help me again pls

[bqvkhag]

I am planning a Mun lander, can anyone tell me how to view my delta V and determine if it is enough for a Mun trip?

Edited June 10, 2021 by bqvkhag

[Snark]

Moving to Gameplay Questions, where a lot of the question-answerers hang out. 

1 hour ago, bqvkhag said:

I am planning a Mun lander, can anyone tell me how to view my delta V and determine if it is enough for a Mun trip?

The "stage view" shows all your stages. Little vertical row of buttons, in the bottom right corner in the VAB, or bottom left when in flight. These should have little blue labels on each one, saying how much dV the stage has. Your total dV is the sum of the dV for the individual stages.

One thing to bear in mind is that fir any engine, the dV will be different depending on whether it's operating in atmosphere or vacuum. For some engines the difference is just a little, for others it's a lot. BB default, the VAB shows your atmospheric dV for all stages. You can toggle the display from atmospheric to vacuum via one of the settings buttons, in gray on the bottom right corner of the screen.

As for how much dV you need, is this a return mission or one-way?

[bqvkhag]

Just now, Snark said:

 

As for how much dV you need, is this a return mission or one-way?

I am planning for a return mission.

[Echo__3]

A ∆v Map like this one is very useful. According to it you need

About 3400 m/s to get into orbit.
860 m/s to transfer to the Mun
310 m/s to circularize around the Mun
580 m/s to land (This is for a very efficient landing you may want more than 600 m/s for this)

For the return trip, you read the map backwards
580 m/s to take off into orbit around the Mun (you again may want to budget a margin of error)
310 m/s to eject the Mun and aerobrake back at Kerbin.

 

[bqvkhag]

24 minutes ago, Echo__3 said:

A ∆v Map like this one is very useful. According to it you need

About 3400 m/s to get into orbit.
860 m/s to transfer to the Mun
310 m/s to circularize around the Mun
580 m/s to land (This is for a very efficient landing you may want more than 600 m/s for this)

For the return trip, you read the map backwards
580 m/s to take off into orbit around the Mun (you again may want to budget a margin of error)
310 m/s to eject the Mun and aerobrake back at Kerbin.

 

So, do I need to read the delta V at atmo or vacuum level or about halfway? Because, the delta V almost doubles when switching to vacuum from atmo level.

[Snark]

38 minutes ago, bqvkhag said:

So, do I need to read the delta V at atmo or vacuum level or about halfway? Because, the delta V almost doubles when switching to vacuum from atmo level.

The atmospheric dV mainly applies to just the first 10 km or so of altitude-- after that you're mostly in vacuum.

So a good rule of thumb is to use the atmospheric dV for your very first stage where you lift off the launchpad, and vacuum for everything else.

[swjr-swis]

6 hours ago, bqvkhag said:

So, do I need to read the delta V at atmo or vacuum level or about halfway? Because, the delta V almost doubles when switching to vacuum from atmo level.

Any of the dV recommendations you see (like the various dV maps) are always listed as vacuum dV.

Mind what @Snark said though: you will want to check the sea level numbers too, to check if the TWR of the first stage is enough to lift off the surface.

[bqvkhag]

7 hours ago, swjr-swis said:

Any of the dV recommendations you see (like the various dV maps) are always listed as vacuum dV.

Mind what @Snark said though: you will want to check the sea level numbers too, to check if the TWR of the first stage is enough to lift off the surface.

Tysm!