The standard vent hole formula assumes subsonic airflow and static pressure equalisation. For rockets exceeding Mach 0.8+, standard vent holes may produce erroneous altimeter readings due to shock-induced pressure effects.

• Use flush-mounted static ports instead of drilled holes where possible
• Use smaller holes with a larger tube volume to create a pneumatic low-pass filter that dampens dynamic pressure spikes
• Place holes away from any fins, rail buttons or protrusions that create local shock interactions
• Consult your altimeter manufacturer for supersonic-specific guidance

hole_dia = 0.004396 × tube_dia × √(tube_length / num_holes)