Delta V calculations

[rustysocket]

I don't think I'm calculating delta V right. The  v_e nuke engines is 7874 right mine has 8. its full mass is 133.7 tons and empty mass is 67.1 tons. Delta V=V_e ln(full mass/dry mass.  So {Delta V=7874xln(133.7/67.1 } I get 5428 and I know I can go interplanetary with this thing.

Edited February 2, 2016 by rustysocket

[Guest]

Make sure you don't have any oxidizer in tanks the LV-N engines will draw from, they only use LiquidFuel.

[Exploro]

Math appears to be fine; I got a total DV of 5399. Regex is likely correct; remove the useless mass and your DV calculations should improve.

[rustysocket]

no oxidizer

 

[Gaarst]

Should there be anything concerning ? Unless you're planning on landing, 5 km/s of dV is enough to get you anywhere and back (maybe not Moho depending on the inclination difference).

Anyway, if you're really concerned about dV, you might want to take a look at Kerbal Engineer which does the calculation for you (accurately most of the time).

[rustysocket]

it says you need almost 100,000 m/s of delta V for a jool trip

[Guest]

2 minutes ago, rustysocket said:

it says you need almost 100,000 m/s of delta V for a jool trip

What says?  Did you just click randomly in a porkchop plot?  Maybe run it with a really tight timeline?

[Gaarst]

5 minutes ago, rustysocket said:

it says you need almost 100,000 m/s of delta V for a jool trip

If you want to get to Jool faster than light, then this might be accurate, otherwise it is way too big.

I suppose you are looking at a "subway" dV map, if so, make sure that you are reading the right things.
100 km/s of dV might be the requirements to land and orbit from Jool's surface... except that Jool doesn't really have a surface (actually yes, but it is made of explodium) and an extremely dense atmosphere, so don't pay attention to these numbers as dV requirements for a Jool landing will be insanely high and as it is no longer possible to land on Jool.

Edit: just looked at a dV map and transfer window planner: dV map mentions 14 km/s for a landing, and the highest I could get with a transfer window planner was 19 km/s. So I really don't know where these numbers come from, are you sure you didn't add a 0 somewhere ?

Edited February 2, 2016 by Gaarst

[rustysocket]

[Guest]

Numbers inside of the circle are for landing so, unless you're planning on landing on Jool, you don't need that much delta-V

[Gaarst]

First, this map is outdated and somewhat confusing, look here for an updated one for 1.0.5.

Second, as I mentioned earlier, the 40 km/s figure is indeed for a landing and take off from Jool's surface. For a low Jool orbit, from LKO, you'd need about 5 km/s to get there, and as much to get back. That is without aerobraking, which can cut your dV requirements by 3000 in this case, but seeing your ship, it probably won't survive an aerobraking at Jool.

[rustysocket]

Aren't they adding inflate able heat shields in 1.1?

[Gaarst]

Maybe™

[Snark]

Going back to the original dV comments:  as folks have said, don't include oxidizer.  Also, don't use LFO fuel tanks, even if you've emptied out the oxidizer.  You're wasting space, and hauling around fuel tanks that are twice as heavy as they need to be.

The Mk3 airplane parts have some big LF-only tanks that would be perfect for your application.  Ditch those Kerbodyne tanks and replace them with LF tanks.

Also:  Solar power really sucks, out by Jool.  If you can afford it, consider bringing more RTGs.  At Jool, they give you better electricity-per-kilogram than the Gigantor panels you've got on there.  (I see you've already got some RTGs on there.  Just don't go expecting a lot of power from those Gigantors.)

Also:  You're oversupplied with radiators.  For eight LV-N's, you really don't need four of the giant-size folding radiators.  You can probably get by just fine with half that radiator mass.

 

Edited February 2, 2016 by Snark