Help! Mun lander stuck in Polar Orbit around Mun with no fuel... I can rendevouz for the life of me

[kmoney]

Hello dear Kerbanouts,

I am in dire need of some help /guidance.

My first Mun landing was successfull. I sent a pilot and a scientist and they collected 1 billion science (maybe not so much ). It turns out I did not notice I did not have enough fuel for the return, and I got my ship stuck in a polar orbit around the Mun. Thanfully I was a bit forward thinking and I put a docking port on the ship in case I needed to refuel

I have tried to send 3 refueling probes, but to my dismay, I eat up all the fuel trying to match that stupid polar orbit and rendezvous. This is getting costly, and quite annoying. Can someone please help me here. I actually have never docked with anything before.

Any and all help / guidenace is greately appreciated.

Thanks in advance for your time,

Kmoney

[Snark]

Not sure what strategy you're using for docking-- some description would help to debug it.

If what you're doing is "fly to the Mun the usual way into an equatorial orbit, then do a huge burn to manhandle your orbital plane to polar", then yeah, that's gonna eat up your dV; it's not efficient.

A few options, depending on how adventurous you're feeling.

One is to do your orbital adjusting early, as in "right at the start when you're leaving LKO", or even at the midway point en route to the Mun-- don't wait until you get to the Mun. The later you wait to adjust your orbit, the more expensive it gets.

For example, you can do like this: Set up a Mun intercept the usual way. Once you're en route the Mun (and your projected path intersects Mun's SoI), drop a maneuver node somewhere around, say, the halfway point, but don't give it a vector yet. Then click on the Mun and choose "Focus View". This takes you to the Mun and gives a nice view of what your trajectory will be around it. Then, while still focused on the Mun, rotate the camera around it until you can see the maneuver node you just dropped. Now you can fiddle with the vector handles on the maneuver node to adjust your Mun orbit. It'll be cheap: a relatively light maneuver will make a big difference to your munar orbit insertion.

If that's not your cup of tea, here's a completely different approach that's also relatively cheap on dV, as long as you're not in a hurry:

1. Set up a Munar mission the usual way (equatorial plane). Set it up so that your approach will have a really low munar periapsis, like 10km.

2. At periapsis, burn retrograde just enough to be captured to the Mun (i.e. so that you have the highest possible apoapsis).

3. You're now in an elliptical orbit with really low apoapsis and really high periapsis. Coast up to apoapsis.

4. At apoapsis, burn prograde to circularize your orbit (this will be really cheap in dV). You're now in a very high circular orbit around the Mun.

5. Let your orbit progress until you're at the ascending or descending node for your target (i.e. where your equatorial orbit intersects the plane of your target's polar orbit).

6. At that point, burn to rotate your orbit so that it's coplanar with your target. This will also be a cheap burn because you're orbiting so slowly that it's easy to make a right-angle turn.

7. You're now orbiting in the same plane as your target, it's just a normal orbital rendezvous at that point.

[adsii1970]

Hello dear Kerbanouts,

I am in dire need of some help /guidance. It turns out I did not notice I did not have enough fuel for the return, and I got my ship stuck in a polar orbit around the Mun. Thanfully I was a bit forward thinking and I put a docking port on the ship in case I needed to refuel... I have tried to send 3 refueling probes, but to my dismay, I eat up all the fuel trying to match that stupid polar orbit and rendezvous. This is getting costly, and quite annoying. Can someone please help me here. I actually have never docked with anything before.

Never fear, as I am the master of stranding Kerbals in orbit and will offer you a scenario or two to help you out. Back in .24, I managed to strand a Kerbal in 45 degree to equatorial orbit without enough fuel to return to Kerbin from Minimus. At first, I did the same thing you did until it dawned on me - make the rescue mission several stages and not from launch pad to rendezvous, which is our first instinct. Remember, they are Kerbals and do things the Kerbal, er difficult way...

Mission part 1: Launch into 100k orbit an orbital vehicle consisting of a 2.5 probe core, docking port, tanks, and engine. Not knowing if you are playing a vanilla game (stock parts only), use one with decent vacuum thrust. Very important to include RCS thrusters and tank on this. Eventually this will be your gas can to the stranded Kerbanauts. Once it is in orbit, leave it there.

Mission part 2: Launch another identical vehicle into orbit; use this to fine-tune your intercept and docking skills (let F5 and F9 become your greatest friends). Once you can dock and still have at least 2/3 of your fuel in the upper stage, you're good to go. Transfer excess fuel to the other orbital vehicle, and make sure you set the probe core for the just launched vehicle as your "control from here" module.

Mission part 3: Using the just launched vehicle that is now the "command" module for the entire monstrosity, use it to escape Kerbin orbit and on the way to Munar orbit insertion. Once you have expended its fuel you will need to undock it, then immediately use RCS thrusters: "N" to slow it down, and either send it to the left or right of your other vehicle. once its trajectory is changed, then use the "[" key to toggle to the other craft you separated from. This one has a full load of oxidizer, liquid fuel, and mono-propellant.

Mission part 4: Insert it into Munar orbit, then adjust to intercept your stranded Kerbals. The reason I recommended changing the trajectory of your other vessel before leaving it is that it will continue on its path as per the laws of motion. By changing its trajectory, you do not have to worry about running into it as you begin your orbital insertion maneuvers. By the time you enter into orbit, dock, and begin transfer of fuel, you should basically have 2/3 mono-propellant and at least 1/2 to 2/3 of your liquid fuel and oxidizer remaining - more than enough to get your stranded Kerbals home.

Mission part 5: Bring them home... and share some screen captures!

[Xannari Ferrows]

Always be sure to check your Delta-V before launch. If you've tried 3 times without success, then you need more. Higher fuel efficiency, less structural mass, all that good stuff.

What's your current M1/M0 ratio? [Full mass/Structural mass]

[kmoney]

Hi guys. Thanks for the awesome responses. I ended up following a little of everyones advice. Now i am on a matching orbit with a probe and enough fuel. My refueling probe is now chasing the lander. I think i can follow the tutorials online for rendezvous and docking... I will share screen caps when I dock!

Polar orbits are such a pain....

BTW,you guys are all amazing for responding so quickly

Edited May 22, 2015 by sjwt

[gmiddlemass]

Try and get yourself into the correct orbit plane, or at least close to it as soon as you enter the Mun SOI as this will use much less fuel.

If it's the docking itself that's causing problems then put yourself in an elliptical orbit where the fuel ship intersects the stranded ships orbit and select the stranded ship as the target.

Two markers/lines will appear in the orbit path that show your closest approach point and where the target will be at this point. Warp round orbit a few times and these markers will change position, try and get them as close together as possible, ideally less than 2km apart (you can see the distance by hovering the mouse over one of the markers).

Once you have your approach set up warp till a few minutes before it, the nav ball should automatically switch to "Target" mode but if it does not then you can click on the top of it to change modes.

When in target mode it will display your speed relative to the target ship so you need to cancel this speed out. Move your ship to point retrograde and burn until the speed reaches zero, You should now be flying along in close proximity to the target.

Now turn your ship towards the pink marker on the navball, this should point you right towards the target, and make a small burn (up to 10m/s depending on how far away you are) then kill the engines and immediately turn retrograde. Your ship will close the gap with the target, time warp if needed and then burn again to cancel out your speed relative to the target again.

Don't worry if you don't get close enough on the first attempt, just keep cancelling out your speed and then burning towards the target again... there's no rush and you don't want to use too much fuel.

Once you are within a 100 to 200M (press F5 to save your game so that you can return to this point should things go wrong) press "[" or "]" to switch to the other ship and then right click on it's docking port and select "control from here".

Rotate the exetrnal view until you can see the refuel ship, find the docking port on it and select "set as target" you should now see the pink markers on the nav ball again, point your ship so that the marker is in the centre of the nav ball, this will ensure that your docking port is pointed straight towards the refueling ship.

Now press "[" or "]" again to switch back to the refueling ship, click on the docking port and select "control from here", point towards the other ship and click on it's docking port selecting it as the target. Align your ship with the pink marker again and the two docking ports should be pointed pretty much right at each other.

Now for the fun part! either use RCS or a very short burn of the main engine to start closing the gap, try and keep your speed below 1m/s you can always time warp if you need to, it's better to do that than burn too much and lose control. You can switch between ships and make sure that both are still pointing correctly towards each other and adjust if need be.

Once the docking ports get within a few meters of each other the magnetic forces will start to take affect and the two ports should be drawn together, it may take a few seconds for them to couple.

Once they join you can perform a fuel transfer by selecting the full tank and then ALT clicking on the empty tank and using the buttons to transfer the fuel.

Hope this helps and that I'm not being condescending, it sounded like you hadn't docked successfully before.

Good luck...

[ElWanderer]

If you have a polar orbit around the Mun, this will rotate around slowly in terms of how aligned it is with the Mun's orbit around Kerbin. It is easier to transfer between Kerbin and a polar Mun orbit when the orbits are aligned. I realise a picture would probably help to explain this, but I'm on my phone...

I would wait until the polar orbit is almost in line with the Mum's orbit then launch a rescue ship. I would do a standard Hohmann transfer to the Mun and aim to hit the middle of the planet at apoapsis around Kerbin. Once in the Mun's sphere of influence, I would check which way the target ship is going then burn normal or anti-normal as required to push the rescue ship's trajectory over the right pole so as to be going around in same direction as the target. Burn at periapsis to capture into orbit (an elliptical orbit at this point will let you do a plane change burn more cheaply to match the target - you'll probably be a fair few degrees out). Then rendezvous as normal.

[heng]

You will need only a few drop of fuel to reach a polar Mun orbit if you set up the maneuver while leaving Kerbin. I.e. setup the encounter with a high inclination angle. That way you will arrive with a heavily inclined course already.

[Ten Key]

Glad to hear it worked out. . .polar intercepts are indeed a pain.