Lost 800m/s of Delta-V from VAB to Launchpad?

[Mazen]

Hello guys,

I don't understand why Kerbal Engineer in the VAB shows me about 5700 of Delta-V and on the Launchpad there are only 4900 left.

It's probably because of me don't understanding how this whole Delta-V thing works. Can somebody explain why I lose this amount auf DeltaV?

And btw.: I know that rocket-design ist s*hitty, I'm working on that

[Commander Zoom]

Well, first of all I hope you realize that in the first picture, the two sets of numbers (before and after the slash) are for atmosphere and vacuum. It looks like you've done the right thing in the sense that you've used engines on your upper stage(s) that are much more efficient in space.

I'm guessing, however, that what it shows you on the launch pad is what you get at your current altitude. If so, you can expect the numbers for the later stages to actually increase as you climb higher, out of Kerbin's atmosphere and gravity well.

[Mazen]

I thought the number before the slash was the Delta-V for the current stage, and the number after the slash was the Delta-V of all stages before in total?

[tavert]

I thought the number before the slash was the Delta-V for the current stage, and the number after the slash was the Delta-V of all stages before in total?

This is correct. All stages up to and including that line.

I'm guessing, however, that what it shows you on the launch pad is what you get at your current altitude.

So is this. The in-flight KER delta-V readout uses the specific impulse at the current altitude.

[tuguley]

^Yep

After launch you'll notice that your dV actually increases for a while

[Mazen]

Ok, so the DeltaV I get while building is for vaccum and therefore I'll get less on the launchpad?

I recently found a DeltaV-map for the Kerbal-System. For example I need 8000 m/s to get to an other planet, should I aim for 8000 in the VAB or at the launchpad?

[superm18]

if i remember correctly, in the VAB you can choose between atmosphere and vacuum and by default it's atmosphere.

So it seems that there is some delta-v missing, but i think it's either due to a tank and/or engine getting disconnected (hit F3 to view any damage) or it's simply due to Engineer Redux not being updated to .21.1 yet

[superm18]

Ok, so the DeltaV I get while building is for vaccum and therefore I'll get less on the launchpad?

I recently found a DeltaV-map for the Kerbal-System. For example I need 8000 m/s to get to an other planet, should I aim for 8000 in the VAB or at the launchpad?

You got to figure out from what stage you are in vacuum (4500 delta-v to orbit) and then selecting the vacuum stats in the VAB to add the whole thing up.

[tuguley]

Ok, so the DeltaV I get while building is for vaccum and therefore I'll get less on the launchpad?

I recently found a DeltaV-map for the Kerbal-System. For example I need 8000 m/s to get to an other planet, should I aim for 8000 in the VAB or at the launchpad?

Vaccum dV is usually all you need. If you need 8000m/s, then aim for 8500 m/s in VAB or 9000 m/s if you want to be completely safe.

[Stir_Fry_Beans]

It takes 4500 m/s dv to get into a low Kerbin orbit (100 km or so) this is with a fuel optimal ascent like the one you have. I try and use larger engines to get into a orbit then I worry about the actual dv my rocket has. Payloader is handy for doing this! Its simple as picking your payload and picking the launch vehicle.