is my calculation correct?

[Affan]

Hello, I was finding the Delta-V of a section of a craft I made. Please can you confirm my calculation as this is my first delta-v calculation:

(rockomax poodle engine, my weights are correct for the craft)

DeltaV = (9.81*Isp)*(in(Mfuelled/Mempty))

DeltaV = (9.81*390)*(in(20.97 / 12.97))

DeltaV = 3825.9 * (in(1.61680802))

DeltaV = 3825.9 * 0.48045384751060720536776041863122

DeltaV = 1838.16838

Thanks for all responses

Edited November 9, 2013 by Affan

[Nemoricus]

That's correct, aside from "in" needing to be "ln".

[Ravenchant]

Looks good to me.

Edit: dammit, ninja'd

[Specialist290]

I'll vouch for it as well. Let us know if you need any further help

[capi3101]

I get 1838.16837.

If you have to go out to the hundred-thousandths place before you start finding errors, you're probably close enough for jazz (read: one of us is OCD and it's not likely you).

[numerobis]

g0 is 9.82 in KSP for some reason; with that adjustment I get 1840 m/s.

Just make sure that m_empty includes the mass of the poodle and the dry mass of the tanks. From your numbers, I suspect you got that and you're burning an X200-16.

Edited November 6, 2013 by numerobis

[DMagic]

I made up an Excel spreadsheet for calculating delta-v and a few other things that engineer can't handle; I always meant to release this somewhere, I just never got around to it. If anyone is interested here's the link: https://skydrive.live.com/redir?resid=2582013B6F75B5F4!1843&authkey=!AFFJzjos_IJw3z4 (let me know if doesn't work).

It should be pretty self explanatory, the only values you have to input are along the top, the units used are all indicated, and the important values are in bold (most of the rest are just showing my unit conversions and intermediate steps).

Use the total mass (dry mass + fuel mass; shown in the info panel in the map view), and use value for liquid fuel only, not liquid fuel + LOX. You can calculate the average ISP if you have different engine types.

You can also get delta-v values for RCS. You can get the amount of fuel needed for a desired delta-v; this and the RCS values are the primary reason I made this. You can also get burn time, burn rate and TWR for a given surface gravity.