That neon-straight plume is not magic, it is bullying of the air. A climbing rocket forces its exhaust through a de Laval nozzle, squeezing and re-expanding gas so the flow leaves nearly parallel, with high Mach number and low sideways spread. The atmosphere then acts like a mold, compressing the jet where external pressure is higher and allowing it to widen only when ambient pressure falls, which keeps the column visually sharp over a long stretch of sky.
The glamorous part is the beam, but the real trick is drag reduction. By rolling into a gravity turn, the vehicle tilts early, so its thrust vector both fights gravity and gently bends the trajectory, avoiding the brute-force cost of a dead-vertical climb. Aerodynamic shaping then trims pressure drag and wave drag, while the exhaust itself helps fill in the low-pressure wake behind fins and interstage sections, shrinking turbulent vortices that would otherwise smear the plume into a messy torch.
Most uncanny of all is how shock structures sculpt the light. Underexpanded exhaust forms a chain of Mach disks and shear layers; these discrete shock cells locally raise density and temperature, boosting emission and giving the plume its segmented, almost digital look. Engine gimballing and throttling subtly steer these structures so that, to a ground observer, the whole contraption reads as a single, unwavering energy lance punching upward through stratified air.
