Electricity source for magnetoplasmadynamic engines in KSP

KSP does not allow remote control of unattached pieces. Anything not attached to your main cockpit automatically becomes directly uncontrollable as soon as it detaches.

That said, there are a few options available, if you're looking to de-orbit spent stages.

1. Create a dedicated deorbit vehicle that catches your debris, and burns retro to shed some speed. That's rather difficult, as everything needs to be intercepted individually.
2. Attach a probe cockpit (or MechJeb component) to the stage. This will allow you to switch your focus to it. I'd recommend ensuring your primary stage is in a stable orbit before doing so, as fully deorbiting something will take quite some time.
3. The last option is to turn off all debris entirely, as detailed in my answer here. That's the easy way out, but without specific tools to deorbit junk, it's rather involved to manually clean it up.

Any way you look at it, currently KSP doesn't allow control of parts that are not directly connected to your current focus.

I'm still working on getting my controller to work (driver issues), but here's a setup I found that makes perfect sense to use:

• Left stick Up/Down: Pitch
• Left stick Left/Right: Yaw
• Right stick Left/Right: Roll

This makes sure you can navigate the NavBall using the left stick.

The RCS controls:

• Right stick Up/Down: RCS Forward/Backward
• D-Pad controls: RCS Translate Up/Down/Left/Right

Docking will be done with the D-Pad + Right stick.

I have no idea which controller you're using, I'm using the PS button scheme to explain:

• Square (left button): RCS On/Off
• Triangle (upper button): SAS On/Off
• Cross (lower button): Stage advancement
• Circle (right button): Something you use a lot. Lights, Landing gear, map switch, pick your favorite :)

I've heard a lot about issues with the triggers not working in KSP, I suggest you try it out with your controller :)

I've still to test this myself, but it seems to be a reasonably sound control setup.

UPDATE

I Got it working last night, and I'm really happy with this controller setup! Using MotionInJoy, I was able to get all buttons working. I've kept the aforementioned layout, with some extras:

Additional layout:

• L1: Toggle precision steering
• R1: Cut all thrust
• L2/R2: Thrust down/up
• Select: Lights on/off
• Start: Landing gear
• Circle: I mapped it to switching between rocket/orbit view. Oce you've set up a proper viewing angle for both, you can use this button to easily get a peek at your trajectory when trying to get into orbit (or deorbiting).