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Returning from Eve


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Ok, this is the first time playing in Career mode, basically first time playing the game and I need some recommendation. I have started venturing outside the Kerbin influence.

I don't have any mod, but I'm using the calculators to reach other planets:
https://alexmoon.github.io/ksp/#/Kerbin/100/Eve/100/false/ballistic/false/1/1
https://ksp.olex.biz/

So, I have reach Eve without problems. I have more than 5600m/s of delta v. I tried to overestimate the fuel.
One of my problems, is that rotating inverse? or rotating to Eves retrogade

I have a few questions:
- Should I change the direction of the rotation of the ship?
- I understand the Ejection angle and the Phase angle (although I'm eyeballing most of the time), how can I measure the ejection inclination?
- Without any other mod, is it possible to get this angles?
- How should I return to Kerbin?

BTW, Its the year 30 and day 147. The calculator recommends the best window will come on the year 31 day 51, but I'm trying to force the return.

Thanks

Edited by radicaled
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6 minutes ago, radicaled said:

So, I have reach Eve without problems.

By "reach Eve", you mean you're in orbit around it?

Congratulations! :)

If you're in orbit around Eve, 5600 m/s is a lot more than you need to go home to Kerbin.  Assuming that you're not planning to go down to the surface.

7 minutes ago, radicaled said:

One of my problems, is that rotating inverse? or rotating to Eves retrogade

The orbital calculation tools generally assume that you're orbiting in the same direction as the planet rotates.

If you're orbiting retrograde, then that won't affect the size of the burn you need to make to go home.  And it won't affect the timing of the launch window.  It just affects what direction you want to go when you do your burn to eject from Eve at the desired angle.

Basically, as long as you set it up so that you're pointing essentially :prograde: relative to the sun when you eject from Eve's SoI (for an ideal launch window), you'll be fine.

9 minutes ago, radicaled said:

Should I change the direction of the rotation of the ship?

By "change the direction of rotation" you mean change it so it orbits Eve in the opposite direction?

If that's what you mean, definitely no.  It's not necessary, and it would use a huge amount of fuel to do so.

If you're orbiting retrograde, it just means you'll do your burn when you're on the sunward side of Eve instead of on the night side of Eve.  You want to eject from Eve going in the same direction that Eve is traveling around the sun.

10 minutes ago, radicaled said:

how can I measure the ejection inclination?

Assuming you're in an equatorial orbit... just stay equatorial.

11 minutes ago, radicaled said:

Without any other mod, is it possible to get this angles?

Kinda.  You can do this:

  1. Drop a maneuver node in the right spot to eject from Eve to head homeward.  If you're orbiting in the same direction Eve rotates, this will be just a little bit west of the "midnight longitude".  If you're orbiting retrograde, then it will be just a little bit east of the "noon longitude".
  2. Drag the :prograde: handle on the maneuver node until it's got enough dV to generate an escape trajectory from Eve.
  3. Zoom out until you can see both Eve and Kerbin in their orbits around the sun.
  4. Keep dragging the :prograde: handle on the maneuver node.  This will cause your projected Ap around the Sun to climb.  Keep dragging until your Ap reaches and just barely touches Kerbin's orbit.
  5. When you get to that point... look at the "closest approach" markers (pale blue ones).  When you're at Ap at Kerbin's orbit... where is Kerbin?
  6. If you see that Kerbin at that time will be N degrees ahead of where your ship will be... then you're that far early from the launch window.  For example, if Keribin is 30 degrees ahead, it means you need to wait until Eve has caught up another 30 degrees before you launch.

Note that the above strategy is only for the "perfect" launch window.  You actually have a lot of extra dV. From low Eve orbit, you should only need around 1400 m/s of dV to go home to Kerbin with a good launch window.  So if you've got 5600, that means you could have a launch window that's not all that great and still get home.

17 minutes ago, radicaled said:

How should I return to Kerbin?

There are various ways.  Simplest way is to use something like ksp.olex.biz, get the angles, wait until Eve is in the right place, and do the burn.

The more general description looks like:  1. fiddle with maneuver node until you can see in map view that you'll have a Kerbin intercept, and then 2. do the burn.

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If you're interested in using a mod, there are a few to choose from- transfer window planner, astrogator and mechjeb can all help making maneuver nodes for transfers between planets and mechjeb can also perform the maneuvers for you.

If you aren't interested in using a mod, as a general rule the best time to make an outward transfer is when the target planet is 45 degrees ahead of the one you're orbiting. Put your maneuver node so that prograde around the planet is also prograde relative to its orbit around the sun, then add prograde velocity until it meets the target's orbit. Slightly early and you'll have to overshoot a bit to let the target catch up, slightly late and you'll need more velocity and have a longer braking burn. With 5600m/s to play with you should be fine, and there's little/no difference in inclination between Eve and Kerbin so you can probably get away with ignoring inclination for the transfer burn and just correcting at an ascending/descending node en route.

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@Snark and @jimmymcgoochie thanks for the quick reply.

So I tried to force an encounter and got the trajectory. Although, I got a ton of dV, it wasn't enough. I guess, I'm not in the best position for the encounter.
Most of the trajectories, I found, lasted more than an year. But if I wait one more year for the transfer window the trip should last 190 days ~. So, I will try it on the future. :)

Meanwhile, I'm sending probes to Eeloo and Moho :D

B5gvh9s.png

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3 minutes ago, radicaled said:

I guess, I'm not in the best position for the encounter.

You're really not.  ;)  If you wait a bit it'll be better.

Also, be aware that if your trajectory is crossing Kerbin's at a steep angle (as in this picture), as opposed to approaching it in a fairly parallel fashion... it means you'll be arriving at Kerbin with a very large velocity-- which potentially could be a problem, depending on how robust your ship is for resisting reentry heat.

So, yeah, wait a bit!

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10 hours ago, radicaled said:

Most of the trajectories, I found, lasted more than an year.

Yes, that's (one part of) the fun of orbital mechanics: sometimes you can reach your destination sooner by just hanging around and waiting for a while. :D

If you have dV to spare (which you apparently have) and want to go home in a hurry, then you can check for a high-speed transfer a few weeks (or months?) before the actual transfer window. But I recommend to plan the full transfer in that case: it is really annoying to get close to Kerbin just to figure out that you don't have the 2000 m/s dV needed for the plane change because you made an inefficient, high-speed transfer.

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