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How was Apollo supposed to rendezvous in the case of a lunar abort?

Why did Apollo 11 need someone to stay behind in lunar orbit?How did Gemini/ Agena rendezvous?Could the Apollo lunar ascent stage have separated from the descent stage before touchdown in an emergency?What was the purpose of an Apollo 10 test?Could the Apollo LM abort mode be engaged after touchdown? What would have happened if it was?How important is plume impingement in rendezvous operations?How long is the Apollo Lunar Module extraction window?Launch window for the Apollo Lunar Module?In this iconic lunar orbit rendezvous photo of John Houbolt, why do arrows #5 and #6 point the “wrong” way?

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10

$begingroup$

If the LEM had to abort at the point of landing on the moon, the CM/SM would be about 1000 miles ahead of it when the LEM reached the same orbit. How could the 2 craft achieve rendezvous ?

apollo-program abort rendezvous

share|improve this question

edited May 29 at 0:20

DrSheldon

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Alan BorrowmanAlan Borrowman

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$endgroup$

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  $begingroup$
  The LEM could easily have aborted into a lower orbit (thus catching up with the CSM over time) or into a higher orbit (thus allowing the CSM to catch up with the LEM) r simply gine parabolic through the CSMs paths and then slowed down. I'm not sure what they opted to do, but those are the three principles that spring to mind.
  $endgroup$
  – Polygnome
  May 28 at 13:11
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Welcome to Space! I am editing the title of your post so it is a proper question.
  $endgroup$
  – DrSheldon
  May 29 at 0:18
  

  
  
  
  

add a comment
 | 

10

$begingroup$

If the LEM had to abort at the point of landing on the moon, the CM/SM would be about 1000 miles ahead of it when the LEM reached the same orbit. How could the 2 craft achieve rendezvous ?

apollo-program abort rendezvous

share|improve this question

edited May 29 at 0:20

DrSheldon

16.7k66 gold badges6565 silver badges131131 bronze badges

asked May 28 at 12:56

Alan BorrowmanAlan Borrowman

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$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  The LEM could easily have aborted into a lower orbit (thus catching up with the CSM over time) or into a higher orbit (thus allowing the CSM to catch up with the LEM) r simply gine parabolic through the CSMs paths and then slowed down. I'm not sure what they opted to do, but those are the three principles that spring to mind.
  $endgroup$
  – Polygnome
  May 28 at 13:11
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Welcome to Space! I am editing the title of your post so it is a proper question.
  $endgroup$
  – DrSheldon
  May 29 at 0:18
  

  
  
  
  

add a comment
 | 

$begingroup$

If the LEM had to abort at the point of landing on the moon, the CM/SM would be about 1000 miles ahead of it when the LEM reached the same orbit. How could the 2 craft achieve rendezvous ?

apollo-program abort rendezvous

share|improve this question

edited May 29 at 0:20

DrSheldon

16.7k66 gold badges6565 silver badges131131 bronze badges

asked May 28 at 12:56

Alan BorrowmanAlan Borrowman

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$endgroup$

share|improve this question

edited May 29 at 0:20

DrSheldon

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asked May 28 at 12:56

Alan BorrowmanAlan Borrowman

5111 silver badge33 bronze badges

share|improve this question

edited May 29 at 0:20

DrSheldon

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asked May 28 at 12:56

Alan BorrowmanAlan Borrowman

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edited May 29 at 0:20

DrSheldon

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edited May 29 at 0:20

DrSheldon

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asked May 28 at 12:56

Alan BorrowmanAlan Borrowman

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asked May 28 at 12:56

Alan BorrowmanAlan Borrowman

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2 Answers
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19

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Lower orbits are faster, higher is slower, so by adjusting orbit altitude you can get an orbit that gains or lags until you are in position do execute a Hohmann transfer. The orbit period is around two hours and the velocities involved around a mile a second so 1000 miles does not have to take that long to close up. Especially if you get both craft change orbit to get a better ratio. For a worst case surface abort the CSM will be an hour away in that two hour orbit, so an Lunar Module orbit that takes three hours (CSM does 1.5 two hour orbits) will get rendezvous.

The trickier part comes if your inclination is different, but for an abort straight after landing this would be unchanged.

share|improve this answer

edited May 28 at 13:43

answered May 28 at 13:28

GremlinWrangerGremlinWranger

4,51477 silver badges2525 bronze badges

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  "East takes you Out, Out takes you West, West takes you In, In takes you East. Port and Starboard bring you back. North and South bring you back"
  $endgroup$
  – Russell McMahon
  May 29 at 13:54
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Reference to what @RussellMcMahon said
  $endgroup$
  – Daniel Jour
  May 30 at 0:52
  

  
  
  
  

add a comment
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16

$begingroup$

There were specific procedures for an abort at any time during the powered descent and after landing. The abort case at the planned time of landing (about 12 minutes after PDI) is covered in this chart:

It is from the LM Rendezvous Procedures - G Mission PDF page 78. It's a bit crowded, but it shows the relative profile between CSM and LM, centered on the CSM. The important points are ABORT (time and position of the abort) and then INS (time and position of the LM orbital insertion). The insertion orbit would be be 10NM perilune and 30NM apolune. At apolune a first phasing maneuver (C1) is done, based on a crew chart or taken from Mission Control. Half an orbit later CSI1 is done, which is a height adjustment maneuver to get back to the nominal rendezvous profile and the CSI2/CDH/TPI maneuvers are then basically identical with a nominal rendezvous sequence.

So essentially one orbit of coasting in a lower orbit than the CSM is added to the nominal profile so that the LM has time to catch up to the CSM. An even later abort from the lunar surface (at the "No Go for T2" point) would even need one additional orbit to catch up.

share|improve this answer

answered May 28 at 16:43

indy91indy91

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19

$begingroup$

Lower orbits are faster, higher is slower, so by adjusting orbit altitude you can get an orbit that gains or lags until you are in position do execute a Hohmann transfer. The orbit period is around two hours and the velocities involved around a mile a second so 1000 miles does not have to take that long to close up. Especially if you get both craft change orbit to get a better ratio. For a worst case surface abort the CSM will be an hour away in that two hour orbit, so an Lunar Module orbit that takes three hours (CSM does 1.5 two hour orbits) will get rendezvous.

The trickier part comes if your inclination is different, but for an abort straight after landing this would be unchanged.

share|improve this answer

edited May 28 at 13:43

answered May 28 at 13:28

GremlinWrangerGremlinWranger

4,51477 silver badges2525 bronze badges

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  "East takes you Out, Out takes you West, West takes you In, In takes you East. Port and Starboard bring you back. North and South bring you back"
  $endgroup$
  – Russell McMahon
  May 29 at 13:54
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Reference to what @RussellMcMahon said
  $endgroup$
  – Daniel Jour
  May 30 at 0:52
  

  
  
  
  

add a comment
 | 

19

$begingroup$

Lower orbits are faster, higher is slower, so by adjusting orbit altitude you can get an orbit that gains or lags until you are in position do execute a Hohmann transfer. The orbit period is around two hours and the velocities involved around a mile a second so 1000 miles does not have to take that long to close up. Especially if you get both craft change orbit to get a better ratio. For a worst case surface abort the CSM will be an hour away in that two hour orbit, so an Lunar Module orbit that takes three hours (CSM does 1.5 two hour orbits) will get rendezvous.

The trickier part comes if your inclination is different, but for an abort straight after landing this would be unchanged.

share|improve this answer

edited May 28 at 13:43

answered May 28 at 13:28

GremlinWrangerGremlinWranger

4,51477 silver badges2525 bronze badges

$endgroup$

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  "East takes you Out, Out takes you West, West takes you In, In takes you East. Port and Starboard bring you back. North and South bring you back"
  $endgroup$
  – Russell McMahon
  May 29 at 13:54
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Reference to what @RussellMcMahon said
  $endgroup$
  – Daniel Jour
  May 30 at 0:52
  

  
  
  
  

add a comment
 | 

$begingroup$

Lower orbits are faster, higher is slower, so by adjusting orbit altitude you can get an orbit that gains or lags until you are in position do execute a Hohmann transfer. The orbit period is around two hours and the velocities involved around a mile a second so 1000 miles does not have to take that long to close up. Especially if you get both craft change orbit to get a better ratio. For a worst case surface abort the CSM will be an hour away in that two hour orbit, so an Lunar Module orbit that takes three hours (CSM does 1.5 two hour orbits) will get rendezvous.

The trickier part comes if your inclination is different, but for an abort straight after landing this would be unchanged.

share|improve this answer

edited May 28 at 13:43

answered May 28 at 13:28

GremlinWrangerGremlinWranger

4,51477 silver badges2525 bronze badges

$endgroup$

share|improve this answer

edited May 28 at 13:43

answered May 28 at 13:28

GremlinWrangerGremlinWranger

4,51477 silver badges2525 bronze badges

answered May 28 at 13:28

GremlinWrangerGremlinWranger

4,51477 silver badges2525 bronze badges

answered May 28 at 13:28

GremlinWrangerGremlinWranger

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16

$begingroup$

There were specific procedures for an abort at any time during the powered descent and after landing. The abort case at the planned time of landing (about 12 minutes after PDI) is covered in this chart:

It is from the LM Rendezvous Procedures - G Mission PDF page 78. It's a bit crowded, but it shows the relative profile between CSM and LM, centered on the CSM. The important points are ABORT (time and position of the abort) and then INS (time and position of the LM orbital insertion). The insertion orbit would be be 10NM perilune and 30NM apolune. At apolune a first phasing maneuver (C1) is done, based on a crew chart or taken from Mission Control. Half an orbit later CSI1 is done, which is a height adjustment maneuver to get back to the nominal rendezvous profile and the CSI2/CDH/TPI maneuvers are then basically identical with a nominal rendezvous sequence.

So essentially one orbit of coasting in a lower orbit than the CSM is added to the nominal profile so that the LM has time to catch up to the CSM. An even later abort from the lunar surface (at the "No Go for T2" point) would even need one additional orbit to catch up.

share|improve this answer

answered May 28 at 16:43

indy91indy91

1,05666 silver badges88 bronze badges

$endgroup$

add a comment
 | 

16

$begingroup$

There were specific procedures for an abort at any time during the powered descent and after landing. The abort case at the planned time of landing (about 12 minutes after PDI) is covered in this chart:

It is from the LM Rendezvous Procedures - G Mission PDF page 78. It's a bit crowded, but it shows the relative profile between CSM and LM, centered on the CSM. The important points are ABORT (time and position of the abort) and then INS (time and position of the LM orbital insertion). The insertion orbit would be be 10NM perilune and 30NM apolune. At apolune a first phasing maneuver (C1) is done, based on a crew chart or taken from Mission Control. Half an orbit later CSI1 is done, which is a height adjustment maneuver to get back to the nominal rendezvous profile and the CSI2/CDH/TPI maneuvers are then basically identical with a nominal rendezvous sequence.

So essentially one orbit of coasting in a lower orbit than the CSM is added to the nominal profile so that the LM has time to catch up to the CSM. An even later abort from the lunar surface (at the "No Go for T2" point) would even need one additional orbit to catch up.

share|improve this answer

answered May 28 at 16:43

indy91indy91

1,05666 silver badges88 bronze badges

$endgroup$

add a comment
 | 

$begingroup$

There were specific procedures for an abort at any time during the powered descent and after landing. The abort case at the planned time of landing (about 12 minutes after PDI) is covered in this chart:

It is from the LM Rendezvous Procedures - G Mission PDF page 78. It's a bit crowded, but it shows the relative profile between CSM and LM, centered on the CSM. The important points are ABORT (time and position of the abort) and then INS (time and position of the LM orbital insertion). The insertion orbit would be be 10NM perilune and 30NM apolune. At apolune a first phasing maneuver (C1) is done, based on a crew chart or taken from Mission Control. Half an orbit later CSI1 is done, which is a height adjustment maneuver to get back to the nominal rendezvous profile and the CSI2/CDH/TPI maneuvers are then basically identical with a nominal rendezvous sequence.

So essentially one orbit of coasting in a lower orbit than the CSM is added to the nominal profile so that the LM has time to catch up to the CSM. An even later abort from the lunar surface (at the "No Go for T2" point) would even need one additional orbit to catch up.

share|improve this answer

answered May 28 at 16:43

indy91indy91

1,05666 silver badges88 bronze badges

$endgroup$

share|improve this answer

answered May 28 at 16:43

indy91indy91

1,05666 silver badges88 bronze badges

answered May 28 at 16:43

indy91indy91

1,05666 silver badges88 bronze badges

answered May 28 at 16:43

indy91indy91

1,05666 silver badges88 bronze badges