Flight Plan [0.10.7 for KSP2 v0.2.2+] (2024)

8 hours ago, Poppa Wheelie said:

Thank you for this mod! And for the combination of Flight Plan, Maneuver Node Controller, and K2-D2. I use these all the time.

I've noticed one issue with Flight Plan and/or Maneuver Node Controller:

See Also

Kerbal Space Program: The KSP2 thread is not yet ready for releaseFlight Plan [0.10.7 for KSP2 v0.2.2+]Tutorial:How to get to MinmusHow to transfer from Mun to Minmus ?

If I create a node, then load a save previous to this node creation, Flight Plan and Maneuver Node Controller still have a node.

Also for Flight Plan:

When Flight Plan creates a node to do something at a particular point (eg, Circularize at the next Ap), the node is created right on the Ap, which will not result in the most circular orbit (possibly with the Pe still in atmosphere). When I look at the expected future results in a case like this, I do not see a circular orbit.

In these cases, I manually adjust the created node, by walking backwards in time to find the "best" circularization. Could this feature of placing nodes directly on specified points be updated? I think that in every case, we don't really want the resulting node to begin its burn directly on the selected point.

Thanks for the feedback. I'm glad you're finding these mods useful!

The first problem is actually in Node Manager - which is a mod FP and MNC depend on that runs in the background. It's maintaining a list of nodes, and apparently, this is not being cleared and reset when you load a save - hence the stale info from before. I'll get to work on this as it clearly should be handling this more gracefully. Once fixed in NM, the problem should vanish in FP and MNC.

For the second problem, I may need a bit more info, and it also may help if I cast a bit more light on what FP is really doing. I'll start with the latter.

tl/dr: FP is already backing the node off to make it star before the actual point you want the burn to be centered on.

When FP creates a node it does base the *initial* position of the node on orbital mechanics equations that assume the burn is an instantaneous impulse. This is part of the MechJeb heritage and has the virtue that the equations are well-known and not hard to model. However, KSP2 handles burns a bit differently than KSP1, so FP carries on to adjust the time of the node, and consequently the direction of the node so that it will instead start earlier by 1/2 the burn duration. This is a two-putt approach because to get the burn time we must first *create* the node and let the game work out how long the burn needs to be for that craft to get that delta v. So, create the node, get the burn duration, back the node start time off by 1/2 the duration, and then (crucially it turns out) adjust the direction of the node.

The crucial node direction adjustment is most apparent in the circularize after ascent problem. The thing here is that burn vectors are in Prograde, Normal, and Radial, and when you back a node off it will be at an earlier part of the trajectory where the prograde and radial vectors were very likely pointed in a different direction, so FP does a little math to make sure that the node, when positioned at an earlier time, has new P/N/R components that will point in the same direction the original non-adjusted node would have.

Hopefully, that makes sense - now on to the request for more info!

In the example you're using are you basing this on a very steep ascent profile? By steep, I mean one where you've begun your turn quite high and late in the ascent and so arrive at the Ap with not much horizontal velocity. If so, then I have your answer, but if not then I'll need more detail about the example problem so I can try to reproduce it and see what FP may need to do. What type of trajectory are you starting with: suborbital or orbital? for the initial orbit, what are the Ap and Pe?

If you are talking about the problem of circularizing after a very steep ascent trajectory, then here's my answer.

In such cases, particularly when the Ap is not all that far outside of the atmosphere, you can get into a situation where the node FP gives is not ideal. This is because such a trajectory is developing very little horizontal velocity resulting in needing a much longer circularization burn, and this is coupled with a more tightly turning prograde vector at the Ap of the suborbital trajectory. The solution to this is to fly a better ascent profile where you begin the turn earlier and arrive at the Ap with more horizontal velocity. That's more efficient, too. Alternatively, you can use MNC to make precision adjustments to the node, which you can even do with the game paused! So if you prefer the steeper inefficient trajectory, then as soon as you've got a circularization node from FP, press pause and bring up MNC. Now you'll be able to make very precise adjustments without worrying that your Ap is getting closer by the second, and when you un-pause you'll have a node to get the orbit you want.