Skydiving Science

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Some of my fondest memories were jumping out of airplanes while on internships at NASA Goddard Space Flight Center and NASA Ames Research Center! My first jump was at 11 000 feet and my second at 18 000 feet in California.

Skydiving is an old sport. Barnstormer’s in the early 1900’s began by jumping out of air balloons in homemade parachutes to stun crowds at fairs. And it was with these very first parachutists that the technology began to advance  – by stuffing the chutes into a pack. Even women had a hand in revolutionizing skydiving. The first person to purposefully freefall before opening a parachute was Georgia ‘Tiny’ Broadwick, a veteran of over 1100 jumps.

Skydivers jump out of a plane and experience a short period of ‘freefall’ (meaning that the only force acting on you is gravity), prior to deploying a parachute to drastically slow down the fall at a reasonable altitude. Most jumpers exit the plane between 10 000 and 13 000 feet (Skydive Monterey offers jumps from 18 000 feet with close to a minute and a half of freefall).

Before jumping out of the plane, probably the main force acting on anyone is your mind: excitement, maybe anxiety, with adrenaline pumping through you as you wonder why hurling yourself at the Earth, relying only on a parachute to get you to the ground safely, is a good idea. But once you take that step out of the plane, all you can do is enjoy the ride and trust that technology will guide you to a safe landing.

During the fall, there are essentially only two forces acting on you:  the Earth’s gravity pulling you straight down, and friction with the air. At the beginning of the fall, gravity is the more dominant force since air resistance increases with speed. As you accelerate towards the ground, your air resistance will start to increase. Then your body will eventually reach a terminal velocity when the air resistance equals the force of gravity.

By making your body more aerodynamic (i.e. pulling your legs and arms in and creating less surface area), you can go faster and reach a higher terminal velocity. Most skydivers want to achieve dynamic stability so that they won’t spin out of control.

After reaching a certain altitude, divers definitely need to slow down. Hence the need for a parachute! The parachute acts to create air resistance and slow you down. Upon initial deployment, the parachute slows you down drastically and your body feels a definite shock at the sudden change in speeds.

The technology used in skydiving is both simple and impressive. Parachutes come in a range of shapes and sizes and are usually made of a lightweight and strong materials to create the necessary air resistance. Earliest parachutes were made from silk while more modern designs are fabricated from Nylon. Leonardo da Vinci`s early parachute design featured a square frame to create a pyramidal chute. Other designs use circular parachutes with a small hole at the top in order to prevent a flip around. The hole prevents a build-up of air resistance and thus prevents the parachute from flipping a skydiver over. Other shapes are square with the state-of-the-art in the technology using `ram-air`airfoils to optimize control of speed and direction.

Whether you`ve jumped before or it is on your bucket list, enjoy the ride but also recognize all the science required for a soft landing!

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