Trouble Getting Into Mun Orbit or Mun Landing

[Nataris]

I can get close enough to the moon that my trajectory changes to one that I pass by the moon as it slingshots me into deep space. I am having major trouble actually being able to get close enough for a landing attempt or even able to get into its orbit.

Ive tried watching videos and looking through the forums but just cant seem to figure out what to do or if im doing something wrong. Currently my plan of action is as such:

1- Launch rocket straight up till about 15k meters.

2- Start to turn to the 90, staying on 1 plane, and lvl out at about 100k ALT

3- Circularize orbit and then get the trajectory to meet up to the moons estimated position

4- Get close enough to the moon that it switches my trajectory. Usually I am coming up behind the Mun.

5- No idea! No clue as to what to do now.\

6- Get lost in space... Fail!

By trade I am no space expert and so I am new to all this. I am looking for what steps I should be taking so that STEP 5 gets me closer to the moons orbit instead of slingshoting me into deep space.

Can anyone give me some pointers or instructions of what my next step or 2 should be? I have seriously made it close to the moon about 6 times now. All attempts resulted in being lost in space..

I am not entirely sure about what all these rocket science terms such as retrograde etc.. So if you do decide to help me, please be as detailed in what I should actual do as possible.

Please help fellow Kerbalnaughts!

[Twinky827]

WELLLLLL..... Erm this is a problem I have a lot, but from what I understand it\'s trajectory if you hit it from one angle it\'ll send you straight to the Mun. If you hit it from ANOTHER however it puts you into an escape trajectory and you will have to correct it. I hope this kind of helps.......

[Capt'n Skunky]

There are several tutorials and some with videos on how to get to the moon and back. Have a go with the search box in the upper right of the page. Make sure you\'re at the top of the forum or sub forum you wish to search, as it only searches the forum you\'re in as well as any sub forums of that one.

i.e. if you used the search now while reading this post, it would only search the How To forum.

Cheers!

Capt\'n Skunky

KSP Community Manager

[Nataris]

Ill try watching more videos and reading more tutorials. But like I said, I already watched some and am still having trouble figuring out what to do. Or rather, what they are doing differently to actually achieve Mun orbit.

Creating this thread was a last ditch effort of sorts. Though ill keep trying to self learn, I feel I just need someone with more knowledge to say something that turns the light bulb on in my brain.

7 tries now and the light bulb simply isnt turning one

[Capt'n Skunky]

You aren\'t alone, I\'ve only managed to land safely on the moon once and there was no return trip

Arrr!

Capt\'n Skunky

[BillWiskins]

If you\'re being captured by the Mun but ending up \'lost in space\', my guess is that you\'re finding yourself on an \'escape trajectory\'. Basically you\'re being pulled in by the Mun, but due to combinations of your speed, its speed, and your angle of approach, its gravity isn\'t enough to pull you back around for a full, circular orbit.

Essentially, a couple of ways to change this are:

1 - put yourself in such a position that, when your craft meets the Mun\'s gravitational influence, your path intersects with the Mun itself (not that easy without practise), or

2 - when you get captured, slow down! If your path isn\'t going to cause you to hit the Mun itself, the reason you\'re getting shot out into deep space is your speed. If you start moving slower, the Mun\'s gravity will be more able to affect your craft and bring it back around for a lovely complete orbit.

To do this, when you notice the orbit pathway in the map view change from your elliptical Kerbin orbit to a Munar one, make a note of the PE height. When you reach that value, rotate your craft so that you are facing away from your direction of travel. This what is meant by \'retrograde\', and there is an icon on the nav-ball to indicate it. It looks like a yellow (green, if you insist) circle with a dot in the centre, and (importantly) a cross through the middle of it. Align that with the middle of the nav-ball and fire your engines when you get to PE.

Check the map view, and watch your escape trajectory become an orbit. Once you\'ve settled into that...well, there are plenty of landing tutorials but some rules of thumb are: aim for a crater, try to descend as vertically as possible, and go SLOW when you get below 1,000m, because the surface of the Mun is variable in height (and chances are whatever you\'re landing with won\'t take too kindly to more than 10m/s, anyway...).

Hope that helps. I got a lot of valuable advice from these very pages in the past, would be nice if I could return the favour.

[Narwhalasaur]

BillWiskins is right. I\'ve attached a picture with three items (in red).

Number 1: This should be what you see when your Sphere of Influence changes (SOI), based on what you say about a slingshot. (An open hyperbolic orbit).

Number 2: This is the symbol Bill wants you to line up with on the nav ball for your 'retrograde orbit' This symbol points in the opposite direction of your motion (the X in the center tells you it\'s 180 degrees from the normal symbol, which in this case, tells you the direction you are moving.)

Number 3: Since this was the screen cap I had, I threw this in. An elliptical orbit like this (while not perfect) should bring you out of the Mun\'s SOI, and into a somewhat circular orbit around Kerbin. It\'s good for trying moon orbits many times in one flight. I know if you take off from the Mun with a heading of 270, you can get Kerbin orbits with Periapses (Pe\'s) in the atmosphere of Kerbin! (perfect for landing) That maneuver is still beyond me, though.

ADDITION: the Apoapsis (Ap) of the elliptical orbit shown is about 2.5 million meters

Hope this helps!

[BillWiskins]

Thanks for the illustration, sir. And may I say, superbly executed as well.

Saves me having to do them, at least!

[Narwhalasaur]

Thanks for the illustration, sir. And may I say, superbly executed as well.

Saves me having to do them, at least!

If only the program I used (Autodesk Sketchbook Express for Mac) had a text tool!

[Nataris]

Well, I just tried again.. This time I miss judged the Mun\'s pathway timing and had to wait until the moon came around so that I could intersect it. This time I was aimed right at the moon so i was going to naturally hit it directly, no orbiting etc.

Due to a mixture of engineering and piloting fails, I hit at 1715 m/s.... There were no survivors.

This was before I read the replies from Bill and Nar. Thanks a lot guys. Between the post and illustration, the light bulb has went on. I GET what I need to do now.

Mission 9 here I come...

[Narwhalasaur]

Glad to help.

In general for speeds needed (relative to the surface):

Hyperbola >> Circle > Ellipse with same Apoapsis as the circle >> Direct Impact

This time I was aimed right at the moon so i was going to naturally hit it directly, no orbiting etc.

So even a direct impact on the moon is avertable! A burn at a heading of 90 degrees, and level with the equator of mun (The line between brown and blue), will increase your surface speed and move you towards the left on my list of orbits.

[BillWiskins]

No worries.

You probably figured out at some point during your recent rapid descent to the Munar surface that if you do end up with a trajectory that leaves you heading directly into the Mun, reducing speed is one of the more pressing matters... for some reason, parachutes don\'t work up there.

To be honest, this scenario usually happens to me completely by accident, but it\'s nice when it does - it uses less fuel and is quicker. Another nice aspect is that if your Kerbin orbit was reasonably accurate and the plane nice and flat, you end up heading right for the equator of the Mun, which is very convenient for my favourite landing-crater.

[E. F. Kranz]

Go at 270 until you reach 12,500,000m. Watch as the moon captures you. Turn away from the direction of travel, full burn until you\'re slow enough to orbit.

Easiest way, works every time.

[VincentMcConnell]

Well, I just tried again.. This time I miss judged the Mun\'s pathway timing and had to wait until the moon came around so that I could intersect it. This time I was aimed right at the moon so i was going to naturally hit it directly, no orbiting etc.

Due to a mixture of engineering and piloting fails, I hit at 1715 m/s.... There were no survivors.

This was before I read the replies from Bill and Nar. Thanks a lot guys. Between the post and illustration, the light bulb has went on. I GET what I need to do now.

Mission 9 here I come...

As a veteran of about a thousand mun landings and returns, I can help you out...

Get yourself into a 100KM orbit. Burn pro-grade at Munrise so that you get pulled in by the Mun\'s gravity like you said you already know how to do. Start burning RETROGRADE until your PE is at about 6KM. Now wait until you get to your PE and then burn retro again so that your AP levels out with it.

Retrograde on your navball is the small yellow circle with an 'x' in it. You should get captured into Lunar Orbit if you do this correctly. I have a longer guide written here on the forums that goes into more detail about landing, orbiting, return etc.

[Nibb31]

5- No idea! No clue as to what to do now.\

6- Get lost in space... Fail!

5- Fire retrograde (slow down) to insert into munar orbit.

6- Lower your orbit and commence descent.

7- Under 20000m, slow down enough to cut your horizontal velocity. The yellow retrograde marker should be in the middle of the nav ball.

8- Land with a careful combination of main engine to maintain the descent rate and RCS for horizontal direction.

[Nataris]

UPDATE!

So, Mission 9 blew up at the launchpad.. Mission 10 however was able to get into the Muns orbit. FINALLY! Yay! However, I was NOT able to even attempt a landing.

My orbit around the Mun was pretty huge.. Something like 600k meters. I couldnt figure out how to properly manipulate the gravity so that it would put me on a crash course.

When I burned retrograde, I would get an orbit but it would be very elongated. When I burned Pro or towards the Mun directly, it went back to that trajectory that launched me into space.

This is quite difficult. Getting into an orbit with the Mun was my initial problem, now I need to figure out how to get a landing attempt out of it

Any tips? Ill search around for some more tutorials.

[Awaras]

Once in orbit, burn retrograde until the periapsis (the lowest point of your orbit) is inside the mun. Try to do this when you are above the dark side of the mun so that the spot where your orbit touches the surface is on the day side.

Increase time compression and wait until you reach an altitude of about 50 km. Burn retrograde until your lateral velocity is close to zero (the retrograde icon on the navball should be close to the dot in the middle of the blue hemisphere of the navball.

Center the navball on that dot and turn on ASAS to keep your lander perfectly vertical. Keep falling down until you reach around 15 km. Again try to \'kill\' any residual lateral velocity and start burning retrograde to slow down until you speed is about 100 m/s. Keep slowing down as you descend. Approach the surface slowly. The altitude meter shows an altitude above zero level, the surface might be higher, at 2-400 meters depending on the terrain. If you are landing on the day side of the mun, you can look for the shadow of your lander to see how far above the surface you are. If you see that you are heading to a landing at a steep slope, boost up and try to find a nice flat spot. Ideally, you should land with very little lateral velocity (you can use rcs to kill any lateral velocity). You should touchdown at less then 2 m/s or bits will fall off your lander.

[BillWiskins]

I find it helpful to think of gravity in terms of a roulette wheel. I know - bear with me a minute. The middle of the wheel = the centre of your source of gravity (in this case the Mun), and the ball = your ship. The ball will happily fly around the outside of the wheel so long as it has enough speed (=an orbit), but when it slows, it falls inward towards the wheel because it doesn\'t have the speed to continue to overcome the grade of the slope it\'s on (or the gravity of the Mun).

Urm, clumsy metaphors aside, it\'s mostly about speed. Burn retrograde enough when in orbit around anything, and lose enough speed, and you will be pulled in by gravity. So, when you convert that escape trajectory to an orbital one, you probably won\'t want to increase your speed for a while.

Fiddling with orbits is something you\'ll find yourself doing a lot in KSP. It can be tiresome sometimes, but when it goes smoothly it\'s very satisfying. Plus, it will set you up for upcoming fun stuff like meeting up with other ships in orbit. Really simple instructions for that: burn prograde at AP to increase PE, burn retrograde at AP to decrease PE. The opposites also apply.

[Nataris]

Thanks guys. I\'ll be trying again tonight after I cook/eat dinner.. I bet Jeb doesnt have to cook his own meals before flight missions.. Maybe thats why he is so bad ass. I need me a chef... Or a women that can cook (dont tell my girl I said that )

Anyway, the metaphor works well Bill and I see where you are going with it. Your last bit about Really simple instructions also helps a bit. As simple as it is, i forget the principles of orbit sometimes while im in the thick of things. The stress of the situation causes me to brain fart lol..

Also, what would have been the reason behind why i went from escape trajectory to orbit, back to escape trajectory? The orbit was getting weird and as I started testing different things out (retro/pro burn etc) I messed up so that it made me on an escape once again.

Just so I avoid that in the future, what did I do to make that happen?

Thanks again. Ill keep you guys posted how Mission 11 goes.

[BillWiskins]

I expect you just increased your speed. Just as slowing down gives the Mun\'s gravity a chance to capture you fully, if you speed up on your existing course you\'ll overpower it again and be back with \'flung out to space\' issues looming...

It\'s all trial and error (or it was for me). I refused to go looking for assistance to begin with, until I got really stuck with an unstable rocket and I headed here for help. Wish I\'d done that sooner, to be honest! The beauty of KSP is having the freedom to just do what you like, whether it ends in a beautiful orbit or a melted pile of melted Kerbalnauts.

Glad to be able to help so far, though!

[Thiel]

And remember, there\'s no problem that can\'t be solved by the proper application of more thrust.

Anyway, if your goal is to land anywhere on the Mün just keep retro burning until you orbit intersects the surface.

Landing is easier if you burn until you\'re falling straight down, but it\'s not a necessity.

[Nibb31]

My orbit around the Mun was pretty huge.. Something like 600k meters. I couldnt figure out how to properly manipulate the gravity so that it would put me on a crash course.

When I burned retrograde, I would get an orbit but it would be very elongated. When I burned Pro or towards the Mun directly, it went back to that trajectory that launched me into space.

First, you have to learn how to adjust your orbit. You can practice that in Kerbin orbit first. To raise your apogee or perigee, burn prograde at perigee or apogee (on the opposite side of the orbit). To lower your apogee or perigee, burn retrograde at perigee or apogee. To obtain a nice circular orbit, you need to burn at least twice to adjust both the apogee and perigee to the same altitude. Easy once you get the hang of it.

To get a nice landing trajectory, you simply have to burn retrograde to make your perigee intersect with the ground. Then it\'s a matter of maintaining a slow enough vertical velocity, horizontal velocity and attitude. Use the nav ball.

[SmiteZero]

People have already said it, but you need to turn retrograde and fire to slow down. The best place to do this is at your Pe mark in the map view, but you may want to do it sooner to start the process and lower your Pe. Turn backwards and give it all you\'ve got until you get an orbit. On approach to the Mun when you change to the Mun\'s influence, you might not have a Pe marker. If you don\'t want to just do a direct approach, you\'ll have to thrust sideways (sideways to your direction of travel when you switch the Navball to 'Orbital' mode) one way or the other to mush your trajectory off to the side. Then continue as above. Thrust retrograde before the Pe to lower it if it\'s too high and then at Pe to finally give yourself an orbit you can work with.

[Narwhalasaur]

It seems like you\'re getting a ton of help!

My last two cents:

Remember it takes two burns to go from one circular orbit to another. http://en.wikipedia.org/wiki/Hohmann_transfer_orbit

I attached a picture:

To go from high to low, you need to retrograde burns. The first at A, will turn your circular orbit into the red ellipse. (Stop the burn when your Pe is where you want it.) The second burn at B (your new Pe), is ALSO retrograde! Do this burn until your Ap comes down to the same height as your Pe (the definition of a circular orbit.)

If you flip Ap and Pe, and replace retrograde with prograde, you have the recipe for a low to high Hoffman transfer.

P.S.

You don\'t need to start with a circular orbit to do this, either. As Bill said: To reduce your Pe, burn retro at Ap. To increase your Ap, burn pro at Pe. Once I memorized this, everything else fell into place.

[SmiteZero]

^ Wot he sed

Burning prograde will raise the opposite side of your orbit. Obviously then burning retrograde will lower the opposite side. It\'s pretty easy.