Comments by "H. de Jong" (@h.dejong2531) on "Rockets in a Vacuum Chamber - Newton's third law of motion Visualized" video.

  1.  @Nehner  Earth still isn't flat.
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  2. I can see satellites pass overhead with the naked eye, proving space is real. I can use simple experiments to prove Earth is a moving sphere.
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  3. 10,000 successful satellite launches demonstrate that propulsion does work in a vacuum.
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  4.  @papalegba6796  The pressure inside the combustion chamber is tens to hundreds of bars, not zero, obviously.
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  5. Rockets ARE used in zero gravity and zero atmosphere all the time. Every orbital rocket launch ends in zero gravity and zero atmosphere.
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  6. Every single one of Newton's laws of motion and gravitation has been extensively tested and found to be valid, i.e. we know he wasn't lying about any of those.
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  7. Experiments like Cavenish's torsion balance prove that any two masses attract each other.
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  8.  @papalegba6796  The laws of physics, like Newton's third law, which says rockets work in a vacuum? Or Einstein's general relativity, which describes gravity?
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  9.  @papalegba6796  There is nothing in the laws of thermodynamics that says rockets can't work in a vacuum. There is nothing in the laws of thermodynamics that says our atmosphere cannot exist next to a vacuum.
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  10. ​ @papalegba6796  The temperature in the combustion chamber is thousands of degrees, so Q is not zero. The pressure in the combustion chamber is hundreds of bars, so P is not zero, which means W is not zero.
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  11. Have you ever had satellite TV, or known anyone that has/had satellite TV? That's made possible by satellites orbiting at 36,000 km, ie far higher than 500 miles. Those satellites were put there by rockets, proving there is no dome.
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  12. What proves propulsion is possible in space is the 10,000 satellites we've launched successfully.
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  13. The term "infinite" vacuum is meaningless. A vacuum chamber on Earth can get the pressure down to 10E-6 Pa, which is similar to the pressure found at 400 km altitude. Rocket tests on Earth are done at a pressure of about 0.1 Pa. The difference between that and a vacuum is 0.1 Pa, i.e. very small. Drawing down to a lower pressure than 0.1 Pa does not change the test result noticeably.
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  14. 10,000 successful satellites operating in space prove that Newton's laws do work in a vacuum.
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  15.  @papalegba6796  Of course internal pressure is relevant. The work done by the gas is proportional to its pressure.
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  16.  @papalegba6796  The work is done in the combustion chamber, so we have to use the pressure in the combustion chamber for the calculation. Basic physics, but that's far beyond a parrot like you.
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  17.  @papalegba6796  No, the Work formula does NOT specify that the pressure has to be external. In fact, we use the pressure at the point where the work is done, i.e. in the combustion chamber of the rocket. I predict you will ignore this and keep lying, instead of conceding that you were wrong.
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  18. When a Falcon 9 launches, it starts out with a mass of 550 tons. The first stage pushes 395 tons of propellant out the back at a speed of 3 km/s, accelerating the remaining 155 tons to a speed of 1.6 to 2.2 km/s (depending on flight profile and payload). The second stage repeats this, pushing 92 tons of propellant out the back at a speed of slightly over 3 km/s. We don't have to prove propulsion in a vacuum chamber, you can just look up to see the results of a rocket launch.
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  19. No, he doesn't prove that at all. He only proves it's difficult to test a rocket in a vacuum chamber.
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  20. When you launch a rocket, part of it ends up on the ocean floor: the first stage. The second stage achieves orbit, along with the payload. We have successful measurement of curvature going back centuries. Every single geodetic survey in history shows that Earth is curved, not flat. Even observations as simple as looking at the horizon while a ship goes over the horizon demonstrate that Earth cannot be flat.
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  21.  @papalegba6796  Ignoring the evidence doesn't make you right.
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  22. Forward momentum is independent of atmospheric pressure or a magnetic field. As Newton predicted: objects continue to move in a straight line when no force works on them. Rockets don't hit a "dome", they achieve orbit. You can see satellites with the naked eye. You can measure their speed and altitude from the ground, and find that they are in space.
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  23.  @jareddavis4980  I'm saying I don't just "think" it's 400 km: that 400 km is not a guess. I know it's 400 km because that is the value I measured.
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  24. Amateurs carry out these tests in small vacuum chambers because that's what they can afford. NASA and other space agencies test their rocket engines in much larger chambers, which are designed to extract the exhaust gases so the chamber stays a vacuum during the test.
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  25.  @papalegba6796  Newton's first law: A body remains at rest, or in motion at a constant speed in a straight line, unless acted upon by a force. When you run a rocket engine, fuel and oxidiser are mixed in a combustion chamber, then ignites. This increases the pressure in the combustion chamber, producing a force in all directions. The force components to the sides of the chamber cancel each other out. The force on the front of the chamber is not canceled out because the back of the combustion chamber has a hole. This imbalance creates a net force pushing the rocket forwards.
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  26.  @papalegba6796  So you'd rather stay dumb than learn something? Yeah, that does not surprise me.
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  27.  @papalegba6796  You didn't quote anything. You just made a false assumption.
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  28.  @pantheraleoromanus6241  The difference between 10E-17 Torr and 0 is negligible when you are talking about systems influenced by pressure.
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  29.  @gilqueiroz  Every orbital launch reaches true space. Every year, satellites are launched to geostationary orbit, above the van Allen belts. India just demonstrated landing on the moon, again.
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  30.  @gilqueiroz  NASA tested its rocket engines in a vacuum chamber before launching. They built a chamber that can maintain a vacuum while a rocket is running, see e.g. the Plum Brook station In-space Propulsion Facility.
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  31. NASA does not lie. Every day, you use services provided by satellites. You can see satellites with the naked eye, and verify that htey are in space.
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  32.  @jareddavis4980  Most satellites are larger than basketballs. In LEO, typical weights are on the order of a ton, and they have several square meters of solar panel. In the evening, when the sun has set on the surface but LEO is still sunlit, those satellites are easily visible to the naked eye. With nothing more than a photo camera, I can measure the distance to those satellites and prove they are at least ten times higher than any balloon has ever been, proving those satellites are not suspended from balloons. Once I have the altitude, a few more photos prove those satellites move at a speed of 8 km/s, i.e. orbital speed, which can only be achieved by a rocket working in a vacuum.
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  33.  @jareddavis4980  I don't think I can see satellites, I know I can, because I've done it. With the naked eye you can't resolve a satellite, but it reflects enough light to be visible to the naked eye. And with a photo camera and some math, I can measure their altitude: they're at 400 km and higher, proving they are not hanging from a ballon: no balloon has ever been that high. I can also measure their speed. At 28,000 km/h, satellites move a hundred times faster than any balloon has ever been. So, simple observations anyone can do prove that satellites are in space, not in our atmosphere.
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  34.  @jareddavis4980  The "battery" on the Voyagers is a radiosiotope thermal generator. Plutonium decays and produces heat, and this heat is converted to electricity. When the Voyagers were launched, the Pu on board produced more than 4 kW of heat, which was converted to 470 W of electricity. Pu-238 has a half-life of 88 years, so after 88 years the heat output will drop by 50%. At the moment, the RTG still produces more than 250 W of power. The antenna on the Voyagers has a beam width of about 0.5 degree. At a distance of 15 billion km, even a beam that narrow covers most of Earth's orbit, which means the Voyagers don't have to adjust their antenna to track the Earth during the transmission. We're able to lock onto that signal because we use an antenna with a diameter of 70 meters, with a received cooled to 4 Kelvin. See? information trumps incredulity every time.
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  35.  @jareddavis4980  That is nonsense. I don't think satellites are at 400 km altitude, I know because I can measure that with enough accuracy to know that they're not at 40 km altitude but ten times higher.
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  36.  @jareddavis4980  No, I can treat the satellite as a point source. I'm doing parallax measurements: for the altitude, I take two photos from positions a few km apart (at the same time), and I measure how the position changes relative to the background stars. For speed, I can then take two photos with a known interval between them and measure how the position changes relative to the background stars. Scott Manley has a video that shows how to do this.
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  37.  @jareddavis4980  Just using synchronized watches you can get within one second. And it's not that hard to calculate the error introduced by that.
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  38.  @jareddavis4980  Yes. We can get a lot closer than one second though. Several options are available: 1. use a transit. e.g. the satellite passing in front of the sun or the moon. 2. use the transit of the satellite into or out of Earth's shadow 3. more accurate options to synchronize the cameras: a countdown gets you within a few tenths of a second, electronic means can give a time difference several orders of magnitude smaller.
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  39. Every time a spacecraft approaches or leaves the ISS, you can see them using thrusters to maneuver.
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  40.  @alexanderbreston9918  The ISS is in space. We can measure its speed and altitude from the ground: take two photos of the ISS at the same time from different locations, and you can use parallax to measure its altitude. Take two photos a known time apart, and you can calculate its speed. We find that the ISS is at an altitude of 400 km and a speed of 8 km/s. Anything flying at 8 km/s in our atmosphere glows like a meteor, the ISS doesn't do this, proving that it is not in our atmosphere. Another indication that it's not in our atmosphere is that the ISS keeps flying for years on end, without constantly using engines.
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  41. Solid rocket motors contain both fuel and oxidiser. You can run them in a vacuum, or under water.
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  42. I can prove you wrong just by looking at the sky. I can see satellites pass overhead.
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  43. Anyone can prove space is not fake, just by looking up at night. Satellites are visible to the naked eye.
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