Gilly is killing me (if skimming, key question is in bold)

[James_Eh]

I don't know why, been playing for quite a while, have never gone to Gilly. (Mainly because I felt I didn't have the patience for the landing process.)

But I have decided for the first time ever (in 24.2, only took me like 7 versions to dip my toe in) to try the science tree thingy. Plus FAR (first time). And was thoroughly enjoying the experience, despite all the blowed up rockets and landers. (I miss my MJ/KER info panels though. A lot.) Now, in the name of SCIENCE (plus a contract), I have to get there.

I feel I did everything right. I oh-so-gently aerobraked (grrr FAR) at Eve enough times to set my AP right up against Gilly's orbit, then waited. As expected, in a relatively short period of time I came up with this approach. Man, I was so proud of managing to get my inclination matched up... (See below. Sorry, I really had trouble with the angles to get the text for the separation untangled from the orbital info.)

AND I CAN'T MAKE IT ANY BETTER!! I can not generate a little "encounter bubble" despite my best efforts with the nodes. Since the SOI is barely over 100 km, do I have to wait until closest approach and then treat it like a rendezvous??? (My current plan is to time warp to the triangles, then drive straight at the target which I hope I will be able to see onscreen by then. I'll bet that's a non-optimal plan.)

Edited September 18, 2014 by James_Eh
clarify: first time science guy

[Fendleton]

It's non-optimal, but it should work. Gilly is annoying to get an encounter with and your orbital speed there will be tiny. Aim for it when you're close enough, then burn for an encounter. At 250km or so you should be able to see it.

....You'd probably end up burning downwards for your landing anyway, since it's really really boring and hard to aim if you don't.

[RocketPilot573]

You can probably get an encounter once you get closer. Gilly's SOI is REALLY tiny, and the orbital speed is like 20 m/s or less.

[Dave Kerbin]

Treating Gilly as if it was a docking target does work. The low velocities involved make things very interesting, I've been able to capture at Gilly for a reasonable amount of fuel despite being in a retrograde Eve orbit. If all else fails get close like you have already plotted and then treat the navball target indicator and relative speed to target the same way you would when trying to reach a space station.

[James_Eh]

Righto, will proceed as planned tomorrow once my computer stops melting. (I must have done something terrible, it's decided to crash in a very odd way.) Will mark as answered tomorrow assuming nothing goes horribly wronorwonnwwzqzdaqzx...

Fendleton - agreed. I don't even want to be bothered with landing, just want to get close enough for science. And rep for your sig - we broke out a VIC-20 last month and both kids have been amusing themselves with GOTOs and POKEs...

[Kryxal]

I'd probably adjust things around the AN ... alternatively, drop a node right near the not-quite-intercept and take a close look (use tab) at how you're missing.

[kurja]

Righto, will proceed as planned tomorrow once my computer stops melting. (I must have done something terrible, it's decided to crash in a very odd way.) Will mark as answered tomorrow assuming nothing goes horribly wronorwonnwwzqzdaqzx...

Fendleton - agreed. I don't even want to be bothered with landing, just want to get close enough for science. And rep for your sig - we broke out a VIC-20 last month and both kids have been amusing themselves with GOTOs and POKEs...

Just get the close encounter like you did, once nearer (at an/dn preferably) try again if you can get an encounter.. Nodes always get more precise when you're closer to the target. Maybe a second correction if needed when even closer. Ofc you can just coast to point of closest encounter and then having selected gilly as target, it'll show up in your navball and you can "rendezvous and dock" with it, but that's not really fuel-efficient.

Had so much fun with a vic-20 when I had one! =D

[Yasmy]

1) Drop a maneuver node near your current location.

2) Go to map mode and hit tab to change your focus until it lands on Gilly,

then zoom in so that your orbit and Gilly are the only things in view.

3) Now when you adjust the maneuver node, you can see exactly how each little tug moves your orbit towards or away from Gilly, and it is pretty easy to figure out how to set exactly the encounter you want.

It helps to have a node editor mod so fine adjustments are possible, and you don't have to keep zooming out and clicking your node to make the handles pop up every time you click somewhere on the screen.

I use this method to fine-tune all my encounters, whether it is an initial transfer burn, a mid-course correction, or a near-SOI last minute adjustment. Works great. If you can't generate the encounter you want from your current location, move the maneuver node to the AN/DN and try again.

Edited September 17, 2014 by Yasmy

[Kasuha]

Notice how far the inclination line is from the closest approach marker. You're missing Gilly slightly above or below its orbit. To have certain intercept, you need to have the closest approach at the inclination node. So just apply a short normal burn in a suitable place to move the inclination node to the closest approach and you'll be able to get an intercept.

I don't recommend matching inclinations completely. It's usually easier to work with slight inclination difference and to position the inclination point precisely to the meeting point than to match planes perfectly and keep that match throughout all burns of the approach. Therefore the 'suitable place' for the normal burn might does not have be the inclination point.

Edited September 17, 2014 by Kasuha

[cantab]

Yeah, treating it like a rendezvous should be OK. Or you could make a course correction at some point. Possibly without even setting a manouvre node - just use dabs of RCS and watch how the close approach changes.

[Aedile]

If you don't care where on gilly you want to land, the least annoying way to do it is "direct" collision course, without establishing an orbit.

[kurja]

If you don't care where on gilly you want to land, the least annoying way to do it is "direct" collision course, without establishing an orbit.

That's not exactly helpful when his problem was that he couldn't get an encounter with Gilly's SOI, much less a 'direct collision course'. What Kasuha wrote was exactly to the point - inclination difference albeit small is enough to miss Gilly's SOI as it's so tiny.

[Kryxal]

And to fix inclination at apoapsis, you ALWAYS have to do a mid-course correction. Periapsis is directly opposed, so you can alter the angle you reach the apoapsis at, but can't move it up/down...

[magnemoe]

Note that intercepting Gilly near its Pe is tvice as expensive as at its Ap because you fly so much faster than it, expect 7-800 m/s braking speed.

I like to match planes it makes it much easier to set up intercepts, if not any change result in having to change inclination too.

You however don't have to have intercept from the start, stop warp from time to time and adjust, use rcs or reduce power of engine to 5% or something to increase accuracy.

I just landed on Gilly and had to think a bit outside the box solving it: problem, 25 degree of plane and coming in fast (quick trip to Eve) and only 1200 m/s left.

This was the solution:

Aerobraked so my Ap was close to Gilly orbit, lifted Pe with the first burn so my trajectory was not so far off Gilly orbit, this also reduced the cost of the plane change.

Next burn was a 10 m/s adjustment burn who gave me Gilly intercept, used just 180 m/s to get into orbit.

[James_Eh]

Well, thanks to all for the advice. I used Kashua's suggestion of a normal burn to twist my orbit into an encounter, but I didn't manage to do it completely correctly and only generated a small pathetic chord through the teeny sphere I was aiming for. At least we DID manage to hang on in Gillyspace to do some science.

To magnemoe directly above, yep - nuts I didn't think about the fact that it would be cheaper to meet it way out at the far end. Doubly frustrating since I went to a lot of effort to match at peri. During my brief stay in the SOI (and before, when I was trying to sort out what to do next...) I was a bit taken aback at the dV required to create an orbit, and yah something like 750 m/s seemed to be the ongoing theme, and since I had something like 10 seconds worth of SOI time and a rapidly dwindling fuel load, I elected to skip the Gilly landing.

Then I crashed at Eve. Then I tried to make a little plane to fly to the Island Airport for science, and broke it. Repeatedly. Yet another fun evening of KSP. This whole FAR / science tree thing has reminded me that I have lots of stuff still to learn...