Maneuver node question

[cephalo]

When I am getting ready to do a prograde burn on a maneuver, do I follow the prograde direction or the maneuver target direction during the burn? I'm having a bit of trouble getting accurate burns. Jeb can hold prograde, but maybe I don't want that in this case?

[Anquietas314]

For short burns or where you're aiming (anti-)radial/normal you're generally better off following the maneuver target. For very long burns (say 3-4 minutes - break it up if it's longer) I generally get better results following a point roughly half way between the maneuver marker and the prograde marker (particularly when the maneuver marker is close to "towards the planet")

[Zamolxes77]

Uhm, if you bother to establish a maneuver, follow the proper reticle. Why would you burn half way between maneuver reticle and prograde? That must be an extremely simple maneuver you established. Once you start playing with the other vectors besides prograde and retrograde, the blue reticle might not even be in same postcode as the prograde vector ... Also by not burning the right way, you waste more fuel because you have to adjust the result again.

For most transfer orbits, I actually execute 2 maneuvers. First gets me to a good solid encounter, with lowest periapsis I can manage, then I follow up with a second one that refines the result.

[Anquietas314]

Uhm, if you bother to establish a maneuver, follow the proper reticle. Why would you burn half way between maneuver reticle and prograde? That must be an extremely simple maneuver you established.

Because burning directly at the reticule in those specific cases (low kerbin orbit, long burn, mostly prograde) means you'll lower your periapsis inside the atmosphere, which is never a good idea when you're not trying to aerobrake.

Once you start playing with the other vectors besides prograde and retrograde, the blue reticle might not even be in same postcode as the prograde vector

Yeah, I covered that. those other vectors are called radial and normal, with the "anti" version being directly opposite those.

Also by not burning the right way, you waste more fuel because you have to adjust the result again.

Yes, but in some cases - like unintentional aerobraking - that works out less problematic (sometimes a lot less) than dealing with the aerobraking, especially now reentry heat is a thing in stock; ladders and similar parts overheat rather easily. In either case, for long burns the precise timing of the burn matters a lot more than exactly what direction you're pointing.

[katateochi]

If you just want to do a straight forward prograde burn without setting up a manoeuvre node then just manually point to the prograde marker, or use the pilot's ability to automatically turn the ship to face prograde. However I don't like using the pilot abilities (the buttons down the left of the nav ball) to hold a heading because they waste a ton of power and can make the ship judder. But you can hit the prograde button, wait till you're lined up and then switch it back to regular stability assist (which doesn't waste so much power).

If you are using a manoeuvre node then you always want to be lined up exactly on the blue manoeuvre node marker. One key thing to making an accurate burn is when you time the burn. Don't start the burn at t=0, you want to reach t=0 exactly half way through the burn. So for example if you set up a manoeuvre and it says the Estimated burn is 2m then start the burn when "NodeinT" is 1m.