Trying to get to the Mun

[Silverwood]

Ok I have tried several times to complete the Min 1 tutorial, but I just can't get the manoeuvre modes right. Sometimes I get a purple line off to the right, as I approach the Mun, I can't seem to find out why. I also can't get a manoeuvre right to actually get to the Mun.

Is there anywhere a written easy set of instructions to follow please?

Keith

[Streetwind]

When your trajectory intersects the sphere of influence of the Mun, then the Mun's gravity will influence it. If you come up from behind and pass above it (from Kerbin's point of view), for example, it will accelerate your ship like a slingshot, causing you to leave the sphere of influence with more speed than you entered - this might even result in a trajectory that escapes Kerbin's sphere of influence later-on. Similarly, if you come up from behind but pass below it, it will actually slow your ship down.

The magnitude and direction of this effect depends on your specific direction of approach, and how close to the surface you pass - it's even possible for your trajectory to be nearly completely reversed (but that would actually be a surface impact trajectory, since it requires you to be closer to the Mun than the Mun is large). Therefore it's hard to give a simple answer like "this always happens when you do X".

But at the same time, there's no need to let it confuse you.

The important part is that you get an encounter. Any encounter. Ignore what your trajectory does after the encounter, it is not important. Because of physics, you need to fire your engines when you get there later, causing your trajectory to change again anyway. Just try to execute the maneuver node to the best of your ability.

As for making the maneuver node, there is an approach that always works for the Mun:

1.) Create your node somewhere. Anywhere is fine.
2.) Focus on Kerbin, and look at it from the top down, zoomed out far enough that you can see the orbit of the Mun as a perfect circle around it.
3.) Drag the green prograde marker of your node until your predicted apopasis touches the orbit of the Mun.
4.) Drag and drop the maneuver node itself around your current orbit. This will make your predicted apoapsis move, too. Move the node until you find an encounter. It should be roughly 45 degrees ahead of the Mun's current position.

 

Edited May 23, 2017 by Streetwind

[Silverwood]

OK thanks. I will try that, but I still don't know why when I get close, a new purple line appears away from the original orbit line.

Sorry to be a bit dumb, but the various tutorials, videos don't seem to be helpful on that point.

Keith

[Cpt Kerbalkrunch]

18 minutes ago, Silverwood said:

OK thanks. I will try that, but I still don't know why when I get close, a new purple line appears away from the original orbit line.

Sorry to be a bit dumb, but the various tutorials, videos don't seem to be helpful on that point.

Keith

The purple line is your projected orbit after leaving the Mun's SOI. This is good. It means you actually have a Mun encounter, but if you don't adjust your course sometime between then and now, the purple line will be your new orbit.

I'll try to save you some headaches and tell you one of the biggest "aha" moments I've ever had in this game. Once you have a Mun encounter (or any other body for that matter), when you see the purple orbital path for instance, click on the Mun and select "set focus". You will now focus in on the Mun and you'll be able to see your orbital path through it's SOI. This will help you see exactly where you'll pass by the Mun, but even better, it'll allow you to set another maneuver node (do it on your current path, a few minutes or a few hours ahead, whichever works better) to get a better encounter. When you start moving the dials on the node, you'll actually see your path as it moves through the Mun's SOI. This is one of the biggest keys to the game. It will allow you to turn a bad encounter into a good one.

[Streetwind]

46 minutes ago, Silverwood said:

OK thanks. I will try that, but I still don't know why when I get close, a new purple line appears away from the original orbit line.

...Oh! Okay. I see what you mean now.

That's due to the way Kerbal Space Program calculates trajectories. See, in real life space, there are dozens upon dozens of objects with significant gravity wells, all of which influence one another, while the whole bunch of them is also spinning around each other at different speeds. This royal mess is called, in mathematics, a "N-body problem", and it has no general solution. In other words, it is incredibly, incredibly complicated, and the tiniest difference in initial conditions can dramatically change everything down the line. And while you can solve a N-body problem for a known set of actors and initial conditions, such as the KSP solar system that always spawns the exact same way at game start, the devs still decided against doing it, for three reasons. One, it's very difficult to debug and fix if something goes wrong, because it is so complicated. Two, it takes a lot of CPU power to simulate with sufficient precision, especially when trying to fast forward. And three... because it is so complicated, it would be difficult to play in, especially for newcomers. Every orbit you assume with your spaceship would constantly change, and you would find your space stations randonmly deorbited or ejected from the system by subtle gravitational perturbance built up over time.

What the devs did instead is use a simplification. Instead of simulating all the things in a N-body problem, KSP only ever simulates two things: your spacecraft, and the currently dominant gravity well. Thus it becomes a "2-body problem". And that is very easy to solve into very consistent and easily understandable results.

However, it comes with an inherent issue: if you only ever calculate against the currently dominant gravity well, then what happens when which gravity well is dominant changes? When you get far enough away from one body and close enough to the other that the new one overpowers the old? This is where, finally, your dotted purple line comes into play.

In order to be able to smoothly transition from one body to the next, KSP employs what is called "patched conics". The game has precalculated areas in which one body becomes stronger than another: the so-called "spheres of influence". If you want to transition from one to the other - say, to go from the influence of Kerbin into the influence of the Mun - then the game first solves the 2-body problem for your spacecraft with Kerbin, and then solves the 2-body problem for your spacecraft with the Mun (using the result from the former as the initial conditions for the latter).

Now the game has two partial pieces of orbital trajectories ("conics"). It takes them, and "patches" them together where they meet, to form one full and coherent line.

 

So the purple line you see sometimes is a different "conic". It's a part of your orbit that is colored differently because there was a SOI transition somewhere before it. And that's a good thing! Because they only show up when your orbit changes from one sphere of influence to the other... which is precisely what you want to do, right? You want to go to the Mun. And to go to the Mun, you need to travel into its sphere of influence.

The purple line is exactly what you're looking for. It is the sign that you have found an encounter. In fact, it's probably already the third conic in the series - the part of the orbit you get after exiting the sphere of influence of the Mun again and returning to that of Kerbin. There's probably another differently colored one in between the yellow line going towards the Mun, and the purple one that leads away from it. That middle line is the segment of your orbit that is inside the Mun's SOI. That's when you have arrived where you want to go, and where you then have to perform a "capture burn" to stop yourself from coasting back out again.

 

Edited May 23, 2017 by Streetwind

[Silverwood]

Wow, very technical but needed.

I have retried the tutorial now and achieved the orbit around the Mun. So thank you. I think because I did not know what the new line was for, I did not create the mode on that line, once I worked that out the rets feel into place.

One thing, though, the space bar did not work in the tutorial for decupling the used fuel tank. Not sure if that is a mysterious bug, the manual decople worked.

Anyhow thanks for the extra info.

I may ask another newbie question, as my next target is to try and land something!!!

Keith

[Streetwind]

2 hours ago, Silverwood said:

One thing, though, the space bar did not work in the tutorial for decupling the used fuel tank.

I get that too - sometimes I need to hit space twice to stage. I don't know any rhyme or reason about it. Pretty sure others get it too. Little bug, perhaps, but you get used to it

Congratulations on your successful Mun orbit, either way!

 

Edited May 23, 2017 by Streetwind

[Spricigo]

3 hours ago, Silverwood said:

I may ask another newbie question, as my next target is to try and land something!!!

Keith

3 methods:

 

Vertical drop: just kill all the horizontal velocity and then control the vertical velocity until touch down. Not much fuel efficient, you are doing a 90° turn instead of a smooth curve, but landing close to a target is easy.

Then reverse gravity turn: tilt your lander just a bit up from retrograde and burn. Fuel efficient because the burn is mostly aligned with the direction of the movement, somewhat difficult to get the initial tilt right and somewhat easy to land close to a target.

The constant descent: approaching in a horizontal trajectory start a retrograde burn, as you slow down turn the lander up just enough to maintain a constant vertical speed while reducing the horizontal speed. Fuel efficient because it prevent vertical speed to build up, difficult to land close to a target.

All three methods can be done as a suicide burn, that is performing the burn in the last moment, at full throttle, cutting the engines just before touching down with velocity close to zero; all three method will benefit from a generous TWR.

In practice its common to combine the different methods, either for difficulties in following a particular method or just convenience. (e.g starting with a constant descent, change to gravity turn above the target area, finalize with a vertical drop).

[Silverwood]

Ok thanks. Before I try that I need to research the thrusters, I am pretty sure I would need those to make a successful landing, unless it can be done just on engines?

[Spricigo]

18 minutes ago, Silverwood said:

Ok thanks. Before I try that I need to research the thrusters, I am pretty sure I would need those to make a successful landing, unless it can be done just on engines?

You can probably land just fine with 1-2 Terrier engines. Thud and Spark and are good alternatives depending on lander weight, player skill and player style. Smaller engines allow for a more precise control of the velocity but it will require longer burns.

1 minute ago, Cpt Kerbalkrunch said:

 

@Spricigo, you are quick on the draw, sir.

I'm a time traveller

Edited May 23, 2017 by Spricigo

[Cpt Kerbalkrunch]

If you mean RCS thrusters, no they're not necessary. Your engines' gimbal will be fine. And if you use ungimabaled engines, reaction wheels alone will be fine. You probably won't be landing a monster ship this early in the game. Shouldn't be difficult to keep under control.

@Spricigo, you are quick on the draw, sir.

Edited May 23, 2017 by Cpt Kerbalkrunch

[Silverwood]

Ok sounds good.

I am trying to practice with a small capsule, small fuel tank and 1 terrier engine, but its hard to get the descent right. That is on Kerbin of course!

I realise on the Mun, there is no atmosphere, but I wanted to get used to it first. Perhaps I will run through the Mun 2 tutorial first!

Cheers.

Keith

 

 

[Spricigo]

Just now, Silverwood said:

Ok sounds good.

I am trying to practice with a small capsule, small fuel tank and 1 terrier engine, but its hard to get the descent right. That is on Kerbin of course!

I realise on the Mun, there is no atmosphere, but I wanted to get used to it first. Perhaps I will run through the Mun 2 tutorial first!

Cheers.

Keith

 

 

 

You may design a mun lander and use alt+F12 to set orbit around the mun/minmus/whatever.

[HvP]

46 minutes ago, Silverwood said:

Ok sounds good.

I am trying to practice with a small capsule, small fuel tank and 1 terrier engine, but its hard to get the descent right. That is on Kerbin of course!

I realise on the Mun, there is no atmosphere, but I wanted to get used to it first. Perhaps I will run through the Mun 2 tutorial first!

Cheers.

Keith

 

 

Just a quick note to let you know that the Terrier engine might not work well for landing practice on Kerbin. It's made to work best in the vacuum of space and so doesn't produce much thrust in dense atmosphere.

Unless your craft is super lightweight the Terrier might not have even enough thrust to slow you down before you hit the ground. You can test this by trying to throttle the engine on the launch pad. If it can't lift its own weight then it can't slow itself down enough to stop either.

Are you familiar with the cheat menu? Pressing Alt+12 will give you a menu full of options to test out the game. One of them is called "Cheats" and one of the options under that is called "Set Orbit." If you put your ship on the launch pad and then use the set orbit menu and select from a list to put that ship around any planet or moon you like to practice crashing with style landing on. Don't worry about the numbers in the orbit fields. Just set them all to zero and then when you click the Set Orbit button it will give you a warning but will fill out the fields with the lowest safe orbit possible. Then just click Set Orbit again and you're there.

Edit: ninja'd

Edited May 23, 2017 by HvP

[Cpt Kerbalkrunch]

23 minutes ago, Silverwood said:

Perhaps I will run through the Mun 2 tutorial first!

The guys above have already run through the Terrier's benefits (I think it's the engine of choice for your 1st Mun landing; good enough power and gimbal, but also lightweight and cheap), so I think that's covered. I'll just say this might be the only game where tutorials and training missions are absolutely essential to get you started. That being said, once you've got the basics down, there's no substitute for experience. You can use the cheat menu (personally, I like it for testing Eve landers because of the difficulty and the amount of time it takes), but it's not all that necessary. These aren't real lives or real money you're playing with, so why not have some fun with it? Just go to the Mun and see what happens. Every failure in this game is an invaluable learning experience. I've played my entire time "on the fly" so to speak. Success is pretty much guaranteed if you just keep trying. And before you know it, things will make sense and you'll look back and wonder why you were having such a hard time in the first place.

[Spricigo]

25 minutes ago, Cpt Kerbalkrunch said:

 I'll just say this might be the only game where tutorials and training missions are absolutely essential to get you started. That being said, once you've got the basics down, there's no substitute for experience.

I don't go as far as say they are necessary but for sure tutorial make a huge difference. Some people have advantage knowing how those things work in real life (a knowledge that translate well to the game) but for us, mortals, it saves a lot of headache.

QFT: there's no substitute for experience.

[Cpt Kerbalkrunch]

27 minutes ago, Spricigo said:

I don't go as far as say they are necessary but for sure tutorial make a huge difference. Some people have advantage knowing how those things work in real life (a knowledge that translate well to the game) but for us, mortals, it saves a lot of headache.

QFT: there's no substitute for experience.

Agreed. Some of these threads are so far beyond my education level that they may as well be in another language. And yet...I know exactly what they mean because I've played the game so much and read all the conversations. Probably still couldn't describe it all or explain why it works, but I know how it works and how to make it work for what I want to do.

Hope I didn't give the OP the impression above that testing is bad or unnecessary. Nothing could be further from the truth. I think we all test our ships and landers over and over 'til you've got it right. It just sounds like he has his lander and he's ready to go. Especially for your first landing. There's no real experience to draw from. You just gotta try it. I think I crashed at least a dozen times before I finally made it. Quite literally jumped off my couch when it finally happened.

No feeling like that first time. 

Edited May 23, 2017 by Cpt Kerbalkrunch

[Silverwood]

10 hours ago, HvP said:

Just a quick note to let you know that the Terrier engine might not work well for landing practice on Kerbin. It's made to work best in the vacuum of space and so doesn't produce much thrust in dense atmosphere.

Unless your craft is super lightweight the Terrier might not have even enough thrust to slow you down before you hit the ground. You can test this by trying to throttle the engine on the launch pad. If it can't lift its own weight then it can't slow itself down enough to stop either.

Are you familiar with the cheat menu? Pressing Alt+12 will give you a menu full of options to test out the game. One of them is called "Cheats" and one of the options under that is called "Set Orbit." If you put your ship on the launch pad and then use the set orbit menu and select from a list to put that ship around any planet or moon you like to practice crashing with style landing on. Don't worry about the numbers in the orbit fields. Just set them all to zero and then when you click the Set Orbit button it will give you a warning but will fill out the fields with the lowest safe orbit possible. Then just click Set Orbit again and you're there.

Edit: ninja'd

Thanks about the 'cheats', no I did not know about those. Certainly being able to set an orbit would be very useful!

The terrier did not work too well, first time I hit the ground far too hard. Reset and tried again, managed to hit the ground with limited damage, so I kpet that one (Career mode). For the proper attempt it might work, but at least Ic an try!

So with these cheats, theoretically could you go to orbit straight away simulating an auto pilot and then return? In career mode of course. I know its not in the spirit of the game, but it would make things  a little easier!

Keith

 

 

[bewing]

Yep, the debug menu provides a very wide variety of info, and allows you to do many things in the game that would normally be difficult. Infinite fuel, Infinite electricity, Setting orbits, Creating Kerbals, Completing and Creating contracts. Changing gravity levels.

[MiffedStarfish]

If you are going for landing, I would highly recommend doing it on Minmus first. The lower gravity is much more forgiving, and you don't need nearly as much fuel, opening up the possibility of a return mission. Encountering it is slightly harder than encountering the Mun, but the basic principle is the same, and the fuel cost is made up for in the easier landing. Hope this helps!

[HvP]

11 hours ago, Silverwood said:

Thanks about the 'cheats', no I did not know about those. Certainly being able to set an orbit would be very useful!

The terrier did not work too well, first time I hit the ground far too hard. Reset and tried again, managed to hit the ground with limited damage, so I kpet that one (Career mode). For the proper attempt it might work, but at least Ic an try!

So with these cheats, theoretically could you go to orbit straight away simulating an auto pilot and then return? In career mode of course. I know its not in the spirit of the game, but it would make things  a little easier!

Keith

 

 

Honestly, I don't use the set orbit cheat very often myself. Usually only when I want to test out aspects of my communications satellite network. I think you are on the right track just running various test flights. That's the Kerbal way of doing things. I'd recommend using the cheats sparingly, or not at all unless you find there is something tedious that requires "simulations" to get right. Just make sure that you put in the practice to do it "for real" at some point.

And I have to agree with Cpt Kerbalkrunch that there is no better feeling in the game than finally nailing a landing on your own. Flying by the seat of your pants, pulling off dicey maneuvers and then coming out looking like an ace at the end of it is very satisfying (no one has to know if you planned it that way or not, haha.) Even if it was a bumpy ride that just adds to the drama and fun of it. It's a game. Have FUN playing around with it!

And MiffedStarfish is right too. Minmus is a great target to practice landing on. Lower gravity than the Mun, and a slower descent.

Edited May 24, 2017 by HvP

[Silverwood]

23 hours ago, bewing said:

Yep, the debug menu provides a very wide variety of info, and allows you to do many things in the game that would normally be difficult. Infinite fuel, Infinite electricity, Setting orbits, Creating Kerbals, Completing and Creating contracts. Changing gravity levels.

Oh ok. That is really useful, I have very little money left now, so some extra cash would be good.

Oh and for newbies - a little lesson, always double check your craft. I followed all these instructions and got to the Mun myself, made an orbit, got a return path and came back. All without any cheats!

I had just enough fuel to get an orbit and a tiny bit to get a landing site. All looked good, clicked space to release the fuel & engine, nothing happened. I had forgot to add a decoupling section.

Burnt up. So check & double check.

Keith

 

[bewing]

If you are really stuck for cash, and it's making the game not be fun -- you can go into the debug menu and type (in the "console" text bar) "/funds 100000" (without the quotes). And then you will have 100 grand to spend (or whatever number you choose).

 

[Silverwood]

Ok I have now cracked the getting to Mun & back bit. All ok now. No Cheats either.

I am now trying to get to grips with a landing, do any of you have some advice on the actual lander?

Most of the posts don't really cover the lander in detail.

Keith

[Spricigo]

34 minutes ago, Silverwood said:

 

I am now trying to get to grips with a landing, do any of you have some advice on the actual lander?

 

https://kerbalx.com/Spricigo/Gossiper

Notice that is actually designed for Duna. But its not that different from once designed for the mun/minmus.

Edited May 26, 2017 by Spricigo