During SpaceX's recent test launch of its Starship rocket, the rocket's super heavy booster generated a massive "mach diamond" or "shock diamond" as it lifted off the launch pad. This was created by the exhaust from the booster's 33 Raptor engines combining. Mach diamonds form due to pressure differences between the rocket exhaust and surrounding atmosphere. As the rocket ascended, the shock diamond angle changed to become parallel to the rocket due to decreasing atmospheric pressure.