Science Sunday 12-10-17

A Brief History of Flight – The Space Age, Part 1

John Glenn

Although Yuri Gargarin was the first person to orbit the Earth, John Glenn was the first American to do so, and he did so, in spectacular fashion.

Born in 1916, Glenn was already a distinguished fighter pilot, having served in World War II, China and the Korean War.

Partly because of his stature, but mostly because of his flight record, Glenn became one of a select number of astronauts first called Astronaut Group 1, and then later called the Mercury Seven, because they would be flying the first group of missions designed to get humans to the Moon, Project Mercury.

Glenn’s orbital mission lasted a mere 5 hours as he completed three orbits around the Earth.  His capsule did not fly that high: at perigee, he was only 100 miles off the surface of the Earth.

Glenn’s mission was not without concern and worry.  After insertion into orbit, ground control received a signal from his space capsule, Friendship Seven, indicating that his re-entry heat shield was perhaps not firmly attached.  He was instructed to re-enter Earth’s atmosphere manually and with the retrorocket package still attached.  The retrorocket package burned up on re-entry, but the the heat shield was in fact firmly attached, and Glenn splashed down on mother Earth unscathed.

Glenn would go on to a distinguished career as a US Senator from Ohio, serving 24 years.  In 1998, while still a Senator, he returned to space aboard the Space Shuttle Discovery.

Glenn also achieved the status of 32nd degree mason.

Glenn died in late 2016 at the ripe old age of 95, the last remaining member of the Mercury Seven.

 

Gus Grissom

No review of the early days of space flight would be complete without a sincere remembrance of Gus Grissom, perhaps the second best known member of the Mercury Seven astronauts.

A bit of a maverick but extremely popular, Grissom was the second American to go into space, after Alan Shepard, flying a sub-orbital arc for a mere 15 minutes and 37 seconds in the Liberty Bell 7 capsule.

Unfortunately, after splashing down, the capsule hatch inadvertently blew open, and the capsule took on substantial water.  Rescue helicopter pilots were able to fish Grissom from the turbulent Atlantic, but the capsule was too heavy for the helicopter, and it sank.

[The capsule would be retrieved much later, in 1999, by a private salvage firm.]

Grissom went on to successfully command the two-man Earth orbiting Gemini 3 mission, in a capsule playfully dubbed the Molly Brown (in honor of the unfortunate sinking of the Liberty Bell 7 capsule).  The mission was the first time astronauts were able to change the characteristics of their orbital motion using small rockets on the capsule.

Unfortunately, Grissom’s next mission, Apollo 1, was to be his last.  He was to fly with fellow astronauts Ed White and Roger Chaffee, but during a launch pad test for the flight, a fire occurred in their oxygen rich capsule.  The capsule filled with smoke, and all three astronauts were asphyxiated when they inhaled carbon monoxide from the fire.  The air tubes to their suits, as well as parts of their suits, had melted from the intense heat and flames of the fire.

Grissom was only 40 years old.

 

 

 

 

 

 

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Science Sunday 12-2-10

How Airplanes Fly

A good place to start discussing how airplanes fly is to look at the four forces acting on the plane while in flight:

four forces

Thrust comes from the planes jets or propellers, and is a third law effect: as the air is pushed to the rear, it pushes back, causing the plane to go forward.

Weight of course is the Earth’s attraction of the plane to it, and is universally downward.

Drag is just air friction.

Lift is what causes the airplane to go up and stay up.  It is caused by the flow of air over the plane’s wings.

Lift happens because of the cross-sectional shape of the wings (called the airfoil) and the wing’s angle of attack:

airfoil

The airfoil, the shape of which can change on takeoff and landing, creates a difference in pressure between the top and bottom of the plane’s wings.  This difference in pressure is caused by two factors: Bernoulli’s Principle and Newton’s Third Law.

According to Bernoulli, air travelling faster over a surface exhibits less pressure on that surface than air travelling slower over that surface.

Air travels faster over the top of the wing than the bottom of the wing, so there is a pressure difference between the bottom of the wing (higher pressure) and the top of the wing (lower pressure).  That pressure difference is up, and the plane is lifted up, once the lift force exceeds the plane’s weight.

Lift can also be explained as Third Law action-reaction pairs between the air flowing under and over the wing and the wing itself.   Because there is much confusion about whether the Bernoulli explanation or the Third Law explanation is dominantly correct in explaining lift, let’s look at a video on that very same subject:

When a plane is taking off, the angle of attack is changed to create the lift needed to lift the plane off the ground.  This is accomplished by the wing’s flaps and slats:

flaps and slats

Flaps (at the back of the wing) and slats (at the front of the wing) increase the wing’s surface area, which increases lift.

[The spoiler shown in the illustration above is located on the top and back of the wing, and is used to decrease lift on landing, or to aid in slowing down the plane once it has landed.]

Lift is also enhanced by the Coanda Effect, which states that a fluid will tend to hug a convex surface.  On the top of the wing (with flaps and slats extended, or not), the air flow over the wing is redirected downward due to the Coanda Effect.  By Newtons Third Law, the air pushed downward by the wing reacts by pushing back upward on the wing, causing lift.  (It also induces some additional drag.)

[Of course air flowing under the wing is also directed downward, because of the angle of attack.  So Newton’s Third Law will result in additional lift here as well.]

Notice the separation between successive flaps in the illustration above.  Air flowing below the flap is redirected to above the flap, at which point the Coanda Effect causes it to hug the top of the flap so as to redirect that air downward.  The overall lift enhancement due to the Coanda Effect is shown here:

Lift Coanda

[Here we see that the slats also enhance the Coanda Effect by redirecting air flow to above the wing.]

In researching the subject of the Coanda Effect, I ran across a video that illustrates it nicely:

Note that flaps and slats are normally retracted during steady flight.

Of course, once airborne, it is necessary to control the airplane as to its direction and its altitude (collectively called navigation).  This is done using three devices: the ailerons, the rudder and the elevator.

The ailerons are at the wing tips and work at cross purposes: when one aileron goes up, the other goes down.  The aileron that is up causes its wing to go down (because it has less lift).  The aileron that is down causes its wing to go up (because it has more lift).

When ailerons are used, the plane rolls around its front to back axis of rotation, and this causes a change in the plane’s overall direction and altitude, while maintaining its pointing direction.

The rudder is on the vertical stabilizer at the end of the plane.  When it is used, the plane will yaw around its top to bottom axis of rotation, and this causes a change in the plane’s pointing direction but not its altitude.   The rudder is sometimes used to inhibit a yawing motion that occurs when the ailerons are used to change direction and altitude.

The elevator is on the horizontal stabilizer at the end of the plane.  When it is used, the plane’s pitch will change, meaning it will rotate around the horizontal axis going through the plane’s wings.  This changes the plane’s altitude (up if the elevator is up, and down if the elevator is down) without changing the plane’s direction.

Here is a nice illustration of the three axes of rotation of a plane in flight:

roll pitch yaw

Here also is a nice illustration of the three in-flight control devices just described, and their purposes:

navigation

Notice that a plane has to maintain a minimum speed in flight to keep the lift force equal to the plane’s weight.  When a plane is landing, the flaps and slats are opened to increase wing area and lift to compensate for the slower plane speed.

A plane also needs to avoid too great an angle of attack, because then the plane will stall due to insufficient lift.

Here is video that summarizes everything regarding takeoff, landing, and in-flight navigation:

One final comment worth noting: recently, some commercial jets were grounded in Phoenix because it was too hot to fly.  It turns out that lift force is affected by air density.  If the air is too hot, the air density will be too low for safe flight.

You can read about this density issue here.

 

 

Science Sunday 11-26-17

A Brief History of Flight – The Rocket Age, Part 2

Telstar 1

On July 10, 1962, Bell Laboratories, in conjunction with NASA and other telecommunication organizations, launched the first true transatlantic telecommunication satellite from Cape Canaveral.

Launched from a Thor-Delta rocket, the satellite, known as Telstar 1, occupied a highly elliptical orbit, with perigee at 903 miles, and apogee at 3505 miles.  It weighed 170 pounds, was 3 feet in diameter, and ran on a mere 14 Watts of solar assisted power.

Telstar 1 was the first satellite to relay television images across the Atlantic Ocean.  The first image was that of the US transmission station in Andover, Maine.  Subsequent images included part of a Chicago Cubs and Philadelphia Phillies baseball game, a press conference by then President John Kennedy, and a singing performance of the French legend Yves Montand.

Unfortunately, the satellite suffered irreparable radiation damage while travelling through the Van Allen Belts, radiation deposited there by a US high altitude nuclear bomb detonation.  It ceased functioning in November of 1962, a mere four months later.

 

Yuri Gargarin – First Man in Space

On April 12, 1961, a most remarkable event occurred.  Soviet cosmonaut Yuri Gargarin became the first human to orbit the Earth.

It was not a routine journey.  Gargarin had only a 50 percent chance of returning safely to Earth.  He would orbit the Earth only once, travelling 25,000 miles, in 108 minutes, at an average speed of nearly 14,000 miles per hour.

Gargarin was chosen to be the first human in space in part because of his short stature, but also because he was athletic and a very level-headed person.  He had grown up in Nazi occupied Russia, and had to live for a while in a mud hut, while his older brothers were shipped off to a Nazi slave labor camp.

His capsule, the Vostok 1, did not fare as well as he did.  Part of the capsule was supposed to detach before reentry, but it failed to do so, causing his reentry to be virtually uncontrollable.

Fortunately, the unwanted part detached from his capsule because the tether connecting it burnt up in reentry.  Gargarin was able to eject from the Vostok 1, as planned, at 20,000  feet somewhere over Siberia.  The capsule, by contrast, crashed and burned up.

Unfortunately, Gargarin did not live very long after his successful orbiting of the Earth.  Just eight years later, on March 27, 1968, Gargarin died in a MIG-15 military jet aircraft training accident.

He was only 34 years old.

 

We Choose to Go to the Moon

On September 12, 1962, President John Kennedy gave a most extraordinary speech at Rice University in Houston, TX, where he challenged Congress, and the nation, to inspire the United States to become the preeminent agent in space travel, and all activities contingent to that goal.

Kennedy repeated the mantra “We choose to go to the Moon” three times, explaining that we, the United States will land on the Moon, in less of a decade, not because such a task is easy, but precisely because it is difficult.

As a result, the budget for NASA quadrupled, and the Mercury, Gemini and Apollo programs were set in motion, culminating in the landing of the Apollo 11 mission on July 20, 1969, less than seven years later.

Science Sunday 11-08-17

A Brief History of Flight – The Rocket Age, Part 1

Rocket Bombs

During World War II, the Germans were way ahead of the Allies in all matters Rocketry.  Even as they were decisively losing the ground war, London (and later Antwerp, in the Battle of the Bulge) were being bombarded by rocket bombs called the V-1.  The British dubbed these rocket bombs “buzz bombs” because of their distinctive buzzing sound.

The V-1 was powered by a pulsed jet engine, and was launched from airplanes.  It had no inherent guidance system, and just turned off and fell after a set amount of time.

Contrary to popular belief, less that 20% of the “buzz bombs” fired ever reached their intended targets.  They were relatively slow, and could easily be shot out of the air by allied antiaircraft guns and war planes.

Nevertheless, as the allies advanced towards Berlin, intact V-1 bombs were captured and sent back to the US, and thereof was born the first US guided missile, the JB-2.

 

The X-15

After WWII, The US embarked on a program to develop the first true rocket plane or space plane, the X-15.  Because the X-15 was a liquid fueled manned rocket, it could go into true space, which at the time was defined as an elevation of 62 miles.

The X-15 was not a warplane, but a research plane built for NASA.  It used up its fuel in a mere 2 minutes, so it was launched from the underside of a specially modified B-52.

The X-15 flew 199 missions from 1959 to 1968, and during that time set world altitude and speed records for a manned aircraft that have never been exceeded.  In October, 1967, pilot William J. Knight flew at a speed of 4,519 miles per hour, or Mach 6.72, at an altitude of 102,100 feet.

The X-15 was originally considered as part of a low-Earth orbit satellite delivery system, but that idea was retired with the encroaching successes of the Mercury, Gemini and Apollo space flight programs.

 

The Russians Are Coming

On October 4, 1957, Americans (and the whole world) woke up to find that the Soviets (the USSR) has launched a satellite into near-Earth orbit for the very first time in human history.

At an altitude of about 560 miles, this satellite, Sputnik I, was moving at about 18,000 mph, and took a little over 90 minutes to circumnavigate the Earth.

There was no doubt that the Soviets had done this: any amateur radio operator could easily pick up Sputnik’s radio signals broadcasting at 20MHz and 40MHz.   The space age, and the space race, had begun.

Launched from Baikonur Cosmodrome, the Soviet space mecca in what today is called Kazakhstan, Sputnik I was quite small by today’s satellite standards, only being 23 inches in diameter, but it certainly made a big splash in the worldwide press, as indicated by the above video.

The satellite made only 1440 revolutions of the Earth before reentering Earth’s atmosphere and burning up in January of 1958.

 

Science Sunday 09-03-17

A Brief History of Flight – Part 3

The Jet Age

Much like the development of FM radio and television, the development of truly operational military and commercial jet aircraft was delayed by the exigencies of World War II.

The “fathers” of turbojet propulsion and jet aircraft were an Englishman named Frank Whittle and a German named Hans Von Ohain.

Ohain’s work led to the first jet powered fighter aircraft, the Heinkel He 178, which first flew in August of 1939.  Whittle’s work led to the Gloster E.28/39 jet aircraft, which first flew in March of 1941.

The drawings for the Gloster E.28/39 were shared one month later with Major General Henry “Hap” Arnold, commanding officer of the US Army Air Force, who immediately requested that Bell Aircraft design an American equivalent.  Bell Aircraft did this in a mere 6 months, and the first American jet-powered aircraft, the XP-59A (featured in the above video), flew for the first time in October of 1941.

Unfortunately, the speed, handling and reliability characteristics of piston-driven propeller aircraft far outperformed all early jet aircraft, and so jet aircraft development floundered during the war.  The only jet aircraft to make it into action in World War II was the German Messerschmitt Me 262, which flew combat missions in 1944, too late in the war to affect its outcome.

Commercial jet flight first became a household item in the early 1950s, when British manufacturer De Havilland introduced the 36 seat Comet 1 to the public in May of 1952.  Unfortunately, the design of the plane led to some early crashes, which allowed American manufacturer Boeing to capture the jet aircraft market, when it introduced its now famous 707-120, with Pan-Am airlines flying from New York to London in October of 1958.  Rival manufacturer Douglas would introduce its DC-8 aircraft eleven months later.

During this period, Boeing continued its relationship with the US military, manufacturing the B-52 “Stratofortress” long range jet bomber, a plane still in service today.

For a nice summary of early jet aircraft, click here.

 

Cold War Reconnaissance: U2 and the SR-71

After World War II, tension between the United States and the USSR (Russia and its satellite countries) were at the highest level.  Spy satellite imagery was just a dream, decades away.

So it was imperative that the US develop high altitude planes capable of flying over any rival’s territory so as to take pictures of military installations, preparations and the like.

Lockheed Corporation was tasked with developing such planes, and the first one was the U2.  Americans and the world first heard of the U2 in 1960, when one of them was shot down over the USSR.  The pilot, Gary Powers, survived and was captured, much to the embarrassment of then President Eisenhower.

In the vast diaspora of Kennedy assassination conspiracy theories, it has been suggested that Kennedy’s alleged assassin Lee Harvey Oswald, having worked at a secret military airfield in Japan, may have tipped off the soviets as to the altitude at which the planes flew (70,000 ft) when he defected to Russia in 1959.  Certainly the Soviets knew of the flyovers, tracked them, and shot at them prior to Powers’ plane being shot down.

The U2 would prove very useful again during the Cuban Missile Crisis of 1962, when pictures of the missile installations were obtained by flyovers of U2 planes.  One U2 was shot down during the crisis.

It was clear in the early 60s that a new reconnaissance plane was needed, one that could fly higher and faster.  Enter Lockheed’s SR-71, the Blackbird.

The SR-71 was a remarkable plane, as indicated in the video above.  With a crew of 2, it regularly flew at Mach 3.2 (that’s 3.2 times the speed of sound, or 2,458 miles per hour, or 3,600 feet  per second), at an altitude of 80,000 feet.

Because of its speed, the SR-71 would experience temperatures at high altitude of over 900 degrees Fahrenheit, with the inside of its windshield registering a temperature of about 250 degrees Fahrenheit.  These temperatures required that the plane be 90% composed of titanium.

Today, there is much speculation that Lockheed has produced and is testing a SR-71 successor code-named Aurora, with a purported maximum speed of Mach 5 to Mach 6, but there is almost no hard evidence to verify this speculation.

 

Science Sunday 08-26-17

A Brief History of Flight – Part 2

Lucky Lindy

No other pilot of the 1920s is better known than the American  Charles Lindbergh, who flew his Ryan Monoplane, the Spirit of St. Louis, from Long Island, NY, to Paris, France, in May of 1927.

Lindbergh was the first person to fly a fixed wing aircraft from the United States to continental Europe, but not the first person to fly a fixed wing aircraft from North America  to Europe.  That honor goes to the team of Alcock and Brown, who flew from Newfoundland to County Galway, Ireland in a mere 16 hours, traversing about 1900 miles at an average speed of 115 mph.

Lindbergh learned how to fly the “old fashioned” way, first as a post World War I barnstormer, then as a flying ace in the US Army Air Service, and finally as a US airmail pilot.

Lindbergh’s transatlantic flight was long and arduous, flying a little more than 33 hours and 3600 miles through icy storms and fog, and without a front window, landing finally at Le Bourget Field just outside Paris, to the acclaim of 150,000 witnesses.  For Lindbergh’s efforts, he won the Orteig Prize of $25,000 (in today’s money, $342,000), and received two medals, the Distinguished Flying Cross, and The Medal of Honor, from President Calvin Coolidge.

The remainder of Lindbergh’s life was no less exciting.  His first son and namesake was kidnapped and murdered, to much notoriety.  Lindbergh was an avowed isolationist prior to World War II, only seeing the error of his ways after Pearl Harbor.

During World War II, Lindbergh flew 50 combat missions in the Pacific theater, as a private consultant.

Lindbergh died in Maui, Hawaii, in 1974.

Le Bourget Airport is no longer used for commercial flights, but is home to the world famous yearly Paris Air Show.

 

Amelia Earhart

Perhaps the best know female pilot of all time is the aviatrix Amelia Earhart.

Earhart only lived 40 years, but in that time she accomplished many aerial feats, including being the first woman to fly solo non-stop across the Atlantic, flying from Newfoundland to Derry, Northern Ireland, in May of 1932, in a single engine Lockheed Vega 5B.  For this feat, she received the Distinguished Flying Cross from President Herbert Hoover.

Married to promoter and publicist G. P. Putnam, Earhart bounced from one record flight to another, until in 1937 she decided to aerially circumnavigate the globe.  Her first attempt, from east to west failed, when she accidentally damaged her plane in Hawaii.

Her second attempt, flying from west to east was initially more successful.  She had travelled an astounding 22,000 miles when she and her navigator Fred Noonan departed Lae, New Guinea, on July 2, 1937, destination the American territory of Howland Island situated on the Equator and the International Date Line.

The date of their departure was no coincidence: they intended to be back in the states in time for the Fourth of July.  But that was not to be, because Earhart and Noonan disappeared somewhere between Lae and Howland Island.

There continues to be controversy as to whether Earhart and Noonan perished at sea, or whether they ended up on some other island, possibly even a Japanese possession.  No one knows for sure what happened to them.

We should remember Earhart not only for her aerial derrings-dos, but also for her service as a nurse’s aide in Toronto helping returning World War I veterans, and her work teaching English to impoverished children.

 

Aircraft of World War II

Many innovations in aircraft design happened in the run up to (and during) World War II, but I thought it would suffice in this brief history to talk about one plane that probably won the war for the Allies.

I speak of the B17, the flying fortress.  Originally designed by Boeing Corporation, during the war the plane was manufactured by Douglas and Lockheed as well.

The bomber had the deserved reputation of taking a terrible beating while still being able to limp back home to England.

More than 12,000 B17s were made during the period of 1935 to 1945 inclusive.  At the end of production, the bomber had four 1200 hp engines, 13 machine guns, could drop from 8,000 to 17,500 lbs. of ordnance, and sported a 10 man crew.

For a truly moving recollection of what it was to fly bombing raids over Germany in 1943 without a fighter escort, read Half a Wing, Three Engines and a Prayer.

For a review of the “25 planes that won World War II”, see this fascinating article.

Science Sunday 08-13-2017

A Brief History of Flight, Part 1

The Wright Brothers

I am in the process of developing a new physics course for students interesting in the field of unmanned aerial vehicles (UAV), commonly known as drones.  It occurred to me to put together a brief history of human flight.

Most of us are familiar with the immense and courageous achievements of Orville and Wilbur Wright, brothers who owned a bicycle shop in Dayton, Ohio, and who shared an inextinguishable passion for manned flight.

While there were many pioneers in manned flight, no one now doubts that the Wright brothers achieved the first heavier-than-air, fixed wing, controlled and powered flight at Kitty Hawk, North Carolina, on December 17, 1903.

At first ignored by the press and the US government, the brothers would go on to become world celebrities, showing off their latest aircraft design in Europe and the US in 1908.

Wilbur died at the relatively young age of 45 years, of typhoid fever.  Orville was more fortunate, living to the ripe old age of 76, when he succumbed to his second heart attack.

The video above is a short but reverential bio of the Wright brothers and their indispensable sister and business partner Katharine.   A more direct and compact biography of the Wright brothers early achievements can be viewed here:

 

The Montgolfier Brothers

Lesser well known are the Montgolfier brothers Joseph-Michel and Jacques-Etienne, who invented the hot air balloon in the early 1780s.  The first human flight was in one of their balloons.  It flew over Paris for over 5 miles at a height of 3000 feet on November 21, 1783, to the incredulous surprise of many dignitaries, including John Adams, his wife Abigail, and Thomas Jefferson.  HBO recreated this event at considerable expense in its award winning series John Adams.  The above video shows that part of the series, including some brilliant dialogue between the principals.

 

Icarus

Icarus

Of course, the desire of humankind to fly did not start with the Montgolfier or Wright brothers, as witnessed by the Greek legend of Icarus, son of Daedalus.

As the story goes, Daedalus was an Athenian craftsman who designed and built the labyrinth for King Minos of Crete, a maze meant to imprison the half-man half-bull monster, the Minotaur.

Imprisoned in the labyrinth by Minos himself, Daedalus fashioned wings of wax and feathers for himself and his son to escape with.  He warned his son not to fly too close to the Sun, but Icarus could not control his impetuous self, and flying too high, his wings melted over the sea on their way back to Greece, with Icarus plunging to his death.

 

The Red Baron

Manfred_von_Richthofen

After the Wright brothers showed the world that manned flight was possible, many improvements in aircraft design rapidly ensued, including using aircraft in war.

Blimps or dirigibles were used exclusively at first, for reconnaissance only, but it soon became apparent that fixed wing aircraft could do a better job of both reconnaissance and warfare.

The Germans were the first to realize that a machine gun could be synchronized to fire between an airplane’s propellers, and they quickly took advantage of this design improvement.

The most notable of German World War I flying aces was the inestimable Baron von Richthofen, also known as the Red Baron (his plane was painted red).  He is credited with 80 confirmed aerial combat kills, but was himself shot down before the end of the war.

 

Bessie Coleman

Anyone who lives in the Chicagoland area and has visited O’Hare Airport has driven by or on Bessie Coleman Drive, named after Bessie Coleman, the first African-American and Native-American woman to earn a pilot’s license.

Born the 10th of 13 children to George Coleman, a Texas sharecropper, and his wife Susan, Bessie distinguished herself in school, but soon grew restless, wanting to make something of her life.  She moved to Chicago, saving her money as she worked both as a manicurist and in a chili restaurant.  Wanting badly to be a licensed pilot, but denied that opportunity in her home country, she set sail for France, where she soon learned how to fly.

She returned to the states with her pilot’s license to much notoriety, but soon realized that she would need additional flight training to make a living as a barnstormer, or aerial acrobatic pilot, so she returned to Europe for additional advanced training.

She returned to the US and to a successful career as a barnstormer, but died unexpectedly in a plane crash in 1926.