Reverse probe's 'UP' (prograde vector) or at least mark it.

[cicatrix]

In the beginning of my career I often made the same mistake during the construction of my crafts - I placed a probe core upside-down before I learnt (the hard way) to double check the direction what probe thinks 'prograde' was. While with Stay-putnik the question is irrelevant, the other probes are not so obvious. It might be that I didn't pay too much attention, but from what I gather, you cannot tell where's the 'UP' of a probe by its sight. They all look the same from both up and down:

So, we come to the first suggestion: make probes look differently from its up and down (at least paint them in different colors).

The following issue extends the first one. While in flight (usually when the lander is separated and only a probe-controlled tug remains in orbit) I sometimes find out that I installed the probe core 'upside down'. Now's nothing can be done at that point - just remember, that your prograde marker is now retrograde and vice-versa (forget about maneuver nodes too - you'll need to remember how much dv you needed and by it's increase during the burn you should guess, how much did you spend).

So, the second suggestion is: make the option 'Reverse prograde' in the probe's right-click menu.

Edited December 10, 2014 by cicatrix
added pics

[Sean Mirrsen]

If you're having problems with checking which side of a probe core is "up", pick it up in the VAB (or SPH) and hit the spacebar. The part will orient to its default state - in VAB, the "front" of the probe will be its topside. In the SPH, it will be whichever side is pointing towards the open hangar door.

[cicatrix]

I know I can. But I repeat - when you're in flight - it's too late. Besides - wouldn't a little rad arrow on the side of a probe core be more obvious and intuitive?

And there's this problem too:

Here's a craft:

>||<

where | - is a probe and < is a nozzle

Now I have to put two probes because depending on which particular nozzle I want to use for burn I should select the appropriate probe and click 'Control from here'.

Why I have to use 2 probes where I need only 1 but with the ability of 'prograde reversal'?

[Vaporo]

I would like a setting that allows you to simply invert the control axis while in flight. Often I have reason to place my command pods upside-down, and it's annoying to have to remember that prograde is actually retrograde.

[Red Iron Crown]

I've made some ships with double-ended propulsion and a single command part, it does get a bit confusing to remember to point prograde for a retrograde burn when one power plant is active, and it thoroughly confuses Mechjeb.

I agree that this would be useful, but I wouldn't limit it to probe cores only. Have all command parts able to redefine their control axis, preferably while in flight through action groups. Also handy for rovers.

[DBowman]

I've struck the same issue also. Even if you catch it during some double check or shakedown it can still sometimes be painful to disassemble the craft to flip it. It seems to me a simple, natural addition with real value.

[Tery215]

Support - I was flying these ships the other day with monoprop engines, and it turns out the probe core was backwards..

Could never finish any maneuver nodes with the primary monoprop engines, had to use RCS.