Interplanetary rockets?

[KSPNewbie]

Okay so I've been playing KSP for almost 120 hours and have successful missions to the Mun and Minmus matter of factly i have a base on the mun  but how in god's name do i get to Duna i've watched Scott Manley and did the whole interplanetary calculator thing but I just can't do it!!

[Plusck]

It's dead easy once you've done it once.

1 - First wait until Duna is diagonally ahead of Kerbin in orbit around the sun. Apparently it's 43° ahead, but I always use this to give me the best date: https://alexmoon.github.io/ksp/

2 - Then build a ship that has a bit more fuel than you'd need for Minmus. Not a huge amount more. Simple way of doing it is just to take your latest Minmus craft and add a drop-tank or two, or just scale up the lifter section a bit. Again, not much...

3 - Then start plotting a burn as if you were going to Minmus, only target Duna. Add a burn of about 1050 m/s (assuming you've waited for the right date). You'll find that the burn takes you far off to the right, and you'll see your orbit around Kerbol appear. Slide your maneuvre node around until the solar orbit goes through Kerbin. That basically means that your Pe around the sun is at Kerbin where you are now, and your Ap should be on the other side of the sun, where Duna will be when you get there.

4 - Fine tune your escape burn until you get an encounter. It shouldn't be far off the figure that the launch window planner gives you. You might need to correct your inclination to get a hit: simply zoom out when you've got something close to the target, add a node about halfway around and correct. It should only be a few m/s unless your LKO is very far off the equator. If AN or DN is somewhere along the trajectory, drop the correction node there.

5 - Burn!

6 - Once you're outside Kerbin SOI, fine-tune that midway node. Select Duna, Focus to it, and rotate so that you can interact with the node you dropped earlier. Normal and anti-normal should be obvious to you by now. What is more interesting for interplanetary corrections is the combination of radial in or out, combined with prograde or retrograde. Basically, if you make changes in pairs you can not only change your arrival angle, but also the arrival date. That means you can intercept Ike on the way in to Duna at any time along its orbit, simply by making paired changes to prograde/radial in or retrograde/radial out (i.e. with raidal in, you intersect later along Duna's path, so Duna will have got further ahead of you, but with prograde you get there faster, so you catch up more). By getting a good encounter with Ike before you get to Duna, you can reduce your capture burn. You can also aerobrake at Duna if you want. I generally don't bother because the dv needed to capture with a good Ike encounter is not very high, and I get bored drifting through the atmosphere at 1x speed.

[Evanitis]

Short answer: you need to leave Kerbin's SoI by a specific speed, at the specific angle at the specific time.

The time you need is the launch window - when Kerbin and the target planet is alligned so that you need the least dV to get there. Here is an excellent tool to find your window. It might give you an intimiditaing amount of information, but all you -really- need is to enter your starting conditions, click plot, find a deep blue spot on the graph, and check the departure time. It will also tell the required dV for the dransfer. From there, it's pretty much the same as going to the Mun.

Except that to save fuel, it's best to depart in an angle that needs minimal or no course correction to intercept the target. You can kinda' eyeball that - it's a lot less critical than timing, but you can also dig into precise aiming at launch. The above linked planner also tells you the required ejection angle - here's a guide about what it is and how to use it.

[Plusck]

* caveat one: it isn't much more expensive than going to Minmus, but Ike is about midway between Minmus and the Mun. So it's more like a combination of what you'd send to Minmus, plus what you'd send to the Mun. With a bit more fuel to get you back.

** caveat two: although you should be able to plot the burn perfectly well without ever zooming out on the map, it's still a good idea to zoom out before committing to the burn, to make sure that your escape trajectory is actually following Kerbin's orbit prograde, and make sure that you're not vastly exceeding Duna's orbit and catching it on the way back down, which is a waste of fuel.

[KSPNewbie]

okay I've been working on it but my manuever nodes are rapidly ascending in required delta-v like going from 200 to 1300

[Snark]

4 hours ago, KSPNewbie said:

Okay so I've been playing KSP for almost 120 hours and have successful missions to the Mun and Minmus matter of factly i have a base on the mun  but how in god's name do i get to Duna i've watched Scott Manley and did the whole interplanetary calculator thing but I just can't do it!!

So, lots of good advice from the folks who have already posted, but it would be a lot easier to give advice if we had an idea of exactly what the problem is.

When you say "can't do it", what exactly is the problem?  For example,

• "I planned a route but I always run out of fuel."
• "I can't figure out how to plan a route."
• ...something else?

What happens when you try?  Screenshot?

[KSPNewbie]

and i'm not changing the retrograde or prograde...

 

[Plusck]

6 hours ago, KSPNewbie said:

okay I've been working on it but my manuever nodes are rapidly ascending in required delta-v like going from 200 to 1300

As Snark said, a bit more information about where the problem lies would be helpful.

The advice given above is assuming that you are starting from low Kerbin orbit (LKO). If you have already left Kerbin's sphere of influence (SOI) then things are (a) simpler and (b) far more expensive in fuel. Simpler in that you're just raising or lowering your orbit around Kerbol, and more expensive because you lose the Oberth effect.

However, when you say that your "manuever nodes are rapidly ascending in required delta-v like going from 200 to 1300", what do you mean exactly?

Since you regularly do Mun and Minmus trips, I'm assuming that you are talking about maneuvre nodes after the change in SOI. If so, then yes, that happens. When you first place a maneuvre node in another SOI and alter it, then the values that it gives should all be normal and consistent (so if you mouse over a midway correction node, for example, it should say "Maneuvre node" together with the time to get there and something in the region of 1m/s to 150 m/s). However, if you then change SOI (e.g. you pass through the Mun's SOI), there is a bug of sorts that recalculates the maneuvre node from your new SOI's perspective, so you get a big jump.

I've only really enountered this when planning a course among Jool's moons. I can set it up perfectly outside the system, but as soon as I get inside the figures all jump to around 2900-3300 m/s. If I try to delete and recreate these nodes, it'll give me 2900 m/s as soon as I place it. Generally this is because I'm about to get a Tylo gravity assist and the game doesn't deal well with the SOI change.

However, once you no longer have any SOI change before reaching the node, it should return to its normal, correct value.

 

Edited January 21, 2016 by Plusck

[HebaruSan]

Since you mentioned interplanetary calculators, I'm going to assume you've already got the various key numbers but are stuck at how to interpret and apply them.

You picked Duna, which is further from the sun than Kerbin, so luckily that means we can draw some analogies to what you've already mastered. Think of the start of a normal Mun mission, except with the sun where Kerbin normally is, Kerbin where your ship normally is, and Duna where the Mun normally is. Imagine that Kerbin is a huge ship, and you're piloting it. If you wanted to burn to make Kerbin intercept Duna, you'd need two things, the right time to do it, and the right amount to burn; these are the things the calculators give you. And just like going to the Mun, the burn should be prograde to raise Kerbin's apoapsis the necessary amount (plus or minus some small corrections).

Now, you're not going to move all of Kerbin, you're just moving your ship. But the core concept is the same, because your ship is orbiting Kerbin, so it inherits most of Kerbin's orbital velocity around the sun, plus its own velocity around Kerbin. So you want to wait till the right time, then point your ship solar-prograde and Kerbin-prograde at the same time (that way you're already moving in the right direction), and burn the right amount. This alignment of the prograde vectors works out to burning on the night side, i.e., opposite from the sun.

There are many other subtle factors that complicate things, but once you grasp the main idea, those things can be figured out as needed.

[KSPNewbie]

4 hours ago, Plusck said:

As Snark said, a bit more information about where the problem lies would be helpful.

The advice given above is assuming that you are starting from low Kerbin orbit (LKO). If you have already left Kerbin's sphere of influence (SOI) then things are (a) simpler and (b) far more expensive in fuel. Simpler in that you're just raising or lowering your orbit around Kerbol, and more expensive because you lose the Oberth effect.

However, when you say that your "manuever nodes are rapidly ascending in required delta-v like going from 200 to 1300", what do you mean exactly?

Since you regularly do Mun and Minmus trips, I'm assuming that you are talking about maneuvre nodes after the change in SOI. If so, then yes, that happens. When you first place a maneuvre node in another SOI and alter it, then the values that it gives should all be normal and consistent (so if you mouse over a midway correction node, for example, it should say "Maneuvre node" together with the time to get there and something in the region of 1m/s to 150 m/s). However, if you then change SOI (e.g. you pass through the Mun's SOI), there is a bug of sorts that recalculates the maneuvre node from your new SOI's perspective, so you get a big jump.

I've only really enountered this when planning a course among Jool's moons. I can set it up perfectly outside the system, but as soon as I get inside the figures all jump to around 2900-3300 m/s. If I try to delete and recreate these nodes, it'll give me 2900 m/s as soon as I place it. Generally this is because I'm about to get a Tylo gravity assist and the game doesn't deal well with the SOI change.

However, once you no longer have any SOI change before reaching the node, it should return to its normal, correct value.

 

well when I make a manuever node it estimates 530 m/s then when i aim my ship at the manuever node the m/s ascends to around 3000 m/s

 

[Evanitis]

Aren't the command pod or control module facing backwards? I can imagine no other explanation for the stock dV readout to raise instead of decrease when you start burning. Did you try the exact opposite direction?

[KSPNewbie]

no they aren't upside down might it be possible there's a glitch that is causing this?

[WhiteKnuckle]

Just now, KSPNewbie said:

no they aren't upside down might it be possible there's a glitch that is causing this?

Possible, can you take some screenshots?

[KSPNewbie]

never mind I've escaped Kerbin Orbit and have maneuvers planned for reaching Duna SOI but now I can't control the ship, not the first time this has happened in my game a rover was unresponsive once as well

and how do i upload screenshots, sorry everyone 

 

[ineon]

Posting screenshots:

http://forum.kerbalspaceprogram.com/index.php?/topic/128907-how-do-you-post-pictures/#comment-2342176

[Wemb]

16 minutes ago, KSPNewbie said:

never mind I've escaped Kerbin Orbit and have maneuvers planned for reaching Duna SOI but now I can't control the ship, not the first time this has happened in my game a rover was unresponsive once as well

 

Oh dear - did you forget the solar panels? Or, if you didn't, did you put the littles ones on radially, and then point the nose of your vessel at the sun?  That's what happened to my first interplanetary ship - the batteries ran flat and I ended up with a very expensive brick.  I think the power came back after it got slung out away from Duna and the plane it was on changed, but by that point it was on a useless trajectory.

I made sure the next time I used extending solar panels.  And then I blocked them with my saddle tanks. Same result.

Wemb

[Evanitis]

I met 'ship goes unresponsive' bug before when I had power, yet the 'control from here' options were missing from all modules where it should have been.

Switching to Space Centre and going back always fixed it, so I didn't bother.

 

Congratz on the Duna encounter anyways! Giant leap for Kerbalkind etc..!

Edited January 21, 2016 by Evanitis

[KSPNewbie]

Thanks for all the help guys I really appreciate it

[KSPNewbie]

it failed miserably forgot to attach fuel lines to rockets on sides of rover remodeled and prepping for launch now

 

[Plusck]

That happens.

I went through a few attempts to set up the LV-N with parallel stacks of tanks. Testing on the launchpad seemed to show everything was fine. It was (in-game) weeks later that I started the interplanetary burn only to find that only the last couple of mini-tanks were actually feeding the LV-N, so every 150 m/s dv or so I had to stop the burn, manually refill tanks (while ensuring balance, so it couldn't be done during the burn), and continue. Got old fast. Managed to do the same thing exactly with the 2-to-1 aero tank. It doesn't feed from the double side, only the single. FYI.

This is about where I gave up trying to be pure and free of mods, and installed KER. I'm glad I didn't do it earlier, because if anything it gives too much information, but having proved to myself I can do without mods it is nice to know during the build that something isn't adding up. If a stage has zero m/s dv or very little, even though you know it should be capable of landing or whatever, then you realise something is messed up.

[KSPNewbie]

okay this was success ful but the burn to start orbit is like 2345 dV so I seriously need help!!!

 

I'm not touching the game until i figure it out I'm quite nervous

 

[HebaruSan]

7 minutes ago, KSPNewbie said:

I'm not touching the game until i figure it out I'm quite nervous

Press F5 to quick save, then try something, then hold F9 to quick load and try again. Repeat until you at least feel less nervous.

[KSPNewbie]

yeah but the engine does not have enough have enough fuel

 

[Foxster]

I'm not advocating "something is hard so mod around it" but you could try MechJeb's Advanced Transfer to Another Planet feature just to learn how it does it. Then emulate it yourself. 

It's how I learned to do it. Though I do now only occasionally plot interplanetary missions. Once I'd done it a few times it became tedious and I'd rather spend my time on craft design and mission goals. 

Edited January 23, 2016 by Foxster

[Plusck]

8 hours ago, KSPNewbie said:

okay this was success ful but the burn to start orbit is like 2345 dV so I seriously need help!!!

 

I'm not touching the game until i figure it out I'm quite nervous

 

Hang on a second, what burn are you talking about here?

If this is your burn from LKO to Duna, there is something seriously wrong. It shouldn't exceed about 1100 m/s.

And if this is your capture burn into Duna orbit, again something is seriously wrong.

Please upload a screenshot. Best way is to save it to imgur, the get the image's URL (I do this by right-clicking the image to "view" it then copy the content of the address bar)  then click this forum's "Insert other media" buttton (bottom right) and paste the URL of the image.