Go to near Kerbol space, and come back

[kermand]

So, I would like to send some probe in space near the sun and get it back to maximize the science gain. And why not, send a Kerbal so he/she can EVA near the sun and tell me about it. Obviously, I need the Kerbal back as no one shall be left behind.

My plan was to compute an orbit around Kerbol with a periapsis under 1.000.000.000 m, an apoapsis at Kerbin level and a period in resonnance with Kerbin's, so that after a few years the probe returns to Kerbin's SoI on its own.

Alas, the only such orbits I could compute using a spreadsheet have resonance like 15:8, which place the next encounter with kerbin approximately 120 years ahead.

I was wondering if there is another method outside of the brute force approach, packing 20000 dv in my probe. Maybe gravity assist or a refuel at eve or moho ? Or am I just computing wrong and there actually is an orbit fitting my needs within an acceptable time frame ?

Edited July 7, 2017 by kermand

[Human Person]

55 minutes ago, kermand said:

Or am I just computing wrong and there actually is an orbit fitting my needs within an acceptable time frame ?

I think that, but I'm not sure. Try it out with maneuver nodes: 

- place one node to escape Kerben and get to about your desired perihelion.

- place a 2nd node so where on your predicted solar orbit (0m/s)

- see where it gets you in 2 or more orbits

 

Edit: 

Aawww, it doesn't work! I just tried it and I can't select Kerben as Target while still in Kerbins SOI

 

Edit2: It works: You don't need to set Kerben as Target:

My results for the perihelion:

2:1 resonance: 3280 Mm

3:1 resonance: seems to be impossible. wait, let me do some math. 

 

Edit 3:

 

What I just did: 

 

I computed the minimum Time for a theoretical orbit wit an infinite eccentricity (crash course with the sun) And compared it to one Kerben year.

One Kerben Year is roughly 2.8 times that.

 

so year: a 3:1 resonance is impossible.

what you could do: lower your aphelion in the first pass by the sun and raise it again in the 3rd.

 

I think I just did a bad job at explaining, please tell me if that's the case.

Edited July 7, 2017 by Physics Student

[FancyMouse]

Well, you don't need to stay in your (Ap=Kerbin, Pe=1Gm) orbit until you enter Kerbin SoI - after visiting your LSO, you could burn to an appropriate orbit at apoapsis (i.e. keep your orbit tangent to Kerbin's orbit), so that the next time or maybe the second next time when you orbit back, it meets Kerbin. So the whole trip is like almost exactly 2 or 3 years because you would be returning to almost exactly where you start.

The other way to think about it is just another LKO rescue mission at a grand scale.

Edited July 7, 2017 by FancyMouse

[Kryxal]

I'd consider using Eve slingshots, but overall I think there's going to be a lot of brute force involved any way you do it.

[wumpus]

Since orbital velocity is roughly half of escape velocity, you are trying to get a delta-v sufficient to wipe out your solar (kerbol) orbital velocity.  This is roughly equal to escaping Kerbol, so you really should be thinking about a Jovian slingshot.  Scott Manley had a video on "dumping things into the Sun" and showed how important Jovian slingshots are.

Adjusting a jovian slingshot to be roughly in a good return for Kerbol sounds difficult, but it should be easier to bring along more delta-v to correct things (plus all the Oberth of Kerbol).

Judging from the wiki, you might even be able to do science in the atmosphere.  I'm not sure making probes survive at those levels.

[Snark]

EDIT:  Irrelevant suggestion moved to spoiler section, since it turns out that the OP wanted science near the sun, not just "high over the sun", which I missed.  Oops.

Spoiler

Lots of good discussion here ... but with all due respect, I kinda get the feeling that everyone here is missing the point and making things far more complicated than they need to be.  You don't need to worry about the math of your solar orbit.  At all.

4 hours ago, kermand said:

Or am I just computing wrong and there actually is an orbit fitting my needs within an acceptable time frame ?

^ This.  It's really, really simple:  don't worry about your solar orbit at all.  Just barely "peek" outside Kerbin's SoI, then scurry right back into it and go home.  The whole trip from takeoff to landing is just a few days (i.e. the time to transit Kerbin's SoI and back).  You only need to spend a few minutes outside Kerbin's SoI to gather your science, and you never go far from Kerbin.

It's easy, it's quick, and it requires less dV than landing on the Mun.  Here's how:

1. Do your escape burn from LKO so that it's just barely enough to leave Kerbin's SoI.  That is, it's a prograde burn that raises your Ap just barely enough that it gives you a Kerbin escape.  This is ~950 m/s from LKO, depending on your orbit.
2. Warp forward until you exit Kerbin's SoI.  But only just past.  Don't warp days or weeks past the SoI exit.
3. As soon as you're out of SoI, do all your science gathering.
4. Don't bother setting any maneuver nodes at this point.
5. Point your nose straight at Kerbin.  (This is easy to do:  just go to the map screen, set Kerbin as your target, and then use the navball to put at the center of your crosshairs.)
6. Burn.  Doesn't have to be big, just a few hundred m/s will do.
   • This works because your Kerbin-relative velocity was very small when you left SoI.
   • Therefore, doing a burn straight at Kerbin will send you right back into its SoI again.
   • By "right back", I mean soon, as in "just a few minutes after you left its SoI."  None of this multiple-orbits-around-the-sun nonsense.
7. As soon as you're back in Kerbin's SoI, do a burn to get your Pe down inside Kerbin's atmosphere.  (Or use a maneuver node if you like, whatever works for you.)
8. Reenter and land.
9. Profit! 

 

Edited July 7, 2017 by Snark
Solved the wrong problem.

[FullMetalMachinist]

@Snark the issue is that the OP wants science from space near the sun. 

[Snark]

32 minutes ago, FullMetalMachinist said:

@Snark the issue is that the OP wants science from space near the sun. 

Ah.  Missed that one.  Oops. 

I guess my eyes kinda skipped over that part, because I've practically never bothered with getting near-Sun science, since it's simply not worth it:  lots and lots of dV needed, for a pretty darn small return.  I'd get a lot more science for a lot less hassle by just stopping off at a couple of extra biomes on Mun or Minmus.  (Of course, there can be other reasons than just science return, i.e. just doing it for the challenge!)

Anyway,

4 hours ago, kermand said:

My plan was to compute an orbit around Kerbol with a periapsis under 1.000.000.000 m, an apoapsis at Kerbin level and a period in resonnance with Kerbin's, so that after a few years the probe returns to Kerbin's SoI on its own.

Alas, the only such orbits I could compute using a spreadsheet have resonance like 15:8, which place the next encounter with kerbin approximately 120 years ahead.

Not sure why everyone's talking about computing a return trajectory.  That's the hard way.  Why not just do it with maneuver nodes, and let KSP do all the computation for you?  No math required at all.

1. Big escape burn from Kerbin that lowers your solar Pe down low enough to get the science you want.
2. This puts you on an eccentric orbit with a Pe down where you need it, and an Ap that's right at Kerbin's orbit.
3. Set a maneuver node at your solar Ap (the one that happens after your initial Pe), and use the usual multiple-orbits-ahead trick to do a prograde or retrograde burn that adjusts your Pe just enough to get a Kerbin encounter a few orbits ahead.  Just how many orbits will depend on what your initial Pe was, but it shouldn't be any more than 5.  I'm guessing 3 or 4 should be sufficient.  It comes down to how much dV you have to spare (the smaller the burn you want, the more orbits ahead you'll need to adjust).
4. Reenter Kerbin's atmosphere and land, probably less than five years after launch.  Maybe just two or three.
5. Profit! 

Blow-by-blow description of what I refer to as "the usual multiple-orbits-ahead trick" in a spoiler section, in case anyone's unfamiliar with it.

Spoiler

This trick relies on the KSP behavior that the "closest approach" markers are always shown for the closest approach that happens after the last maneuver node.

So you can basically trick KSP into showing you a closest approach that happens multiple orbits ahead of where you're doing your burn, thus:

1. Set your maneuver node in the spot where you plan on doing your burn, as usual.  For purposes of this discussion I'll assume it's at Ap (since that's what the OP here wants to do), but this technique would work just as well for a Pe burn if you were navigating somewhere else.
2. Don't try to give it its final dV amount.  Just drag a smidgeon of prograde burn on it; we'll come back to it later.  The only reason we're giving it any dV yet is so that the dotted-line projected trajectory post-burn is different enough from the original pre-burn trajectory to make it clickable, since we're about to plop down another maneuver node on it.
3. In this case, your Ap burn is already on Kerbin's orbit, which means as soon as you plop down the maneuver node, you'll get a closest-approach marker for Kerbin.  Of course, Kerbin is in completely the wrong place, so you don't have a rendezvous set up yet.  That's what we plan to fix. 
4. Now go drop another node somewhere after the first one, on the dotted-line path that happens after your first burn.  This is your "dummy node"-- don't give it any dV, just leave it at 0.0 m/s.  Doesn't matter much where you put it-- you could put it at Pe, if you like.
5. Note that when you drop the dummy node, the "closest encounter" marker may have jumped around.  That's because now KSP is showing you the closest encounter that happens after the dummy node.
6. Now click the "+" button on the dummy node to make it happen one orbit later.  See how the "closest approach" marker jumped?  That's because you're now seeing the closest approach two orbits ahead.
7. Is it pretty close to an encounter now, or not?  If it's not, go back to step 6 above and click one additional orbit into the future (which will make the closest-approach marker jump again).
8. Repeat steps 6 and 7 until you get a closest approach that's "reasonably" close (say, within 1/6 of a Kerbin orbit or so).  It shouldn't take all that many jumps into the future, maybe just five orbits at most.
9. Now leave the dummy node, and go back to your original "real" node.  Try gently dragging the prograde/retrograde handles (which will adjust your Pe, since your node is located at Ap).  Notice that when you apply just a little dV to the node, your projected closest approach marker moves by a lot.  (The more orbits in the future it is, the more it moves for a given amount of dV.)  That's because your burn adds a timing difference to each orbit, and you're stacking up multiples of that over multiple orbits.
10. So now you should be able to get to an encounter with a fairly modest dV investment.  Don't worry about trying to get a low Pe or an atmospheric entry, at this point-- just get an SoI intercept, that's plenty good enough for now.
11. Do your sun orbit thing, gather your science, do the burn at the maneuver node.  (You can delete the dummy node now, if you want.)
12. Coast through a few orbits until you're on your last orbit before hitting Kerbin.
13. A week or two before hitting Kerbin's SoI, you can do a tiny correction burn to adjust your Kerbin Pe so you get the atmospheric reentry altitude you want.

Ta dah!  Look, Ma, no math! 

 

[Weywot8]

Realistically though, low sun orbit is about 0.1KU, so SMA = 0.6KU meaning period = (0.6)^3/2= ~0.46476 kerbin year, or 2.15 orbits every 1 kerbin orbit. The actual take away message is that you CAN complete your mission in one Kerbin year.

As @FancyMouse said, all you have to do is burn at Ap after the first orbit so that your second orbit is ~(1-0.46476)=0.53524 Kerbin years long. This does increase your AP velocity meaning you'll have to pack extra dV both for the maneuver and for the orbital capture, if aerobreaking isn't enough to do the job. 

 

Edit: @Kryxal is correct. Truncated my explanation in the above: we might think that dV spent adjusting the orbit to a longer period would also have been spent getting captured into Kerbin orbit as it whizzes past you, because it's now moving relatively slower. So "just pack the amount of dV same as for capture in a full resonance orbit".  However, by raising the Pe in deep space, there is much less Oberth effect. Also, probably not a big enough change to safely rely on full aero capture. So pack extra dV for the manuever and orbital capture. 

 

 

 

Edited July 8, 2017 by Weywot8

[Kryxal]

It increases your velocity at apoapsis, but that's a good thing ... Kerbin's going to be catching up to you, and going faster means it's not blowing by you as fast.

[Human Person]

17 hours ago, Snark said:

Not sure why everyone's talking about computing a return trajectory.  That's the hard way.  Why not just do it with maneuver nodes, and let KSP do all the computation for you?  No math required at all.

Look at my post, I tried this out. Then I did math, proving that a 3:1 resonance with the same aphelion is impossible. 

[Human Person]

I did more math!

a 2:5 and a 3:8 resonance should be possible

 

Spoiler

The semi major axis of your ship is required to be between 13.86 Gm and 14.86 Gm

The orbital period is dependent of the square root of your semi major axis cubed.

 

semi major axis of kerbin = 27.2 Gm => orbital period of 141.9 times something

your orbital period must be between 51,60 and 57,28 times that something.

In other words: Kerbins orbital period must be between 2.48 and 2.75 times that of your own ship.

 

we want to have an a:b resonance, where a and b must be natural numbers. We search for the smallest a.

 

Now we take multiples of Kerbins orbital period and see if the range of the required b contains a natural number.

 

1. a = 1 (Kerbin intersect in one year)

  => 2.75 > b > 2.48  (no possible natural number for b)

 

2. a = 2 (Kerbin intersect in 2 years)

 => 5.5 > b > 4.96

 => 5 is a possible value for b

 

 => 2:5 resonance possible

 

3. a=3

 => 8.25 > b > 7.44

 => 3:8 resonance possible

 

and so on.

 

Btw, a 8:15 resonance wouldn't put your encounter 120 years ahead, it would put your encounter 8 years ahead (Kerbin does 8 revolutions and you do 15)

Edited July 8, 2017 by Physics Student

[Snark]

4 hours ago, Physics Student said:

Look at my post, I tried this out. Then I did math, proving that a 3:1 resonance with the same aphelion is impossible. 

Well, sure. 2 ^ 1.5 = 2.82, which is less than 3. Few seconds with a calculator, no pencil and paper required.

But this is relevant to what I said, ... how, exactly?  Where did anyone, myself included, suggest attempting a 3:1 resonance?

And in any case, attempting to hit any particular resonance relationship on the initial Kerbin ejection burn may be irrelevant, depending on the OP's needs. Doing that would constrain the initial Pe to a particular value, which may or may not meet the requirements, depending on what arbitrary altitude Squad chose to set the "near space" boundary for the sun. The OP needs to set initial Pe based on that requirement, which may or may not be compatible with any particular resonance target.

So my point is that he doesn't have to worry about it. Just set the initial Pe to whatever he needs, then use the maneuver node technique at his first Ap so that he gets a Kerbin encounter. It's straightforward, it's simple, it's just a few mouse clicks and visual eyeballing, with no math required.  Which is especially relevant here, because if you don't initially eject from Kerbin on a resonance relationship to start with, your initial Ap will be at some arbitrary non-integer phase angle to Kerbin, so resonance per se kinda goes out the window at that point.

The technique I describe has the advantage that not only does it work in basically any arbitrary orbital situation, but also it's a useful *general* technique that is easy to learn regardless of a player's math and physics skill, and, once learned, can be applied to any similar future problems as well.

Thus my "why is everyone trying to do this with math" comment. Much as I enjoy a good mathematical solution myself, being a physics major, it's not necessarily the right solution for every situation, nor is it everyone's cup of tea. Plus, I prefer giving people solutions that they can apply in the future, rather than just handing them an answer to an individual problem. As Terry Pratchett pointed out:  Give a man a fire, and he's warm for a day; but set a man on fire, and he's warm for the rest of his life.

[Human Person]

42 minutes ago, Snark said:

But this is relevant to what I said, ... how, exactly?  Where did anyone, myself included, suggest attempting a 3:1 resonance?

The OP asks specifically for resonance orbits and time optimization. Attempting a 3:1 resonance is the first logical step. Unfortunately impossible, moving on to 2:x resonances. Sure, trying it out can be done but the OP suggests that he already tried to deal with the problem using maths, why discourage him?

It's not like this is rocket sc...

 

Quote

The technique I describe has the advantage that not only does it work in basically any arbitrary orbital situation, but also it's a useful *general* technique that is easy to learn regardless of a player's math and physics skill, and, once learned, can be applied to any similar future problems as well.

I agree, it's a good technique.

What I mean is, I followed OP's original approach, while you gave him a new one. Both is good, we shouldn't argue

 

PS: I love that Pratchett Quote

Edited July 8, 2017 by Physics Student

[Snark]

1 hour ago, Physics Student said:

The OP asks specifically for resonance orbits and time optimization.

Actually, no, he doesn't, or at least that's not my impression. What he's asking for is basically just "how can I get back to Kerbin in a reasonable time frame."  That's what he wants.  Trying for a resonance orbit may or may not be a viable solution.  He tried math, and got snarled, and is looking for help to solve the problem ("get back to Kerbin and don't take a century"), not necessarily help with the math, per se.

If the math works, and is straightforward enough that doing the math is the most practical and/or least painful and/or most generally useful solution, then great!  My point is simply that that's not a foregone conclusion, particularly after looking at an OP that got snarled in math and then a bunch of follow-on posts that either got snarled in math, or else use math to show what won't work, or else use math to demonstrate the existence of potential solutions that may or may not meet the OP's needs and in any case are highly specific to just this one exact case and may not be useful to other cases in the future.

So my point is simply that maybe spreadsheets aren't the right tool for the job here, and why not just use the built-in tools that the stock game gives you to solve the problem simply, quickly, efficiently, and in a way that will enable the OP to solve such problems easily himself in the future.

[wumpus]

1 hour ago, Snark said:

Thus my "why is everyone trying to do this with math" comment. Much as I enjoy a good mathematical solution myself, being a physics major, it's not necessarily the right solution for every situation, nor is it everyone's cup of tea. Plus, I prefer giving people solutions that they can apply in the future, rather than just handing them an answer to an individual problem. As Terry Pratchett pointed out:  Give a man a fire, and he's warm for a day; but set a man on fire, and he's warm for the rest of his life.

If you are already willing to wait a few years for the resonances to match, I'd strongly re-consider the Joolian slingshot.  Delta-v to Low Kerbol Orbit from Kerbin = ~20km/s.  Delta-v to Jool from LKO ~1km/s.  Don't forget that slingshoting close to Jool gives you tremendous Obereth (just in case you need more of that 20k that Jool doesn't directly give you), and you will have even more Obereth doing a burn at Low Kerbol Orbit (to fix your return trajectory).

Even if you find the resonance, you still have to build a ship capable of getting on that trajectory.

https://www.youtube.com/watch?v=uNS6VKNXY6s [Scott Manley delivers an incredibly bad game into the Sun using RSS/RO.  Direct burn of a SLS-based/sized rocket got roughly to Mercury, Jovian slingshot (plus correction) got into a collision course with the Sun].

[XLjedi]

On ‎7‎/‎7‎/‎2017 at 8:30 AM, Physics Student said:

I think I just did a bad job at explaining, please tell me if that's the case.

Yes, you did a BAD JOB of explaining!

...and when you follow it up with a "good job" I'm still not gonna understand it. 

[Human Person]

@Snark I understand what you mean, I don't agree. In my opinion, giving up on math problems is the one and only reason so many people are bad at math.

Being bad at something is the first step in becoming good at something.

I admit having done a terrible job at explaining what I was doing, I got too excited and shot a fast, very unfinished reply.

@XLjedi, or anybody else interested in a better math explanation, PM me and I'll work it out with a nice explanation for every step.

Edited July 8, 2017 by Physics Student

[Snark]

4 hours ago, wumpus said:

If you are already willing to wait a few years for the resonances to match, I'd strongly re-consider the Joolian slingshot.  Delta-v to Low Kerbol Orbit from Kerbin = ~20km/s.  Delta-v to Jool from LKO ~1km/s.

Where are you getting these numbers?  You're vastly overstating the dV needed to get to the sun from Kerbin, and understating the dV needed to get to Jool.

It doesn't take anywhere near 20 km/s of dV to get close to the sun from Kerbin.  Not even vaguely.  From LKO, 4 km/s of dV will get you down to within 1G meters of the sun, and it's less than 6 km/s of dV to lower your solar Pe down to zero.

Even if you include the roughly 3.4 km/s of dV needed to get to LKO, it's nowhere close to 20.

And from LKO, it takes much closer to 2 km/s of dV to get to Jool from Kerbin, rather than the 1 km/s you suggest.  (for example 1900 m/s from an altitude of 100 km).

So, if the user wants to get to, say, 1Gm altitude over the Sun, from LKO, he can spend 4 km/s to go straight there, or 2 km/s to get to Jool and then need to do further maneuvering.  The dV savings are just not all that big.

Yes, maybe you can manage somewhat less dV if you use some sort of Jool slingshot... but you'll take a lot longer to get home, and the navigation is considerably more complicated.  It's up to the player which is more important to them-- i.e. do they want to save some dV, in exchange for taking many more years to get home and a considerably more complex set of navigation.

 

2 hours ago, Physics Student said:

@Snark I understand what you mean, I don't agree. In my opinion, giving up on math problems is the one and only reason so many people are bad at math.

Being bad at something is the first step in becoming good at something.

Believe me, I get where you're coming from.  Speaking as a physics major, an eager explainer of things, a parent, and a former schoolteacher, I'm totally with you on the desire to explain the math and the underlying principles of things.  However, we're kinda getting off topic here from the OP's question of "how do I get home, folks?", so remainder of response in spoiler section.

Spoiler

However, I'd say that being bad at something is the second step in becoming good.  I'd say that the first step is having an interest.  And sure, as would-be explainers we can do our best to pique people's interest... but it's really not possible to teach somebody something unless they have any interest in it in the first place.  You can't push a rope.

The goal here is to solve the problem that the OP actually is interested in solving.  If the OP here had said "This is an interesting problem and I'd like to understand the math behind it," I'd happily stand by the sidelines and cheer on all the math explainers.  But from reading the OP here, it sounds more like "I want to make a thing happen in KSP" than "I want to learn physics."  So the question is, how is the OP best served, based on expressed interest? 

Bearing in mind that the analytical solution here for a resonance will be of limited usefulness in KSP, given that most orbits aren't perfectly circular... and a resonant orbit at a certain Pe doesn't help if that Pe may not match the requirements of gathering science... and even if he does learn all the math, how will he know that he's nailed everything so exactly that he'll have a good Kerbin intercept on the way back?  (Especially since it's not easy to precisely locate a maneuver node for perfect alignment so that he ejects exactly retrograde.)  To know whether a certain burn will get him back to Kerbin N orbits from now, he has to actually see the intercept-- which will need some sort of technique for projecting the orbit.  Such as, for example, the maneuver-node trick that I mention-- which, incidentally, if you use, the need for the math is obviated anyway.

There's a place and time for everything.  If a user says "I'm in LKO and I want to get to the Mun, how do I find an intercept?"  How does one explain that?  A couple of approaches:

• "Drop a maneuver node on your orbit.  Drag prograde until the Ap is out by the Mun's orbit.  Slide the node forward and back along the orbit until you get a Mun encounter with a reasonably low munar Pe."
• Teach them about the vis-viva equation, so they can mathematically calculate the amount of dV needed.  Then show them how to calculate the Mun's orbital period, their transfer-ellipse period, and combine the two to work out the proper phase angle that they'd need to be at in order to do the burn.  Then, after they've waded through all that math... drop a maneuver node anyway, and slide it to a particular burn amount that they would have arrived at anyway, and then have to manually slide it back and forth a bit anyway because it's impossible to eyeball an exact number of degrees when plopping down a maneuver node.

The second one teaches a lot more math than the first, and is great if the user has any interest in learning the math.  But it's not actually needed and you end up having to do all the same things with maneuver nodes anyway.  It doesn't actually add any value to the game experience other than the math learning itself, which the player may or may not be interested in.  And if you approach it from the standpoint of trying to give them all the math first, you run the risk of scaring them off, if they don't realize that actually they can do it easily without it.

What it boils down to is:  here in the Gameplay Questions forum, when we're answering a person's problem, we have to understand what their actual problem is-- and it's the asker, not the answerers, who is the final authority on what that problem is.  So rather than try to impose our preferred methodology, let's try to understand what they want and help them with it, is all I'm saying.

So, to get back on track for the OP:

@kermand, broadly speaking, there are two categories of solution that have been proposed in this thread for your problem.  Which one is "better" depends on what you want (i.e. what your priorities are):

• A mathematical / analytical approach, which involves solving various equations.  This is "better" if your goal is to learn more about the physics behind orbital mechanics.
• A graphical UI-based approach that uses KSP's built-in maneuver node functionality.  This is "better" if you'd like to just quickly and simply come up with an efficient path home, and/or if you prefer not to do calculations.

[Spricigo]

2 hours ago, Physics Student said:

@Snark I understand what you mean, I don't agree. In my opinion, giving up on math problems is the one and only reason so many people are bad at math.

Which math problem?  The questions were:

1.there is some alternative methods?  ( Yes,  as explained above,  make an adjustment after first orbit to get an encounter) 

2. OP computed something wrong?  (Yes,  15:8 ressonance means a encounter each 8 kerbin's orbits) 

Notice that while you explored a mathematical explanation,  the question itself was not formally a mathematical one. 

@kermand you may use Eve gravity assist to reduce the deltaV requeriment.  But be careful,  it may change the inclination and apoapsis in such way that will end up being retuning to kerbin even more expensive than the deltaV you saved in the way down.  Moho,  giving the smaller gravity and higher inclination,  probably better to be left alone. 

 

[Snark]

2 hours ago, Spricigo said:

Moho,  giving the smaller gravity and higher inclination,  probably better to be left alone.

Moho's probably virtually useless, even if it weren't at an awkward inclination.  Not only does it have a small gravity well, but any craft passing by it is going to be doing so at a fast clip, shooting past so quickly that its trajectory will barely be deflected.  So I doubt you'd be able to get any significant benefit from it at all.

[kermand]

Lots of nice discussion here, thank you all. (^o^)/

I have to admit i did not think about correcting my orbit the first time I return to apoapsis. Definitely a brain fart on my part, as this looks the simplest approach. The 15:8 confusion did not help either, but a 8 years mission would be too long anyway for a manned mission with no stop at another body, as I play with life support. A one or two years mission is the best.

As for the worth of getting low solar space science, it is definitely not worth it as far as completing the tech tree goes. But if i wanted to do that i could just press the Mun, Minmus and Duna like lemons and it would be done. The goal here is mostly to get the satisfaction of having done a type of mission I never did before, bonus satisfaction if it is done elegantly.

As for "do the math"/"use the UI" controversy, isn't it mostly a matter of personal taste ? I enjoy the trial/error approach most of the time, but it is also cool to plan a mission starting from the equations, bringing with you just the necessary fuel and beeing able to say "exatly as planned !" when you land your vessel home. The most satisfactory experience i had in KSP was probably my first Apollo style Mun trip, and i planned every tiny bit of it using equations from Wikipedia (had just bought the game, did not even know that KER existed). The feeling after returning Jeb Bill and Bob as planned with barely the fuel necessary was great. It got old afterward, but it is nice to binge in calculations again from time to time.

This is also why I don't want to use brute force, i like my missions to look realistic-ish. (I know KSP is easier than real life, so the "look" is the important part. For example, I like my rockets to look like rockets, not 15 LF boosters with a giant ring station on top of it)

Edited July 9, 2017 by kermand

[kermand]

I tried to set the maneuver nodes, see where it goes.

• one 4083 m.s^-1 burn to get a Kerbol periapsis under 1.000.000.000 m
• then one 3322 m.s^-1 burn at apoapsis 171 days later to match Kerbin at the second pass.
• then a 1800 capture  m.s^-1 burn to return home after a one year trip. Probably less if aerobraking.

total 9200 m.s^-1 not including the losses due to the most definitely long burn times. 

The Jool slingshot option looks even more sexy now ^^

Edited July 9, 2017 by kermand

[Snark]

1 hour ago, kermand said:

I tried to set the maneuver nodes, see where it goes.

• one 4083 m.s^-1 burn to get a Kerbol periapsis under 1.000.000.000 m
• then one 3322 m.s^-1 burn at apoapsis 171 days later to match Kerbin at the second pass.
• then a 1800 capture  m.s^-1 burn to return home after a one year trip. Probably less if aerobraking.

total 9200 m.s^-1 not including the losses due to the most definitely long burn times. 

The Jool slingshot option looks even more sexy now ^^

That sounds pretty reasonable.  The 1800 m/s at the end, you can just skip completely, as in zero. That's what heatshields are for.  So, about 7400 m/s overall, from LKO. Not too bad.

Using a Jool slingshot is certainly a fancier option, if you want to do it just for the navigational challenge. But it doesn't seem super practical to me, otherwise.  It's only a 2000ish m/s savings over your initial 4083 m/s burn, and you'd still have to get *home* again, and the trip will be many, many years (you mentioned time constraints due to life support).

But of course it's up to you. Sometimes the fun of KSP lies in looking at a problem and saying to yourself, "There's gotta be a more difficult way to do this."

[kermand]

2 hours ago, Snark said:

Using a Jool slingshot is certainly a fancier option, if you want to do it just for the navigational challenge. But it doesn't seem super practical to me, otherwise.  It's only a 2000ish m/s savings over your initial 4083 m/s burn, and you'd still have to get *home* again, and the trip will be many, many years (you mentioned time constraints due to life support).

Now that i think about it, the constraint of having to return to Kerbin makes the Jool slingshot a poor option indeed. It's much more difficult to perform in terms of navigation, and I would approach Kerbol with all the kinetic energy acquired from Jool's altitude, most of which i would have to get rid of in order to set my return apoapsis at Kerbin. Not sure mister Oberth has enough magic in his hat to make this profitable.