Need some advice on modular landers...

[michaelvf]

So - I built this three stage monstrosity. The idea was the usual, first stage get me to orbit. Second stage get me to Minmus and then third stage would detach, land, get back up, reattach to the second stage, and then we would fly back home.

My lander was built around a lander can mk1. I thought Jeb would just exit the Mk1 command pod, EVA to the lander can and then control it from there. Since I still suck at much of the docking/landing stuff, I stuck a MechJeb on the lander can. So Then I got Jeb into the lander can and used the docking port to deattach the second stage from the lander.

Well.... Things went south from there.. I managed to get control of the lander can by switching into the tracking station and switching targets. But I was unable to access MechJeb even though it was attached to my service module on top of the lander can. The whole Lander was constructed as a sub-assembly and plugged into the other parts. Also I seemed to have a hard time selecting other targets. Minmus was nearly impossible to target.

Second and third stage attached:

http://i.imgur.com/SjAt4zV.png

http://i.imgur.com/sG0aWMY.png

Big monstrosity:

http://i.imgur.com/HrC8kLl.jpg

So my questions are:

1) Is EVA really necessary to get to the lander can? Theres no way to internally go there?

2) How to get MechJeb to work on my lander

3) Are there any smarter ways of doing this?

4) Another minor issue is that Mechjeb seemed unable to calculate the correct transfer to Minmus, It didnt get an intercept course even if inclination and proper orbit was in place... No idea why though...

Edited May 6, 2015 by michaelvf

[Sirrobert]

Did you transfer Jeb to the lander can BEFORE detaching it? If there's no Kerbal, you can't control it. Mechjeb is not a probe core.

As for a smarter way to do it: You can use [ and ] to switch between ships in the area

And a smarter way to transfer Kerbals: Click on the hatch. You get a list of the Kerbals in the associated Command pod, with a button EVA and Transfer next to it. If you click Transfer, it highlights all the available commandpods. If you click on one, the Kerbal transfers to it. No need for EVA

[Randazzo]

So - I built this three stage monstrosity. The idea was the usual, first stage get me to orbit. Second stage get me to Minmus and then third stage would detach, land, get back up, reattach to the second stage, and then we would fly back home.

My lander was built around a lander can mk1. I thought Jeb would just exit the Mk1 command pod, EVA to the lander can and then control it from there. Since I still suck at much of the docking/landing stuff, I stuck a MechJeb on the lander can. So Then I got Jeb into the lander can and used the docking port to deattach the second stage from the lander.

Well.... Things went south from there.. I managed to get control of the lander can by switching into the tracking station and switching targets. But I was unable to access MechJeb even though it was attached to my service module on top of the lander can. The whole Lander was constructed as a sub-assembly and plugged into the other parts. Also I seemed to have a hard time selecting other targets. Minmus was nearly impossible to target.

Second and third stage attached:

http://i.imgur.com/SjAt4zV.png

http://i.imgur.com/sG0aWMY.png

Big monstrosity:

http://i.imgur.com/HrC8kLl.jpg

So my questions are:

1) Is EVA really necessary to get to the lander can? Theres no way to internally go there?

2) How to get MechJeb to work on my lander

3) Are there any smarter ways of doing this?

4) Another minor issue is that Mechjeb seemed unable to calculate the correct transfer to Minmus, It didnt get an intercept course even if inclination and proper orbit was in place... No idea why though...

1) Click on the crew hatch of the Mk1 pod while Jeb is inside. A small window should pop up displaying his name and two buttons, "Transfer" and "EVA". Click transfer, then click on the lander pod.

2) First, don't take offense to this if you can help it. Can you confirm that it was in no way user error? Was the unit actually in there? Did you visually confirm it was there? I see that you have mechjeb windows up in those screenshots, and if the only unit was inside the service bay on top of the lander capsule, it would go with the capsule. If you have two units, try removing the one from the upper stage and see if you still get functions. If not, try attaching it elsewhere.

3) There are definitely more efficient ways, but I don't know what tech you have available. If that gets you there, then it's good enough.

4) Keep an eye on your TWR. If it gets too close to 2 (I try to keep it around 1.5), your engines are unlikely to throttle down fast enough, even if Mechjeb cuts throttle entirely. This usually leads to an overshoot, and the autopilot may try to correct for it, but it screws with the encounter. It's not the fault of the Mechjeb unit, it's a function of the engine throttle.

[Sirrobert]

4) Keep an eye on your TWR. If it gets too close to 2 (I try to keep it around 1.5), your engines are unlikely to throttle down fast enough, even if Mechjeb cuts throttle entirely. This usually leads to an overshoot, and the autopilot may try to correct for it, but it screws with the encounter. It's not the fault of the Mechjeb unit, it's a function of the engine throttle.

You can always fix to high thrust by manually reducing the max thrust of the engine. Right click the engine, and reduce the thrust limiter to a more managable number. Especially usefull for high TWR ships where you want fine control

[michaelvf]

It *might* be an error... Maybe the mechjeb is not properly attached in the service module or something. I will try to stick it on the outside of the lander to make 100% sure it is attached.

One other thing, If I put a scientist in the lander will I be able to control the lander at all? Or do I need a pilot? I would like to send a scientist to do the ground survey and reset some experiments

[Randazzo]

It *might* be an error... Maybe the mechjeb is not properly attached in the service module or something. I will try to stick it on the outside of the lander to make 100% sure it is attached.

One other thing, If I put a scientist in the lander will I be able to control the lander at all? Or do I need a pilot? I would like to send a scientist to do the ground survey and reset some experiments

You won't have SAS, but the scientist can fly it. If you're using mechjeb's smartASS feature, you won't miss it. The "Kill Rot" button functions similarly to the standard SAS hold.

[Sirrobert]

It *might* be an error... Maybe the mechjeb is not properly attached in the service module or something. I will try to stick it on the outside of the lander to make 100% sure it is attached.

One other thing, If I put a scientist in the lander will I be able to control the lander at all? Or do I need a pilot? I would like to send a scientist to do the ground survey and reset some experiments

All kerbals can steer, but you need a Pilot to be able to use SAS

[Laie]

3) Are there any smarter ways of doing this?

If you meant to ask "am I doing it all wrong?", the answer is no. You've build a nice vessel. I'd probably attach the lifter below the lander for reduced drag (it should fit to the two outrigger fuel tanks); and I for one wouldn't even bother with a dedicated lander and docking, just land and return on the last stage and be done with it. But here we're entering the realm of taste and preferences.

[SpeedDaemon]

4) Another minor issue is that Mechjeb seemed unable to calculate the correct transfer to Minmus, It didnt get an intercept course even if inclination and proper orbit was in place... No idea why though...

For multi-stage craft with MechJeb, mind what stage your active engines are in when doing anything where MechJeb has to calculate a burn (transfers, especially landings, etc.). Unless it's been rectified, you're best off making sure the active engines MJ will use for the burn, and only those engines, are in the "bottom" stage.

[michaelvf]

Thanks for all the tips. I somehow managed to actually seperate, land, do science and aaaallllmooooost return to the second stage before I ran out of monopropellant for RCS... Then I ran out of MP for the second stage... So thankfully due to some wasteful design I had both the lander and the second stage return home seperatly where they both survived reentry. I got enough science off that one mission to get all of tier 4 and some of tier 5

I thought I would need a lot more dv to get home.... but I did it with remarkably little...

[Sirrobert]

Thanks for all the tips. I somehow managed to actually seperate, land, do science and aaaallllmooooost return to the second stage before I ran out of monopropellant for RCS... Then I ran out of MP for the second stage... So thankfully due to some wasteful design I had both the lander and the second stage return home seperatly where they both survived reentry. I got enough science off that one mission to get all of tier 4 and some of tier 5

I thought I would need a lot more dv to get home.... but I did it with remarkably little...

Yes, it's very cheap to return.

Essentially, all you have to do to return is cancel out your orbital velocity relative to Kerbin, and you do that by escaping Mun SOI in the right direction.

Offcourse it's a little more tricky now that we have rentry heat, but that's what shields are for.

Congratulations on a succesfull mission