I think you need to think very carefully about frames of reference, here...
Kinetic energy comes from something moving relative to something else. If you cancelled the kinetic energy relative to the Sun then the object would be in a nice safe orbit, I think (the handwavium would like that). I'm pretty sure you are not messing with the kinetic energy due to movement relative to the galaxy, or relative to the local group of galaxies. I think your current logic assumes an absolute frame of reference.
There may be problems with the pseudo physics used by this weapon, making sure people agree about what it does. I'm assuming that the cannon is limited by either the mass of the vehicle it's mounted on, or the power of the drive of that vehicle, how much can it move around. And it can't affect anything more massive than those limits.
If what the cannon does is knock-out the vehicle's ability to maneuver that would be nearly as useful. So it continues at the same velocity. But, that'd be a totally different sort of way of working.
I don't think I've got any good answers here. Sorry...
--
"It is the business of the future to be dangerous" - Hawkwind
Kinetic energy comes from something moving relative to something else. If you cancelled the kinetic energy relative to the Sun then the object would be in a nice safe orbit, I think (the handwavium would like that). I'm pretty sure you are not messing with the kinetic energy due to movement relative to the galaxy, or relative to the local group of galaxies. I think your current logic assumes an absolute frame of reference.
There may be problems with the pseudo physics used by this weapon, making sure people agree about what it does. I'm assuming that the cannon is limited by either the mass of the vehicle it's mounted on, or the power of the drive of that vehicle, how much can it move around. And it can't affect anything more massive than those limits.
If what the cannon does is knock-out the vehicle's ability to maneuver that would be nearly as useful. So it continues at the same velocity. But, that'd be a totally different sort of way of working.
I don't think I've got any good answers here. Sorry...
--
"It is the business of the future to be dangerous" - Hawkwind