HI. First let me add to all the praise by saying that MechJeb is fantastic. It makes KSP so much more fun. Thank you very much.

I just did the KSP update to 0.21 (I bought last week, so it was updated from the last version (Steam)). After I updated, MechJeb 1.9.8 wasn't showing the SmartASS box so I updated MechJeb to 2.0.9.0.

SmartASS was working very well before these updates, but after the updates it is trying to kill me (or the astronauts). When I launch, then immediately click Execute (set at SURF/90/90) the rocket makes a loop at the ground and then back to the sky, and continues on to orbit.

It did not do this with the previous versions. The rocket does not do this during manual ascent or during MechJeb "Ascent Guidance" mode.

When you're on the launchpad, is your navball attitude straight up like normal? It seems in 0.21 the "control from here" part can get set to the MechJeb part by default, and if you've got MechJeb mounted on the sloped side of a command pod, it will be at a funny angle... Does anything change if you right-click your command pod and do "control from here" first? If not, probably best to post a craft file, or screenshots and/or video of what's happening.

Is there a recommended place to put mechjeb? I try to avoid sticking it on the command pod. I was considering putting it on the lowest fuel tank - kind of away from everything else. Does it matter?

The navball is blue. I had the upsidedown MechJeb problem in 1.9.8 and have learned the "control from here" workaround.

@r4m0n or @Anatid since there is a lot a people with the "control form here" issue maybe you should change the part to not be a command pod, like this : https://raw.github.com/sarbian/MechJeb2/Raf04_Sarbian/Parts/MechJeb2_AR202/part.cfg

This issue is NOT related to the "control from here", upsidedown MechJeb. The upsidedown MechJeb would aim at the ground, and crash the rocket. With this issue, the rocket does a loop at the ground and returns to fly on to space, without any correction from me. And it persists even if I set the MechJeb to "control from here",

That was a guess, based on the very limited text-only information you've provided so far. Please post a craft file, video, and/or screenshots, as much additional information as you can provide.

@dpraptor no it shouldn't matter, as long as you place it somewhere on your final stage (so you don't lose the MechJeb part when you drop spent boosters, for example).

I had the exact same issue, and "control from here" did fix it, but only partially.

My navball was blue, just like yours, but my "north" marker was facing the wrong way. Hitting "control from here" fixed it, as did controlling from the Mechjeb pod, but changing the "roll" setting on the Smart ASS. This allowed a safe liftoff, but later on in the flight the rocket started performing the same looping behavior. Making large changes to the "roll" setting in flight also induced looping.

The rocket in question weighed over 100 tons, and was controlled by the reaction wheels of a probe core and the thrust vectoring of a single Mainsail engine. This meant it had essentially no control authority on the roll axis. When the Smart ASS detected that the vehicle was not oriented correctly on the roll axis, it made wild pitch and yaw changes in an attempt to swing the rocket into the correct roll orientation. When I launched without switching control to the probe core or changing the assigned roll value, the vehicle was 90 degrees off when it left the pad. When I did switch control or change the assigned roll value, the vehicle still drifted away from the "correct" roll, eventually causing Smart ASS to try to correct. Vehicles with lots of roll authority do not encounter this problem.

In short: the problem is caused by Smart ASS not being that smart. Quite simply, it needs to not try to make roll adjustments by deviating from the correct pitch and heading.