Getting there from here: tips for the ignorant on how to navigate between planets.

[SSgt Baloo]

So far I've navigated missions to Duna and Eve. My usual method, once leaving Kerbin's SOI is to drop my periapsis to about 6,000,000 km (Duna) or 3,500,00 km (Eve). From there I circularize, match inclination with the target, then do a Hohman transfer to intercept the target planet. As I have a bit of a tremor in my hands, I use Mechjeb to navigate my ships, as my ability to move the mouse with accuracy just isn't there, except for nearby objects (Mun, sometimes Minmus, etc.)

I am, as yet, very unskilled at interplanetary navigation. How can this be done to minimize the amount of time it takes to get where I'm going? How do these techniques differ from the ones used to minimize fuel consumption?

Also, unless you're more green than me, you've all been at this part of the slope of the learning curve. Are there any questions you think I should ask if I knew enough to ask? Please share.

Edited March 29, 2016 by SSgt Baloo

[Armisael]

I think that the most popular way to do transfers is by burning directly from low Kerbin orbit to set up an intercept with the body in question (using a maneuver node, obviously). Personally, I use a launch window calculator to figure out when and where to place that node in the first place - this is the most popular of those, though this other one has better pictures for figuring out what the output of the calculator means.

You can minimize travel time by taking a more direct route

Edited March 22, 2016 by Armisael

[Mastikator]

Doing a straight hoffman transfer is faster and more efficient. Since you're using mechjeb you could use the navigation thingamabob to "find" the next transfer maneuver node.

If time is a more scarce resource than delta velocity then you can do a "faster" hoffman transfer

Spoiler

 

[zarakon]

This is one of the things that I find really lacking in the stock game.  There's no straightforward way to find interplanetary transfer windows without using a mod or external calculator.

 

One trick is to put something in orbit around the sun just ahead of or just behind Kerbin, in exactly the same orbit.  Then you can create a maneuver node from that craft to see where the window is.  Only really works one-way though, unless you take the time to set up a similar thing near each planet before doing any return trips.

[regex]

1 hour ago, Mastikator said:

hoffman transfer

"Hohmann" transfer.

[Mastikator]

1 minute ago, regex said:

"Hohmann" transfer.

David "The Hoff" Hasslehoff-man transfer.

[regex]

Just now, Mastikator said:

David "The Hoff" Hasslehoff-man transfer.

Yeah, I know you were joking but OP, who is trying to learn, doesn't, and your post doesn't make that clear.

[Laie]

2 hours ago, SSgt Baloo said:

I am, ,as yet, very unskilled at interplanetary navigation. How can this be done to minimize the amount of time it takes to get where I'm going? How do these techniques differ from the ones used to minimize fuel consumption?

In real life, they calculate thousands upon thousands of possible maneuvers; each will take you from target to destination, but the parameters and cost vary wildly. The numerous results can be combined in a single graphic, called "porkchop plot", that is surprisingly easy to understand.

Since you are using MechJeb: it comes with a porkchop plotter that's well integrated with everything else. Once you are in orbit around Kerbin...:

1. enter map view
2. right-click your target planet, "Set as Target"
3. open MechJeb's maneuver planner, "Advanced Transfer to Another Planet"

If you don't see a colorful picture right away, press "Reset".

If you want to know more about what a porkchop plot is and how it works, the best advice I can give is that you visit https://alexmoon.github.io/ksp/. This site uses the same mechanism that has been integrated into mechjeb, but with more text and labels to explain what it all means, and it's easier to play with (so you can try different inputs and see what comes out).

[MiniMatt]

I think I'm correct in stating the New Horizons mission to Pluto was vaguely "kerballed" in that the mission was sent with only* a best guess as to where the planet would be when they got there - it's extremely long orbital period (~250 years) and it's relatively late discovery meant that humanity had only witnessed about a quarter of it's orbit at the time of launch and had to extrapolate it's most likely path from that we'd already borne witness to. Mid mission corrections were allowed for to adjust trajectory as we got closer.

Apologies for the tangent, the actual answer to your question has already been ably addressed above by those less prone to waffle than myself.

 

* actual rocket scientists best guesses being orders of magnitude more accurate than mine

Edited March 23, 2016 by MiniMatt

[wumpus]

1 hour ago, MiniMatt said:

I think I'm correct in stating the New Horizons mission to Pluto was vaguely "kerballed" in that the mission was sent with only* a best guess as to where the planet would be when they got there - it's extremely long orbital period (~250 years) and it's relatively late discovery meant that humanity had only witnessed about a quarter of it's orbit at the time of launch and had to extrapolate it's most likely path from that we'd already borne witness to. Mid mission corrections were allowed for to adjust trajectory as we got closer.

Apologies for the tangent, the actual answer to your question has already been ably addressed above by those less prone to waffle than myself.

 

* actual rocket scientists best guesses being orders of magnitude more accurate than mine

I suspect that most of the vagueness was how the Jupiter flyby effected its trajectory.  Considering the distance to Pluto, the error in distance for the Galillean moons (and the gravity the pulled the New Horizons with) was a lot bigger than any uncertainty where Pluto was.  Pluto showed up fairly well (as a multi-pixel blob) on Hubble: they knew where it was.  New Horizons was another story, and part of that was a SRB (final stage) that burned a bit longer than expected. 

[moogoob]

If you use MJ (which you said you did!) you might want to try the Advanced Interplanetary Transfer, under the Maneuver Planner. It lets you use "Porkchop" plots, which are a graph of Delta-v to intercept a target planet ordered by colour, with Departure time on one axis and travel time on the other. What it lets you do is find out what combo is most efficient, or plan a quicker transfer if you prefer to get there faster versus saving fuel. In either case, it should send you directly to the planet in question.

My piece of advice - don't activate it from a low orbit. I've had it try and dip me into the atmosphere when burning aggressively to Eeloo once or twice. I don't need to add that that's a bad idea, especially at interplanetary velocities. Activate the maneuver planner from a 200 or so KM orbit instead.

[SSgt Baloo]

On 3/22/2016 at 11:31 AM, regex said:

Yeah, I know you were joking but OP, who is trying to learn, doesn't, and your post doesn't make that clear.

I am approaching my 58th birthday at breakneck speed. I have been around long enough to know that David Hasselhoff isn't a rocket scientist by trade or training.

Also, Mechjeb II never seems to complete calculations when I try to get it to give me an "Advanced Transfer to Another Planet". Rather, it tells me it hasn't finished calculating yet.

Time after time after time.
 

I still think it's a bit quicker to drop to a lower orbit before making the transfer, at least when it doesn't look like I can go direct from where I'm at using a reasonable amount of fuel.

Edited March 23, 2016 by SSgt Baloo

[regex]

1 minute ago, SSgt Baloo said:

I am approaching my 58th birthday at breakneck speed. I have been around long enough to know that David Hasselhoff isn't a rocket scientist ny trade or training.

One never knows.

[Tourist]

1 hour ago, regex said:

One never knows.

Before this year, who would of thought that Donald Trump could be president? I expect the 'Hoff' to setting off for Mars at anytime now. 

[SgtSomeone]

There's a bunch of great web calculators our there, but I never managed to figure out how to use them (how do I measure my ejection angle? Burn angle? In reference to what now?). I don't have any relevant mods, so I've done Hohman transfers to every planet just using a window rule of thumb: start the Hohman transfer burn when the target planet (for those farther from Sol than Kerbin) is aligned with Kerbin's tangent line. IOW it's directly in the path that Kerbin would travel if suddenly gravity from Sol was no longer a thing. For inner planets, start the burn when Kerbin is aligned in the tangent of the target planet. It gets awkward for plane changes, but it'll get you where you need to go without that much of an efficiency hit.  

If you want to practice in a gentler environment, try going from the Mun to Minmus or vice-versa. Same principles apply (though there is a plane change)

In case I misunderstood and you were wondering about more efficiency, other factors to consider that I generally don't bother with:
-Oberth affect (rockets are more efficient when going faster, and thus a lower periapses); To get to Eloo it may actually be more efficient to first drop your periapsis below Eve's orbit. 
-Gravity assists: Useful around Jool and all the moons, but a real pain to figure out with planets. New Horizons did something like 5 Venus flybys, and I can't imagine trying to schedule those. 
-For shorter time (and more delta-v) try starting your Hohman early, and add more delta-v until you hit the planet. 

If you're looking for real inspiration, take a look at real NASA missions like Curiosity! 

https://en.wikipedia.org/wiki/Orbital_maneuver#Transfer_orbits

Edited March 23, 2016 by SgtSomeone

[regex]

11 minutes ago, SgtSomeone said:

how do I measure my ejection angle? Burn angle? In reference to what now?

Go into map view, center the view on the planet you're orbiting, rotate the view so you're looking at it top-down, then zoom out until you can see the planet's orbital line.  Then rotate the view around the polar axis until the planet's prograde vector is at the top.  That's 0 degrees ejection angle from prograde.  Clockwise is positive ejection angle from prograde until you reach 180 degrees, or the planet's retrograde vector.  From the planet's retrograde vector clockwise is ejection angle from retrograde until you reach 180 degrees, or the planet's prograde vector.

A better illustration.

You can eyeball this stuff pretty easily with practice, no aids.  Once you're in the general area just adjust your planning maneuver node to get a good transfer.

If you're using Alexmun's transfer planner it'll tell you the magnitude of the inclination portion of the maneuver you need to plan, just set that first (so-called "normal" vector) before setting the pro/retrograde portion of the vector (which you can get correct from the final maneuver node vector sum, the total m/s of the burn).  Even with aids, I personally find it easier to simply create nodes myself to find the best transfers, using the aids to tell me when a good transfer window is and give me an estimate of the delta-V required.

[Archgeek]

Also of note, ejection angle has a slightly confusing name (as you want your actual angle of ejection to be parallel to the orbit of the body you're leaving for a low-energy transfer), but it's just a convenience number, telling you where in your orbit to start the burn in order to end up parallel when you leave, based on how energetic and what altitude you're burning from, and is something you can actually kinda ignore in favour of moving your node around the orbit to get the ejection nice and parallel with the planet's orbit.  Though it'll likely need adjustment when you reduce the burn delta-v to bring your encounter back, so the given angle remains convenient.

I ran afoul of this planning a Gily => Eve => Moho => Kerbin assistravaganza last weekend, wondering why in the heck the planner was telling me to burn nearly radial to the sun in order to go from Eve to Moho, or telling me strange numbers like 178 degrees from prograde ("Isn't that almost retrograde?  What's wrong with this thing?!").  I felt a bit dumb after looking up what it meant.

[Vim Razz]

A little trick I picked up from someone on the forums here (I've forgotten who) for figuring out when to travel from one planet to another (without using external tools or resources) is to pitch a small probe just outside of Kerbin's SOI so it orbits the sun in an orbit very similar to Kerbin's.

Then you can use that probe's orbit to plan out maneuver nodes, and compare how much it's going to cost to travel from various departure times in Kerbin's orbit.

[Draco T stand-up guy]

On 22/03/2016 at 6:26 AM, zarakon said:

This is one of the things that I find really lacking in the stock game.  There's no straightforward way to find interplanetary transfer windows without using a mod or external calculator.

Yep. And it's the type of thing that Mission Control should be doing.

Contracts should be done in Administration.

[JT531]

How to I get into orbit with my nuclear engines?! I can get an encounter with Duna/Eve fairly easily, but my engines never have enough power to get into orbit. I'll end up getting a flyby, which is great for science but very frustrating.

Help?

[regex]

4 minutes ago, JT531 said:

How to I get into orbit with my nuclear engines?! I can get an encounter with Duna/Eve fairly easily, but my engines never have enough power to get into orbit. I'll end up getting a flyby, which is great for science but very frustrating.

Start burning earlier.

[JT531]

Just now, regex said:

Start burning earlier.

hmm never thought of that

[Armisael]

Eve and Duna also have atmospheres, so you can partially or fully aerocapture (if your ship is shaped right).

[Biff Space]

There's a mod which gives you an in-game version of the AlexMoon planner:

 

If you use KAC, you can click on the porkchop plot to pick a transfer, click a button, and you get an alarm set for that transfer. The alarm has burn dV and other details in the text, and another button will even draw the ejection angle on the map screen. It's excellent.

[I_Killed_Jeb]

I strongly recommend using precisenode, you don't ever have to fiddle with mouse control for nodes