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Thread: Rockets need an atmosphere to propel. There's no air in space.

  1. #31
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    I think i see rocket hunter’s point in testing rockets in a vacuum chamber which fills with smoke. So we need a different test to show the truth of the ejected mass explanation. A rocket final jet shape does develop pressure of the expanding hot gases and particles when in the vacuum of space, just as it does in an atmosphere. So the rocket thrust is a combination of mass ejection and pressure difference in both cases. The error is in assuming a sudden chemical generation of hot products needs atmosphere to cause forces. A plie of black powder from a firework can be ignited and it explodes or combusts very fast, pushing hot products out regardless of atmospheric pressure. The evidence form these explosions was no doubt the inspiration for rockets and if you work on rockets you soon discover the importance of the shape of the exit nozzle to help control the burning reactants. This little conspiracy is afailure tounderstand both physics andengineering.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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  2. #32
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    Quote Originally Posted by rockethunter View Post
    At the end vacuum is present? Even with all that smoke visible? He opened the chamber and you could see the smoke come out
    After he opened the valve to allow the vacuum to dissipate.

    ETA, Yes the smoke escaped when the end was removed.

    Additionally I'll ask again a direct question what experiments have you done to satisfy your belief. Again what did you measure? This is a third request.
    Last edited by bknight; 2019-Mar-13 at 01:02 PM.

  3. #33
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    Out of curiosity I started analyzing the first video. It is really pathetic.

    If you are holding up a 5kg mass that otherwise would fall to the ground, you are applying a 50 newton force upward against it, and simultaneously applying an equal and opposite force against the ground with your feet. That adds to the force of your body weight and would show up if you were standing on a scale. When you let go of the object, those equal and opposite forces go away and the force applied to the ground by your feet simply reduces to your body weight alone.

    It gets worse. In the example of the buoyant object immersed in water, she is just playing fast and loose with words and numbers in a technically incoherent babble. She doesn't even give the volume of the object to show where some of the numbers come from. She makes no effort to show just how the opposing forces function in this type of system.

    I could go on but it is not worth the trouble at this point. I have seen enough to be confident in my opinion that this video is not a reliable source for proper guidance in learning the pertinent points of physics.

  4. #34
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    Quote Originally Posted by rockethunter View Post
    Rockets needs an external resistance to push off of and there is no such resistance in space. There is no equal and opposite reaction from gas movement due to pressure gradient force. For those who think they know all about Newton's 3rd law, watch this first before commenting. https://www.youtube.com/watch?v=AubI...ature=youtu.be
    rockethunter

    You say there is no air in space. How do you know? If, as you claim, rockets can't work in vacuum, then either we never sent a rocket there, or it isn't a vacuum. Please present the evidence and the data showing there is no air in space.
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  5. #35
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    Quote Originally Posted by rockethunter View Post
    Do you have any proof of this? When I dead lift 100kg (I am 75kg) and I drop it from a height, do I get lifted off the ground. Because that is basically what you are saying.
    No, I already explained this to you. When you drop something, YOU don't accelerate it so YOU don't feel a counterforce. Earth's gravity accelerates it, so earth feels a counterforce.

    Take that same barbell, put on rollerskates (be careful) and throw it violently horizontally in front of you. You will notice a force pushing/rolling you backwards.

  6. #36
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    Oh and by the way, when you are talking about rockets not throwing solid objects out: true, but mass is mass. And they throw out an ENORMOUS amount of gas mass at enormous velocity. Saturn V had an empty weight of 130 tons and a full weight of 3000 tons. Allowing for 50 tons of payload, that's roughly 2800 tons of fuel and oxidizer expelled as gas thrown out at velocities between 2.5 and 3 km/s. Enough mass and acceleration for you?

  7. #37
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    Quote Originally Posted by Nicolas View Post
    Oh and by the way, when you are talking about rockets not throwing solid objects out: true, but mass is mass. And they throw out an ENORMOUS amount of gas mass at enormous velocity. Saturn V had an empty weight of 130 tons and a full weight of 3000 tons. Allowing for 50 tons of payload, that's roughly 2800 tons of fuel and oxidizer expelled as gas thrown out at velocities between 2.5 and 3 km/s. Enough mass and acceleration for you?
    And the fuel and oxidiser react to make a lot of energy to accelerate that mass as hot particles and gases. A rocket is an engineered burn directed in mostly one direction.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  8. #38
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    Quote Originally Posted by Nicolas View Post
    Take that same barbell, put on rollerskates (be careful) and throw it violently horizontally in front of you. You will notice a force pushing/rolling you backwards.
    This brings to mind a necessary consequence of arguing that thrust must be due solely to pushing against ambient air. If that were the case in the rollerskating exercise, I think we would expect to see similar results whether we're throwing a basketball, a feather pillow, or a 75 Kg dumbbell, as long as each has the same air resistance and we throw them at the same velocity. But we don't see that, of course.
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  9. #39
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    Very good point.

  10. #40
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    Quote Originally Posted by Hornblower View Post
    Out of curiosity I started analyzing the first video. It is really pathetic.

    If you are holding up a 5kg mass that otherwise would fall to the ground, you are applying a 50 newton force upward against it, and simultaneously applying an equal and opposite force against the ground with your feet. That adds to the force of your body weight and would show up if you were standing on a scale. When you let go of the object, those equal and opposite forces go away and the force applied to the ground by your feet simply reduces to your body weight alone.

    It gets worse. In the example of the buoyant object immersed in water, she is just playing fast and loose with words and numbers in a technically incoherent babble. She doesn't even give the volume of the object to show where some of the numbers come from. She makes no effort to show just how the opposing forces function in this type of system.

    I could go on but it is not worth the trouble at this point. I have seen enough to be confident in my opinion that this video is not a reliable source for proper guidance in learning the pertinent points of physics.
    Out of continuing curiosity I gritted my teeth and watched it to the end. The buoyancy in water segment and the remaining presentation were variations on the pressure gradient theme. At the end it displayed a Flat Earther web address. If I had somehow had any remaining doubts about my opinion, that would have clinched it.

  11. #41
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    Quote Originally Posted by Hornblower View Post
    Out of continuing curiosity I gritted my teeth and watched it to the end. The buoyancy in water segment and the remaining presentation were variations on the pressure gradient theme. At the end it displayed a Flat Earther web address. If I had somehow had any remaining doubts about my opinion, that would have clinched it.
    Bad physics all the way around.

  12. #42
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    rockethunter's idea works for leg thrust. Legs thrusting/pushing downward (aka Jumping) are pushing against the earth propelling the body up, but floating in space legs thrusting/jumping doesn't work too well as there is next-to-nothing to push against. A rocket launch (jump) isn't thrusting/pushing against the earth as legs do but rather the thrust is pushing against the rocket making it "jump". Unlike legs, rockets work well in space to get around, no earth required.........The Mr. Rogers version ;-)

  13. #43
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    Fun fact: if you'd thrust your legs so violently in space that your knees would fail and shear right off, your lower flegs flying off into space would generate an equal and opposite force on your now seriously maimed body. It's all about expelling mass, be it barbells, exhaust gasses, or severed limbs.

  14. #44
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    Quote Originally Posted by rockethunter View Post
    Experiments in ...
    Crank videos such as Rockets Cannot Propel In Space with an obvious "There is zero evidence of rockets in space" lie as a description are not science disproving fundamental physics (Newton's third law).

    The lie is obvious. There is enormous amount of evidence of rockets in space.
    We have tracked at least dozens of spacecraft moving through space using rockets.
    We record spacecraft moving through space using rockets, e.g. ISS supply missions.
    We record astronauts moving through space using rockets, e.g. ISS EVA missions.
    We put machines on other planets with spacecraft moving through space using rockets, e.g. Curiosity on Mars.
    We have put people on the Moon with spacecraft moving through space using rockets.
    We have returned samples from space with spacecraft moving through space using rockets. Sample return missions from the Moon, a comet, an asteroid and the solar wind.
    The OSIRIS-REx mission should return samples rom an asteroid in 2023.
    Personal accounts of astronauts in rockets in space starting with Yuri Gagarin. We can ignore the launches - how do astronauts return from space if their rockets have no air to push against, rockethunter?

    ETA: How did the Apollo astronauts get to and return from the Moon with their personal accounts, photos, videos, Lunar samples with parts and photos of the Surveyor 3 probe by Apollo 13? How did we bounce lasers off a reflector on a Lunar lander for decades if it is impossible to get to the Moon?
    Last edited by Reality Check; 2019-Mar-14 at 12:28 AM.

  15. #45
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    Quote Originally Posted by PetersCreek View Post
    This brings to mind a necessary consequence of arguing that thrust must be due solely to pushing against ambient air. If that were the case in the rollerskating exercise, I think we would expect to see similar results whether we're throwing a basketball, a feather pillow, or a 75 Kg dumbbell, as long as each has the same air resistance and we throw them at the same velocity. But we don't see that, of course.
    Throwing is not the same thing as gas movement due to pressure gradient force. When you want to move gas from one room from another, you can't push it, you have to use pressure gradient force.
    https://www.shodor.org/os411/courses...pgf/index.html

  16. #46
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    Quote Originally Posted by profloater View Post
    I think i see rocket hunter’s point in testing rockets in a vacuum chamber which fills with smoke. So we need a different test to show the truth of the ejected mass explanation. A rocket final jet shape does develop pressure of the expanding hot gases and particles when in the vacuum of space, just as it does in an atmosphere. So the rocket thrust is a combination of mass ejection and pressure difference in both cases. The error is in assuming a sudden chemical generation of hot products needs atmosphere to cause forces. A plie of black powder from a firework can be ignited and it explodes or combusts very fast, pushing hot products out regardless of atmospheric pressure. The evidence form these explosions was no doubt the inspiration for rockets and if you work on rockets you soon discover the importance of the shape of the exit nozzle to help control the burning reactants. This little conspiracy is afailure tounderstand both physics andengineering.
    The nozzle shape only causes extra pressure differential, that is all.

  17. #47
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    What's your point? when a container holds pressure it applies force in all directions. When pressure is released that force is also released. Just like the force of the 5kg weight is released when you let if go.

  18. #48
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    Quote Originally Posted by rockethunter View Post
    I believe I have experimented to my satisfaction. There is no other proof, other than NASA fake video footage, of rockets working in a vacuum.
    Hello rockethunter,

    Regarding other evidence, could you please explain how you believe spacecraft and satellites that I have tracked and viewed from my own yard got into space if not for rockets? (Which, of course, anyone with fair vision and access to a dark sky can also view with a little effort).

    Or the satellites that make GPS, satellite TV service, sat phones, satellite emergency beacons, etc. possible?

    And is there some reason you're focusing in NASA, considering all the other visual evidence from other space agencies and non-government sources? (SpaceX, for example).

    Thanks.

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  19. #49
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    Quote Originally Posted by rockethunter View Post
    There is no equal and opposite reaction from gas movement due to pressure gradient force.
    Could you please explain, in your own words, what you believe is the relevance of the pressure gradient force to the function of a rocket? Thanks.

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  20. #50
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    Without pressure gradient force, the high pressure in the rocket wouldn't move outside the rocket chamber.

  21. #51
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    Quote Originally Posted by rockethunter View Post
    Without pressure gradient force, the high pressure in the rocket wouldn't move outside the rocket chamber.
    Pressure doesn't move. Mass moves.

  22. #52
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    Under Pressure

    Quote Originally Posted by rockethunter View Post
    Without pressure gradient force, the high pressure in the rocket wouldn't move outside the rocket chamber.
    Not bad. At least we can agree that hot gases leave the ignition chamber via the rocket nozeat at a high temperature and a high velocity, right? 'Yes' or 'No' is good enough.

    Thanks, John M.
    Last edited by John Mendenhall; 2019-Mar-14 at 01:51 AM. Reason: typo
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  23. #53
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    Quote Originally Posted by rockethunter View Post
    Without pressure gradient force, the high pressure in the rocket wouldn't move outside the rocket chamber.
    Then are you saying that the pressure of gas leaving a rocket must be at least as high as ambient pressure?

    Why would this be an issue for a rocket working in vacuum? Obviously gas pressure will be above ambient.
    Last edited by Van Rijn; 2019-Mar-14 at 02:32 AM. Reason: clarification

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  24. #54
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    rockethunter, how did the Curiosity rover get to Mars through the vacuum of space?
    This is an example of the many probes we have sent outside of the Earth's atmosphere using rockets.
    Last edited by Reality Check; 2019-Mar-14 at 03:13 AM.

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    Rockethunter:

    I am still wondering whether you think it's possible or not for a person to build a vacuum chamber here on Earth. Yes or no?

    Assuming you answer "yes" to the above question, are you under the impression that NO ONE over the past 70 years had ever thought to test your idea in a vacuum chamber here on Earth? Do you really think that YOU are the very first person to ever think of this?

  26. #56
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    Quote Originally Posted by rockethunter View Post
    What's your point? when a container holds pressure it applies force in all directions. When pressure is released that force is also released. Just like the force of the 5kg weight is released when you let if go.
    How many more times do we have to explain this very basic concept?

    -if YOU accelerate something (throwing an object horizontally, accelerating gas out of a rocket nozzle...) YOU feel the force.
    -if EARTH GRAVITY accelerates something, EARTH feels the force. Not you.

    By the way, this principle needs Newton's second law (F = m.a) to explain why there is a force in the first place, and Newton's third law (equal and opposite reaction) to explain why the force felt by object 2 accelerating mass 1 is in the opposite direction of the acceleration.

    Newton's third law is about equal and opposite forces. What it means is that when you hold a 10kg (100N) item up with your arm, that item is pulling down with 100N on your arm. End result = balance of forces, proven by the fact that the arm and the object do not move. If you simply let go of the object, you do not apply any force on the object and the object does not apply any force to you. So your arm will still not move. And this example is totally irrelevant for rocket motors. Rocket motors do not just ever so gently let go of their exhaust masses, they expel them at large velocity. Welcome Newton's laws: by accelerating a mass (the exhaust gasses) in one direction (towards the back of the rocket), you generate a force (thrust) in the opposite direction (towards the front of the rocket).

    If you want to prove rockets don't work, you'll have to come with examples that are at least relevant to rockets and disprove Newton's laws. Just repeating the same example which is not relevant for what a rocket does AND still abides by Newton's laws anyway if you interpret it correctly, is not helping your case no matter how many times you repeat it.
    Last edited by Nicolas; 2019-Mar-14 at 08:48 AM.

  27. #57
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    But seriously, how easy do you want it to be to prove that Newton's laws do not need air resistance?

    -sit on a good skateboard on a smooth floor, throw away a cannonball. You'll roll backwards.
    -sit on that same skateboard, throw away a balloon as large as the cannonball with the same velocity. You will not roll backwards. Same air resistance as the cannonball (same shape and size), but far less mass.

    (You actually can still do this test wrong if you fling your arms foreward too much. You'll have to do it using rotation of your wrists only for the best results.)

    Alternative test for those not willing to hurl cannonballs:
    put a spring in a tube. Put a golf ball (or steel ball if you have one) inside. Have a simple locking mechanism that compresses the spring and then holds it there. Mount horizontally with a scale behind it. Let go the locking mechanism and measure the peak on the scale. repeat with a balloon as large as the golf ball. You'll measure far less force.

    You can imagine countless such tests in which you accelerate 2 objects of same shape and size but vastly different mass. Same air resistance, different force. Ergo: Newton's laws are not simply a case of air resistance.
    Last edited by Nicolas; 2019-Mar-14 at 09:05 AM.

  28. #58
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    I see lots of arguments about pressure, pressure gradient force and so on. You do realize that, on a molecular level, pressure is nothing else than a mass at speed impacting an object and as a result (due to Newton's second and third laws) exerting a force on that object? Just like you can explain a wing's lift by talking pressure or by talking Newton's laws, any explanation using pressure is in fact an explanation using Newton's laws. As long as you say pressure exists, Newton's laws exist.

    But OK, let's talk pressures.
    Situation 1: at launch. Rocket engine's combustion chamber: 200 bar. Outside: 1 bar.
    Situation 2: in space. Rocket engine's combustion chamber: 200 bar. Outside: 0 bar.

    So actually, there is even MORE pressure gradiŽnt in space than in the atmosphere. Do tell me, how is that a bad thing?

  29. #59
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    Quote Originally Posted by rockethunter View Post
    The nozzle shape only causes extra pressure differential, that is all.
    No the rocket has a hole at the back releasing combustion products but not at thefront! The nozzle design directs a large fraction backwards where a hole would waste expansion sideways. The rocket generates pressure in that way and by ejecting mass it has a reaction force. This has little to do with the outside pressure, be ause as pointed out, it is many times less than the nozzle pressure.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  30. #60
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    Quote Originally Posted by rockethunter View Post
    I believe I have experimented to my satisfaction. There is no other proof, other than NASA fake video footage, of rockets working in a vacuum.
    Here is my footage completely independent of NASA or SpaceX, showing the Falcon Heavy boosters turning around and reversing their direction while at around 100 km altitude in a vacuum:
    https://www.youtube.com/watch?v=z5K7HKFkZ8o
    Here is additional footage from a Russian amateur astronomer of a geostationary satellite being inserted into orbit:
    http://russianspaceweb.com/images/sp...expressam8.gif
    The telescope is tracking it based on its transfer orbit and the satellite is rapidly accelerated out of the view when the engine is lit to insert it into its final orbit.

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