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Thread: The space flight thread

  1. #131
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    Anyone walking on the moon is a little fishy to me still. Heres my question, why not go back? Some say because there is nothing there? Some say because we dont have the technology to force our way through the highly highly radioactive Van Allan Belts. If the tech isnt here yet in damn near 2020, then in the 50's it wasnt even a thought in anyones mind. Also, didnt china get caught faking their last SPACE WALK? Some underwater facility is where they shot that. That is why IMO america isnt covering it really well. Probably faking.... why not everyone else does right?

  2. #132
    Verified VCDS User PetrolDave's Avatar
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    Quote Originally Posted by RBgonzo View Post
    Anyone walking on the moon is a little fishy to me still.
    What I don't understand is why doesn't someone independent from NASA with a decent telescope point it at the locations on the moon where the LEMs landed and take pictures of the bottom half of the LEMs to prove they are there?

  3. #133
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by PetrolDave View Post
    What I don't understand is why doesn't someone independent from NASA with a decent telescope point it at the locations on the moon where the LEMs landed and take pictures of the bottom half of the LEMs to prove they are there?
    Do earth-based telescopes have sufficient resolution to pick out objects on the lunar surface that are only a few meters across? I'm really not sure.

    The single most compelling bit of evidence that the moon landings were not faked is from Russia. The period between 1969 (Apollo 11) and 1972 (Apollo 17) was during the height of the Cold War. The Soviets had invaded Czechoslovakia during the summer of 1968. There was a proxy war going in Vietnam. And of course, there was the whole "space race" between the USA and the USSR. The Soviets gave up a manned moon landing after repeated launch failures of their N1 rocket, but there is no doubt that they had pretty decent space tracking capabilities. Heck, they managed to retrieve lunar soil samples themselves using robotic probes starting in 1970. In any case, you can bet that the Soviets were tracking the US Apollo missions and listening in on every word, and that they would have called us out right then and there if those transmissions had not come from the published trajectories of the Apollo spacecraft or the surface of the moon.
    Last edited by Uwe; 07-14-2018 at 10:14 AM. Reason: typo
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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  5. #134
    Verified VCDS User PetrolDave's Avatar
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    Quote Originally Posted by Uwe View Post
    Do earth-based telescopes have sufficient resolution to pick out objects on the lunar surface that are only a few meters across? I'm really not sure.
    I'd be surprised if telescopes like those at Mauna Kea aren't powerful enough?

    https://www.ifa.hawaii.edu/mko/

  6. #135
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by PetrolDave View Post
    I'd be surprised if telescopes like those at Mauna Kea aren't powerful enough?
    https://www.ifa.hawaii.edu/mko/
    Doing a bit of digging into this, it seems that the best earth-based telescopes have a resolution of approximately 0.5 arcseconds. This limitation is primarily due to turbulence in the atmosphere. The Hubble space telescope avoids this by being above the atmosphere and its resolution is limited to about 0.1 arcseconds by the diffraction limit of its objective mirror diameter.

    The distance to the moon is ~400,000 km, or ~400,000,000 meters.

    Now my geometry is a bit rusty, but from shooting sports, I know that 1 minute of arc is ~2.5 cm at 100 meters. That would be 2.5 meters at 10,000 meters, right? So one minute of arc would be 2.5 * 40,000 m at the distance of the moon, and one arc-second at the distance of the moon would be ~1,667 meters. This means a ground-based telescope would have a resolution of ~833 meters at the distance of the moon, and the Hubble would have a resolution of ~167 meters at the distance of the moon.

    Doing a quick reality check on my back-of-the-envelope calculations:
    http://www.wolframalpha.com/input/?i...d+at+400000+km
    That number (6362 feet / 1939 meters) for one arcsecond is a bit higher than mine, but in the same ballpark.

    The Lunar Excursion Modules are listed as 9.4 meters in width in Wikipedia.

    So nope, telescopes can't actually see them.
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

  7. #136
    Verified VCDS User PetrolDave's Avatar
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    Quote Originally Posted by Uwe View Post
    So nope, telescopes can't actually see them.
    Oh well, another "great idea" bites the dust

  8. #137
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by PetrolDave View Post
    Oh well, another "great idea" bites the dust
    I apologize for raining on your parade. But I find it humbling to realize just how poor our perception, i.e. our ability to see things in detail across astronomical distances is, and it explains why there's no substitute for physical exploration, either in person or at least via some sort of robotic probe.

    BTW, the 1939 vs. 1667 meters discrepancy was bugging me, so I pondered it a bit. It's cumulative rounding error, primarily due to my off-the cuff conversion between imperial and metric units. The marksmen's rule of thumb for one MoA (Minute of Arc) is actually one inch at 100 yards. Well one inch is 2.54 cm, and 100 yards is only 91.44 meters, which means it's more like 2.78 cm at 100 meters. Plugging that back into calculations above gets me 1852 meters / arcsecond at the distance of the moon. The rest seems to be one more rounding error in the rule of thumb itself. One MoA at 100 yards is actually 1.047 inches. Multiplying the most recent 1852 meters by 1.047 gets me 1938.9 meters, which I'll call spot-on.
    Last edited by Uwe; 07-14-2018 at 01:11 PM. Reason: typo
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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  10. #138
    Verified VCDS User PetrolDave's Avatar
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    Quote Originally Posted by Uwe View Post
    I apologize for raining on your parade.
    Progress is only achieved by throwing out theories and some get proven but many more get shown to be wrong - so I'm happy for you to show my thinking was flawed

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