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I read that when the Apollo 11 spacecraft reached the earth's orbit then the engines burnt to initiate TLI(Trans-Lunar Injection) which increased the speed of the spacecraft to 24,500 miles per hour, this happens so the spacecraft overcomes the earth's gravity. When you convert this speed to meter per second then you get 6800 meters per second which means the astronauts were controlling an object that was covering 7 kilometres per second. If this holds then they didn't need three days to travel to the moon. The distance from the earth to the moon is 384, 400 kilometres. If you divide the speed the astronauts were moving at from the Trans-Lunar injection with the distance to the moon's orbit then you get roughly 15 hours to get to the moon. Its also not possible to control an aircraft moving at that speed. How do you defend that?

user51882
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If you divide the speed the astronauts were moving at from the Trans-Lunar injection with the distance to the moon's orbit then you get roughly 2288 days

I believe you've confused seconds for hours. 384000 km / 6.8 km/s = 56470 seconds, which is less than a day. The trajectory is not a straight line towards the moon, and slows as the altitude above Earth increases, just like if you throw a ball up into the air, so it takes about three days to meet the moon.

Its also not possible to control an aircraft moving at that speed.

Apollo is not an aircraft. You can't control a car moving at 500 mph, but airplanes routinely fly at such speeds. How do you defend that?

Speed is not really a significant factor in controlling an object moving through space. There's essentially nothing to hit, there's no wind to blow you off course, and the distances are so great that there's plenty of time to make adjustments.

Control of a spacecraft is a cycle of determining where you are and where you're going, comparing that to where you want to be, and making the necessary corrections. For Apollo, ground-based radar stations tracked the spacecraft to determine its position and trajectory, and the spacecraft used either its main engine (for large corrections) or its smaller thrusters to correct its course. The radar tracking was very accurate, and the position of the spacecraft when it entered lunar orbit didn't need to be exact, so Apollo 11 (for example) only needed to make one course correction, about one day into the flight.

Russell Borogove
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  • if its less than a day, why did it take them three days? – user51882 Aug 08 '23 at 17:44
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    Because the trajectory is not a straight line, and the trajectory slows as the altitude above Earth increases, just like if you throw a ball up into the air. – Russell Borogove Aug 08 '23 at 17:49
  • according to the technology available then(1969), is it possible to control an object moving at that speed? – user51882 Aug 08 '23 at 17:52
  • we are talking about seven miles per second? even the laws of Physics frown at such. That is like faster than the blink of an eye – user51882 Aug 08 '23 at 17:55
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    I've edited my answer to explain a little bit about guidance and control. The laws of physics work just fine at seven miles a second. – Russell Borogove Aug 08 '23 at 18:02
  • what about the Van Allen radiation belt, how did the astronauts survive that? – user51882 Aug 08 '23 at 18:05
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    The spacecraft's trajectory was inclined so as to avoid the densest part of the Van Allen belt, and they passed through the belt very quickly. They did pick up a fair dose of radiation, which may have contributed to later health problems, but this was considered an acceptable risk. – Russell Borogove Aug 08 '23 at 18:15
  • I accept your answer but I highly doubt that the computer technology used to control that spacecraft existed in 1969 even before the micro chip was invented – user51882 Aug 08 '23 at 18:19
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    Electronic computers have existed since the 1940s. They were certainly larger and slower in the 1960s than they are today, but the computations needed for control of a spacecraft are actually not that complex, and they had plenty of time to do them. – Russell Borogove Aug 08 '23 at 18:20
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    That said, you are falling prey to the fallacy of argument from incredulity. – Russell Borogove Aug 08 '23 at 18:21
  • The computers actually doing orbital calculations were on the ground. Houston took the radar data, calculated the necessary adjustments on the big room-sized machines, and the only thing they transmitted back was the output of that process, which is just a fairly brief instruction to fire for some amount of time in some direction. The onboard system in the capsule wasn't nearly so capable, its only job was to keep the ship pointed in the specified direction relative to the gyros and keep time. – Darth Pseudonym Aug 08 '23 at 21:32
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    @DarthPseudonym your claims in this comment are incorrect. Houston also uplinked REFSMMATs and other data to the AGC. The AGC was capable of much more than just pointing the ship. https://www.sciencedirect.com/science/article/pii/S147466701768772X – Organic Marble Aug 09 '23 at 00:56
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    @OrganicMarble REFSMMAT is "point this direction" data. It's not a complex navigational calculation being performed on orbit. I was probably over-exaggerating, but my point is that the AGC was not making computations for navigational activities like correction burns. If I remember correctly, most of what the AGC was doing was just tracking current position and speed so it could show it to the pilot just in case they lost contact with Houston. – Darth Pseudonym Aug 09 '23 at 04:17
  • The fuel they packed for the whole journey was also not enough for the visit and return journeys. We are talking about 400, 000 miles here. – user51882 Aug 09 '23 at 05:15
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    @user51882 Oh, did you do the math on that? – Russell Borogove Aug 09 '23 at 10:21
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    @user51882 Margaret Hamilton was director of the Software Engineering Division of the MIT Instrumentation Laboratory, which developed on-board flight software for NASA's Apollo program. A famous photo of Margaret with the printout of the Apollo software she developed with her team – PM 2Ring Aug 09 '23 at 12:52
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    @user51882 I'm sure you think you're asking incisive, hard-hitting questions but all everyone else is hearing is "I have absolutely no idea how any of this works, but my ignorance trumps your knowledge so checkmate" and frankly I'm amazed anyone is still taking you seriously. – Shadur-don't-feed-the-AI Aug 09 '23 at 17:53
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    @user51182 Your core error is that you understand absolutely nothing about orbital mechanics and are thinking in terms of a terrestrial journey. Your assumptions are failing because of all the ways the former is not like the latter. – Shadur-don't-feed-the-AI Aug 10 '23 at 16:17
  • The trajectory is not a straight line towards the moon, and slows as the altitude above Earth increases, just like if you throw a ball up into the air, so it takes about three days to meet the moon. This is not true because there is no friction in space. A ball moving up the air will eventually stop due to being acted on by forces of friction and gravity but the Translunar Injection itself is for overcoming gravity and when an object is in space it continues in that direction unless acted upon by an external force. – Dong Li Aug 12 '23 at 17:09
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    @DongLi Gravity is still in effect. Earth's gravity is what keeps the Moon in a circular orbit, and the same gravity steadily slows the spacecraft from the end of the translunar burn until it reaches the point at which the Moon's gravity is more significant than the Earth's. – Russell Borogove Aug 12 '23 at 20:03
  • Then in that case, The TLI is not needed to overcome gravity. What are we overcoming with TLI if that gravity influences the spacecraft up to the lunar orbit? – Dong Li Aug 13 '23 at 03:47
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    Everything in space is always influenced by gravity to different degrees. The force of gravity is reduced by the square of the distance between any two masses. Think of getting into low Earth orbit as throwing a baseball ten feet into the air, and getting to a lunar intercept as throwing a baseball one hundred feet into the air. – Russell Borogove Aug 13 '23 at 06:04