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Hello,

I have this question since some years so I will ask now:

How does the flightpath looks, from a (let's say ~circular) lunar orbit to landing with v almost 0 at the end, for a ~100% fuel optimized lunar landing? (Le't ignore terrain etc. in the first step)

And what's the "optimal" procedure in this sense?

My "feeling" is as follows:

1. Burn horizontal into the direction you are flying (Almost retrograte but with a pitch of 0) The result is, that the horizontal speed will be reduced and the ship wil begin to fall faster and faster into the direction of the ground (So vertical speed will increase more and more)

2. This will result in a curve from a straight line (parallel to the horizon) into a curve to another straight line (With a specific angle to the horizon). If this reqired "line" is reached, the engine has to be rotated so that horizontal ans vertical speed will be reduced proportionaly to it's values (The ship will follow the straight line, so the angle of the decent path is constant for a while). In an optimum case, an orbit has been selected before step one, that the length of this line is zero

3. The engine has to be rotated into a "specific" angle (which has to be calculated and is depending on the engines acceleration and the acceleration by gravity of the celestial body). The angle has to be selected that the following values are zero at the same time over the desired landing point: Horizontal speed, Vertical speed and altitude (plus some meters for final touchdown).

4. The engine has to be rotade exactly downwards for touchdown.

Is my feeling right?

Was that the way for the lunar moduels in the apollo program used in their "automatic procedure" or did they have to repsect other aspects (like a good view to the landing site ect.)?

Is there any documentation etc. how to calculate this things? (I havn't found anything I can understand)

Thanks!

Topper

Oh I just googled "apollo pitch over p66" and in pictures I found this interesting link:

https://dodlithr.blogspot.com/2014/08/lm-descent-to-moon-part-1-theory-and.html

I will study it now... Not sure if it's "fuel optimized"...

I have this question since some years so I will ask now:

How does the flightpath looks, from a (let's say ~circular) lunar orbit to landing with v almost 0 at the end, for a ~100% fuel optimized lunar landing? (Le't ignore terrain etc. in the first step)

And what's the "optimal" procedure in this sense?

My "feeling" is as follows:

1. Burn horizontal into the direction you are flying (Almost retrograte but with a pitch of 0) The result is, that the horizontal speed will be reduced and the ship wil begin to fall faster and faster into the direction of the ground (So vertical speed will increase more and more)

2. This will result in a curve from a straight line (parallel to the horizon) into a curve to another straight line (With a specific angle to the horizon). If this reqired "line" is reached, the engine has to be rotated so that horizontal ans vertical speed will be reduced proportionaly to it's values (The ship will follow the straight line, so the angle of the decent path is constant for a while). In an optimum case, an orbit has been selected before step one, that the length of this line is zero

3. The engine has to be rotated into a "specific" angle (which has to be calculated and is depending on the engines acceleration and the acceleration by gravity of the celestial body). The angle has to be selected that the following values are zero at the same time over the desired landing point: Horizontal speed, Vertical speed and altitude (plus some meters for final touchdown).

4. The engine has to be rotade exactly downwards for touchdown.

Is my feeling right?

Was that the way for the lunar moduels in the apollo program used in their "automatic procedure" or did they have to repsect other aspects (like a good view to the landing site ect.)?

Is there any documentation etc. how to calculate this things? (I havn't found anything I can understand)

Thanks!

Topper

Oh I just googled "apollo pitch over p66" and in pictures I found this interesting link:

https://dodlithr.blogspot.com/2014/08/lm-descent-to-moon-part-1-theory-and.html

I will study it now... Not sure if it's "fuel optimized"...

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