Getting to Minmus with MechJeb.

[Fredonia]

Ok, So after a few MechJeb and manual flights to Mun and back in the past couple days I've decided to get to Minmus. I decided I'd try to use MechJeb to get there at first, so I can see what it does about having to adjust itself because of Minmus' orbital plane(is that the right term?) not being level with Kerbin's or Mun's.

I've got a ship that I'm pretty sure will get there and back...with a couple problems:

1.) In transferring to Minmus, my final booster stage runs out of fuel and I have to stage out to my lander stage, using fuel. Now, I had to do this with my Mun lander and it was no problem. However, being that the burn takes longer and that my landing engine doesn't exactly have the "oomph" that the others have, this takes a while.

2.) When MechJeb gets to the "Mid course adjustment" stage, the whole thing just goes to heck and I have to end it. It never makes the proper adjustment.

I highly suspect that it isn't a problem with MechJeb, because I used the MechJeb pod on top of someone's anti-matter engine add-on to land on Minmus and come back, and did it with no problems whatsoever, same orbit height, ascent paths, aps, peris and everything.

So, I'm thinking that it's my ship that I have built...well...wrong. I'll attach the .craft file for someone to look at and see if they can tell me what I did to make MechJeb not send this thing to Minmus.

Cheers to you all, and thanks in advance to anyone that can help me.

[ATTACH]32964[/ATTACH]

[togfox]

Its probably taking too long to raise your AP to minmus height. This means MJ knows it needs to adjust but it took solong for your engine to get there, your now out of position and MJ cant compensate and gets confused. Long story short - a failed transfer.

Your transfer engine needs to be a little stronger. I build three stages into my rockets. A lifter + kerbin circulariser, a transfer + mun/minmus circle and then a lander. I can then tune the fuel and engines for each phase of the mission because the requirements really are quite different. HTH.

Edit: or fly it manally.

Edited September 15, 2012 by togfox

[Kosmo-not]

There is nothing wrong with your ship. If mechjeb can't do it, then fly manually.

[Fredonia]

Ok, I was able to just manually fly myself there after a couple of modifications(a totally new craft, as my transfer engine somehow ended up being my landing/return engine...not the best design.) However, I'm bent on making the first one work with MechJeb, would setting the inclination on the auto ascent to either 84 or 96 degrees help any? As I understand, that inclination would place me on the same plane as Minmus, thus ridding myself of the need for mid course adjustment.

Thanks for the suggestions.

[Ziff]

However, I'm bent on making the first one work with MechJeb, would setting the inclination on the auto ascent to either 84 or 96 degrees help any? As I understand, that inclination would place me on the same plane as Minmus, thus ridding myself of the need for mid course adjustment.

Thanks for the suggestions.

Only if you launch at the appropriate time. Go to the launch pad, go into map view and flatten out Kerbin's orbital plane so it forms a single horizontal line. Zoom the map out and then time warp until the plane of Minmus flattens out into a single line as well. If the orbital plane looks like

then you would launch at 84 degrees. If it is opposite this one then launch at 96 degrees.

[EndlessWaves]

Did mechjeb actually cut out entirely? Sometimes the map and mechjeb readouts can go temporarily screwy even when the burn is happening correctly so I'd let it run until it turns itself off and see what happens.

Mechjeb isn't infallible though, I frequently have to do Kerbin ascent myself or on ASAS because mechjeb tends to wildly gyrate.

[Khrissetti]

I've had the same problem with Minmus flights. I now tend to (If I use MJ for the transfer at all) use MJ to start the transfer burn then turn it off and complete the transfer myself.

No idea why it goes wrong, I only know that it does.

[Fredonia]

Thanks, Ziff.

My problem was really two-fold. My engine was too weak and what I was using as my transfer burner would always burn out about 1/4 the way through my injection burn, thus using the fuel in my lander. While it ended up not being THAT big of a deal, it caused minor frustration. Either way, I just need to perfect my ship building seeing as .17 is out now, and I'm jonse-ing to get a manned mission to Duna.