100km Mun orbit - cant even get close to the mun's sphere of influence!

[nathanbarlow]

Hi all,

new to the game, been playing for about a week now, I downloaded Mission manager and am going through the NT Space Programme missions, one of them requires a probe to be launched to the Mun and acheive a 100KM orbit around the Mun, then return back to KSC. I can get to a stable orbit around Kerbin, then trying to burn to transfer to the Mun always ends up with me stranded in space, no where near the Mun. I'm using Mechjeb for the transfer, as im still learning how to do things (I can get to a semi-stable kerbin orbit without mechjeb). Any advice appreciated Im pretty sure i should be able to just transfer, then sort out the orbit requirements once Im there using circulize?

[Nurph]

When and where are you starting your burn? The general rule is that you burn prograde as soon as the Mun rises (from a 100km-ish Kerbin orbit).

[stupid_chris]

What version of MechJeb are you using?

[sanity]

rocket pic always helps, may just be a case of not enough fuel or wrong engine types, it can be hard to judge when you're just starting out

[Sathurn]

With mechjeb, what is your dv left when in kerbin orbit?

[Benie]

It really sounds like to me, you don't have enough Delta-V to get to the Mun. Are you sure you're selecting the Mun as a target, then using Maneuver Planner and selecting "Hohmann transfer to target"? I just tried and I have a Mun encounter.

If you're using "transfer to another planet", that's only to get to another planet in another system.

Edited July 22, 2013 by Benie

[Tw1]

The solution to the problem is simple, and complex. You need a better rocket.

Moar Boosters!

You must get into orbit with more fuel available.

A munar transfer is pretty simple to do by hand. Set up a maneuver node, putting the apoapsis at 11,400 000 meters. Then drag the node about untill it's about 45 degrees ahead of Mun, and you should get an encounter. Or stick with MJ for now.

[nathanbarlow]

hi all,

thanks for the replies. Screenshot here: http://s9.postimg.org/kgpyc91cv/mun_probe.jpg

pretty sure i have enough fuel

Using TRANS function highlighted by mouse once in kerbin orbit

mechjeb v1.9.8

[stupid_chris]

Your MechJeb is outdated, it doesn't work correctly for .20 if I remember correctly, you should download 2.0.8

Then again, you might not have enough delta V, your second's stage TWR is too low for when you're gonna need it. YOu're probably wasting too much fuel fighting gravity, you end up with not enough fuel to go to the Mun. You really want to rework your rocket.

[King Arthur]

I have went to the Mun countless times using MJ 1.9.8 with its "TRANS" function under Orbital Operations in 0.20, so I can confirm that it does in fact work.

To the OP, what kind of orbit are you starting your injection burn from? MJ assumes a circular, equatorial Kerbin orbit with a +/- inclination divergence of <0.1 degrees for its injection burns; if you are in an elliptical and/or eccentric orbit, MJ will fail to execute an injection burn.

[Xeldrak]

Actually, a Mün-Tranfer is quite easy - when you are in Kerbinorbit. Wait for münrise (mün apears over the horizon), then burn prograde...

[mellojoe]

Actually, a Mün-Tranfer is quite easy - when you are in Kerbinorbit. Wait for münrise (mün apears over the horizon), then burn prograde...

This.

Or, set a maneuver node at the point where Mun rise would be visible and adjust the arrows. Sometimes using MechJeb when you are new actually hurts your learning curve. Trust me. I'm a better Kerbalnaught now since I've stopped relying on MechJeb so much.

[SiliconPyro]

Try planning the maneuvers manually and having MechJeb execute them. Instead of using the transfer function, place a maneuver node that will get you a close Mun encounter and have MechJeb execute the node. When you reach the Mun's SOI, use the retrograde button and burn at your PE until you have orbit.

[The Deep Space Kraken]

You can also wait till you are 90 degrees behind the mun in your orbit. Then burn prograde untill your orbit reaches the mun's orbit at which point you should get an encounter.

[draeath]

I <3 the maneuver nodes.

Mechjeb can help - use the new version's maneuver planner to add nodes. Then, you can see what it is going to do - and you can fly it yourself instead of just pushing the button

[Amoun]

Maneuver nodes...definitely.

The way that I do it (not sure if thats the best way or not, but it does work) is leave the atmosphere or cut my engines when my Ap (higher point of my flight) is above say...100k (usually gives me enough time to tinker with the node) and I try to get is close to the Mun, but I am usually satisfied with the fact that I would get the "Mun influence" icon. When I get that, I do the maneuver and warp. THEN when I get into the influence, I can plan the orbit. Usually you can do that with a maneuver node as well but one of the easy way is to literally just slowdown (retrograde) and then see your orbit take shape.

I hope that helps.

[draeath]

You should be able to just circularize at 100km for (not all that much) ÃŽâ€v which gives you as much time to fiddle with the node as you like - and unless your initial launch was perfectly timed you'll probably save more fuel doing this than trying a straight-shot from a non-optimal phase angle.