Is there any way I can prevent my own Manapult from sucking me into it?

I received the Manapult truck as part of the Professor Genki DLC. However, running around and sucking up helpless citizens and shooting them as cannonballs tends to raise your notoriety with the police pretty fast. I was pulled from my truck and when I ran around in front of it during the firefight in order to get into it again, it promptly sucked me up to use me as ammo.

When this happens, the only way I can seem to get out of it is to fire myself from it, and this can take away a lot of my health and sometimes even kill me if my health is low enough from the firefight and I wasn't shot at a high enough trajectory to open my parachute.

Is there any way I can prevent the car from using me as ammo?

Unfortunately there seems to be no way to deactivate the "suck" function of the Manapult, unless you're already full of people.

You can get out of it using the same method as if you are driving it. I only know the keyboard controls, so if you are on PC/Mac/Linux just use E to exit if it sucks you up.

I'm not sure there's a way to keep it from sucking you in, but you can prevent dying from it by activating the cheat whatitmeanstome. Click it a few times to raise your respect, thus giving yourself more money. Then, go to the upgrades section, go to damage, then upgrade your fall damage resistance to level four. This will make you completely immune to fall damage.