Mechjeb Help

[Floppy Pancake]

Can anyone explain to me how to orbit the Mun with Mechjeb? I don't want to land on the Mun. I can't figure out how to circulize around the Mun instead of crashing into the Mun. Help would be appreciated. =)

[jhendriks87]

Plan a transfer to the mun....then plan a circulization burn at the mun.....

[Joschi]

If you make a Kerbin -> Mun Homann transfer with MJ it will likely put your periapsis right in the center of the Mun, so you will want to lift that to ~20k - 30k meters and then go to maneuver planner and select circularise at next periapsis.

The automated circularisation will only work once you are in the sphere of influence of the Mun I believe...

As you can probably tell from the short how-to above: MJ is NOT a subsitute for knowledge on orbital mechanics. If you do not understand on how things work on the physics level you will have a very hard time playing KSP even with MJ.
I always recommend to do everything manually (lots of times, not just once!) and use MJ only as assistance for routine things. E.g. I like to let MJ handle docking manouvers of crafts with several hundred parts at <10 FPS. But that is just my personal recommendation :-)


Also: brace for impact - RoofCatA is about to be around :p

[Xcorps]

Originally posted by brodpr23:

Can anyone explain to me how to orbit the Mun with Mechjeb? I don't want to land on the Mun. I can't figure out how to circulize around the Mun instead of crashing into the Mun. Help would be appreciated. =)

The easiest way:

From a Kerbin circular orbit with less than a degree of inclination difference:

1) Select Mun as target

2) Hohmann transfer to target, execute, clear all nodes

3) When burn is complete, Fine Tune closest approach 150km, create node, verfiy that the node gives you a prograde orbit. If not, adjust the node with Node Editor using the 1m/s button (retrograd probably) Execute. clear all nodes

4) Warp to SOI.

5) After SOI, create new, change Peri to [altitude] after a fixed time (30s or whatever) because it will probably not be the 150km you asked for in the fine tune. execute. clear all nodes.

6) Create New, circularize, peri, execute. clear all nodes.

Voila.

[Chibbity]

Why would you use Mechjeb to do something so easy?

You literally just have to burn retrograde at Mun Ap till you have an equal Pe.

Boom, circular orbit.

[Floppy Pancake]

Originally posted by Chibbity:

Why would you use Mechjeb to do something so easy?

You literally just have to burn retrograde at Mun Ap till you have an equal Pe.

Boom, circular orbit.

Because it is good pratice to help me get to other planets so I can get to know the system and such. Plus I know how to do it without Mechjeb just fine.

[Floppy Pancake]

Originally posted by jhendriks87:

Plan a transfer to the mun....then plan a circulization burn at the mun.....

Done that and it just crashes on the Mun

[Xcorps]

Originally posted by brodpr23:

Originally posted by jhendriks87:

Plan a transfer to the mun....then plan a circulization burn at the mun.....

Done that and it just crashes on the Mun

If your intercept was plotted by Mechjeb, then it uses the center of the body for the transfer. It's plotting an intercept, which you are following. Check your orbital path in map mode as soon as you change SOI. If the orbital path goes through Mun, you need to change your Periapsis by burning radial or anti-radial, (the blue marker) depending on your approach. If you are trying to burn prograde or retrograde, you will fail every time. You want your ship to travel parallel to the orbital plane and perpendicular to the prograde vector.

Go to map view and bring up the navball. Point your ship at the radial marker and fire your engine. You will see your Periapsis marker begin to change. If you are using MJ, have the Orbital Info data screen up. Watch the Periapsis altitude and inclination. You want to get your Periapsis to above 50km. Once it gets to 50km or above, throttle down. Plot a new manuever at Periapsis and drag the retrograde marker for a "slow-down" burn to reduce your orbital velocity without changing your heading relative to the orbital plane or prograde vector. The execute that burn. Then, at the equatorial AN/DN (ascending or descending node, the point at which an inclined orbital plane meets the equatorial plane of the body either "up" or "down" on the orbital path) and make a burn so that you have zero inclination.

In other words, you need to fly sideways a little bit so you miss the Mun. Then you need to slow down so that you fall up and then back down without hitting the Mun.

[Plus I know how to do it without Mechjeb just fine.]

You know how to make the transfer. You don't know how to plot an orbit. Just saying.

[Floppy Pancake]

Originally posted by Xcorps:

Originally posted by brodpr23:

Done that and it just crashes on the Mun

If your intercept was plotted by Mechjeb, then it uses the center of the body for the transfer. It's plotting an intercept, which you are following. Check your orbital path in map mode as soon as you change SOI. If the orbital path goes through Mun, you need to change your Periapsis by burning radial or anti-radial, (the blue marker) depending on your approach. If you are trying to burn prograde or retrograde, you will fail every time. You want your ship to travel parallel to the orbital plane and perpendicular to the prograde vector.

Go to map view and bring up the navball. Point your ship at the radial marker and fire your engine. You will see your Periapsis marker begin to change. If you are using MJ, have the Orbital Info data screen up. Watch the Periapsis altitude and inclination. You want to get your Periapsis to above 50km. Once it gets to 50km or above, throttle down. Plot a new manuever at Periapsis and drag the retrograde marker for a "slow-down" burn to reduce your orbital velocity without changing your heading relative to the orbital plane or prograde vector. The execute that burn. Then, at the equatorial AN/DN (ascending or descending node, the point at which an inclined orbital plane meets the equatorial plane of the body either "up" or "down" on the orbital path) and make a burn so that you have zero inclination.

In other words, you need to fly sideways a little bit so you miss the Mun. Then you need to slow down so that you fall up and then back down without hitting the Mun.

[Plus I know how to do it without Mechjeb just fine.]

You know how to make the transfer. You don't know how to plot an orbit. Just saying.

Really Dude? Do you not understand the point of wanting to try to do it purely on mechjeb? Instead you go on and say I do not know how to plot an orbit without mechjeb? I know how to plot an orbit without mechjeb. Thanks for your assumption that since I can't do it with mechjeb mean I cant do it without it... Your part is actually on you because you only said "Plan a transfer to the mun....then plan a circulization burn at the mun....." which is no where near enough informations. Xcorps gave me the informations I needed and helped. You didn't. Just saying...

[Floppy Pancake]

Originally posted by Xcorps:

Originally posted by brodpr23:

Can anyone explain to me how to orbit the Mun with Mechjeb? I don't want to land on the Mun. I can't figure out how to circulize around the Mun instead of crashing into the Mun. Help would be appreciated. =)

The easiest way:

From a Kerbin circular orbit with less than a degree of inclination difference:

1) Select Mun as target

2) Hohmann transfer to target, execute, clear all nodes

3) When burn is complete, Fine Tune closest approach 150km, create node, verfiy that the node gives you a prograde orbit. If not, adjust the node with Node Editor using the 1m/s button (retrograd probably) Execute. clear all nodes

4) Warp to SOI.

5) After SOI, create new, change Peri to [altitude] after a fixed time (30s or whatever) because it will probably not be the 150km you asked for in the fine tune. execute. clear all nodes.

6) Create New, circularize, peri, execute. clear all nodes.

Voila.

Thanks, for the help ~_^. I found out that doing the Fine Tune closest approach helped a lot. At that time I was able to tell if I am making orbit or not instead of crashing into the moon.

[Chibbity]

Stop using Mechjeb and actually play the game.

Problem solved.

Originally posted by RoofCatA:

on a funny note it seems some people miss me more than I do care about them. If I had ego, it would feel well fed now.

Trust me, no one misses you.

[`digitaL.braVo]

Originally posted by brodpr23:

Can anyone explain to me how to orbit the Mun with Mechjeb? I don't want to land on the Mun. I can't figure out how to circulize around the Mun instead of crashing into the Mun. Help would be appreciated. =)

Easy: don't use mech jeb.

[Chibbity]

Originally posted by RoofCatA:

Originally posted by Chibbity:

Trust me, no one misses you.

this guy obviously does. I'm surprised as well.

Originally posted by »BoH.Crew×IRA™:

Also: brace for impact - RoofCatA is about to be around :p

Warning people you are about to show up = missing you?