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Post by rmc on Jun 14, 2020 12:51:05 GMT
Okay, this IS going to have to have elements of opinion involved. But, I think there is some science too. Who knows? It may even involve a sort of myth that declared Armstrong was the best lunar lander pilot, and that HIS landing was spotless.
So, basically, who did pilot the NASA Lunar Laner the best? Which landing was best?
Naturally, one would likely assume Armstrong, since he was first. And, because he had alarms to contend with, ... so on and so on. Plus, each additional lander would be modified and tweaked based upon the findings from the previous landing. Making each subsequent landing "easier and safer"...
Or would it?
In some way, each was going to the moon for the first time (for themselves at least). Was there a best landing other than Armstrong's? Or, did NASA truly select the best pilot and commander to go first?
Just a topic other than what's seen here recently.
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Post by the light works on Jun 14, 2020 14:28:52 GMT
you know, it's something I've never considered. I don't even have a dataset to compare performance of lander pilots.
of course, all of the landings meet the basic criteria for both good and great landings - with the qualification that each lander was a single-use vehicle.
(a good landing is one you can walk away from - a great landing is one in which you can reuse the vehicle)
so first, we'd need to establish criteria. the obvious three are how accurately the pilot landed in the target site, how gently the craft touched down, and how much fuel was left in reserve.
but do you know where we'd find data on the landings?
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Post by wvengineer on Jun 15, 2020 13:04:41 GMT
I don't know about the rest, but the Apollo 11 landing was far from perfect. At lot of it was simply due to the fact that it was something that no one had ever done before and noone fully knew what to expect. It is a historic and amazing achievement, but the Apollo 11 landing was far from spotless. 1. There were repeated computer error due to the computer getting backlogged with work.* ** 2. The access tunnel between the LEM and command module was not completely evacuated prior to disconnect. When they separated, the air popped the LEM off harder than expected and the added momentum changed the descent rate by a very small, but important amount. 3. The Moon's gravity was not fully understood. People thought that the moon center of gravity would be in the middle like earth. Turns out it is not, it is a few thousand miles towards earth. This changed how the moon pulled on the lander at different points during the descent. 4. Due to 2 and 3, they missed the targeted landing zone. They ended up going into a much rockier area with larger boulders. They had to maneuver around some to avoid them. 5. Due to 2, 3, and 4, they used more fuel than expected. They were well into their fuel reserve. They had less than 20 seconds of fuel left when they touched down. * www.discovermagazine.com/the-sciences/apollo-11s-1202-alarm-explained** For Apollo 12 and later, the memory in the computer was increased from 12 to 24 kilowords to prevent the same issue. |
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Post by the light works on Jun 15, 2020 14:22:22 GMT
I don't know about the rest, but the Apollo 11 landing was far from perfect. At lot of it was simply due to the fact that it was something that no one had ever done before and noone fully knew what to expect. It is a historic and amazing achievement, but the Apollo 11 landing was far from spotless. 1. There were repeated computer error due to the computer getting backlogged with work.* ** 2. The access tunnel between the LEM and command module was not completely evacuated prior to disconnect. When they separated, the air popped the LEM off harder than expected and the added momentum changed the descent rate by a very small, but important amount. 3. The Moon's gravity was not fully understood. People thought that the moon center of gravity would be in the middle like earth. Turns out it is not, it is a few thousand miles towards earth. This changed how the moon pulled on the lander at different points during the descent. 4. Due to 2 and 3, they missed the targeted landing zone. They ended up going into a much rockier area with larger boulders. They had to maneuver around some to avoid them. 5. Due to 2, 3, and 4, they used more fuel than expected. They were well into their fuel reserve. They had less than 20 seconds of fuel left when they touched down. * www.discovermagazine.com/the-sciences/apollo-11s-1202-alarm-explained** For Apollo 12 and later, the memory in the computer was increased from 12 to 24 kilowords to prevent the same issue. so bsed on that, I would say Apollo 11 should be in a class by itself. then the other landers, which had the benefit of the information from 11, could be compared on who piloted the landing the best. as for #3: are you saying that they assumed the moon's gravity would be just the moon's ACTUAL gravity, but that the moon's APPARENT gravity was affected by its relationship with earth's gravity? or are you saying the actual center of mass in the moon is offset? an offset center of mass would explain why the moon is tidally locked. either would explain an unexpected trajectory. |
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Post by wvengineer on Jun 15, 2020 15:45:55 GMT
The center of gravity is not in the center of the moon. It is towards the earth. It has to do with how the moon formed. In the early day, the moon was much closer to the earth and this pulled the center of mass in that direction. Over the last few billion years as the moon has slowly drifted away, the mass of the moon has moved more towards the geometric center of the moon, but it is still off by a noticeable amount. Yes, this does play into why the moon is tidally locked with earth. www.intechopen.com/books/lunar-science/on-the-deviation-of-the-lunar-center-of-mass-to-the-east-two-possible-mechanisms-based-on-evolution-In 1969, this was only barely understood. It wasn't until Apollo 15 and 16 used laser altimeters from orbit that they finally had the needed data and even then it took until the 90's to really understand what was really going on within the moon. They did a good job of accounting for the Earth's gravity. How that offset affected Apollo goes back to your college physics. F=G*M1*M2/R^2. While in orbit of moon, this results in gravity being different in different parts of the orbit. Basically the gravity doesn't always pull at the same rate due to your R changing. This results in your flight plan not quite matching up with the actual altitude reading coming from the radar. |
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Post by the light works on Jun 15, 2020 15:53:28 GMT
The center of gravity is not in the center of the moon. It is towards the earth. It has to do with how the moon formed. In the early day, the moon was much closer to the earth and this pulled the center of mass in that direction. Over the last few billion years as the moon has slowly drifted away, the mass of the moon has moved more towards the geometric center of the moon, but it is still off by a noticeable amount. Yes, this does play into why the moon is tidally locked with earth. www.intechopen.com/books/lunar-science/on-the-deviation-of-the-lunar-center-of-mass-to-the-east-two-possible-mechanisms-based-on-evolution-In 1969, this was only barely understood. It wasn't until Apollo 15 and 16 used laser altimeters from orbit that they finally had the needed data and even then it took until the 90's to really understand what was really going on within the moon. They did a good job of accounting for the Earth's gravity. How that offset affected Apollo goes back to your college physics. F=G*M1*M2/R^2. While in orbit of moon, this results in gravity being different in different parts of the orbit. Basically the gravity doesn't always pull at the same rate due to your R changing. This results in your flight plan not quite matching up with the actual altitude reading coming from the radar. an interesting concept I hadn't thought much about, before, but it makes sense. |
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Post by wvengineer on Jun 15, 2020 16:09:29 GMT
The variation of the landings is an interesting topic.
In Apollo 13, the movie, there is a scene where Jim Lovell is talking to his son about flying the landing. He says: " And I take the controls, and I steer it around, and I fly it down, adjusting it here, the
attitude there, pitch, roll, for a nice soft landing on the Moon. Better than Neil Armstrong. Way better than Pete Conrad." Pete flew Apollo 12.
I don't know 1. If that is based on a actual conversation, or if that is something makeup for exposition dump in the movie. 2. what the circumstances are for it. Was there actually issues, or was it a friendly jab at a co-worker and fellow test pilot?
So what happened with 12, 14, 15, 16, and 17 on their landings? You don't hear much about those ones.
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Post by the light works on Jun 15, 2020 16:23:14 GMT
The variation of the landings is an interesting topic. In Apollo 13, the movie, there is a scene where Jim Lovell is talking to his son about flying the landing. He says: " And I take the controls, and I steer it around, and I fly it down, adjusting it here, the attitude there, pitch, roll, for a nice soft landing on the Moon. Better than Neil Armstrong. Way better than Pete Conrad." Pete flew Apollo 12. I don't know 1. If that is based on a actual conversation, or if that is something makeup for exposition dump in the movie. 2. what the circumstances are for it. Was there actually issues, or was it a friendly jab at a co-worker and fellow test pilot? So what happened with 12, 14, 15, 16, and 17 on their landings? You don't hear much about those ones. and is there a trend - each successive landing better than the landing before? |
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