Landing/Getting off the Mun?

[Olsson]

Hi so I\'ve actually landed on the mun and got home a few times. Though it was probably done very inefficiently so I have a few questions about mun travelling.

1. Taking off from the mun decoupling the lower landing part (Apollo esque) and leaving the landing platform behind. When I do this my engine sometimes gets injured since it falls trough the decoupler and stops for abit and then I turn on the engine since I had to turn off the engine for my landing stage if you get what I mean? Like I have third stage landing engines and the stage after that decoupler and my take off engine. Is there a way for me to go from 0 engine power to 100 instantly?

2. Getting off the mun smoothly? I just get an orbit and then do aposis or whatever to make my orbit towards Kerbin until I\'m in Kerbin orbit, its kinda inefficent. Anyone know a better way?

3. Landing. Am I supposed to get a low orbit, even out my horizontal speed at like 1000m and then descent vertically all the way or what\'s the best way?

[rkman]

2. Getting off the mun smoothly? I just get an orbit and then do aposis or whatever to make my orbit towards Kerbin until I\'m in Kerbin orbit, its kinda inefficent. Anyone know a better way?

The standard way seems to be to burn when your orbit crosses Mun orbit ahead of the direction of motion of the Mun, so that the ellipse extends toward the opposite of the direction of motion of the Mun. The length of the ellipse should be approximately 10 times the diameter of the Mun (guestimated from memory, your milage may vary). As you follow that orbit Apo will automagically move toward Kerbin so that you\'ll get inside its SOI.

3. Landing. Am I supposed to get a low orbit, even out my horizontal speed at like 1000m and then descent vertically all the way or what\'s the best way?

I find it\'s easiest/safest to do a close-to-vertical descent from at least several 10\'s of km altitude. Most fuel efficient is to burn as late as possible, in practice you\'ll have to compromise unless you rely on a landing auto pilot.

Downside of a low orbit (<~10k) is that it\'s harder to aim the point of touchdown.

Downside of landing from a very high orbit is that the surface of the Mun will turn below you by a significant amount during your descent.

Sorry, I can\'t help you with the decoupler problem at takeoff from the Mun.

[Kosmo-not]

Best method of landing is to put your periapsis very low (1-2km) and start your landing burn just before then (altitude varies according to how much acceleration you can put out). For the craft I fly, I start my landing burn at 5-7km.

Best method of returning from the Mun is to do your TKI burn shortly after passing its prograde side. The trajectory you will have after the burn will not be an ellipse, it will be hyperbolic. The new patched conics system allows you to easily do this burn.

[Nibb31]

1. Another approach is to use a crasher stage like in the Soviet space program. One stage was used for the lunar orbit insertion and the deorbit and braking burn. Then the Lander dropped it near the surface and used the same engine for the final decent and the ascent. This is more efficient, but it has a few disadvantage, especially if you are landing at a lunar base, because dropping a bomb on your buddies each time you land is considered bad etiquette.

2. I take off by burning west (270 degrees) and firing my return burn when I arrive above the Mun\'s orbit vector point. This takes advantage of the Mun \'s orbital speed.

3. The most efficient descent is to go down on a shallow slope and to brake at the last second. That is, however, extremely tricky and dangerous unless you go into some complex calculations about thrust, altitude, speed and time. It\'s easier to cut most of your speed higher up and to come down at a controlled descent rate.

[Kosmo-not]

3. The most efficient descent is to go down on a shallow slope and to brake at the last second. That is, however, extremely tricky and dangerous unless you go into some complex calculations about thrust, altitude, speed and time. It\'s easier to cut most of your speed higher up and to come down at a controlled descent rate.

How is having a shallow slope tricky and dangerous? It\'s easier and safer than just coming in steeply like most people do. If you think you\'re going to impact the surface, just burn straight up.

[Nibb31]

Because you are going faster horizontally, with the risk of not carrying enough delta-v to brake at the last minute before an unplanned destructive lithobraking event occurs.

[maltesh]

Best method of returning from the Mun is to do your TKI burn shortly after passing its prograde side. The trajectory you will have after the burn will not be an ellipse, it will be hyperbolic. The new patched conics system allows you to easily do this burn.

Agreed. Prior to the 0.15 update, I\'d get into an eastward orbit at about 10km altitude, wait until my spacecraft crossed the middle of the near face, and then burn up to about 900-925 m/s.* This put me in a hyperbolic orbit that exited near the center of the trailing point of the SOI and 19 times out of 20, this would result in an orbit that dropped my spacecraft onto Kerbin with no further burning. The rare times that it didn\'t, only very brief correcting burns were needed.

If all you care about is returning to Kerbin, the most fuel-efficient way of doing so is similar to that method.

(*)The velocity window is actually wider than this, but I haven\'t really explored how much wider. 900-925 is designed to lhave a velocity close to the 545 m/s of the Mun\'s velocity just before you leave the SOI, but in the opposite direction.

[Olsson]

Agreed. Prior to the 0.15 update, I\'d get into an eastward orbit at about 10km altitude, wait until my spacecraft crossed the middle of the near face, and then burn up to about 900-925 m/s.* This put me in a hyperbolic orbit that exited near the center of the trailing point of the SOI and 19 times out of 20, this would result in an orbit that dropped my spacecraft onto Kerbin with no further burning. The rare times that it didn\'t, only very brief correcting burns were needed.

If all you care about is returning to Kerbin, the most fuel-efficient way of doing so is similar to that method.

(*)The velocity window is actually wider than this, but I haven\'t really explored how much wider. 900-925 is designed to lhave a velocity close to the 545 m/s of the Mun\'s velocity just before you leave the SOI, but in the opposite direction.

I don\'t understand the method. What is a TKI burn?

[maltesh]

I don\'t understand the method. What is a TKI burn?

TKI stands for Trans-Kerbin Injection

[Nibb31]

Trans Kerbin Insertion = Return to Kerbin.

The major burns as defined during Apollo are described here:

[rkman]

900-925 is designed to lhave a velocity close to the 545 m/s of the Mun\'s velocity just before you leave the SOI, but in the opposite direction.

Doesn\'t that put you at near 0m/s relative to Kerbin, and thus at the start of a path straight toward Kerbin? I don\'t understand what the additional ~400m/s are for.

Hm never mind, i misunderstood. Getting to 0m/s relative to Kerbin is the whole point.

You get up to 900 quickly while still near the Mun so that there\'s ~500 left when you exit Mun SOI.

[Olsson]

Trans Kerbin Insertion = Return to Kerbin.

The major burns as defined during Apollo are described here:

Oh alright but. How am I supposed to do this burn, what\'s the prograde side? I always land on the light side of the moon thats towards the earth. When I take off what am I supposed to do? Get orbit, do the burn when I\'m on the side that mun is moving towards?

[deadshot462]

Olsson - that\'s exactly the procedure you would do to return to Kerbin. Usually a 10 km Mun orbit is high enough to perform the return burn

[Olsson]

Olsson - that\'s exactly the procedure you would do to return to Kerbin. Usually a 10 km Mun orbit is high enough to perform the return burn

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Alright cheers I\'ll make sure to give this a try next time I visit the mun!