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(1) introduction
(a) Luke Aikins
https://en.wikipedia.org/wiki/Luke_Aikins
(1973- ; He is the first person to intentionally dive from mid-tropospheric altitude and land safely without a parachute or a wingsuit and the second skydiver to intentionally jump and safely land without using a parachute)
(b) All About Parachute Steering, Skydive OC (website of Ocean City (hence 'OC'], MD-based Ocean City Skydiving Center, Inc), May 8, 2017
https://www.skydiveoc.com/about/ ... parachute-steering/
(section 2 in part: "THE INTRODUCTION OF ROUND PARACHUTES [which is sectional heading; It should be 'OF RAM PARACHUTES'] Ram air parachutes were first introduced in the late 1970s, having been designed by Domina Jalbert in the 1960s.) * * * It's the lines at the back of the parachute that enable us to fly it. We call these lines the steering lines (for obvious reasons!). These lines are situated along the back edge and they join together part way down, becoming one line on each side of the parachute")
(i) The first phase of parachuting is skydive, before parachute opens. That is why both are discussed together, in Wiki, too.
(ii) Domina Jalbert
https://en.wikipedia.org/wiki/Domina_Jalbert
(1904–1991; born in Quebec and lived in US at least from high school on; developed ram parachute 1956-1963)
was a white male.
(iii) High-Performance Ram-Air Canopy with Improved Directional Steering. DEVCOM Soldier Center, US Army, undated
https://techlinkcenter.org/techn ... 3-9b2c-af872f458d61
(image of ram parachute without lines)
DEVCOM stands for United States Army Combat Capabilities Development Command
https://en.wikipedia.org/wiki/Un ... Development_Command
(table: 2003- , Role Research and development)
(iv) lines of a ram parachute
(A) Storm (that is a given name) Dunker, Chapter 31 Ram-Air Wing Design Considerations for Airborne Wind Energy. In Uwe Ahrens, Moritz Diehl and Roland Schmehl (eds), Airborne Wind Energy. Springer 2013, at page 518
https://link.springer.com/chapter/10.1007/978-3-642-39965-7_31
(Fig 31.1)
(B) Ram-Air Parachute Training Guide; A comprehensive Guide to USFS smokejumper ram-air parachute system. United States Forest Service, Department of Agriculture, 2018
https://www.fs.usda.gov/sites/de ... 26feb2018signed.pdf
(view Figures 1-3 at pages 7 and 8)
Pay attention to Fig 2's three "crossports" in between adjacent cells in a ram parachute.
smokejumper
https://en.wikipedia.org/wiki/Smokejumper
(c) skydive
(i) Tina Zdawczyk, OH, CHUTE! The Science of Skydiving. Smithsonian Science Education Center, Aug 28, year not indicated
https://ssec.si.edu/science-of-skydiving
"Oh, Chute" is wordplay on "Oh, shoot." A woman was not supposed to curse, so she would say this instead of "Oh, shit" and Nowadays a layt "darn" rather than "damn." Nowadays, a lady says things this way.
(ii) The Science of Skydiving. The Skydiving Co (owned by Justin and Diane Silvia and based in Texas)
https://www.theskydivingcompany. ... ience-of-skydiving/
two consecutive paragraph:
" * * * But eventually, the strength of the gravity force equals the strength of the air pressure and you will have reached terminal velocity. You won't accelerate any faster. Most people fall at a rate of about 120 miles per hour once they hit terminal velocity.
"The friction that you feel in the air (which may begin to feel like an industrial-sized fan is blowing wind up at your belly from below you) is how skydivers control their movements. Pressing down on that friction with one arm, for example, will cause you turn. Pushing your legs straight back down on the friction will cause you to move forward. If you want to fall faster, you would reduce your surface area (think bringing in your arms and legs and scrunching into a ball). If you wanted to fall at a slower rate, you'd widen your arms and legs and create as much surface area as possible as though you’re a parachute attempting the capture the wind
(iii) Skydive Tecumseh, Skydive Positions and the Arch: What to Know. Dec 16, 2020
https://www.skydivetecumseh.com/ ... tions-what-to-know/
("Way back when a bunch of former WW2 paratroopers began eyeing up their old equipment and wondering if they could use it just for fun, not a lot was understood about freefall. People used to believe it was necessary to remain tucked into a ball until the time came to deploy your parachute, as the force of the wind might be enough to tear your limbs clean off. Over time we figured out that: not only was this not a problem but while falling with your belly pointing at the ground you could actually use your arms and legs to aid with stability and even control your movement in the sky. This led to the birth of the well-known skydiving arch body position")
(d) "In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it [without air friction]." en.wikipedia.org for "free fall."
(e) Humans' tolerance of ACCELERATON has a limit. That is what g-force is about.
(i) John Papiewski, What Does G Force Mean? Scienceing.com, updated on Mar 29, 2018
https://sciencing.com/what-is-th ... ation-13710471.html
("G force refers to a unit based on the Earth's gravity: the constant, invisible pull that keeps you from floating off into space. Because the value of this force is well-known, scientists use it as a convenient yardstick to measure other forces, such as the acceleration of a car, the impact of two colliding football players or a fighter jet pulling out of a steep dive. In physics, acceleration is a change in speed or velocity. * * * The Value of 'g'[:] Researchers measure speed in units of distance divided by time, such as meters per second; The units for acceleration are speed divided by time, such as meters per second per second, or meters per second squared. For gravity on Earth, the value is 9.8 meters per second squared * * * This means, if you throw a ball from atop a very high building, the ball has a speed of 9.8 m/s after one second, 19.6 m/s after two seconds" IMAGINE THERE WERE NO AIR FRICTION)
(ii) g-force
https://en.wikipedia.org/wiki/G-force
("The unit g [in g force] is not one of the SI units, which uses 'g' for gram. * * * The term g-'force' is technically incorrect as it is a measure of acceleration, not force. section 3 Human tolerance and section
3.1 Vertical: g with subscript 0 is standard gravity. -- click he term at section 1 of this Wiki page)
(f) World First - Skydiver Luke Aikins Jumps 25000 Feet Into Net With No Parachute/ YuTube.com, uploaded by "Wonder World" on Aug 26, 2019
https://www.youtube.com/watch?v=aPC_h9Vmlxw
("On July 30 2016, Skydiver Luke Aikins, made history, when he jumped from 25,000 feet out of an airplane without a parachute, landing safely in a net set, setting a world record")
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发表于 4-30-2022 11:14:10
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