How to read the delta-v map?

[rolypoly]

There's this handy map
wiki.kerbalspaceprogram.com/wiki/File:KerbinDeltaVMap.png
but I'm having trouble understanding how to use it?

I want to find out how much dv I need to get from the surface of the Mun back to Kerbin. Surely it's not the sum of all the numbers counting down from the Mun to Kerbin? That would be the exact same dv as is required to get to the Mun from Kerbin in the first place. Should be much less than that, no?

[Aragosnat]

GEt something like MechJeb or Engineer *** (don't remember the rest of the name) MechJeb does work with teh current version as long as you get the working one. Otherwise ignore that chart as it is outdated as the new aerodynamics made it obsolite. IT involves a lot of math to figure out by hand.

[rolypoly]

Well in the atmosphere maybe. And speaking of new atmosphere what is the new dV needed to reach orbit now?

But in space it should still be the same I think?

[magus_ordinarius]

First, for the way back from Muns surface to Kerbin you need to escape Muns sphere of influnce, so add the numbers from Mun to Mun Intercept. Depending on your exact Orbit leaving Muns SOI, you might already be falling straight into Kerbin (no additional dV needed, except for breaking/choosing your landing spot). You shouldn't need more than a few hundred DV extra for that.
The new dV from Kerbins surface to Low Kerbin Orbit is about 3700-4000, depending on how efficient your ascent/gravity turn and rocket design is (the pointier, the better. No more pancake rockets!)

[Aragosnat]

True. They should be. Just that I know they changed how the parts work. Getting MeckJeb has a way to display your current total Delta-V as well as Engineer REdux?. And If I remember right on the Squads website people mentioned the Delta-V needed to leave Kerbin was 3200(?) instead of the 4550 needed. (I would have to go back and find said post.) But, most of my old designs that had 4550 no longer have it. And the good old LV-909 with 2 T400 fuel with over have fuel barely makes it to the Mun and back (true I am not usign patched conics that might make me waste more fuel then needed). But, if I was in 0.90 or older. I would have no problem with such as the fuel consumtion was way less then it is now.

Edit: What magus said.

[Sapidus]

The dv's are the same going both ways. The exceptions, are the "areobraking arrows." If you are going in the direction of the arrows along that map, you potentially need significantly less if you do your orbits / burns right.

For example from Eve intercept to Eve you potentially do not need much in the way of dv. But from the surface of Eve back to the the edge of Kerbals SOI you will need the total listed along the path. However, from the edge of the SOI to the surface of Kerbal you potentially need none if you have things lined up right (even though you needed it going the other way).

[Rhedd]

What Sapidus said.

I hadn't yet realized all my atmospheric dV calculations were going to be different. Ugh! This is going to be like being a noob again! ^_^

[Aragosnat]

Yeah. Also it seems the fuel consumption is a bit off too? At least when I used the Lv-909's they seem to be eating moar fuel. The Nukes sure do. But, that is likely they added what was being used for oxidiser to the fuel consumption.

[piraneous]

I can't seem to make sense of some of the numbers on these maps. I'm trying to get to dres. All the numbers seem legit till I break out of kerbin's SOI, the plane change came in about 100m/a less than the map said which is good, but instead of the 600 or so to get an intercept, its more like 1900m/s. I used Kerbal engineer to fast forward till my intercept angle was close to 0 but it didn't seem to matter.

[piraneous]

Oh yeah, and my capture burn takes minimum of 1800 m/s. Not the 1200 the map says

[rolypoly]

Have you used the departure time calculator to depart at the most optimal time?

[Aragosnat]

Have to agree. You need to make sure you are departing at the right time to get the best burn possable. My First Dres Window is at Year 1 Day 341 to give you an Idea. And I'm only on day 245? Slowly creeepingh to the window date already have a ship waiting in orbit to leave.

[andylaugel]

Looks pretty spot on, except for the LKO to Kerbin's surface part. I usually just drop the periapsis to 45 to 50 km, and let aerobraking take care of the rest. So at least 7 km/s dV for a round trip to the Mun.

I'd suggest more, as the dV map assumes the most efficient of maneuvers. Landing is rarely that efficient. A quick rule of thumb for me is 150% orbital speed to land on an airless body. A typical Mun orbit is around 500 m/s, so landing is 750 m/s.

[Chibbity]

Not sure about the Dv without starting the game up but a Command pod/Decoupler/FL-T200 fuel tank/Terrier engine will get you from the Mun's surface back to Kerbin with not much fuel left over.