaffles


    jogdish wrote: »
    No you don't, any acceleration is the same as gravity. A rocket accelerating at 9.8ms^-1 in empty space free of gravity will feel it

    There is no such thing, that we know as empty space free from gravity. Everything in space has gravity right down to something the size of a grain of sugar. Everything is attracting or being repelled; this is how celestial bodies form. In terms of the G-Force you would feel going around a round about, it will not be present on board the ISS, this is what I am referring to. In the weightlessness of space where the ISS orbits you are not going to feel the normal G-Force you feel on celestial bodies such as the Earth.

    In fact there should be about 0.9g felt where the ISS is orbiting but the ISS is simultaneously accelerating downward at about the same force hence weightlessness, the orbit needs a boost about every month to stop it falling back to Earth. Zero-G is not exactly 0.


  • #71
    ps200306
    Registered Users Posts: 1,589 ✭✭✭ps200306


    iLikeWaffles wrote: »
    There is no such thing, that we know as empty space free from gravity.



    The intergalactic voids come pretty close. Nearer to home there are the equipotential locations at Lagrange points.


    iLikeWaffles wrote: »
    ... the orbit needs a boost about every month to stop it falling back to Earth. Zero-G is not exactly 0.


    The boost requirement is due to atmospheric drag though, not Earth's gravity.


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  • #72
    iLikeWaffles
    Registered Users Posts: 4,325 ✭✭✭iLikeWaffles


    ps200306 wrote: »
    The intergalactic voids come pretty close. Nearer to home there are the equipotential locations at Lagrange points.

    The boost requirement is due to atmospheric drag though, not Earth's gravity.

    I didn't say it was due to Earths gravity! Lagrange points are where 2 celestial bodies exert the same gravitational pull and attraction if I recall. So no, they are not free from gravity the gravity is just equal in both directions. In terms of intergalactic voids free from gravity. Have they been measured? Are they in our Galaxy? They will still have a gravitational influence.


  • #73
    ps200306
    Registered Users Posts: 1,589 ✭✭✭ps200306


    iLikeWaffles wrote: »
    I didn't say it was due to Earths gravity! Lagrange points are where 2 celestial bodies exert the same gravitational pull and attraction if I recall. So no, they are not free from gravity the gravity is just equal in both directions. In terms of intergalactic voids free from gravity. Have they been measured? Are they in our Galaxy? They will still have a gravitational influence.
    I think jogdish's point was that if there are no net forces you will be weightless. If there are net forces you will feel an acceleration and there's no local experimental way to distinguish between different sources. Doesn't matter if you are balancing the forces centrifugally (e.g. a gravitational orbit), at an equipotential point (Lagrange) or in the intergalactic void (Newton's shell theorem).


  • #74
    OldRio
    Registered Users Posts: 5,907 ✭✭✭OldRio


    Great pass tonight about 15 mins ago. Clear sky.
    Another pass at 2250 tonight. Although it will be a lot lower. Scrub that. The pass will only last about 45 seconds. Sorry.


  • #75
    iLikeWaffles
    Registered Users Posts: 4,325 ✭✭✭iLikeWaffles


    OldRio wrote: »
    Great pass tonight about 15 mins ago. Clear sky.
    Another pass at 2250 tonight. Although it will be a lot lower. Scrub that. The pass will only last about 45 seconds. Sorry.

    Yeah, Earths shadow! "Heavens above" is great for showing when a pass will be visible. Line will just cut off to that point. My mate was caught out with an ISS transit from this. Told him he is in line for the exact centre, forgot to mention it was not a visible pass and only will be visible when it crosses the moon, so was missed. The transits when it is not visible are the hardest but also the most photogenic as you get a silhouette of the ISS instead of the reflection from the Sun.

    https://heavens-above.com/
    https://transit-finder.com/


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