Paintarmours has achieved a new record height for ballistically launched minecarts: 45 zlevels in a single jump. Actually, we ran out of horizontal space, it's not said this was the actual apex height.
For reference, the greatest height reachable by a cart coming from the longest possible line of impulse ramps is 26z (may be one more or less, i don't have it memorised). So how did we get a cart to fly higher than a cart travelling at terminal velocity, you ask?
By breaking the speed limit
New research shows that in some cases, momentum in minecart collisions is properly conserved, in such a way that speed increases can result. The simple application is to generate derail-capable minecarts applying only rollers and collisions, without using ramps.
But of course i had my sights set on the prize: what'd happen if i sent two carts down an insanely long ramp drop before colliding them? Right enough, with different-weight carts (oak vs. willow, weight ratio ~1,85:1) a pushed lighter cart can gain increased speed (185% of the ~250k speed the oak cart brought to the party, so something between 450k and 500k probably).
The willow cart shot away five tiles from the collision point in a single step, then passed over the launch ramp and went up. And up. And up. Around z+25, the ascent started slowing down from 2z per step to 1z per step. The cart smashed into the embark tile border at z+45 and had not yet started descending.
Practical uses? None, of course. A dwarf riding any of the carts would dismount and blow apart. Cargo would be released from both carts at the moment of collision. It's just a stupid dwarf trick to create supercharged carts that zip around at speeds in excess of terminal velocity.