Eve hates me.

[Starwhip]

Why is it that I cannot seem to get an equatorial Eve orbit? I even matched its inclination, but still no cigar. I hate it. Or it hates me.

Either way, the mission is for Gilly. I intend to get there, rendezvous with Gilly, then land and return to Kerbin. With SCIENCE!!!

Wait. I may have forgotten the parachutes... Krap.

Here's the craft. It has around 3.4 km/s of Delta-V, plus around 500 m/s for Gilly landing and return to orbit. (And a TWR of something like 25 with an ANT engine!)

All I need help with right now is the equatorial orbit. How do you do it?

EDIT:

And eyup, I forgot the 'chutes. [RAGE]

Time for some redesigning!

Edited June 4, 2014 by Starwhip

[Red Iron Crown]

Don't take it personally, Eve hates everyone.

Don't bother going equatorial, Gilly is in an inclined orbit. Set Gilly as the target and put a maneuver node on either the ascending or descending node, then perform a normal burn to match planes with Gilly (12 degrees inclination IIRC).

[Starwhip]

Yes, but the problem is I'm coming into Eve's SOI in a polar orbit, practically. It takes more Delta-V to match planes with Gilly than I have on the ship.

All I want, really, is to get a more equatorial orbit.

[Random Tank]

Here's a tip: Write down a checklist on a sheet oh paper, which just asks you: Did I put on batteries? Did I put on solar panels/RTGs, did I put on chutes? Did I set my action groups? Etc etc...

Then stick this sheet on your wall/keyboard/screen/forehead or anywhere else extremely obvious; then all you have to do is to see the sheet, and it will remind you to put on any parts you forgot. I pre-empted forgetting things (cause I have a bad memory) and did this from the get go, but it will save you many hours of redoing missions! Try it!

[Red Iron Crown]

You should have refined your entry into Eve's SOI before arriving, but it might be too late for that.

Probably easiest to just get one of your apses really close to Gilly's orbit and timewarp until you get an encounter, then do a regular capture burn once in Gilly's SOI. You're not using life support, are you?

[Starwhip]

Nah, no life support. And I have a quicksave from way before I did the transfer burn. I'd have like a two-week window in-game to build a new ship. Because I forgot the 'chutes.

And I tried after I left Kerbin's SOI to redefine, but it failed. I'll put some screenshots in a few minutes.

[Red Iron Crown]

Better to do your refinements when you get closer to Eve. I usually do one about halfway through the transfer, then another if necessary a bit before entering the target's SOI.

Basically, the further away you are when making the refinement, the less costly and less accurate it is.

[Kasuha]

Don't take it personally, Eve hates everyone.

Don't bother going equatorial, Gilly is in an inclined orbit. Set Gilly as the target and put a maneuver node on either the ascending or descending node, then perform a normal burn to match planes with Gilly (12 degrees inclination IIRC).

Don't bother matching planes, especially if you're in lower orbit than Gilly. It's waste of dv.

1/ select Gilly as target

2/ take a look at your inclination markers. Select one, preferably the one where the distance between your orbit and Gilly's orbit is smaller

3/ put a maneuver at opposite end of your orbit and pull prograde till your trajectory intersects Gilly's orbit. You can try pulling the maneuver along your orbit to find where it will take least dv but the ultimate target is that intersect.

4/ execute that maneuver

5/ put a maneuver at intersect with Gilly and adjust your orbital period to get an intercept at that point. Preferably that maneuver should raise your other inclination point towards Gilly's orbit, not go away from it. The intercept does not have necessarily to come in single orbit.

6/ execute that maneuver, coast to the intercept and circularize at Gilly.

Notice that the circularization will raise your speed to the Gilly's and match orbital planes at the same time.

You save dv once because you're doing two burns in one.

You save dv once more because you're matching orbital planes at higher altitude, i.e. at lower orbital speed.

[StuntMax]

Heh, the purple b*tch hates everyone.

First time I managed to ship something in that soupy air, it was a seismic probe.... promptly landed in water (or whatever they have there to make oceans out of), some 100 m away from the shore.

I don't get why you can only get a polar orbit... after doing my halfway correction burn I take a quick look at the resulting conic, and with a few tiny wee burns (RCS is more than enough for this) I make the minimal correction to enter the target SOI exactly how I need to.... if you set your path from far enough, the correction needed to switch between a polar, prograde or retrograde orbit is really tiny, a fraction of m/s.

I even managed a gravity turn that dropped me directly in Gilly's SOI, I only had to burn for the Gillan insertion.

Also, be sure to exit timewarp at each change of SOI.

[Starwhip]

So here's the conic of my third course correction (After transfer, plus the intercept-to-SOI burn)

Not that I only have 2500 m/s of Delta V left in the stage to get me back to Kerbin.

I haven't executed the maneuver yet, though. Here it is:

Tips? Is that a good enough periapsis and orbit? And what altitude should the aerobrake be?

[allmhuran]

The most efficient way to change the inclination of your orbit at your target is to burn normal/antinormal in solar orbit 90 degrees out from the intercept point.

When you burn normal/antinormal the plane of your orbit pivots around the point you perform the burn. So any normal burn has the greatest effect 90 degrees around the orbit.

If, however, you want to be equatorial you do indeed have to burn at the ascending or descending node. But in this case you don't, so no worries!

Failing this, the best place to burn to change your inclination after capture is immediately after your apoapsis falls within the SOI (ie, when you no longer have an escape trajectory). Loop around to your apoapsis and perform a plane change maneuver there. This is efficient because your velocity at an apoapsis that is only just within the SOI will be incredibly low. If we're going 5ms in one direction, it costs us only a little over 7ms to change that to be 5ms in a perpendicular direction (yay Pythagorus). So when you perform your Eve aerobrake, don't aerobrake so low that you nearly circularize. Instead aerobrake just enough to leave you with a super high apoapsis. Then perform your plane change. Then aerobrake again on your next loop to bring your apoapsis down.

Now, having said that: If you aerobrake at Eve your periapsis will be just above the atmosphere while your apoapsis will be high up near Gilly. As I mentioned, this means you will be moving very slowly at apoapsis, which means your relative velocity with Gilly will be very high, and landing will be expensive. I'm not sure if anyone has actually done the math, but it might be cheaper not to aerobrake, and instead enter Eve's SOI and capture on engine power at the altitude of Gilly. This, however, removes the possibility of a cheap inclination change, so make sure you get your entry right!

Edited June 3, 2014 by allmhuran

[Kasuha]

Tips? Is that a good enough periapsis and orbit? And what altitude should the aerobrake be?

That periapsis is too high, you need to get it lower to get aerobraking. Atmosphere ends at about 96 km I think. MechJeb has aerobraking calculator built in, the next best approach is trial and error with quicksave after entering the SOI. I'd probably start with periapsis at 70 km.

To visit Gilly, get only enough aerobraking so your orbit closes in the SOI. The higher your ending apoapsis the better. Then from that apoapsis, raise your periapsis to meet Gilly at inclination point. That shouldn't require more than some 200 m/s. And then braking at Gilly shouldn't exceed 300 m/s or so.

Edited June 3, 2014 by Kasuha

[Starwhip]

So, it would take a total of 1750 (With generous FudgeRoom^tm) to do this orbit.

I'll "quicksave as" and try it.

[allmhuran]

Thinking that through a little further... I wonder if Eve's SOI is big enough, and Gilly far enough away, that an aerocapture followed by a bi-elliptic transfer is possible....

Edit:

So, it would take a total of 1750 to do this orbit.

Mhm, and half of that looks to be the inclination correction. Very interesting. So with a good (perfect) inclination at capture, circularizing directly at Gilly (without aerobraking) appears to take about 800 m/s (including fudge factor). That's certainly comparable to an aerobrake-into-Hohmann-transfer solution. I'm sorry I've never actually tried these various options myself in order to be able to provide a more definitive answer.

Edited June 3, 2014 by allmhuran

[allmhuran]

OK, I checked the Wiki because I'd forgotten how eccentric Gilly's orbit is. Apparently its orbital velocity ranges from 274 m/s at apoapsis, to 945 m/s at periapsis. So if you manage to put your periapsis at Eve opposite Gilly's apoapsis and aerobrake there (thus putting your apoapsis at Gilly's apoapsis), circularizing at Gilly would cost somewhat less than 274 m/s (because we would only need to accelerate from our current apoapsis velocity up to 274 m/s).

So in an ideal scenario, it seems like aerocapture is the best bet, but that's *only* if you can do so at such an angle that your apoapsis after the aerocapture is very near to Gilly's apoapsis. And there's nothing much you can do to ensure this other than arriving at Eve at the right time of year, which would also then imply leaving Kerbin at the right time of year... but that is unlikely to coincide with a Kerbin-Eve launch window unless Squad was VERY kind when they set up Gilly's orbit.

Edited June 3, 2014 by allmhuran

[Starwhip]

Final orbit and remaining Delta V. I'll just timewarp until I get closer, because it looks like I can just do that to get to Gilly. I'm behind and in a smaller orbit.

[Starwhip]

Little bit of orbital tweaking (I was in a synchronous orbit... what are the odds???) and I've got it!

Now the question is: can I get back?

[allmhuran]

Well you clearly have more than enough to land on Gilly and get back into Gilly orbit or Eve orbit, but I have a hunch that you don't *quite* have enough to get back to Kerbin. Someone who likes doing the math can tell you for sure (that person is not me!)

[Starwhip]

Righty-ho.

Now I just need to get home.

[allmhuran]

Best of luck to you! How much delta V do you have left after landing? I'm curious about the accuracy of my hunch. I am guessing (wildly, wildly guessing, based solely on the fact that LKO to Eve costs about 1000m/s) that the cost of the return flight is about 1200 m/s starting from Gilly orbit.

Edit: about 1500 according to the calculator. And unfortunately getting to Moho is only a little less, so you can't do a Gilly-Moho-Eve-Kerbin slingshot. On the bright side, you now have a permanent Gilly outpost.

Edit again: Wait a sec... EVA packs have about 500m/s right?... you might JUST be able to get the Kerbal back to Kerbin via slingshot, if you're willing to arrive without the rest of the rocket

Edited June 3, 2014 by allmhuran

[Starwhip]

The rocket has ~800 m/s left, plus x m/s in RCS fuel, plus getting out and pushin'.

And um... *sly laugh* I am known to kick just a little bit with "Infinite Fuel."

I think I can get home. Remember, those measurements are from Low Eve Orbit, not Gilly orbit. At apoasis (Gilly apoapsis) I'll circularize and have a high Eve orbit.

EDIT:

Plus rescue missions. I do like those.

[allmhuran]

Nah, that's from Gilly. It's not much cheaper than launching from LEO, because while you start out "closer to escape" (further away from Eve), you lose the benefit of the Oberth effect during your burn (very powerful at Eve due to its high gravity).

[cantab]

Indeed it's much cheaper to get from Gilly to Kerbin than from Low Eve Orbit to Kerbin. Scott Manley got a Kerbal home from Gilly using *just* the EVA pack.

There are some comprehensive delta-V charts on Reddit, one for each planet and its moons (if any). More complicated to use but essential for getting accurate results when visiting moons of other planets.

PS: When leaving Gilly you have two options. Either burn directly to escape and transfer, or burn to drop periapsis low over Eve (while leaving your apoapsis level with Gilly's orbit) then burn at Eve periapsis to escape and transfer. Try setting nodes for both to see which needs less delta-V.

Edited June 3, 2014 by cantab

[allmhuran]

Hm, I'm not sure how. The calculator ( http://alexmoon.github.io/ksp/ ) says just under 1500m/s starting from an Eve orbit of 48825 km (Gilly's apoapsis).

Edit: That can't be right...

Edited June 3, 2014 by allmhuran

[Starwhip]

Heh. I'll wing it.

I've got Protractor installed, and it's fairly accurate. Right now, the question is not how much Delta-V, but how much battery my laptop has.

Should I go for it?