[1.8-1.9] CircBurn 1.1.0

[taniwha]

While the Oberth effect means that a rocket that is traveling at a high velocity can make much larger changes to its energy than can a rocket traveling at low velocity, this does not mean that it is always best to perform maneuvers as deep as possible in a gravity well, even to circularize an orbit or depart for interplanetary travel. It is, however, always best to circularize an orbit at either its periapsis or apoapsis . CircBurn?s purpose is to indicate the optimal periapsis for a given hyperbolic trajectory. Due to the complications involved in attaining the optimal periapsis, CircBurn is only informative: it will never alter a vessel?s current trajectory or flight plan .

Download: CircBurn 1.1.0
Documentation: Manual (in the zip, but may update more frequently)
Source code (GPL): github
Support my efforts:

Edited March 29, 2020 by taniwha

[taniwha]

I've already found a couple of bugs I missed in my initial testing:

• Pe distances are given as radial rather than altitude. (already fixed locally)
• Flight plan updates invalidate the selected patch (for planned trajectory).

So an update will be coming out (with docs in the zip!) as soon as I get the second issue sorted out (assuming I don't find more nasties), though I might add an option to hide non-hyperbolic trajectories: they get messy fast.

[taniwha]

I have released version 1.0.1 of CircBurn.  I've got those two issues sorted out, and the manual is included in the zip this time.

BTW, the optimal Jool circularization periapsis for a fairly good Kerbin-Jool transers seems to be about 1.6 Pol orbital radii.

[Joal ban Kluane]

1 hour ago, taniwha said:

I have released version 1.0.1 of CircBurn.  I've got those two issues sorted out, and the manual is included in the zip this time.

BTW, the optimal Jool circularization periapsis for a fairly good Kerbin-Jool transers seems to be about 1.6 Pol orbital radii.

Thanks for the mod! Unfortunately, I get a 404 not found when trying to download it.

[hab136]

So... if you have an encounter with a celestial body, this tells you the best height to circularize.  The example picture shows that you're going to get a 63 km Pe around the Mun, but you should change that to 230 km Pe, because then you can circularize for 532.2 m/s instead of 605.4 m/s.  Right?

If your final destination is a low orbit (or landing), do you save anything overall by circularizing at the optimal height and then going lower/landing?  For example if I wanted to eventually circularize at 15 km around the Mun, should I still circularize at 230 km first, or just circularize directly at 15 km?

[taniwha]

33 minutes ago, Joal ban Kluane said:

Thanks for the mod! Unfortunately, I get a 404 not found when trying to download it.

Sorry about that, I had forgotten to commit a file so the zip was misnamed (fully automated build and upload process and I failed to notice). Fixed, however.

24 minutes ago, hab136 said:

So... if you have an encounter with a celestial body, this tells you the best height to circularize.  The example picture shows that you're going to get a 63 km Pe around the Mun, but you should change that to 230 km Pe, because then you can circularize for 532.2 m/s instead of 605.4 m/s.  Right? 

Correct, except adjusting your encounter Pe is likely to adjust the optimal Pe, so it's a bit of an iterative process (part of why it's information-only).

24 minutes ago, hab136 said:

If your final destination is a low orbit (or landing), do you save anything overall by circularizing at the optimal height and then going lower/landing?  For example if I wanted to eventually circularize at 15 km around the Mun, should I still circularize at 230 km first, or just circularize directly at 15 km?

No, the multiple burns will cost you more. This mod may come in handy for those "orbit body X" contracts. There's even the possibility of the maneuver to optimize your Pe costing more than the optimization gains. One possible use, though, is planning those "pop out into solar orbit" missions as it shows your velocity at the SoI boundary, allowing you to estimate how much delta-v is required to return to Kerbin.

The reason this mod exists is the deeper your periapsis is in the body's gravity well, the cheaper it is to close a hyperbolic trajectory into an elliptical orbit (even if the orbit's apoapsis is still outside the body's SoiI), but the more expensive it is to pull that apoapsis down to a circular orbit, or even worse, come to a stop on the surface.

As an aside: ironically, after doing a pile of math, the optimal periapsis radius is simply -2 * semi-major axis (both radial, not altitude. also, remember that the SMA for a hyperbola is negative), and the delta-v for circularization is the orbital velocity for the circular orbit (I noticed that during testing: the code actually computes the velocities). The hard part of this mod was the actual display :P.

Edited October 31, 2018 by taniwha

[taniwha]

I have released version 1.0.2 of CircBurn, fixing a misnamed .version file and preventing input blocking when the mouse is over the window (it's rather inconveniently big and it blocking control input can be rather troublesome).

[taniwha]

Seems to be working well in 1.7.1

[taniwha]

I have released version 1.1.0 of CircBurn. The only change is to update the build for KSP 1.8[.1].

[taniwha]

I have confirmed that CircBurn 1.1.0 works in KSP 1.9.1 and updated the thread title accordingly.