The way that maneuver nodes seemingly work is quite silly

[OPERATOR571]

So I've just started playing KSP2 since For Science! came out, and one of my biggest annoyances so far has been the maneuver nodes.  Many times so far I have had to reload a quicksave because I, despite following the timer on the node as best as possible, have way overshot it, sometimes to the order of hundreds of meters per second.  Initially it confused me as to why this was happening, for in KSP1 I am a very accurate burn-starter and stopper, but after some examination I think I know why: when you plan a maneuver, the game calculates the burn time based on the current max acceleration of your craft; using the max acceleration and the deltaV, it does some simple dimensional analysis to find out what that time should be (ex. 10.0 m/s² max, 800.0 m/s deltaV, burn for 80 seconds).  Now, this system is quite simple and effective if your mass doesn't change, say for small burns where it for all intents and purposes the mass is a constant, but once you start burning a significant percentage of the fuel of a craft, it can start to cause problems.  Acceleration is force divided by mass, so if your mass is cut in half then you will accelerate twice as quickly, but (from what I can tell) the game doesn't take this into account.  Therefore, because the burn time is seemingly only calculated when you make a maneuver node, you get situations where you end up burning far above the deltaV of your maneuver if you trust and follow the tools provided by the game.

So, how should the devs fix this?  Well, they could implement some complex dynamic calculation where it takes in to account how much mass you'll lose over the course of a burn and accounts for it in the burn time, but this would still be susceptible to errors if you, say, throttle down near the end of a burn to be more precise.  Or, they could have the game recalculate the burn time across the course of a burn, constantly recalculating it based on the changes in your acceleration (which I believe is done in KSP1, though that may be a mod that I use).  OR, and this is by far the most radical suggestion, they could just reimplement the deltaV based system used in KSP1.  That way, you could actually tell how close you are to the desired orbit, regardless of however fast you accelerate.  Like, if for some reason you want to use RCS, or not use full throttle, or you want to do anything that is not exactly in the vanilla, proscribed method of doing things.  Isn't this game supposed to be about being creative? about not following the rules?  This is by far the biggest design issue (in my opinion) of the game so far: a single-minded, rigid approach which the devs think is the best is the only way of doing so many things, from the topic of this post, to not being able to even plan a maneuver past your max deltaV (also susceptible to calculation errors), to the timewarp limitations, is hard built into the mechanisms of the game.  Hopefully, though, these artificial restrictions that stifle the spirit of KSP are seen as what they are -- restrictions to creativity and fun -- and are removed so that this game can reach to and beyond the heights of KSP1.

(I'm sorry if this seemed negative, I really do like so much of the game and have been really impressed playing it so far.)

Edited December 29, 2023 by OPERATOR571
I thought that ctrl+Enter was how you made a new line, not shift+Enter.

[Superfluous J]

I haven't noticed that, even on long burns like one-shot interplanetary burns that use most of the stage's fuel.

What I do notice is that they don't recognize engine changes, like if you plan it with a nearly empty stage, and then stage it away the maneuver node assumes the TWR of the prior stage until you start to burn.

I've also noticed very occasionally when a burn is a small fraction of a second, the game tells me some large number like 45 seconds.

Also, sometimes the line is yellow, sometimes its red, and sometimes it's nonexistent and I have no idea what causes which to occur.

[OPERATOR571]

4 minutes ago, Superfluous J said:

I haven't noticed that, even on long burns like one-shot interplanetary burns that use most of the stage's fuel.

What I do notice is that they don't recognize engine changes, like if you plan it with a nearly empty stage, and then stage it away the maneuver node assumes the TWR of the prior stage until you start to burn.

I've also noticed very occasionally when a burn is a small fraction of a second, the game tells me some large number like 45 seconds.

Also, sometimes the line is yellow, sometimes its red, and sometimes it's nonexistent and I have no idea what causes which to occur.

Really?  I've had it overestimate the burn time by like half a minute before.
Also, I completely concur with the line not making much sense.  I've had it go down, go up, go down then up, literally just ping-pong across both while I have been accelerating and not accelerating, and I'm pretty sure I've seen it be more colors than this game turns my mouse.

[The Aziz]

Don't watch the line or the timer, watch the trajectory in map view. If you point the rocket in maneuver direction node, and don't mess with thrust, you'll end up nearly exactly where the planned path was.

[Vl3d]

Also please consider that the burn starts exactly where the maneuver node is placed. So if you want to burn half-half of PE for efficiency of if you want a circular orbit you have to move the maneuver node back so the PE splits the red line in half. It's different from KSP1, in which this was done automatically.

[JoeSchmuckatelli]

Aziz's suggestion is what seems to work - although it does equate to 'don't trust the timer' 

It's a good planning tool, but like SuperfluousJ writes it's a bit confusing in action. 

Ofc I did what Aziz suggested in KSP, too.  Start the burn looking at the ship and timer because that's cool, then switch to map view and eyeball when to stop via the orbit lines.  Allows you to fairly quickly adjust Intercepts and the like if you fudge timing 

[hatterson]

8 hours ago, Superfluous J said:

I haven't noticed that, even on long burns like one-shot interplanetary burns that use most of the stage's fuel.

What I do notice is that they don't recognize engine changes, like if you plan it with a nearly empty stage, and then stage it away the maneuver node assumes the TWR of the prior stage until you start to burn.

I've also noticed very occasionally when a burn is a small fraction of a second, the game tells me some large number like 45 seconds.

Also, sometimes the line is yellow, sometimes its red, and sometimes it's nonexistent and I have no idea what causes which to occur.

This also applies to you changing the maximum thrust of an engine. For example if you're doing a gilly landing or something where you want your max thrust to be very low so you actually have some throttle control, then you plan a maneuver, it'll assume you're thrusting at whatever your current max it. If you then update the max thrust, it won't modify the burn calculation until you do something with the node or start burning.

The current maneuver planner is actually incredible and a huge improvement on KSP 1 when it works as intended. It takes into account staging events and everything. The only minor issue is that with staging events it assumes they happen exactly on time and the thrust from the next stage is immediately available. Usually the player is gonna be a second or two off on that and if you're using an engine like the tuba, that takes a second or two to extend which delays the thrust. That makes a very minor difference in projected outcome in a single planetary system, it's a bit higher at interplanetary, and at interstellar there likely needs to be some solve for it unless the solve is "*shrug* do a mid course adjustment for a couple m/s dv"

I have noticed some minor bugs where it doesn't seem to start the progress bar going down when I start burning, but if I follow the timer it still works.

Here's as example showing the staging system working. I loaded up a sandbox with a stupid rocket. Command pod, fuel tank, mainsail engine, stack sep, small fuel tank, trumpet engine.

I teleported it into LKO and created a node that was 100% normal burn and this is what it showed:

Long shallow turn as the trumpet does it's low TWR thing, the staging event (first plus) then a sharper turn as the mainsail kicks on, then the end of the burn/fuel (second plus).

I then reverted and flipped the stages (keeping the fuel tanks with the engines so they each has the same burn time as before) and created the same node. Here's the difference:

Sharp quick turn as the mainsail pushes hard then a low slow continuation as the more efficient/less thrust trumpet kicks in after staging.

I flew both maneuvers and my final trajectory was very close to the projected, the difference only due to, as mentioned above, inefficiency in stage transitions.

[Sea_Kerman]

Yeah, the actual calculation of the path is really nice but they left out the one important thing. Time matters little, what actually matters is remaining delta-v. They should really count down the delta-v readout as required. If I use the maneuver node controller or micro engineer mod to display remaining delta-v and go off of that, my burns are quite precise.

[OPERATOR571]

14 hours ago, The Aziz said:

Don't watch the line or the timer, watch the trajectory in map view. If you point the rocket in maneuver direction node, and don't mess with thrust, you'll end up nearly exactly where the planned path was.

That's what I have been doing, but I just find it frustrating that they gave up what was such an effective way of doing it in KSP1.

[OPERATOR571]

8 hours ago, Vl3d said:

Also please consider that the burn starts exactly where the maneuver node is placed. So if you want to burn half-half of PE for efficiency of if you want a circular orbit you have to move the maneuver node back so the PE splits the red line in half. It's different from KSP1, in which this was done automatically.

I've also been doing this (and also burning slightly radial-in), but the projected trajectory should be accurate regardless of whether I make it as efficient as possible or not (which it has not been for me).

[hatterson]

18 minutes ago, OPERATOR571 said:

I've also been doing this (and also burning slightly radial-in), but the projected trajectory should be accurate regardless of whether I make it as efficient as possible or not (which it has not been for me).

Are you able to capture a video of this happening? Or a bunch of screenshots? I've done a ton of different burns and they complete on time and on target basically all the time.

[Wheehaw Kerman]

15 hours ago, Sea_Kerman said:

Yeah, the actual calculation of the path is really nice but they left out the one important thing. Time matters little, what actually matters is remaining delta-v. They should really count down the delta-v readout as required. If I use the maneuver node controller or micro engineer mod to display remaining delta-v and go off of that, my burns are quite precise.

You can manage this in some cases by subtracting the planned delta v from the delta v remaining shown in the staging stack in lower right, and stopping the burn when the delta v remaining hits the resulting number.