Orbital mechanics question:

[Danger45]

I've been working on my interplanetary rocket, and made a few one way lander trips to scout out Duna and Eve.

Here's my stupid question: is it extremely inefficient to take a direct/parabolic route from sun rise or sunset to Kerbin escape (depending on whether you're going to inner or outer planets) and then making your transfer burn from there? I always see people circularizing LKO then making several transfer burns, but when I try it with my rocket, I burn way more fuel that way (the proper way). Pretty new to KSP and rocket science in general, am I just flying wrong? Help!

[EndlessWaves]

There was a discussion about it a week or two ago and a couple of people ran tests and got different results.

The orbit side is irrelevant, you pass through an orbit doing it the other way so it's essentially free.

Launching with the planet's rotation should be more efficient but whether it actually is or not I'm not sure, It may even depend on the particular spacecraft (e.g. how much drag it generates).

[Kiershar]

I've been working on my interplanetary rocket, and made a few one way lander trips to scout out Duna and Eve.

Here's my stupid question: is it extremely inefficient to take a direct/parabolic route from sun rise or sunset to Kerbin escape (depending on whether you're going to inner or outer planets) and then making your transfer burn from there? I always see people circularizing LKO then making several transfer burns, but when I try it with my rocket, I burn way more fuel that way (the proper way). Pretty new to KSP and rocket science in general, am I just flying wrong? Help!

Last week I was arguing in favor of direct ascent (which is what you're talking about) and was proven wrong. Circularizing will get you better result for less fuel. Likely the problem you have is not executing your gravity turn properly.

[Danger45]

Likely the problem you have is not executing your gravity turn properly.

This is a definite possibility. Any pointers or rules of thumb? It seems like a waste of fuel to either burn nearly horizontally through atmo or coast to apoapsis while still in atmo, I always seem to end up doing one or the other.

[Vanamonde]

Also, from what Olex's transfer calculator is telling us (and it seems to be correct), sunrise/set are not the optimum times from which to start your burns.

[Kosmo-not]

Launching with the planet's rotation should be more efficient but whether it actually is or not I'm not sure, It may even depend on the particular spacecraft (e.g. how much drag it generates).

Launching with the planet's rotation is ALWAYS more efficient.

[The Destroyer]

This is INCREDIBALLY helpful.

Itll help you know when to burn and your closest approach, so you will see how close to the planet you will get! (VERY useful, I just burn positons till it goes down and i get an intercept! Useful for ecentric orbits and High inclination.)

[Kiershar]

This is a definite possibility. Any pointers or rules of thumb? It seems like a waste of fuel to either burn nearly horizontally through atmo or coast to apoapsis while still in atmo, I always seem to end up doing one or the other.

I'm not exactly sure how to perform a perfect gravity turn but i can tell you what i do. At slightly more than 10k (past the light blue section), i tilt the pitch to ~70 degrees toward 90degrees heading. Then, when im out of the slightly darker blue i slowly tilt all the way to 30degrees and let my apoapsis rise to my target orbit. After that, fast forward to 20seconds before apoapsis, set ship pointing at 10degree pitch 90 heading and burn until periapsis is fine.

Do that a couple times and check your remaining fuel after reaching target orbit. Then you can benchmark your gravity turns and refine it by making it smooth.

Edited October 11, 2012 by Kiershar