Circular Parachutes

• Circular parachutes expand into a bubble and do so rapidly as soon as they are employed by the falling person or object. The faster the parachute falls, the more resistance the bubble encounters as it opens, meaning the bubble is optimal for slowing or even stopping a descent as quickly as possible. The circular shape actually traps more air inside of it, meaning the faster it falls, the faster it will stop or slow down. Some circular parachutes actually stop so fast that falling to quickly can destroy them, which is why many circular parachute types employ other deceleration devices such as reefers, which slow the rate at which the parachute opens.
  
  

Square Parachutes

• Actually made of rows of rectangular ribs or smaller squares, square parachutes cannot open to the depths of circular ones, since they feature several shallow centers instead of one deep one. For this reason, they cannot slow the decent of falling as quickly as circular parachutes can. Square parachutes are more stable, however, and are easier to maneuver because the airflow is only temporarily redirected and not trapped. Square parachutes allow skydivers to blend with the existing currents of the air, and some feature steering devices that allow them to direct the airflow across the parachute and actually steer it.
  
  

Conical Parachutes

• Although not in use much today, conical parachutes were some of the earliest parachute types used and have their own distinct advantages. The parachutes designed by Leonardo di Vinci were mostly conical, for example, and were designed to save people from short falls rather than from falling out of airplanes at high elevation. Conical parachutes get the most air resistance by trapping air drastically and actually would not be practical for skydiving or other high-altitude falls.
  
  

The Physics of Parachuting

• The resistance of the air trapped by the parachute determines how much the parachute slows the fall. The falling person or object generates wake turbulence on the downwind side --- in this case, on the other side of the parachute material from the trapped air. This effect creates a pressure differential between the trapped air, which is under high pressure, and the wake air, which is low pressure. The high-pressure air strives to join the low-pressure air, pulling the parachute up and fighting against gravity, which causes it to slow its fall. the different shapes of the parachute create different intensities of pressure differentials and different types of wake turbulence, which is why they function differently.