3 Rs




Tuesday, November 2, 2010

STAO Hot Book Review: Understanding Flight

Understanding Flight. Anderson, David F. and Scott Eberhardt,
Second Edition. New York: McGraw-Hill Companies, 2009. ISBN
978-0-07-162696-5. $43.95 Cdn.

As appeared in Volume 32 • 2 November 2010 of Elements Online
««« Reviewed by Stan Taylor

David Anderson is a retired Nuclear Physicist. He has degrees from the University of Washington, Seattle and a PhD in Physics from Columbia University. He has had a 30 year career in high energy physics at Los Alamos National Laboratory, CERN in Geneva and the Fermi National Accelorator Laboratory. Scott Eberhardt has degrees from MIT and a PhD in aeronautics and astronautics from Stanford University. He was a Professor of Aeronautics and Astronautics at the University of Washington in Seattle for 20 years and is now lead engineer, Design Division at Boeing in Seattle. Both men are private pilots.

The authors scientifically challenge the Bernoulli explanation of flight found in many textbooks and pilot’s manuals. Anderson and Eberhardt explain and prove that the Bernoulli explanation is just plain wrong.

The authors make the argument that an airplane wing produces lift in response to
huge amounts of air being drawn across the top of its wings and diverted down off
the trailing edge of the wing. From a simplistic and explanatory perspective, with all that air being redirected down which is the action, the reaction is the plane goes up.

Presto: Newton’s Third Law. The authors go on to explain that it is the Coanda Effect, viscosity, and the boundary layer that keep the air bent over the curvature of the wing. Without these phenomena flight is not possible.

The book is written for the average reader who does not have a degree in physics. It
is a non-mathematical approach to the physics of flight that reads like a novel.

There are insertions, like sidebars, which contain facts about flight and aviation history. These make for fascinating reading, yet do not take away from the flow of the book. The many illustrations and pictures complement the points the authors are making.

This second edition to the first one published in 2001 has two additional chapters: One is on helicopters and autogyros, and the other is about how airplanes are constructed. As the authors state in their Introduction, “…this book is a
complete course in the principles of aeronautics, presented in straightforward, physical terms. We believe that the information will be accessible to nearly all who read it.”

I would strongly recommend this book to anyone interested in flight.

Stan Taylor is a retired elementary school teacher. He currently does science workshops for Scientists in School and is a member of the Crucible and Elements Editorial Committee (CEEC).

Sunday, June 6, 2010

Space Exploration – Saturn

Curriculum Connections: Grade 6 Space; Grades 9 and 12 Astronomy.

The first spacecraft to photograph Saturn was Pioneer 11 on September 1, 1979.

Voyagers 1 and 2 also photographed Saturn, but the vast acquisition of knowledge did not really begin until the arrival of the Cassini-Huygens Spacecraft on June 30, 2004.

The dark side of Saturn's rings was photographed by Voyager 1 as it flew by the side opposite the sun. The dense B-ring -- the reddish-brown band --appears dark because it blocks much of the sunlight. It is the brightest ring when viewed from earth.

Image credit: Spinrad, Hyron. "Saturn." World Book Online Reference Center. 2004. World Book, Inc. http://www.worldbookonline.com/wb/Article?id=ar492440)

After its seven-year journey through the Solar System on board the Cassini spacecraft, ESA’s Huygens probe successfully descended through the atmosphere of Titan, Saturn’s largest moon, and safely landed on its surface. The probe started its descent through Titan’s hazy cloud layers from an altitude of about 1270 km at 11:13 CET. During the following three minutes Huygens had to decelerate from 18 000 to 1400 km per hour. A sequence of parachutes then slowed it down to less than 300 km per hour. At a height of about 160 km the probe’s scientific instruments were exposed to Titan’s atmosphere. At about 120 km, the main parachute was replaced by a smaller one to complete the descent. It touched down at 13:34 CET. The probe began transmitting data to Cassini four minutes into its descent and continued to transmit data after landing at least as long as Cassini was above Titan’s horizon. (www.esa.int/esaMI/Cassini-Huygens/SEMQ1QQ3K3E_0.html).

Recently [April 3/10], activity taking place in the rings has scientists buzzing. "According to theory, astronomical discs should be uniform and smooth, with everything moving serenely along, but our observations have shown that life isn't as simple as that," said Burns. Instead, the researchers see particles ranging in size from a few centimeters to many meters in radius. And, according to studies by Hedman and Nicholson, two competing forces -- gravitational attraction that tries to clump ring particles together and tidal forces that pull them apart -- cause particles in the A and B rings (the two main rings) to form self-gravity wakes, or elongated clumps. as they orbit the planet.

Saturn's moons, meanwhile, exert their own influence on the ring particles, causing a scalloped pattern that rotates with the moon and ripples away, with individual particles moving in and out of the ripple, like water molecules moving in and out of a wave in the ocean. These ripples, so-called spiral density waves, push the moons that caused them outward, away from the rings. (www.saturntoday.com)

On 6 October 2009, the discovery was announced of a tenuous outer disk of material that is in the plane of Phoebe's orbit, which is tilted 27 degrees from Saturn's equatorial plane. The ring is from 128 to 207 times the radius of Saturn, and is thought to originate from micrometeoroid impacts on Phoebe. (www.sciencenews.org/view/generic/id/48097/title/Largest_known_planetary_ring_discovered).

Information comes in almost daily about some new discovery about Saturn. For further inquiries and the latest developments log onto one or more of the following web sites:

Stan Taylor

This article was first published in Crucible Online, June, 2010 www.stao.org