How to get anywhere beyond Kerbin's moons?!

[jros83]

I've become a pro at orbits, getting to the Mun, getting to Minmus, manned and unmanned. This is not bragging, because I've only become so darn good at it because it's ALL I CAN DO

For the life of me, I can't get a small little probe anywhere else. Forget a manned mission. I either A. just can't get a transfer or B. I can get a transfer but I run out of fuel.

I just want to get a stupid probe to orbit Duna once and fling it back to Kerbin with enough fuel left to get it to start hitting atmosphere so I can recover it. I want it to carry 2 each of goo, barometers and thermometers (for "high above" and "near") and a Science Jr. I could transmit for the science, but I'd prefer the 100% science of a recovery. I'm willing to forego the Science Jr.

I'm starting to lose interest. The Kerbin system is becoming very boring. At this rate I'll never be able to get a manned mission anywhere else and it's driving me nuts.

I wish I could be more specific but quite honestly I suck SO BAD at this that I'm having a problem with basically everything, lol.

HELP?

Edited December 11, 2015 by jros83

[Gaarst]

Transfer Windows 

[Goody1981]

Can you go directly from the Mun to Minmus?

If so, you already have the skill to get to other planets. Just gotta scale up (and use the transfer window planner linked above by Gaarst)

[Phil deCube]

If it wasn't for the Mechjeb mod, I probably would have given the game away long ago. Some people see it as a cheat. For me it enhances the game. As to your problem, Mechjeb will plot, plan, and execute transfers to other bodies for you. Sure, you can work it out with a slide rule, and a protractor, and some people love this. I prefer to use technology, just like NASA does, and let the computer work it out.

[Superfluous J]

I hate to suggest a mod as well but Kerbal Engineer to tell how much dV you have - plus a transfer calculator or dV chart to tell how much you need - is in my opinion critical to an enjoyable interplanetary experience. You can do it without but I personally don't want to and don't think anybody should be forced to like the stock game does.

Check out this dV chart and start building your ship at the top, with what will return from Duna. Make sure it has the 800 or so m/s to get home from Duna orbit. Then below that build a ship with the 1100-1700 m/s you need to get there and get into orbit. Then put that on top of a launcher with the 3300-4000m/s of dV you need to get that into Kerbin orbit.

Then actually do it

(Don't try to land or anything. Start small)

Edited December 11, 2015 by 5thHorseman

[Geschosskopf]

47 minutes ago, jros83 said:

For the life of me, I can't get a small little probe anywhere else. Forget a manned mission. I either A. just can't get a transfer or B. I can get a transfer but I run out of fuel.

If you can get to Minmus, you can get to Duna.  It's only about 100m/s more dV to get there.  Coming back is a bit more tricky but there are a number of options there which I'll try to note briefly and leave the details for you to sleuth out.

The only difference between going to Mun and going to any other planet outside Kerbin's SOI is that you can't leave any day you want but need to wait for Kerbin and the target planet to align.  You can, of course, go at other times but that can cost you insane amounts of dV so it's customary to wait for the transfer window, which is when the dV cost of the trip is lowest.  To know when transfer windows happen, you need some tool that will tell you.  These can be both in-game (mods like MJ and several others) and external (various web sites).

Knowing when to go is just 1/2 the problem, however.  You also need to know where to place the maneuver node for the transer burn in relation to Kerbin.  If you look down on Kerbin from above in the map view, call 12 o'clock the direction Kerbin is moving around the sun.  Normally, if going to a planet further from the sun than Kerbin, your node needs to be somewhere in the neighborhood of 4-5 o'clock.  If you're going inwards from Kerbin, the node will usually be about 10-11 o'clock.  The same tools that tell you when transfer windows occur will also tell you where to put the node (or you can have MJ create the node for you).  This is analogous to putting your node for the transfer burn to Mun at Munrise.

But anyway, the node is set at the proper position on the proper day, and then you just burn it and you're on your way.  You'll probably have to make a minor tweak somewhere en route once in solar orbit to fine-tune your approach to the target planet but otherwise it's no different than going to Mun.  The burn will just take more dV than going to Minmus.

So that's getting there.  Coming back is pretty much the same because that also needs a transfer window based on the relative positions of Kerbin and whichever planet you went to.  This is a different positoin than was needed to get to the other planet and also requires the transfer burn node to be in a specific place relative to the planet you're now at.  So again, you need the transfer window tools.  The upshot of this is that normally you can't just go to another planet, do a fly-by, and comes straight home, but instead have to capture into orbit at the other planet and wait there for months until Kerbin's in the right place to transfer back to, even though you might have finished your mission within hours after arriving at the new planet.  This means your ship needs enough fuel to 1) get to the other planet, 2) capture there, and 3) leave there and then do whatever maneuvers are necessary to set up for a safe landing at Kerbin.

You can probably do this with about 2000m/s in the tank before you leave Kerbin, but until you get the hang of this you might want to take 2500-3000.  A lot depends on how much you need to burn to capture back at Kerbin, which depends on how aggressively you can aerobrake in Kerbin's atmosphere and/or use Mun to gravity-brake you.  Coming home from Duna means you'll hit Kerbin's atmosphere somewhat faster than coming home from Minmus so the heat will be that much worse.  It's quite possible that aerocapturing without a retro burn is impossible---if you go low enough in Kerbin's air to capture, you'll burn up, but if you're high enough to survive the aerobraking, you won't capture so will have to burn at least some.  And it's also quite likely that gravity-braking off Mun won't capture you either.  So it's a good idea to have enough fuel to capture with thrust alone, without aerobraking or gravity-braking.

You CAN, however, do a Duna fly-by for less fuel than the above.  But as always in KSP, less fuel equals more time.  What you do is, when you get to Duna, pass on the left side of it instead of the right, which will gravity-brake you back down to Kerbin.  The problem here is that this might require your Duna Pe to be too high to get the "low orbit" biome.  But the real thing is the time.  Because you'll be leaving Duna outside a transfer window back to Kerbin, Kerbin won't be there when your ship crosses Kerbin's orbit.  This means you'll have to make 1 or more solar orbits before you meet up with Kerbin, which means much more elapsed gametime to get the ship home than if you'd captured at Duna and then waited for a transfer window.  And you'll likely also have to burn some to actually get an encounter with Kerbin at some point.  Still, your ship won't need as much fuel because you don't need to capture or burn at Duna, and you won't hit Kerbin as fast as if you'd left from Duna orbit after a wait, so you can save a bit more on capturing at Kerbin.

[Snark]

My favorite orbital planner is http://ksp.olex.biz. Just tell it your origin and destination planets and the height of your parking orbit, and it tells you when, where, and how much to burn.

That pretty much takes care of the navigation side of the problem. If you also have issues with ship design (e.g. not enough dV), pics of your attempts would be helpful.

[Arugela]

I think to do transfers you can generally wait for it to be on the horizon and then go for the ascending descending node and basically capture it.

[Geschosskopf]

6 hours ago, Snark said:

My favorite orbital planner is http://ksp.olex.biz. Just tell it your origin and destination planets and the height of your parking orbit, and it tells you when, where, and how much to burn.

That pretty much takes care of the navigation side of the problem. If you also have issues with ship design (e.g. not enough dV), pics of your attempts would be helpful.

I should also point out that navigation is just part of the question.  The other part is time because interplanetary trips take a long time (months to years to even decades if you've got OPM), plus however long you wait for transfer windows, which is often months to a year or so.  The question then becomes, what do you do while this time is elapsing?  Answering this question forces you to make critical decisions about the fundamental nature of your gameplay.

If this interplanetary ship is the ONLY thing you've got going on in your game, and you don't care how much time passes in the game while it's on its mission, then no problem.  Build the ship, warp ahead to the transfer window, launch, transfer, warp ahead until it gets there, warp back, the end.  All this is just fine, unless it nags you that life on Kerbin basically stops for several years while the trip is happening.  Also, you'll miss out on contracts, transfer windows to other planets, won't be able to do supply runs to your moon bases, etc.

So, if you've got anything else happening, I highly recommend Kerbal Alarm Clock.  This lets you basically set up a calendar of future events so that you can have all sorts of things going on in the game at once.

[ForScience6686]

If you're just sending a probe it should be quite easy.  Keep your design light as possible to squeeze the most dv out.  I personally calculate my own dv.  Mods aren't necessary and they take away from your understanding of the mechanics.  

Leaving at the right time is also not necessary.  I sent my probe to duna by day 10 in my 1.0.5 career.  It will cost more dv, but with a light probe that's easy to increase.  I also suggest you build in the ability to drop fuel tanks as they empty to further increase your dv.  

Now to get there, use the window planner to find the dv needed to transfer.  Create a node with that amount of dv, then slide the node around the orbit until you get a rendezvous.

Good luck and enjoy.

 

 

 

[MrOsterman]

I just had a successful probe shot to Duna that is now in the orbit of Ike.  Here's what I had:

The entire build is on 1.25m scale.

Top Stage/ Probe

• Probe Core
• Small reaction wheel
• three batteries
  • Attached are 4 retractable solar panels
  • Thermomator
  • Barometer
• Tank of Xenon Gas
• Electric Engine

Next stage:

• Small sized Tank FL-T200
• Smallest 1.25 Engine - Terrier

Next Stage:

• Max Tank FL-T800
• Smallest 1.25 Engine - Terrier

Next Stage/ Launch Stage:

• In the the Center FL-T800
  • Swivel Engine under it
• Around that 4 FL-T800's, all linked to center tank by Fuel Lines
  • Swivel Engine under them
• Also, another 4 FL-T800's, all linked to previous tanks by Fuel Lines.
  • Reliant engines under them

(This is all from memory so I might have skipped a tank there).

The trick for me was in the fuel lines.  As the outer most tanks run out of gas you drop them off.  But during ascent ALL the engines are firing and burning the fuel for those outermost tanks.  So if A is in the middle, and B is next out and C is the furthest, you get the power of A, B and C all at the same time, until C is out of gas.  Drop C and now A and B are not only still burning but burning with "Full tanks".  It also lets you ramp down your acceleration as you push through the thicker air at ground level and work your way up towards orbit.

Once I was in orbit of Kerbal, I did did a burn to push myself into a general solar orbit.  The cheapest such burn threw me out "ahead" of Kerbal in on the orbital path.  I'm totally lazy and I'd rather use Time Warp to skip ahead while I'm in space rather than while I wait for a transfer window.  I also have REALLY long contracts so I don't mind using a year or two of game time on a given flight.

From there I set Duna as my target and set up a manuever node that would push my probe's orbit to cross Duna's.  There was a LOT of trial and error with various burns, radial and normal as well as Pro and retrograde to finally get the "Intercept" to match up somewhere and it was on the far side of the sun.  Do the burn, and a few adjustments later on to get into the SOI.  From there I did a retro burn and was into Duna orbit.

Here's the thing about what I did:  It was stupid wasteful.  I got going WAY too fast and had to SERIOUSLY brake when I got to Duna.  But it got me there, and somehow I JUST barely started using fuel in my last stage, the FL-T200.  I still haven't even touched the electric engine to see what does or how it even WORKS in space.  My point is that it can be done even with not too advanced parts. 

From my point of view there are some "needs" in this equation:

Fuel Lines (For the staging)

Patched Conics - which require an upgraded Tracking Center.

[ForScience6686]

Fuel lines are not as necessary now that we can allow fuel to follow through de couplers.  Asparagus staging is also a bit wasteful I think for such a small payload.  Use Srbs first to get up whereyyour liquid engines are more efficient.

[Snark]

10 hours ago, Arugela said:

I think to do transfers you can generally wait for it to be on the horizon and then go for the ascending descending node and basically capture it.

That strategy ("burn when it's on the horizon) only works when:

1. your destination is orbiting the same body you are
2. your destination's orbital radius is much larger than your orbital radius

In other words, when you're going to the Mun or Minmus from LKO.  It's a very special case.  It works only because of the mathematics of orbital times, which I'll skip for now unless you're interested.

Admittedly, it's an overwhelmingly common specialized case, because practically every transfer burn you do for the first many, many hours of your career will be exactly that, shuttling between Kerbin-Mun and/or Kerbin/Minmus.

However, for anything else-- including interplanetary transfers, which is what the OP was asking about-- that simple "rule" doesn't work. It's more complex.

[MrOsterman]

47 minutes ago, ForScience6686 said:

Fuel lines are not as necessary now that we can allow fuel to follow through de couplers.  Asparagus staging is also a bit wasteful I think for such a small payload.  Use Srbs first to get up whereyyour liquid engines are more efficient.

But the decouplers... wait.. does it flow laterally through them?  I was about to say it only works down through the stack decouplers but if it works sideways through them, that would change some of my design specs.  Though for that probe build I would still run the fuel lines from the "outer" most tanks/ engines to the next phase in so I can attach the tanks to the main body but send the fuel into the "next" stage.

25 minutes ago, Snark said:

asking about-- that simple "rule" doesn't work. It's more complex.

Would it work to practice doing a planet to planet trip by doing a Minmus to Mun and back again?  It's the same orbital theory as going to Duna but on a fraction of the scale.

[Snark]

9 minutes ago, MrOsterman said:

Would it work to practice doing a planet to planet trip by doing a Minmus to Mun and back again?  It's the same orbital theory as going to Duna but on a fraction of the scale.

Doing a transfer directly between Mun and Minmus is great practice, yes. 

However, it's also worth noting that Minmus' orbital radius is considerably larger than the Mun's, so the "burn when it's on the horizon" plan may actually work reasonably well.  To get mathy for a moment, "burn when it's on the horizon" works because the period of a circular orbit of radius R is twice that of an elliptical orbit whose apoapsis is R and whose eccentricity approaches 1 (i.e. the periapsis is tiny compared to the apoapsis).

So Mun-to-Minmus may not be a great strategy for learning how to go Kerbin-to-Duna.  For a graphic demonstration of this, check out http://ksp.olex.biz.  If you tell it "I'm going to Minmus from a low parking orbit around the Mun), it will show that Minmus should be 90 degrees ahead of the Mun.  But if you do the same thing for Kerbin-to-Duna instead of Mun-to-Minmus, you'll see that the angle is only aboout 45 degrees.

 

Edited December 11, 2015 by Snark

[Arugela]

5 hours ago, Snark said:

That strategy ("burn when it's on the horizon) only works when:

1. your destination is orbiting the same body you are
2. your destination's orbital radius is much larger than your orbital radius

In other words, when you're going to the Mun or Minmus from LKO.  It's a very special case.  It works only because of the mathematics of orbital times, which I'll skip for now unless you're interested.

Admittedly, it's an overwhelmingly common specialized case, because practically every transfer burn you do for the first many, many hours of your career will be exactly that, shuttling between Kerbin-Mun and/or Kerbin/Minmus.

However, for anything else-- including interplanetary transfers, which is what the OP was asking about-- that simple "rule" doesn't work. It's more complex.

I do that for Eve and duna and other cross transfers between planets. It always guarantees an easier capture. I don't know if it's efficient but you will get the capture. Even off of kerbin. I think it has to do with the fact you are burning along the longest edge of a circle where the edges of the circles have the longest time to cross over each other on initial pass to the other circle. And I think they honestly likely made the game simpler that way so people could do it.

You would need a very fast planet for that not to work. And it still probably raises the odds.

I do all of my transfers this way actually. And I do them all manually. Even sometimes blind with no stock in game tool. And I never use mods.

Edited December 12, 2015 by Arugela

[moogoob]

On 2015-12-10, 10:06:08, Phil deCube said:

If it wasn't for the Mechjeb mod, I probably would have given the game away long ago. Some people see it as a cheat. For me it enhances the game. As to your problem, Mechjeb will plot, plan, and execute transfers to other bodies for you. Sure, you can work it out with a slide rule, and a protractor, and some people love this. I prefer to use technology, just like NASA does, and let the computer work it out.

Yup. Mechjeb can do porkchop plots, which give you a graph of delta-v against departure time and travel time for your selected target planet, then plot you a course there based on where in the graph you click. It still makes mistakes, floating point errors and such (plotting a delicate maneuver years in the future tends to get bouncing indicators) forcing you to learn do mid-course correction burns, but that's part of the learning.

I could look up transfer windows and departure angles on a site somewhere to get places (and have!) but find that tedious.

[JackBush]

On 12/10/2015, 9:20:57, Gaarst said:

Transfer Windows 

Link's not working for me.

[Gaarst]

19 minutes ago, JackBush said:

Link's not working for me.

Strange, it does work for me...

Anyway, you got exactly the same thing made as a mod in game, check here.