Should you orbit Kerbin first on an interplanetary journey?

[MBobrik]

I think that most of interplanetary rockets use LV-N, and thus just don't have the required T/W to go straight out of Kerbin's SOI efficiently.

[Hellsbain]

ok kinda new to the math but from what i see here it looks to me like a combination would be the most efficient and complicated. if you did your role and set up for an orbit but then kept going without normalizing you should then reduce gravity drag and in save some fuel right?

like I said Im still trying to rap my head around this so correct me if Im wrong.

[bewing]

39 minutes ago, Hellsbain said:

ok kinda new to the math but from what i see here it looks to me like a combination would be the most efficient and complicated. if you did your role and set up for an orbit but then kept going without normalizing you should then reduce gravity drag and in save some fuel right?

like I said Im still trying to rap my head around this so correct me if Im wrong.

Theoretically, if you do a gravity turn and then keep burning all the way until you are heading to your destination planet and you do it exactly perfectly -- yes, that would be slightly more efficient. However, doing an interplanetary transfer requires fairly precise timing. If you increase to an interplanetary speed while you are still in the atmosphere then you will blow up. If your interplanetary burn ends one minute too late, you will miss your target by 10 Gm. Also, interplanetary travel requires a lot of fuel, so you may want to refuel in orbit before you leave. For these reasons, it's better to establish an orbit first.

[Hellsbain]

so bottom line if your perfect go for it if your me bring 35% more dV then needed and still probably run out of fuel. XP

[Duck McFuddle]

I do both, depending on my mood, but really it just depends how big of a rocket you want to build. If your craft is huge, with way more Dv then needed, efficiency becomes less of an issue - just don't explode.