Was is really necessary for the Lunar module LM to have 2 stages?
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We all know the 2 stages LM design used by Grumman was intended to discard the mass of the landing gear (+ other components) at the moment of launching off the Moon surface to reach back the Service module. But was it really necessarily for the LM to have two stages? The reason I wonder is that, when Armstrong landed, as we know there was about 25 seconds fuel left - however, this was actually 25 sec. of fuel before aborting the landing with the complete LM, not before running out of fuel. After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
apollo-program lunar-landing lunar-module
asked 4 hours ago
MathiasMathias
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add a comment |
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We all know the 2 stages LM design used by Grumman was intended to discard the mass of the landing gear (+ other components) at the moment of launching off the Moon surface to reach back the Service module. But was it really necessarily for the LM to have two stages? The reason I wonder is that, when Armstrong landed, as we know there was about 25 seconds fuel left - however, this was actually 25 sec. of fuel before aborting the landing with the complete LM, not before running out of fuel. After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
apollo-program lunar-landing lunar-module
asked 4 hours ago
MathiasMathias
61
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Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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Do you have a reference for the ascent stage having enough fuel to return to orbit? Every source I have seen talks about the criticality of the ascent stage working because there were no other options. including sub optimal performance choices for better reliability and design of this en.wikipedia.org/wiki/Lunar_escape_systems. AFAIK the abort at 25 seconds involved firing the separation bolts and dumping the descent stage.
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– GremlinWranger
3 hours ago
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related ahttps://space.stackexchange.com/questions/2493/how-was-reserve-fuel-calculated-for-the-apollo-missions/30208#30208. Looks like descent module was designed to land with about 1.8% of the fuel it started out with.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
There are a few documentaries on Youtube that include interviews with astronauts and engineers. It is mentioned that the remaining fuel was simply a measure of the safe point where the mission would have been aborted if the surface wasn't touched at that point. So aborting the landing would have meant going back to the service module with the LM in its complete configuration. An example, in the middle of this page it is mentioned the fact that the remaining fuel was the limit for abort landing moment space.com/26593-apollo-11-moon-landing-scariest-moments.html (a great page btw)
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– Mathias
3 hours ago
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See this previous question for clarity about LEM abort modes. space.stackexchange.com/questions/21686 There’s more than one, but none of them get back to orbit on descent stage engine only
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– Bob Jacobsen
3 hours ago
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"So aborting the landing would have meant going back to the service module with the LM in its complete configuration." -- why do you think that?
$endgroup$
– Russell Borogove
2 hours ago
add a comment |
$begingroup$
We all know the 2 stages LM design used by Grumman was intended to discard the mass of the landing gear (+ other components) at the moment of launching off the Moon surface to reach back the Service module. But was it really necessarily for the LM to have two stages? The reason I wonder is that, when Armstrong landed, as we know there was about 25 seconds fuel left - however, this was actually 25 sec. of fuel before aborting the landing with the complete LM, not before running out of fuel. After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
apollo-program lunar-landing lunar-module
asked 4 hours ago
MathiasMathias
61
New contributor
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
We all know the 2 stages LM design used by Grumman was intended to discard the mass of the landing gear (+ other components) at the moment of launching off the Moon surface to reach back the Service module. But was it really necessarily for the LM to have two stages? The reason I wonder is that, when Armstrong landed, as we know there was about 25 seconds fuel left - however, this was actually 25 sec. of fuel before aborting the landing with the complete LM, not before running out of fuel. After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
apollo-program lunar-landing lunar-module
apollo-program lunar-landing lunar-module
asked 4 hours ago
MathiasMathias
61
New contributor
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
MathiasMathias
61
New contributor
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
MathiasMathias
61
New contributor
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
MathiasMathias
61
asked 4 hours ago
MathiasMathias
61
61
New contributor
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Mathias is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$begingroup$
Do you have a reference for the ascent stage having enough fuel to return to orbit? Every source I have seen talks about the criticality of the ascent stage working because there were no other options. including sub optimal performance choices for better reliability and design of this en.wikipedia.org/wiki/Lunar_escape_systems. AFAIK the abort at 25 seconds involved firing the separation bolts and dumping the descent stage.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
related ahttps://space.stackexchange.com/questions/2493/how-was-reserve-fuel-calculated-for-the-apollo-missions/30208#30208. Looks like descent module was designed to land with about 1.8% of the fuel it started out with.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
There are a few documentaries on Youtube that include interviews with astronauts and engineers. It is mentioned that the remaining fuel was simply a measure of the safe point where the mission would have been aborted if the surface wasn't touched at that point. So aborting the landing would have meant going back to the service module with the LM in its complete configuration. An example, in the middle of this page it is mentioned the fact that the remaining fuel was the limit for abort landing moment space.com/26593-apollo-11-moon-landing-scariest-moments.html (a great page btw)
$endgroup$
– Mathias
3 hours ago
$begingroup$
See this previous question for clarity about LEM abort modes. space.stackexchange.com/questions/21686 There’s more than one, but none of them get back to orbit on descent stage engine only
$endgroup$
– Bob Jacobsen
3 hours ago
$begingroup$
"So aborting the landing would have meant going back to the service module with the LM in its complete configuration." -- why do you think that?
$endgroup$
– Russell Borogove
2 hours ago
add a comment |
$begingroup$
Do you have a reference for the ascent stage having enough fuel to return to orbit? Every source I have seen talks about the criticality of the ascent stage working because there were no other options. including sub optimal performance choices for better reliability and design of this en.wikipedia.org/wiki/Lunar_escape_systems. AFAIK the abort at 25 seconds involved firing the separation bolts and dumping the descent stage.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
related ahttps://space.stackexchange.com/questions/2493/how-was-reserve-fuel-calculated-for-the-apollo-missions/30208#30208. Looks like descent module was designed to land with about 1.8% of the fuel it started out with.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
There are a few documentaries on Youtube that include interviews with astronauts and engineers. It is mentioned that the remaining fuel was simply a measure of the safe point where the mission would have been aborted if the surface wasn't touched at that point. So aborting the landing would have meant going back to the service module with the LM in its complete configuration. An example, in the middle of this page it is mentioned the fact that the remaining fuel was the limit for abort landing moment space.com/26593-apollo-11-moon-landing-scariest-moments.html (a great page btw)
$endgroup$
– Mathias
3 hours ago
$begingroup$
See this previous question for clarity about LEM abort modes. space.stackexchange.com/questions/21686 There’s more than one, but none of them get back to orbit on descent stage engine only
$endgroup$
– Bob Jacobsen
3 hours ago
$begingroup$
"So aborting the landing would have meant going back to the service module with the LM in its complete configuration." -- why do you think that?
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
Do you have a reference for the ascent stage having enough fuel to return to orbit? Every source I have seen talks about the criticality of the ascent stage working because there were no other options. including sub optimal performance choices for better reliability and design of this en.wikipedia.org/wiki/Lunar_escape_systems. AFAIK the abort at 25 seconds involved firing the separation bolts and dumping the descent stage.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
Do you have a reference for the ascent stage having enough fuel to return to orbit? Every source I have seen talks about the criticality of the ascent stage working because there were no other options. including sub optimal performance choices for better reliability and design of this en.wikipedia.org/wiki/Lunar_escape_systems. AFAIK the abort at 25 seconds involved firing the separation bolts and dumping the descent stage.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
related ahttps://space.stackexchange.com/questions/2493/how-was-reserve-fuel-calculated-for-the-apollo-missions/30208#30208. Looks like descent module was designed to land with about 1.8% of the fuel it started out with.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
related ahttps://space.stackexchange.com/questions/2493/how-was-reserve-fuel-calculated-for-the-apollo-missions/30208#30208. Looks like descent module was designed to land with about 1.8% of the fuel it started out with.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
There are a few documentaries on Youtube that include interviews with astronauts and engineers. It is mentioned that the remaining fuel was simply a measure of the safe point where the mission would have been aborted if the surface wasn't touched at that point. So aborting the landing would have meant going back to the service module with the LM in its complete configuration. An example, in the middle of this page it is mentioned the fact that the remaining fuel was the limit for abort landing moment space.com/26593-apollo-11-moon-landing-scariest-moments.html (a great page btw)
$endgroup$
– Mathias
3 hours ago
$begingroup$
There are a few documentaries on Youtube that include interviews with astronauts and engineers. It is mentioned that the remaining fuel was simply a measure of the safe point where the mission would have been aborted if the surface wasn't touched at that point. So aborting the landing would have meant going back to the service module with the LM in its complete configuration. An example, in the middle of this page it is mentioned the fact that the remaining fuel was the limit for abort landing moment space.com/26593-apollo-11-moon-landing-scariest-moments.html (a great page btw)
$endgroup$
– Mathias
3 hours ago
$begingroup$
See this previous question for clarity about LEM abort modes. space.stackexchange.com/questions/21686 There’s more than one, but none of them get back to orbit on descent stage engine only
$endgroup$
– Bob Jacobsen
3 hours ago
$begingroup$
See this previous question for clarity about LEM abort modes. space.stackexchange.com/questions/21686 There’s more than one, but none of them get back to orbit on descent stage engine only
$endgroup$
– Bob Jacobsen
3 hours ago
$begingroup$
"So aborting the landing would have meant going back to the service module with the LM in its complete configuration." -- why do you think that?
$endgroup$
– Russell Borogove
2 hours ago
$begingroup$
"So aborting the landing would have meant going back to the service module with the LM in its complete configuration." -- why do you think that?
$endgroup$
– Russell Borogove
2 hours ago
add a comment |
1 Answer
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After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
Your assumption is not correct. Aborting from the "bingo" (low fuel) call would have required the ascent stage to be used. The stages can be separated, and the ascent engine fired, while in flight; this was demonstrated on Apollo 9 and Apollo 10.
Because there would be a brief delay between staging and the ascent stage coming up to full thrust, the safest way to abort in this case would be to take the descent stage to full thrust to gain altitude and vertical speed, then stage and activate the ascent stage engine once the descent stage fuel was exhausted.
The ascent from lunar surface to rendezvous orbit took about 7 minutes on the ascent stage; there was nowhere near enough fuel in the descent stage to do that.
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
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$begingroup$
After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
Your assumption is not correct. Aborting from the "bingo" (low fuel) call would have required the ascent stage to be used. The stages can be separated, and the ascent engine fired, while in flight; this was demonstrated on Apollo 9 and Apollo 10.
Because there would be a brief delay between staging and the ascent stage coming up to full thrust, the safest way to abort in this case would be to take the descent stage to full thrust to gain altitude and vertical speed, then stage and activate the ascent stage engine once the descent stage fuel was exhausted.
The ascent from lunar surface to rendezvous orbit took about 7 minutes on the ascent stage; there was nowhere near enough fuel in the descent stage to do that.
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
$endgroup$
add a comment |
$begingroup$
After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
Your assumption is not correct. Aborting from the "bingo" (low fuel) call would have required the ascent stage to be used. The stages can be separated, and the ascent engine fired, while in flight; this was demonstrated on Apollo 9 and Apollo 10.
Because there would be a brief delay between staging and the ascent stage coming up to full thrust, the safest way to abort in this case would be to take the descent stage to full thrust to gain altitude and vertical speed, then stage and activate the ascent stage engine once the descent stage fuel was exhausted.
The ascent from lunar surface to rendezvous orbit took about 7 minutes on the ascent stage; there was nowhere near enough fuel in the descent stage to do that.
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
$endgroup$
add a comment |
$begingroup$
After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
Your assumption is not correct. Aborting from the "bingo" (low fuel) call would have required the ascent stage to be used. The stages can be separated, and the ascent engine fired, while in flight; this was demonstrated on Apollo 9 and Apollo 10.
Because there would be a brief delay between staging and the ascent stage coming up to full thrust, the safest way to abort in this case would be to take the descent stage to full thrust to gain altitude and vertical speed, then stage and activate the ascent stage engine once the descent stage fuel was exhausted.
The ascent from lunar surface to rendezvous orbit took about 7 minutes on the ascent stage; there was nowhere near enough fuel in the descent stage to do that.
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
$endgroup$
After these 25 second would have ended, the LM still had enough fuel to ascend with both of its stages right back to the Service module. In other words, the LM was designed to be able to take off from the Moon surface with BOTH stages, even right after touching the surface, in case something would have gone wrong. Then, why using two stages which surely added complexity, weight and a second engine?
Your assumption is not correct. Aborting from the "bingo" (low fuel) call would have required the ascent stage to be used. The stages can be separated, and the ascent engine fired, while in flight; this was demonstrated on Apollo 9 and Apollo 10.
Because there would be a brief delay between staging and the ascent stage coming up to full thrust, the safest way to abort in this case would be to take the descent stage to full thrust to gain altitude and vertical speed, then stage and activate the ascent stage engine once the descent stage fuel was exhausted.
The ascent from lunar surface to rendezvous orbit took about 7 minutes on the ascent stage; there was nowhere near enough fuel in the descent stage to do that.
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
edited 2 hours ago
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
answered 2 hours ago
Russell BorogoveRussell Borogove
90.4k3302387
90.4k3302387
add a comment |
add a comment |
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$begingroup$
Do you have a reference for the ascent stage having enough fuel to return to orbit? Every source I have seen talks about the criticality of the ascent stage working because there were no other options. including sub optimal performance choices for better reliability and design of this en.wikipedia.org/wiki/Lunar_escape_systems. AFAIK the abort at 25 seconds involved firing the separation bolts and dumping the descent stage.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
related ahttps://space.stackexchange.com/questions/2493/how-was-reserve-fuel-calculated-for-the-apollo-missions/30208#30208. Looks like descent module was designed to land with about 1.8% of the fuel it started out with.
$endgroup$
– GremlinWranger
3 hours ago
$begingroup$
There are a few documentaries on Youtube that include interviews with astronauts and engineers. It is mentioned that the remaining fuel was simply a measure of the safe point where the mission would have been aborted if the surface wasn't touched at that point. So aborting the landing would have meant going back to the service module with the LM in its complete configuration. An example, in the middle of this page it is mentioned the fact that the remaining fuel was the limit for abort landing moment space.com/26593-apollo-11-moon-landing-scariest-moments.html (a great page btw)
$endgroup$
– Mathias
3 hours ago
$begingroup$
See this previous question for clarity about LEM abort modes. space.stackexchange.com/questions/21686 There’s more than one, but none of them get back to orbit on descent stage engine only
$endgroup$
– Bob Jacobsen
3 hours ago
$begingroup$
"So aborting the landing would have meant going back to the service module with the LM in its complete configuration." -- why do you think that?
$endgroup$
– Russell Borogove
2 hours ago