Tanks vs range

[demian_travis]

I was wondering: Is there a way to calculate the optimal amount of fuel tanks for a ship? I managed to build a lander with a FL-T400 tank, send it to Minnumus and come back to Kerbin with a lot of fuel to spare. I usually had the FL-T400 tank with four smaller tanks on its side, having the same result - but needing a bigger rocket to send the lander to Minnimus.

Of course, more tanks equal longer range, but the ship gets heavier, spending more fuel. How do I calculate the optimal ratio between tanks, range and efficiency?

Edited April 29, 2014 by demian_travis

[Taki117]

Well, you can use the dV equation and rearrange it to solve for the mass of fuel you will need to get to a certain point. And using thiss you can select the appropriately sized tanks for your mission.

[Claw]

Here is one page that has all the answers you seek. It's loaded with math. http://wiki.kerbalspaceprogram.com/wiki/Cheat_sheet

Unfortunately, there is no way in stock KSP yet to tell you how much delta V your ship has. So if you want to stick with an unmodified KSP, your main option is to do the delta V calculations by hand. If you are not opposed to mods, you can install Kerbal Engineer Redux or MechJeb and it will tell you how much dV your ship has.

How much delta V do you need? Well, that's where the delta V map comes into play (also on that wiki page). It looks like this:

It basically says that from low Kerbin orbit, you need 920 dV to get to Minmus, 80 dV to establish an orbit, and 240 dV to land.

Then you reverse the numbers to find your way back home. 240 dV to take off, and about 80 dV to break Minmus orbit. Although you can shave off a lot of dV from the 920 (Minmus to Kerbin) because you can aerobrake around Kerbin. If you were to return to Kerbin and reestablish an orbit without aerobraking, it would take the full 920 dV.

There is a more complex version of the dV map here: http://i.imgur.com/UUU8yCk.png

I like it better, but if you are unfamiliar with using dV maps, the first one is a bit simpler to start off with.

Edited April 26, 2014 by Claw

[Red Iron Crown]

As the other responses allude to, delta-V is the measurement you're looking for. A craft's delta-V will give you an excellent overview of which destinations it can reach.

The other critical measurement, thrust-to-weight ratio (TWR), will give you an overview of where it can land and take off from.

[xrayfishx]

You may be interested in Kerbal Engineer Redux or MechJeb. Both will calculate lots of useful things for you.

Edited April 26, 2014 by xrayfishx
Got ninjad

[demian_travis]

Thak you! <33333

[Claw]

Thak you! <33333

You are quite welcome. Good luck on your travels!

[technion]

I find KRE doesn't provide all this information quite as well as people suggest. It's a great mod when you're designing, but once you dock a tug and a payload, it seems to have no clue what the transfer stage deltav will be.

Don't get me wrong - seeing the altitude above surface is an absolute requirement imo and it's great at that.

[FREEFALL1984]

I like to use mechjeb to calculate everything for me, it gives me the option of performing my more mundane maneuvers for me, but if you're new to KSP which I imagine you are, then I'd recommend KER, this forces you to perform all your own maneuvers which for a new player is great practice, nobody wants to be that guy who cant fly without mechjeb.