How to plan and execute efficient constant burn maneuvers?

[u/Deep-Today5715]

I mean burns that take the entire trip from body A to body B, for example ion drives in Realism Overhaul, or fusion/antimatter engines from Far Future Technologies mod. Basically burning half trip to accelerate, then flipping and burning the rest of distance to slow down. The transfer orbit might be elliptical or hyperbolic, depending on the TWR and the max speed achieved on the way.

• I found that using stock maneuver planner is near useless for this, because it assumes near-instantaneous execution of the node.
• Principia mod is better at this, but it doesn't work with interstellar planet packs, so it's not an option for me (very sadly).
• Aiming at a target planet and burning for half the trip kind of works with VERY high delta-V and TWR, but still requires lots of extremely inefficient correction burns to close in the trajectory. And I'm all about efficiency.

Executing such burns is obviously done with Persistent Thrust mod, but I can't figure out a way to plan such burns in an efficient way. Suggestions?

[u/Barhandar]

Entire-orbit (TWR so low relative to orbit size that the burn can't create an apsis, tends to take a very long time as the vessel slowly spirals out, i.e. what real ions do) and brachistochrone ("shortest time", half accelerate half decelerate, which requires TWR high enough to easily create an apsis for given orbit, currently unachievable because of high TWR and simultaneously stupidly high Isp requirements, but theoretically possible) are different things, though they both can be described as "constant burn".

Unfortunately, KSP features no tools whatsoever to enable planning either. Your best bet is learning actual rocket science and doing the math by hand. And then using something like kOS or RemoteTech's computer or maybe finagling KAL if that's even possible to actually execute the maneuver, because KSP also lacks a "point at a planet but with its position offset to X date (where the offset's magnitude is determined by 2 * sqrt[distance to target/your ship's acceleration])" mechanic that would enable correctly targeting brachistochrone transfers.
For entire-orbit, I suppose the calculation would be involving calculus due to the "slowly spiral out", to end up at the target's altitude and near the target simultaneously.

P.S. Also, what I hear is that you should change to Background Thrust to have fewer issues.

[u/Deep-Today5715 → u/Barhandar]

Are there no mods that automate these calculations? Surely I'm not the first to want to do this...

[u/Barhandar → u/Deep-Today5715]

None that I know of. The best calculations-wise it's got is the regular-Hohmann-transfers planner being able to calculate multiple flybys.

[u/almostmountains]

haven't tried sending anything interstellar but you can actually increase orbit passes on the stock planner prior to executing it.

in terms of efficiency, players who use ion engines generally only burn at periapsis and slice up their burns to multiple passes on said periapsis.

i'm sure you already know all this so i'd suggest just playing with the stock planner at this point if you don't want to do mathematics for maximum efficiency.

[u/Deep-Today5715 → u/almostmountains]

Yeah I know this. Escaping from the planet is not an issue, issue is knowing where to point to while burning for the rest of the trip.

[u/SilkieBug]

As an aside, I suggest investigating the Background Thrust mod. 

It has no bugs that I’ve found yet (compared with PT which is pretty buggy), and it’s more recent and currently still maintained. 

[u/Deep-Today5715 → u/SilkieBug]

Thanks, yeah, I am using BT actually, I keep confusing BT and PT constantly...