Question about Gilly

[Reinhart Mk.1]

So after my month long Eve expedition I decided the natural step would be to visit Gilly (only because it would be better to refuel there before rescuing Jeb from Eve Orbit). Anyways I could probably figure this out on  my own but asking the forum usually is a more interesting idea. Onto the question... does anyone else find it extremely difficult to orbit Gilly? I get the encounter just find but circularizing takes what seems like W A Y too much dV... I guess it makes sense because of the low gravity but when editing the encounter the actual encounter line (flight path?) never seems to curve like with other bodies. This isn't vital but I rarely hear talk about Gilly so might as well open up a discussion about it

[Geonovast]

Well, Gilly escape velocity is about 36 m/s.  That's why it takes so much dV to get into orbit.  Orbital speed around Gilly is scary slow.  The flight path doesn't really curve because it's gravitational pull is so weak, that flying past it doesn't really affect your path that much.

[Reinhart Mk.1]

1 minute ago, Geonovast said:

Well, Gilly escape velocity is about 36 m/s.  That's why it takes so much dV to get into orbit.  Orbital speed around Gilly is scary slow.  The flight path doesn't really curve because it's gravitational pull is so weak, that flying past it doesn't really affect your path that much.

Crazy how Gilly is almost has the exact opposite conditions than Eve, it's like having diarrhea for dessert after eating a giant s#!^ sandwich (excuse my french)

[Geonovast]

Just now, Reinhart Mk.1 said:

Crazy how Gilly is almost has the exact opposite conditions than Eve, it's like having diarrhea for dessert after eating a giant s#!^ sandwich (excuse my french)

I think that was the point when they were building the solar system.

[Reinhart Mk.1]

2 minutes ago, Geonovast said:

I think that was the point when they were building the solar system.

Definitely seems like it lol, I dont like my nuke engines will be able to slow me down if i try to directly impact Gilly either

[Starman4308]

I suspect part of why Ike and Gilly are the ways they are is to provide different types of challenge to newish players without them needing to go all the way to Jool.

Ike: Very large, can disrupt near-Duna operations, but quite useful for gravity braking. Of course, once you're there, you need a hefty chunk of dV to land.

Gilly: Tiny, relatively hard to rendezvous with, but trivially easy to operate around once you're there.

Of course, the king and queen of "tiny rock" are to be found in Real Solar System: Phobos and Deimos. I haven't yet quite needed to start my insertion burns while still outside their spheres of influence... but it's been close.

[Superfluous J]

Gilly is more like a large asteroid than a small planet. You're better off thinking of landing on it as a docking maneuver than an actual landing one. As in, thrust toward it, turn around, slow down when close to the surface, maybe even use RCS to fine tune the approach.

[The Aziz]

The second to last time I was at Gilly, I had to actually point downwards and fire the engines to speed up the descent.

the last time I was there I shattered the moon but that's another story 

I think in modern days, the game shows you enough info when to start a maneuver burn, so just place the node at Pe and hope for the best.

Edited March 11, 2019 by The Aziz

[FleshJeb]

7 hours ago, Reinhart Mk.1 said:

Crazy how Gilly is almost has the exact opposite conditions than Eve, it's like having diarrhea for dessert after eating a giant s#!^ sandwich (excuse my french)

I need colorful metaphors for this, please advise:

 

[magnemoe]

10 hours ago, 5thHorseman said:

Gilly is more like a large asteroid than a small planet. You're better off thinking of landing on it as a docking maneuver than an actual landing one. As in, thrust toward it, turn around, slow down when close to the surface, maybe even use RCS to fine tune the approach.

This, burn towards it then do an braking burn to slow down, use rsc to keep you down until settled. 
ignore orbital mechanics unless very low on fuel as the orbital speed is so low. 
kerbals on EVA on the surface sometimes tend to get into orbital speed all the time. 

 

[SnakyLeVrai]

 

18 hours ago, Reinhart Mk.1 said:

So after my month long Eve expedition I decided the natural step would be to visit Gilly (only because it would be better to refuel there before rescuing Jeb from Eve Orbit). Anyways I could probably figure this out on  my own but asking the forum usually is a more interesting idea. Onto the question... does anyone else find it extremely difficult to orbit Gilly? I get the encounter just find but circularizing takes what seems like W A Y too much dV... I guess it makes sense because of the low gravity but when editing the encounter the actual encounter line (flight path?) never seems to curve like with other bodies. This isn't vital but I rarely hear talk about Gilly so might as well open up a discussion about it

It all depends how you reach it. From my experience it costs about 1500-1550m/s tops, to get to Gilly from LEO (100x100km around Eve).

1. From LEO, burn so that your orbit intercepts Gilly at its Ap. That's a 1300m/s burn, tops (1287.26m/s if everything's perfect...) ;
2. Wait for Ap to make any orbital inclination change!!!
   1. A bit of orbital mechanics 101 here  According to Gilly's orbital elements, the argument of its Pe is 10°, meaning it's very close to its ascending node...
   2. What does that even mean?? ---> when you'll intercept Gilly at its own Ap around Eve (48125km ASL), you'll be close to its descending node
   3. As inclination change depends on your orbital speed in m/s, a 12° change will not cost much, because @Ap, as you are close to Gilly's DN, your orbital speed around Eve will be low. It's about 15 to 20m/s depending on how close to Ap you are. That's why it is always better to make inclination changes at low orbital speeds...
   4. If you changed inclination at 100km above Eve, it would cost 937m/s, theoretically (on a 48125 x 100km orbit).
3. As you intercept Gilly, you'll have to achieve capture, that'll cost about 201m/s to stay in Gilly's SOI.
   1. Of course, you may merge the capture burn and orbital change in the same maneuver... no big deal here.
   2. Before you perform orbital injection around Gilly, your orbit, around Eve, is still 48125 x 100km, more or less (that's what it would be if you missed Gilly's SOI, I mean...). So, to match Gilly's orbit, you'll have to accelerate so that your orbit becomes "48125 x 13475km above Eve's sea level". That's why the 201m/s burn. That'll get you captured around Gilly. Gravitational help from Gilly won't be much...
   3. It may vary a tad bit, given your final orbit above Gilly... but not by much (1 to 10m/s maybe?).
4. All in all, you'll get there for about 1500m/s ... Costs the same to go back to LEO.

If you tried to intercept Gilly when it is at its Pe around Eve, all in all, it would cost you 1950 to 2100m/s (depending wether you make orbit inclination change @Ap or Pe). I've made myself a spreadsheet to calculate all my maneuvers and determine my dV budget, roughly. Helps a LOT when designing missions... The figures below are not exactly right because inclination change is not exactly at Ap, it's lower. But won't affect it by much. Also, it doesn't take into account the gravitational influence of the bodies I meet (gravitational slingshots and all).

 

[Jan Kerjann]

I found it best to go close to Eve only to get into orbit around the purple one, but to keep the apoeve close to the edge of Eve's SOI. Then go to apoeve and raise the perieve slightly above Gilly's orbit. From there, get your orbit on the same plane as Gilly's orbit and get the apoeve closer (but still outside of Gilly's orbit). That way your velocity will be closer to Gilly's speed and you won't have to spend that much fuel to slow down in time in Gilly's SOI.

[Vanamonde]

Your curve near Gilly doesn't seem to change because Gilly is contributing almost nothing to the curve.  

And your question has been moved to Gameplay, since the issue is a natural consequence of Gilly's size. 

[Reinhart Mk.1]

4 hours ago, Vanamonde said:

Your curve near Gilly doesn't seem to change because Gilly is contributing almost nothing to the curve.

thank you, im never sure if it's the right section

[Chel]

Another thing about Gilly: If you try to land, good luck doing an EVA. One step sends you off the planet completely! 

[GRS]

Here's a not-so-wordy Solution...

Bullseye dat Gilly (If your TWR is relatively good and you got nice small relative velocity)

Or try aiming low areas like 15 Km or so (yet i'll lower it to like 8-9 Km or so)

Thrust limitation is important, extremely important...