Getting to Jool?

[Jack the Kerbonaut]

Right, I am planning a manned mission to Jool for the first time and its says that the delta V needed to get to Jool on the KSP wiki is around 1900ms from a 100km Kerbin orbit. Now when I do the optimum Hohmann transfer it predicts on the maneuver node that the Delta V required is around 3900ms. Now I use the correct phase angles and everything is how it should be but I do not get the 1900ms delta v that I should.

CAN ANYONE HELP?

[Ralathon]

Is your ejection burn maneuver in the correct position? So you don't burn perpendicular to the direction Kerbin moves around the sun?

[spikeyhat09]

make sure the Kerbin-Kerbol-Jool angle is just over 90 degrees (96 IIRC). set up the maneuver node so that the line follows the projected curve exactly, AND gives you an encounter

[Crown]

To leave Kerbin's SOI a ship has to go from 2'300m/sec to ~3'000m/sec (as far as I remember). Without any gravity assist.

Using the moon to catapult a vessel off Kerbin's SOI much can be saved. I think about 640m/sec delta-v is needed to get to the moon. After passing the moon the ship should be in inter-planetary space.

I prefer using a nuclear engine (they are more efficient) and radial mounted fuel tanks which I drop after they are empty.

As usual, can we see some pictures of your vessel so make out some design problems?

[Panichio]

It sounds a lot like that 3900 m/s is including the dV required to also get into orbit. Redo your calculations, maybe?

[Crown]

Here's the maths. At least what they spitted out:

From Kerbin 100km orbit to SOI edge: 917.14m/sec without gravity assist.

From orbit around sun at Kerbin altitude to Jool altitude: 2'719.21m/sec

Total of ~3'636m/sec. Without an Jool orbit insertion.

So 3'900m/sec sounds legit. And as an estimation they could work.

[Jack the Kerbonaut]

Let me clarify, I am not new to the game I know the phase angles I have the encounter in the maneuver node however the maneuver says it takes over twice than what it is supposed to be.

I am following the correct method of transferring following the ksp interplanetary calculator.

I am doing everything by the book, does anyone think that 1915 in delta v is a little optimistic, prove me wrong?

[Johnno]

Let me clarify, I am not new to the game I know the phase angles I have the encounter in the maneuver node however the maneuver says it takes over twice than what it is supposed to be.

I am following the correct method of transferring following the ksp interplanetary calculator.

I am doing everything by the book, does anyone think that 1915 in delta v is a little optimistic, prove me wrong?

I generally head over to Jool with around 2000m/s for the initial burn so that part sounds accurate enough. I rarely wait for optimal transfer windows and burn the extra few hundred whenever I feel like going rather than timewarping for ages.

As for your 3900m/s manouver node, if you keep insisting that you're doing everything by the book and that you're not doing anything wrong then how do you want us to help you?

I just plotted in a quick and dirty transfer to Jool from Kerbin for 2350m/s, Jool is about 70 degrees off optimal right now. Edit: tweaked my transfer to not so quick & dirty, 2105m/s.

I can't conclude anything other than either you're doing something wrong or your game is broken. We can't help if you keep insisting you're doing nothing wrong and we can't help with fixing your game if it's somehow broken.

Edited July 21, 2013 by Johnno

[Jack the Kerbonaut]

Don't worry I just got a 2290ms maneuver dont know how I was getting 3900ms soz for wasting your time lads.

[stoani96]

Don't worry I just got a 2290ms maneuver dont know how I was getting 3900ms soz for wasting your time lads.

ah! 2290 milliseconds delta-v..... sounds interesting!

im sure einstein will get jealous if you do it to jool!