are Minmus encounters supposed to be this... twitchy?

[Drew Kerman]

I've been traveling to Minmus with a small probe and while my goal has been to encounter and insert into a 1,500km orbit, even if I burn to set my Pe at 1,400km and then do nothing the encounter can vanish entirely. Earlier I set course for 1,400km Pe and later when I checked for some reason I was now encountering with a Pe at 600km. I'm not even rotating my space craft around or anything, just burning and coasting. Small body, small SOI and I'm still a ways out only just past the orbit of Mun - should I just wait until I'm closer to tweak my trajectory?

Edited December 16, 2014 by Gaiiden

[DuoDex]

Minmus' SOI is notoriously small and weak.

Also, do you have any pictures? Those can be remarkably helpful.

[LethalDose]

Are you sure you're losing the encounter? Sometimes you'll have an encounter, but it won't show up because the patched conic's system can, as you put it, "twitchy". To help trouble shoot, let us know if you're actually don't have an encounter when you get up to where it was supposed to happen.

[Slam_Jones]

I think this has something to do with the way Unity handles very small decimals. In my experience, the closer you get the less twitchy it gets.

[Drew Kerman]

Are you sure you're losing the encounter? Sometimes you'll have an encounter, but it won't show up because the patched conic's system can, as you put it, "twitchy". To help trouble shoot, let us know if you're actually don't have an encounter when you get up to where it was supposed to happen.

Yup, I just thought "hey why don't I timewarp ahead and see what happens..." and yea I got the encounter after all, even tho the game showed none.

I didn't think about the patched conics display perhaps being an issue. I will play around with that setting and see if I can't find a number that works better.

[Ziff]

This type of problem is typically a floating point error issue that occurs when timewarping across the intercept node. Always slow down to 1x time at the intercept, it is much more accurate that way.

[OhioBob]

Yup, I just thought "hey why don't I timewarp ahead and see what happens..." and yea I got the encounter after all, even tho the game showed none.

This happens to me quite a bit with Minmus. Halfway there the encounter appears to disappear. I always just continue on and when I cross the SOI it comes back.

[Kesa]

Don't bother the inaccurate prediction of trajectory.

Halfway, or whenever it becomes less tiwtchy, make a correction burn (guess what you have to do with manoeuver nodes), so that you get an encounter. when you get closer, make another one to have your future pe where you want to have it.

The sooner the correction, the cheaper, but also the less accurate, so you may need several. For Minmus, it should not take more than 10m/s

also, slow warp time when changing SOI. *1 is ideal but *100 still is fine, depending of the body. *1000 or above, you can miss an encounter you should have. at max warp, you can even miss collision with bodies! (at least the last time it happend to be, which was not in .25)

[Kryxal]

If I have a twitchy-looking encounter with Minimus, I usually set a raw time alarm in KAC. That means you'll slow down at the right time anyway, assuming you have that mod (and why would you not, it's really one of those things that SHOULD be stock).

[LethalDose]

Yup, I just thought "hey why don't I timewarp ahead and see what happens..." and yea I got the encounter after all, even tho the game showed none.

I didn't think about the patched conics display perhaps being an issue. I will play around with that setting and see if I can't find a number that works better.

Glad that helped. Clear skies.

[Drew Kerman]

thx guys. I always go normal time across SOI crossings so that wasn't the issue. Mainly just wanted to make sure the behavior I was seeing was normal, which it seems to be. Will do as suggested to adjusted mid-course as I've been doing and now I know the SOI intercept will actually still be there...