How do you maneuver outside of kerbins sphere of influence

[Victor12]

This pretty self-explanatory, I suck at any form of encounter with other planets. any suggestion, tips, or ideas.

[Snark]

Moving to Gameplay Questions.

2 hours ago, Victor12 said:

This pretty self-explanatory, I suck at any form of encounter with other planets. any suggestion, tips, or ideas.

Easiest way is to use a transfer planner.  There are various ones out there, but my personal favorite is http://ksp.olex.biz, since it's so simple to use, and I like the nice graphical display showing what to do.  Just put in 1. what you're orbiting now, and 2. how high above it you're orbiting, and 3. where you want to go, and it will tell you how big a burn you need, and in what direction, and how the planets need to be lined up for the optimum transfer.

If you need advice beyond that... well, one way that can help folks give advice is if you can show an example of your attempt-- i.e. post some screenshots in map view, so we can see how it is that you're trying to navigate now.  Based on seeing that, we may be able to have a better idea of what you're having difficulty with, and give concrete suggestions (along the lines of "oh, you're doing that, you should do this instead," that sort of thing).

[Guest]

This is what I do.

1. Go to alexmoon's launch window planner page, at https://alexmoon.github.io/ksp/
2. Fill the form (origin, destination, date)
3. Read the answer, if necessary drag around the pointer to pick a less optimal but closer in time transfer window
4. Jot the magic date and ejection velocity on a piece of paper
5. Make a craft with the dV I need
6. Fly my craft to LKO
7. Warp to the magic date
8. Plan the trajectory:
   1. Create a manoeuvre node with roughly the velocity I jotted down in (4)
   2. Set target to the destination body
   3. Drag around the manoeuvre node until I see the white encounter markers
   4. Adjust the burn and the manoeuvre node location until the white encounter markers converge and I get an encounter
   5. Add another manoeuvre node (the exact location can be anywhere along the trajectory, it really depends on where you're going and when)
   6. Focus on the target body
   7. Adjust the correction burn until I have the encounter I want: this burn should be pretty small, it can be as little as < 1 m/s, rarely more than 30 m/s -- drag it around the trajectory to find the sweet spot
   8. Add other burns down the line until they put my craft where I want it, and tally up the dV total to make sure I have enough; if not, start over from 4
9. Execute the first burn
10. Adjust the remaining burns until they put the craft where you want again
11. Repeat steps 9-10 for all remaining burns
12. ???
13. PROFIT!

Notes:

The launch window planner is a real life-saver, and IME there's not much profit in attempting anything other than a simple ballistic transfer. The ejection burn is usually pretty long which means it's really difficult to execute precisely; at least I usually end up off by a bit. More optimal burns would be even harder to execute and I find that anything I theoretically gain from them gets lost in the execution errors. Your midcourse burn makes a huge difference too -- just now I wasn't able to execute mine on a probe that went into comms blackout, and instead of ending up in LKO like I planned, I ended up in a very high polar orbit which means my recovery mission is going to be a lot more complicated than I intended. So, to save fuel:

• Find a good transfer window.
• Go for a good insertion. Ideally you will want to be approaching your destination along its orbital vector so your relative speed will be as low as possible, and you'll want your Pe to be as low as you dare: that way, your insertion burn will be most efficient.
• Find the optimum spot for the midcourse adjustment burn. Otherwise you might be burning hundreds of m/s more than you need. 
• Plan your entire trajectory in advance, and adjust the planned burns to correct for errors executing them as you progress.

Additionally, if your target is Duna, consider aerobraking -- you won't even need heat shields most of the time. And if your target is Jool, definitely make use of gravity braking: it will save you not just hundreds but potentially over a thousand m/s. I'm not all that great at orbital mechanics, but I have managed an insertion into Laythe orbit that cost me all of 350 m/s starting from a rough intercept of the Jolian system. 

Finally, there are tricks you can do with gravity assists -- for example it's cheaper to get to Jool by pinballing off Eve. The transfer windows for these however are a lot narrower and they require a lot more planning; I usually don't bother and just build craft with enough dV instead.

[Streetwind]

The other two have given you advice on what to do, so I'll try and answer your question in a different way - aimed at making you understand why you have to do these things.

 

On 2/9/2018 at 2:57 AM, Victor12 said:

How do you maneuver outside of kerbins sphere of influence?

You maneuver there exactly the same as you do inside Kerbin's SOI. The rules don't change. What does change is the fact that Kerbin is no longer your central body - the Sun is. And in contrast to before, where you started in low Kerbin orbit, you do not start in low solar orbit. You start in a high solar orbit right next to Kerbin itself.

This is important because of a concept called a "transfer window". Think about going from Kerbin to the Mun. You start out in a tight, low orbit, you wait for the right time, and then you burn to raise your apoapsis out to the Mun to get an intercept. It feels like you're trying to hit a moving target from standstill - it's just a question of aiming in the right direction and firing at the right time. But now, once you're in interplanetary space, you suddenly have to hit a moving target while you're also moving. This is so different, and so much harder!

...Except it's not. Because even when you start from low Kerbin orbit, you are already trying to hit the Mun while you're yourself moving. Even then, you have to wait for the right transfer window - the moment in time where the celestial objects are aligned just right to allow you to achieve an intercept with your target. You think it isn't so, because Kerbin's position is static, but it's not Kerbin you should be concerned about. It's your own vessel. Your vessel is also a celestial object, in its own orbit. And it must be properly aligned with respect to your destination body. It's just the same in interplanetary space. People generally use the origin body to track celestial alignment, but you can only make that substituton because your vessel shares your origin body's solar orbit as long as you are within its SOI. Once you exit, you have to go back to thinking about your vessel in its own orbit again.

Going back to the Mun example: what happens if you miss your node? Well, you just loop around once and try again, right? It's quick and painless. But in interplanetary space, nothing ever moves quickly, and you have to wait for ages for the right transfer window. How come?

The reason is simple: since your transfer window is the point where everything is aligned just right, the frequency with which it occurs is related to how quickly the celestial objects in question change position with respect to one another. And there's a very simple rule of the thumb for this: the less similar the orbits, the more frequent the transfer windows are. In addition to that, windows get more frequent based on the absolute size of the smaller of the two orbits. So when you are in low Kerbin orbit and try to hit the Mun, you have both a really tiny starter orbit, and a really big difference between your start and destination, which makes the window reoccur really really quickly. You loop around Kerbin once every 30 minutes. But the Mun takes 38.5 hours to loop once around Kerbin. It has barely moved by the time you come back around. And so the transfer window occurs every 30 minutes (your orbital period) plus 1/77th (the amount of movement the Mun did in its orbit during that half hour) of 30 minutes. That's less than 31 minutes in total.

For Minmus, the interval is technically even shorter, because Minmus moves even less distance in the time it takes you to loop around. The transfer window to Minmus out of a 30 minute low Kerbin orbit reoccurs every 30 minutes plus 1/598th of 30 minutes. ...That's not really a big difference, you say? Correct. because that is just how much your tiny low Kerbin orbit dominates the math.

But what if your Kerbin orbit was different? Let's say you're trying to go from Mun (38.5 hours oribital period) to Minmus (299 hours orbital period). The transfer window there reoccurs every 38.5 hours, plus 1/7.767th of 38.5 hours. Which resolves into roughly 38.5 + 5 = 43.5 hours. (Doing this trip and back, by the way, is a great way to practice interplanetary transfers safely inside Kerbin's SOI.)

And now the counterintuitive part: what if you were trying to go from the Mun to an orbit just a bit higher than the Mun? Not all the way out to Minmus at 47,000km, but rather just to 24,000km, twice the altitude of the Mun. The orbital period of that altitude is roughly 109.2 hours. So the transfer window reoccurs every 38.5 hours plus 1/2.836th of 38.5 hours. Which comes out to roughly 38.5 + 13.5 = 52 hours. Even more than that, technically, because this simple way to calculate it has an error that gets larger the larger the second figure gets. Your target orbit was much closer, much more similar than Minmus before; thus, you have to wait longer for the transfer window to come around again.

(Taking this to its logical extreme: if the orbits are as similar as is possible - in other words, identical - then the time for a transfer window to reoccur is infinitely large. It will never happen, because the relative positions of the two objects will never change. Fun fact: this is part of what makes orbital rendezvous - another concept with which many newcomers struggle - such a tricky business.)

Now, back to interplanetary space. Where does everyone go first? Duna! Because it's right next door, it barely costs more dV than Minmus, and it's a pretty benign place overall. Eve costs about the same dV, but it's a really unfriendly place, so we go to Duna instead. Unfortunately, because it is right next door, that means its orbit is very similar to that of Kerbin. And so you have to wait a long, long time between Duna windows. Many hundreds of 6-hour Kerbin days. As a result of this, many newcomers are confused: how do you get a Duna intercept? Even timewarping several days changes absolutely nothing! Correct, because if you're unlucky, you may have to time warp hundreds of days for the chance to get an intercept.

If you were to go to Moho instead, you'd get a window roughly every 30-odd days. All because Moho is in such a low, tight solar orbit compared to Kerbin. Getting a Kerbin-Moho window is the quickest and easiest of all the planets - which is a bit amusing, considering Moho is also the hardest destination to reach from Kerbin out of all the planets from a piloting and dV perspective. By contrast, Duna has the longest wait for a transfer window from Kerbin out of all the planets, even though it is ostensibly the easiest to reach. Funny how that works out, right?  

Edited January 28, 2023 by Streetwind

[Flavio hc16]

If you want to have the window planner in game:

It work in the same way

[Warzouz]

I don't know if that was said, but any tool able to tweak nodes by controlled increments instead of dealing with that awful node cross helps a lot.

From memory, you can use "Precise Node" mod, but MechJeb also has such a feature (Node Editor, iirc)

[Victor12]

I'm in grade ten and understand none of this. All the planners make no sense to me, can someone tell me how to read one and show how much more intellectually superior they are?

[HebaruSan]

15 minutes ago, Victor12 said:

I'm in grade ten and understand none of this. All the planners make no sense to me, can someone tell me how to read one and show how much more intellectually superior they are?

To go from one planet to another efficiently, you need to leave when those planets are properly aligned. The planners are for finding that time.

If you know how to install mods, you might try Astrogator in my forum signature. It automates a lot of the steps, such as entering your starting orbit info, and can auto-generate maneuver nodes for you. Then you just have to adjust them to get the encounter and arrival trajectory you want.

[klesh]

1 hour ago, Victor12 said:

I'm in grade ten and understand none of this. All the planners make no sense to me, can someone tell me how to read one and show how much more intellectually superior they are?

 

Asking for help with a snarky jab at the end.  You're bound to get tons of help now.  

[Spricigo]

@Victor12 there is only two kind of people in this forum:

• People that know stuff and can teach
• People that don't know stuff and can learn.

Don't feel inferior for being in either situation, see it as an opportunity. Learning and teaching are great things to do. Don't feel superior too, anyone in your place could do the same.

 

About your question:

Take for example https://alexmoon.github.io/ksp/ What part confuses you? 

 

[Streetwind]

I think I once wrote a step-by-step guide on how to use Alexmoon's planner for someone. Let me see if I can find it again...

 

EDIT: Okay, I only wrote about how to make a node with the resulting information, not how to use the planner itself. Here's that first part:

• Make sure your spacecraft is in a circular, equatorial Kerbin orbit, and set the Initial Orbit altitude on the website accordingly. The planner makes the assumption that you start in such an orbit, because it makes the math faster and easier; if you try to execute the calculated transfer from a highly inclined or eccentric Kerbin orbit, you will miss your target. You can make the planner calculate from an eccentric and/or inclined orbit, too, but you have to manually input all the parameters of that orbit through the Add Body menu. And that's both tedious and requires you to have a mod installed that shows you these numbers ingame in the first place, because KSP won't show them you by default. If you are already in interplanetary space, you unfortunately also need to manually input your orbital parameters this way.
• Choose your destination.
• If you are planning a flyby or aerocapture, check the "no insertion burn" box; if you want to enter orbit around your destination, leave it unchecked.
• If you want to enter orbit, enter a useful value for Final Orbit. On bodies with an atmosphere, you want this to be 5-10 kilometers above where the atmosphere ends (you can look up that number ingame, or on the KSP wiki). On bodies without an atmosphere, simply enter 10.
• Set Earliest Departure to your current ingame date.
• Select "Ballistic" from the transfer type dropdown menu (though I believe that's also the default). Sometimes it's cheaper to do a midflight course correction, but I personally tend to not want to bother.
• Click on Show Advanced Settings to bring up two additional settings. They are pre-filled, and do not need to be adjusted in 90% of all cases; but once you undertand how to use the planner, you can use Latest Departure and Time Of Flight to narrow down your results more.
• Press Plot It!

In the colorful plot at the bottom, travel time is on the vertical axis, and departure date is on the horizontal one. <--- This is really important for reading the plot. Make sure you understand it fully. Mouse over the plot; you'll see a dV cost next to your mouse cursor that represents the particular date/traveltime combination you're hovering over. The planner will have pre-selected the cheapest solution it can find between your specified earliest and latest departure dates. This is the next "transfer window" - the moment in time where the celestials are aligned just right. This solution will always be a Hohmann transfer, or as close to one as orbital alignment allows.

You don't have to fly in that transfer window. You can fly at any time you want, and spend more or less travel time, as dictated by your whims and needs; but you will notice that those other departure date/travel time combinations cost more dV. That is because you are either flying "out of window" and/or are performing a "high energy transfer", and have to spend extra dV to force an encounter. In some cases, though, the planner will show you multiple solutions marked in deep blue. That simply means that there are multiple Hohmann transfer windows of similar good quality for you to choose from in the near future.

Either accept the preselected solution, or find a solution that's suitable for your needs by clicking on that spot on the graph. If you want, you can adjust your Latest Departure and Time Of Flight in the advanced settings mentioned before and recalculate, to make the plot more focused on specific areas. When you have found your solution, click on it, then press "Refine Transfer" at the bottom.

As one last step, click on the little blue "i" marker next to the Ejection dV reading in the results list.

Now you can finally proceed to setting up your node in the game.

 

Edited February 2, 2023 by Streetwind

[Victor12]

Thanks! I can actually not miss planets by hundreds of thousands of kilometers now!

PS: that remark wasn't supposed to snarky, it was to show how bad at ksp I am.

[Victor12]

also, thank you for the encouragement Spricigo