Introduction to Parachutes

1. Introduction to Parachutes • Parachutes come in different shapes & styles. They are used for many purposes, including— • EVACUATION from aircraft • DROP of troops, food, medical supplies • FUN • SLOW DOWN of vehicles like space shuttles and race cars

2. Leonardo Da Vinci • One of the earliest written accounts of a parachute concept is found in da Vinci's notebooks (cl495). • He drew a sketch of a cloth material pulled tightly over a rigid pyramidal structure. • Although da Vinci never made the device, he is given credit for the concept of lowering man to the earth safely using a maximum drag decelerator.

3. Andrew Garnerin • In 1797, Garnerin made the first • jump with a parachute without a • rigid frame. • An astronomer who observed the • drop suggested cutting a small hole near the apex of the canopy to inhibit oscillations. • This modification is now known as the vent and does indeed dramatically reduce canopy oscillations. Oscillations are back and forth motions around a point (think pendulums!). • video at https://www.youtube.com/watch?v=N963Tc8R5o0

4. 1880’s In 1887, Captain Thomas Baldwin developed a parachute harness. In 1890, Paul Lettemand & Kathchen Paulus developed the concept of folding or packing the parachute in a knapsak-like container. http://farm1.static.flickr.com/70/204167058_d8ec2c6374.jpg

5. 1930s From World War I to the early 1930's, military air corps in Europe, Russia, and the United States used conventional round silk (“solid cloth”) parachutes.

6. In the 1960s, solid cloth parachutes were modified with slots to provide greater stability and horizontal speed. http://www.trainingworld.co.uk/images/event8.gif http://upload.wikimedia.org/wikipedia/commons/thumb/e/e6/USMC_Paratrooper.jpg/200px-USMC_Paratrooper.jpg

7. Military Parachutes • Here are requirements for parachutes • that will airdrop supplies: • accurate delivery to within a few • hundred feet of a designated position • deployable from a great height, • preferably an altitude over 20,000 feet • deployable from a great horizontal distance from the target • able to be developed and produced at a low cost http://www.pcprg.com/nwv99.htm

8. This ribbon design can be deployed at supersonic speeds that would ordinarily rip a parachute to shreds. 12-gore ribbon parachute at http://www.mtu-net.ru/mosseev/ribbon2.gif

9. Sport Parachutes The parawing parachute, designed for maximum lift as opposed to maximum drag, was primarily used in sport parachuting during the 1970s. http://www.hickoksports.com/images/parawing_chute.jpg

10. The parawing was replaced by the parafoil parachute, also called “square” or “ram-air.” This parachute deploys at terminal velocity. It offers both drag and lift. Its design traps air between two rectangular membranes. Dynamic stalls may be performed with a ram-air so that landings are made with zero velocity. The ram-air may also be flown backwards. http://farm3.static.flickr.com/2321/2482039738_64c93f1a45.jpg?v=0 http://www.fas.org/man/dod-101/sys/ac/equip/gpads-l.jpg

11. Physics involved • Gravity pulls parachutes downward • Air resistance works as an opposing force to gravity • A parachute accelerates until the air resistance equals the gravity, at which point the parachute reaches terminal speed • Bigger parachutes with a larger area fronting the wind create more air resistance than smaller ones, so bigger parachutes reach terminal speed earlier. http://school.discoveryeducation.com/lessonplans/programs/forcesandmotion/

12. Resource Links • Text information at http://www.parachutehistory.com/eng/drs.html • 1930’s parachute at http://www.fsjairshow.com/files/static-images/paratroopers.jpg • Parachute history at http://www.globalsecurity.org/military/systems/aircraft/systems/parachute-history.htm • Types of parachutes at http://en.wikipedia.org/wiki/Parachute • All about parachutes at http://www.aero.com/publications/parachutes/9511/pc1195.htm • Models at http://www.pbs.org/wgbh/nova/teachers/activities/3101_mars.html