How much dV do I need to get to the mun and back?

[Dont]

I don't understand this map http://i.imgur.com/O7nlSLC.png

3200 + 950 + 860 + 310 + 580 + 580 + 310 + 860
kerbin e-orbit mun-trans mun entry land leave orbit entry kerbin
That cant be right..

I need a ship with 7650 dV to get to, land, and back from mun?

[Proteus]

I always calculate it with 6900:

3800 LKO
850 -> Mun FlyBy 30km Alt
300 -> Mun Orbit 30 km
1000 -> Mun landed
650 -> Orbit 30 km
300 -> Kerbin Orbit 45 km Periapsis

With those numbers already containing certain security margins ...
for additional security I design my Mun Landers with a dV of 7-7.5 km however. This gives me a good amount of fuel for additional braking upon return (to lower the Apoapsis and to do the final reentry in a more controlled manner)

[Dont]

Do u guys do this?

get apoap to 70k, then make an +70k kerbin orbit, then transfer to mun, dont orbit just entry then go back.

The way u make it sound, is that u litterally go STRAIGHT to the mun which is against everything I've ever learned.

[Proteus]

I for my part never ...
I do first Kerbin orbit 100km, then transfer to Mun orbit 30km,
After Landing Mun Orbit again and then Transfer to an elliptical Kerbin orbit.

But dV requirements, especially for Kerbin ascent, as well as transfer from Kerbin to Mun can vary considerably, depending on how efficient you ascent profile is and how efficient you plan your maneuver node

[Langkard]

Don't forget that on the return to Kerbin, you don't have to get to a circularized low Kerbin orbit to land. It takes very little Δv to land on Kerbin from the highly elliptical Kerbin orbit you'll be in after escaping the Mun's influence if you correctly took off from the Mun so that you end up leaving the Mun back along its orbital path (the most fuel efficient way to escape the Mun's SOI). Once back in Kerbin SOI out near the Mun, just burn enough retrograde to get your Kerbin Pe down to about 28-30 km and use aerobraking to bring you down. It takes even less Δv if you're willing to make several aerobraking passes higher up in Kerbin's atmosphere (<60 km), so that each orbital pass through the atmosphere slows you down just a little more.

[MAD]

"One test result is worth one thousand expert opinions." Wernher von Braun

Mission Data from my last trip
positive values are burns to prograde, negative values burn to retrograde
Ground to orbit, vary variable, dependant on assent profile, drag etc ..... 3,820 m/s
Transfer from 80km circular to Mun Orbit, Hohman transfer................... 852.6 m/s
Circularize around Mun at 10km ........................................................ -275.0 m/s
(marginal capture is only -77m/s)
Deorbit from circular to suborbital....................................................... -425.8 m/s
Land, varies depending on skill and daring .......................................... -183.2 m/s
Total one way...............................................................................~ 5,556.6 m/s

Mun surface to 10km .........................................................................183.2 m/s
Circularize at 10km ........................................................................... 425.8 m/s
Mun oribit to to kerbin ........................................................................ 275 m/s
Aerobrake at Kerbin, Periapsis at 10km ............................................... free
Total for return trip ............................................................................. 884 m/s
Grand total ......................................................................................6,445 m/s

As the Mun's orbit is circular and 0 degrees inclination with the exception of launch and landing the number won't vary. You dont save anything by not circularizing.

Minmus is cheaper
good luck

[Raincloud Man]

What most people don't remember is that a lot of that d/v is required just to reach orbit, once you're in space, getting to places is usually comparatively cheap, if you count distance traveled/fuel used.

[MAD]

Originalmente postado por Zagreus:

What most people don't remember is that a lot of that d/v is required just to reach orbit, once you're in space, getting to places is usually comparatively cheap, if you count distance traveled/fuel used.

"Once you get to earth orbit, you're halfway to anywhere in the solar system." Robert A. Heinlein

[MAD]

Originalmente postado por Don't:

Do u guys do this?

get apoap to 70k, then make an +70k kerbin orbit, then transfer to mun, dont orbit just entry then go back.

The way u make it sound, is that u litterally go STRAIGHT to the mun which is against everything I've ever learned.

You can do that if your timing is right but you dont actually gain anything by skipping a circularization burn at either end. I tested it

[Proteus]

Originalmente postado por MAD:

Originalmente postado por Zagreus:

What most people don't remember is that a lot of that d/v is required just to reach orbit, once you're in space, getting to places is usually comparatively cheap, if you count distance traveled/fuel used.

"Once you get to earth orbit, you're halfway to anywhere in the solar system." Robert A. Heinlein

Aye ... if one looks, for example, at the Saturn-Rocket (which brought the Apollo CSM and the Lunar Lander to orbit) and compare it to the size of the Apollo CSM itself (which made it to Moon (coupled to the Lunar Lander) and back to earth) then the size difference is truely striking

[Raincloud Man]

Originalmente postado por MAD:

Originalmente postado por Zagreus:

What most people don't remember is that a lot of that d/v is required just to reach orbit, once you're in space, getting to places is usually comparatively cheap, if you count distance traveled/fuel used.

"Once you get to earth orbit, you're halfway to anywhere in the solar system." Robert A. Heinlein

He also spent several paragraphs explaining the same thing about orbit radius and velocity relating to the Moon in "The cat who walks through walls" that the KSP tutorial does in two lines as I recall... =p

[fluxtorrent]

Originalmente postado por MAD:

Originalmente postado por Don't:

Do u guys do this?

get apoap to 70k, then make an +70k kerbin orbit, then transfer to mun, dont orbit just entry then go back.

The way u make it sound, is that u litterally go STRAIGHT to the mun which is against everything I've ever learned.

You can do that if your timing is right but you dont actually gain anything by skipping a circularization burn at either end. I tested it

This is not entirely true, It largely depends on your launch window. An optimal launch window will allow a free return trajectory without the need for a large sum of the DV, circularizing is only necessary if you have a poor launch window and have to make a full or almost full orbit to hit the ideal aposis.

You do it in 2 burns however these burns need to be PRECISE. Your launch burn needs to give you an ideal aposis, this is normally around 90-100 km (depending on the window the degree of your gravity turn will generally pull your perapisis out to about 30km, but again it depends on the window). You then make your mun burn while falling back into the gravity well to use it to slingshot out. Any over or underburn here will either mean you miss the target or you (maybe) kill the kerbal by plunging back into atmo heh

[MAD]

Originalmente postado por fluxtorrent:

Originalmente postado por MAD:

You can do that if your timing is right but you dont actually gain anything by skipping a circularization burn at either end. I tested it

This is not entirely true, It largely depends on your launch window. An optimal launch window will allow a free return trajectory without the need for a large sum of the DV, circularizing is only necessary if you have a poor launch window and have to make a full or almost full orbit to hit the ideal aposis.

You do it in 2 burns however these burns need to be PRECISE. Your launch burn needs to give you an ideal aposis, this is normally around 90-100 km (depending on the window the degree of your gravity turn will generally pull your perapisis out to about 30km, but again it depends on the window). You then make your mun burn while falling back into the gravity well to use it to slingshot out. Any over or underburn here will either mean you miss the target or you (maybe) kill the kerbal by plunging back into atmo heh

A week ago I did a suicide burn from the edge of the muns SOI directly to the surface and measured the Delta-V, I then reset the game and measure the cost to circularize at 10km and then land and the difference was ~4m/s ie pretty much the same.I have the screen captures if you want?

Can you attach a picture or sketch because what you say sounds wierd.
Apo 90-100km around Kerbin yet you burn to the mun while falling back into Kerbins atmosphere.

Also I didnt think you could slingshot off the planet you were launching from.
Slingshoting usually your taking orbital energy off the planet to speed you up.

Have you tested this?
ie take measurments, revert to previouse in game save and try the other way?

[fluxtorrent]

Many times, it's also proofed with just the math as well. There's a reason it's the same way NASA did it for the Moon heh

It is more efficeint but it's a lot harder to pull off. You need to actually wait for the right transfer orbit, where as with circularizing you can do it whenever you want. Unless you are playing with TAC or one of the other life support mods there isn't usually much reason to be this fiddly with the numbers because you can take as long as you want with the flights and your craft tend to be lighter heh.

[MAD]

Originalmente postado por fluxtorrent:

Many times, it's also proofed with just the math as well. There's a reason it's the same way NASA did it for the Moon heh

It is more efficeint but it's a lot harder to pull off. You need to actually wait for the right transfer orbit, where as with circularizing you can do it whenever you want. Unless you are playing with TAC or one of the other life support mods there isn't usually much reason to be this fiddly with the numbers because you can take as long as you want with the flights and your craft tend to be lighter heh.

Please attach picture and maths as I would like to see this

Use upload artwork and copy your artworks URL and past in forum

How much delta-v are you saving?

[Jimmy]

http://wiki.kerbalspaceprogram.com/images/7/73/KerbinDeltaVMap.png 1.0 changed the atmospheric dv requirements and i'm not sure if this was edited to respresent it , but all the in-vaccuum stuff should be the same.