Not sure about my delta-V and how to improve it

[ImpulseSpaceCenter]

Hi,

I have build that massive ship to see if I can use it as a capital ship for my kerbal. But I am not sure of the available delva V I have!

Kerbal Engineer tell me it's 1,189m/s but I think it's wrong so I have had a try at the equation myself

Mass Full tank: 259.574t

Mass Empty tank: 99.574

ISP:

2-6-8 Nuclear : 800ISP 60Thrust

Poodle: 390ISP 220Thrust

All: 579ISP

delta V:

2-6-8 Nuclear: 7519 Dv

Poodle: 3666 Dv

All: 5161 Dv

Are my calculation correct?

I think most of the burns will be done with the Nuclear engine as the ship stay in vacuum all the time, the poodle is here in case I need a bigger thrust.

How can I improve my Dv? I guess removing mass is best way to do it?! It's mainly fuel in it. Except for the cupola and hitchiker.

And this is without all the equipment to bring (rovers, tugs, probes etc...)

Also How do I calculate my accelleration? So I know how much I acccelerate with my engine set up.

Thanks in advance.

Edited June 4, 2013 by ImpulseSpaceCenter

[rryy]

Try using less engines to increase your delta-v. More engines are just dead weight, so start by removing the Poodle and some of the LV-Ns.

To calculate your acceleration, simply use the basic formula F=ma. You take your maximum thrust and your full mass and put it into the equation:

700=262.972a

700/262.972=a=2.66 m/s^2

Now, keep in mind as you burn fuel, you mass decreases, so thus, your acceleration increases.

[Specialist290]

Are you sure all of your fuel tanks are connected to your engines? Some of the structural pieces aren't automatically fuel crossfeed capable, so you might have to use fuel lines to make sure the fuel is actually being used.

[ImpulseSpaceCenter]

Are you sure all of your fuel tanks are connected to your engines? Some of the structural pieces aren't automatically fuel crossfeed capable, so you might have to use fuel lines to make sure the fuel is actually being used.

They are all connected with either fuel line or docking port (which are set for cross fuel capable). I think it's just that the links and ports are disturbing Kerbal engineer.

Try using less engines to increase your delta-v. More engines are just dead weight, so start by removing the Poodle and some of the LV-Ns.

To calculate your acceleration, simply use the basic formula F=ma. You take your maximum thrust and your full mass and put it into the equation:

700=262.972a

700/262.972=a=2.66 m/s^2

Now, keep in mind as you burn fuel, you mass decreases, so thus, your acceleration increases.

Thanks for the info. I guess I need to decide of the amount of engine depending on the acceleration max I want.

I think I need to rethink the design, and may be use less cupolas and hitchikers, so i can free weight for the equipment too. I would like to reach a nice 12-15k Dv, so it would be around 9-10 with the rovers and stuff.

[HoY]

9-10k m/s of delta v is going to be quite a bit more massive than what you've got shown here. With just 8lvn engines you will need about the equivalent of 4 orange tanks to get 9-10km/s without a payload.

And yes, ditch that poodle! If you don't plan on landing this thing on a low grav moon the poodle is dead weight that just costs you loads of deltaV wether its firing or not.

[Nao]

This might be useful:

Chart is from somebody on this forum but i couldn't find who

As you can see only Nuclear engines have the capability to get to 12-15k Dv without staging/refueling.

[ImpulseSpaceCenter]

Thanks guys,

I played around a bit with all the numbers and stuff, to find what is the max deltav the game can offer (about 17k for liquid fuel), but one think I haven't really figure out is that the equation does not considerate directly how much fuel we have.

With Nao graph, if I uderstand well, if I want more delta-V I need to have my fuel taking as much mass as possible.

[Nao]

I'm not sure what equation you have in mind but ...

If we consider only one stage there is a limit on how fast we can accelerate with an engine, depending on its ISP. That is, past some point even if we add more and more fuel the Dv increase would be almost zero.

The lines on the chart cut at 87,5% because what's left on the ship is fuel tank mass. So if you want to break above 17km/s Dv you would have to shed dead weight (empty fuel tanks) with staging. And still with a lot of stages and fuel taking 99% of launch mass you would get only ~36km/s Dv out of LV-N's.

[ImpulseSpaceCenter]

I'm not sure what equation you have in mind but ...

The one from the wiki: http://wiki.kerbalspaceprogram.com/wiki/Tutorial:Advanced_Rocket_Design

If we consider only one stage there is a limit on how fast we can accelerate with an engine, depending on its ISP. That is, past some point even if we add more and more fuel the Dv increase would be almost zero.

I just want to be able to go to orbit around any planet with it, with margin for error and trial, and return to kerbin. Then it will carry other smaller ship that will go on missions to the moons/planets. So i also need fuel to refuel them. and enough extra Dv to compensate the weight of those ships (20ish tons each, 2-3 ships, 1t rover by as much as I can etc...)

The lines on the chart cut at 87,5% because what's left on the ship is fuel tank mass. So if you want to break above 17km/s Dv you would have to shed dead weight (empty fuel tanks) with staging. And still with a lot of stages and fuel taking 99% of launch mass you would get only ~36km/s Dv out of LV-N's.

There won't be staging, but also no launch Dv needed. What take the most weight are the command modules and hitchikers.

I got a smaller design with about 10k Dv, but I need to get a launcher for it as it's in one piece and aronud 200t. my launcher got the struts breaking making everything explode.

Edit: Obviously, once I can get refueling station around each planets, it will be easier)