Why doesn't the sky fall down on our heads?

Aydogan Koc

Why doesn’t the sky fall down on our heads?

Aeronautical and space questions answered in a simple and understandable way

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Inhaltsverzeichnis

Titel

Preface

Introduction – Why doesn’t the sky fall down on our heads?

1. The History of Aviation

2. A Short History of Space Travel

3. Atmosphere

4. Aerodynamics

5. Flight mechanics

6. Flying plants and animals

7. Types of engines required for flying

8. Other types of flight vehicles

9. Helicopters

10. Aircraft

11. Space travel

Closure: Why does the apple fall on our head?

Impressum neobooks

Preface

Imprint

1. Edition, July 2019

Copyright © by Koc Consulting, Potsdam

www.koc-consulting.de

All rights reserved

Proofreading: Eugen Reichl

lllustrations: Stefan Schiessl

Layout: Exploredesign, Dachau

ISBN: 978-3-00-063289-1

Information about the author:

Aydogan Koc (1957) studied Aeronautical Engineering at the universities of Stuttgart and Darmstadt. He began his professional career as a Development Engineer for military aircraft in the advanced design office of Airbus Holding (formerly MBB/DASA/EADS). He then served as a senior manager in the space division. He also worked as the production manager with the “Eurofighter” consortium. Koc played an important role in development of the European aircraft program.

He realized important business developments, cooperation and international projects as a successful manager and entrepreneur in the aerospace industry during his professional career of over 19 years at Airbus and Eurofighter.

“Koc Consulting” was established by Aydoğan Koc in Munich in 2004 and in Ankara in 2006 to meet the demand for quality consulting in the world aerospace market. The company is an assertive company which realizes international defense, space and aircraft technology projects. It is one of the aims of Aydoğan Koc to draw upon many years of European engineering experience.

Aydogan Koc established an Sport and Trainer Aircraft Company at the Ankara Etimesgut Airport in December 2011 with the company name “THK Aircraft Company Inc.“ in partnership with the Turkish Aeronautical Association (THK, founded in 1925). He is also the General Manager and Deputy Chairman of the Advisory Board of the THK Aircraft Company.

He has a private pilot license and spends his leisure time with private flights.

Acknowledgement:

To my son Yiğit for his curiosity and interesting questions and everybody who showed support, interest and thus, contributed to the creation of this book on Aviation and Space.

I would also like to thank:

 Mr. Nahit Ertongur for his generous technical consultancy

 and support,

 Mr. Eugen Reichl who published many popular articles on space,

 and the Koc Consulting team.

This book is dedicated to our little friends, the

bumblebees which are masters of aerodynamics…

Today, considering the knowledge acquired by

mankind in Aerodynamics and Fluid Mechanics,

it stands as a fact that bumblebees cannot fly.

Luckily, they have not been told so until now!

These small and fat creatures continue to fly as

always without caring about the negative views.

My son used to ask me how aircraft fly and how giant rockets manage to get into space. While I was trying to give simple answers to these complicated questions, I realized we, as Aviation and Space engineers, never thought of simply explaining what is going on with aviation in a way to be understood by everyone. This reminded me of the fact that a too detailed knowledge about something can be a disadvantage at times: while trying to explain complicated things, one slowly gets caught up in details and starts to use many technical terms without realizing it and quickly loses the interest of their audience.

I started to give brief explanations, limit my answers to the essence and decorate it with anecdotes and examples to prevent my son from losing his focus. I continued to improve this method with time. You will find many questions that my son asked me and the summary of my answers in this book. This allows everybody to gain knowledge about aviation and space technology and related rules of physics without the need for special technical background.

Nothing can ever be too perfect to be improved. Please write to me if you have any suggestions to simplify the answers, interesting examples and clarifying short stories or maybe new questions. I hope you will contribute to the next edition with your questions.

E-Mail address: koc@koc-consulting.de

Introduction – Why doesn’t the sky fall down on our heads?

You know, almost all children (or those who are still children in their hearts) know Asterix the Gaul, his fat friend Obelix and the fierce and fearless village chief Vitalstatistix very well. He is known to fear neither the Romans nor the Vikings or other dangers in nature. He only has two problems: One of them is his wife, Impedimenta, and the other is the possibility of the sky falling on his head one day. As it is a known fact that men have no chance against women, we can consider the first problem as unsolvable and we can forget about it. But his second fear still exists, he is still anxious about the sky falling down on his head.

When we look at the open sky at night, everything is in order and beautiful harmony exists. All celestial bodies and planets move in the firmament the way they should, the Sun rises in the east and sets in the west, day after day!

That is why humans in the early days believed that the Earth is at the center of the universe. Only in recent centuries did people understand that the planet we live on is one of the eight known planets in our Solar system. These planets keep moving in their elliptical orbits at great distances around the giant Sun.

How insignificant and small our planet is can easily be demonstrated by a scaled model of the universe. Assuming 10 cm represents 1 million km; our Sun would be an orange 14 cm in diameter, looking like a yellowish lantern. Our world is the size of a grain of sand with a diameter of 1.3 mm circling the Sun at a distance of 15 m. The closest star to our Sun is the dwarf Proxima Centauri which is about the size of a cherry and is 4,000 km distance in our scale model. This equals the distance between Ağrı/Turkey and Madrid/Spain.

In our universe, every celestial body is on the move. Our world rotates around its own axis once a day, which is a speed of 1,670 km/h at the equator. Our satellite, the Moon, orbits the Earth in 29.5 days. This is an average orbital speed of 3,700 km/h. The average speed of our Earth orbiting around the Sun for a full circle in 365.25 days is 107,000 km/h. Our life source, the Sun, travels at about 1 million km/h around the center of our galaxy called The Milky Way.

There is only one single force which prevents planets, moons, stars and galaxies from drifting apart: this force is called gravity. It can only be balanced by the centrifugal force which is the result of orbital motion. Consequentially, there is a ballet of celestial bodies in the universe which move around each other in perfect harmony, maintaining their existence thanks to the balance of these forces and, unless this balance is impaired, all these celestial bodies will continue their movements for the next millions or even billions of years. Therefore, chief Vitalstatistix really need not worry about the sky falling down on his head one day.

Maybe we should worry a little. When we consider all the small and large celestial bodies in our solar system, we see that this question is something worth worrying about.

There are millions of large and small meteorites, asteroids and comets other than the known planets and their satellites in our own Solar system. Their orbits easily change when they collide with other bodies or due to gravity when they get too close to other planets and stars. As a result, there is a small risk of colliding with the Earth. It is known that many celestial bodies have fallen onto the Earth as a result of these encounters.

For example, it has been proven that a meteorite hit the Mexican gulf about 65 million years ago. It is estimated that this event turned living conditions on Earth upside down and probably caused the extinction of dinosaurs. The magnitude of the damage to be caused by collision of a celestial body with the Earth depends on the size of the celestial body. The main criterion is whether the average diameter exceeds about 30 m, since these celestial bodies need to pass through the gas layer around us called the atmosphere at a very high speed to reach the surface of the Earth. During this transition, many celestial objects burn to ashes or hit the ground in tiny pieces due to increased frictional heat. The large objects can indeed pose a risk to life on Earth. That is why the focus is on rather large celestial objects. Asteroids and meteorites, with an average diameter of a few kilometers, are closely monitored as soon as they are identified. Luckily, there is no immediate risk to the Earth. The probability that a meteorite with an average diameter of 1 km will hit the Earth is estimated to be once in about 300,000 years. However, not all of the small asteroids are being monitored yet, and the probability to collide with one of them is slightly higher. Therefore, it is theoretically possible that this kind of celestial body can cause a small disaster after hitting an inhabited area on the Earth.

Vitalstatistix, thus, needs to think about taking appropriate safety measures in advance. Scientists already have some ideas.

We don't really need to live in continuous anxiety. The probability of other natural disasters seems to be higher than the collision with an asteroid. As you know, when Vitalstatistix encounters a problem, he always summons two of his best men: the fat Obelix and his cunning friend Asterix. This reassuring attitude is also being taken by the international space community; the first French artificial satellite to be launched with a Diamant-A rocket on 26 November, 1965 was called Asterix.

1. The History of Aviation

When was the first flight in human history?

Let's go back to one of the most popular stories of the Ancient days, the story of the inventor and craftsman Daedalus. A slave on the Crete Island, Daedalus constructed a building for King Midas called the Labyrinth. Looking for ways to escape with his son, Icarus, Daedalus came up with a new idea. He would build large wings for Icarus and himself by combining the feathers of an eagle with wax and then they would fly to freedom.

Daedalus was anxious about the flight as he knew the Sun would melt the wax. Thus, he warned his son not to get too close to the Sun. Overwhelmed by the giddiness of flying; Icarus soured into the sky and then came to close to the Sun which melted the wax. His father's warning became sad truth; Icarus plunged into the sea and was killed. Thus, aviation had its first fatality.

Since then, human beings watched birds and flying creatures with great fascination and slight envy and tried to imitate them. Humans studied, tried, failed but did not give up.

The person who probably designed the first flying machine in the 15th century was a scientist and artist, Leonardo da Vinci. A century later, Francesco di Terzi started to sketch the first lighter than air ships. But humanity had to wait for more than another century for construction of an actual flying machine.

The first man-made flying machine flew on 21 November, 1783. The hot air balloon constructed by the Montgolfier brothers rose into the French sky. A few days later on 1 December, 1783, a French Physics Professor, Alexandre Charles, managed to fly with a hydrogen filled balloon.

When was the first airlift used for ´human transport built?

Paris, the capital of France, was besieged by the Germans in 1870. Paris lost all contact with the rest of France. The people of Paris, looking for a way to send messages to other cities, decided to use manned balloons. For the first time, on 23 September, 1870, Jules Darouf managed to fly over the German lines with his balloon. Jules crossed the occupation lines and landed on independent French territory three hours later.

The second aviator who crossed the enemy lines with his balloon was Gaston Tissandier. He too managed to go beyond the lines unobserved. A new age started in the transportation of messages and cargo. However, using balloons to go beyond enemy lines started to lose its initial surprise effect; the Germans started to shoot at the balloons in the sky. After a while, it was only possible to make flights at night. The world's first airlift completed more than 60 balloon flights. More than 9 tons of cargo and 155 passengers were brought to safety outside Paris. It was a huge success, although some of the balloons arrived in the Netherlands; one even landed in Norway.

When was the first controlled flight independent of the wind direction?

The first controlled and guidable flying machine was the glider constructed by Otto Lilienthal in 1891. He flew for more than 250 m starting from a hill in Derwitz, Berlin. He lost his life in a failed attempt in 1896, but his experience answered many questions and paved the way for future generations in aviation. Finally, Wilbur and Orville Wright performed the first powered flight near Kitty Hawk, North Carolina in the USA on 17 December, 1903.

After this successful experience, the excitement of powered flight spread quickly to the entire world. Governments, private entities and individuals organized big prize competitions to introduce aviation to the public and advance the technology of powered flight.

Louis Blériot flew from France to England over the English Channel on 25 July, 1909 with the Blériot XI built by him. The aircraft had a very modern appearance; the engine and the propeller were in the front, the pilot cabin was right behind them and the flight control surfaces were at the rear. In the first aircraft built by the Wright brothers, the control surfaces were in the front, the pilot was in a horizontal position on the body and the engine was at the rear driving two propellers.

When did aircraft begin to be used for military purposes?

Military aircraft began service in 1911 for some countries in the world. Naturally, they were very different from today’s warplanes, the first missions executed with these aircraft were to take military photographs and replace the unreliable balloons and zeppelins being used for this purpose.

Significant aircraft industry did not exist in any of the powerful states in Europe when World War I began. However, it soon became clear that an aircraft could be used as a powerful weapon and proved to be very effective at war. In the beginning, pilots used to fly over enemy lines and manually throw bombs from their cabins. The maneuverability and high altitude of these aircraft were enough to challenge the range of the weapons of the other side.

Significant technical developments were made during the war years. Especially the development of lightweight and powerful aircraft engines started a new era in aviation. By the end of World War I, the total number of aircraft manufactured exceeded 200,000; 48,000 of them being made in Germany and 60,000 in France.

When was the first passenger aircraft built?

When World War I ended in 1918, many countries were left with thousands of aircraft and unemployed pilots. This capacity triggered the idea of cargo, passenger and mail transport. However, the aircraft and equipment available were insufficient for public transport. Limited usable area in the hold and the short range of aircraft made it clear that new solutions were required to replace former warplanes. Therefore, larger aircraft with double or triple engines were developed. The triple engine Junkers G23/24 aircraft, developed in Germany, is the first standard passenger aircraft which opened a new epoch in public transport. This was an advanced version of the Junkers F13, the first aircraft with metal structure and coverings. In previous aircraft models, the main construction material was varnished canvas, wood and hundreds of stretched wire cables.

Who flew over the Atlantic Ocean non-stop for the first time?

The Atlantic Ocean was crossed non-stop with an airplane for the first time in 1919. British war veterans John Alcock and Arthur Witten Brown managed to fly over the Atlantic Ocean with a Vickers Vimy type double decker aircraft on 14 - 15 May, 1919. They departed from Newfoundland and their flight ended with a crash landing in Ireland. Luckily, the pilots survived this emergency landing. They were awarded for their achievement and announced noblemen.

Another important milestone in civil aviation is the nonstop flight of Charles Lindbergh over the Atlantic Ocean from New York to Paris. He crossed the Atlantic Ocean alone in a 36 hour flight with the aircraft “Spirit of St. Louis” on 20 - 21 May, 1927. The average speed of this heroic flight was around 200 km/h.

Which passenger aircraft has been manufactured the most until now?

When the Douglas DC-3 Dakota aircraft was put into service, airlines started to make good profits from passenger transport. 13,000 DC-3s were manufactured which is the largest number of aircraft of one type produced until now. The success of this aircraft was mainly due to the following innovations implemented in the DC-3:

 Flaps for Take-off and landing

 Retractable landing gear

 Low air resistance engine covers

 Passenger capacity for over 20 people

 Variable pitch Propellers

 Automatic 3 axis flight control system

How did defense requirements before World War 2 affect the development of aircraft?

Developments on aircraft gained momentum after the National Socialists came to rule in Germany in 1933. Nazis were determined to become the most powerful military power in the world by 1938. Therefore, they started to make significant investments to advance military aviation. The German Air Force was established in 1935 and, by 1939, managed to be the most powerful air force in the world.

Many developments were achieved with bomber and fighter aircraft types during the Second World War, including:

 Increased engine power

 Advanced autopilot systems

 Pressurized cabins

 Advanced ejection seats

 Introduction of radar systems

Another development was the first flight of a jet powered warplane, the Heinkel He-178 in 1939. It was possible to achieve much higher speeds with this engine. It was soon discovered that high speed presented many new problems. For example, as the aircraft gets close to the speed of sound, the air resistance increases significantly. The concept of the "sound barrier" started to be discussed. Aerodynamic specialists developed arrow head wings and managed to reduce the resistance when approaching the speed of sound.

How it came to the development of large passenger aircrafts?

Strategic needs during World War 2 led to increased dimensions of bombardment and transport aircraft. After the war, this trend continued in the USA. The six engine Boeing B-47 “Stratojet” military aircraft made its first flight in 1950 in the USA. With a speed of over 950 km/h, this aircraft reached an altitude of 12,300 m and left other fighter planes behind.

An advanced model of this aircraft, the strategic bomber aircraft B-52 “Stratofortress” exceeded 960 km/h and rose to 16,700 m. With these speed and range capabilities, the B-52 remained the most capable and efficient bomber aircraft of the western world for a long time.

The "Comet", the first jet powered passenger plane manufactured by British De Havilland in 1949 completed its test flights and started passenger service in 1952. This aircraft, which gained a bad reputation due to several accidents because the cabin structure was not designed for the pressures at high altitude, was completely withdrawn from service in 1954. In 1959, a brand new and safe model of the aircraft with all the problems solved was put on the market. But the opportunity to control the market was lost. In the meantime, the USA was planning military purpose jet powered transport aircraft parallel to Europe. A civil aviation version of the KC135 tanker plane, which resulted from these projects, was manufactured: the Boeing-707. This popular passenger aircraft made its first flight on 15 July, 1954. The secret to success of the Boeing-707, which conquered the passenger plane market, was its better technical performance compared to its closest rival, the DC-8 by Douglas; and the improved British Comet was not yet ready for the market.

Also known as “Jumbo-Jet”, the large body passenger plane Boeing-747 was a side product of another military project. This passenger plane, designed by Boeing to carry military loads, flew for the first time in 1969. When the military project was awarded to Lockheed for the C-5 “Galaxy”, Boeing quickly transformed its proposed design into the 747 passenger aircraft. Boeing strengthened its market position further towards the end of the 60s by expanding its passenger aircraft family with the medium range Boeing-727 and the short range Boeing-737 aircraft. During this period, the short range French Caravelle aircraft were also very successful in Europe. Plus, the Douglas Aircraft Company emerged as a competitor in the medium range passenger aircraft market with the DC-9 patterned after the Caravelle. In the 70s, other aircraft joined the fleet of wide body passenger aircraft initiated by Boeing. These are the DC-10 by Douglas in 1971, the Lockheed-1011 Tristar in 1972 and the European Airbus A-300 in 1972.

Today, aircraft designer’s main goals are to be ecological, consume less fuel and carry as many passengers as possible.

When was the sound barrier broken for the first time?

Military aviation chose a slightly different path from civil aviation after World War 2. The specifications for military aircraft were high acceleration and superior maneuverability at very high altitude and very high speed.

The rocket powered aircraft, Bell X-1, was the first aircraft to break through the sound barrier in 1947. Thereafter, the research aircraft X-15 reached 7,200 km/h and rose to 108 km altitude between 1959 and 1968. All these operations at “higher speed and higher altitude” also affected the civil aviation sector. The supersonic passenger aircraft "Corcorde", a joint production of Britain and France, made its first flight in Toulouse in the south of France in 1969. A Concorde was the first passenger plane to break the sound barrier with a speed of 2,200 km/h. For this speed, which was twice the speed of sound, Concorde needed to fly at an altitude of 16 to 18 km. The excessive fuel consumption and limited number of passengers prevented the Concorde from becoming a success. Only 16 aircraft were produced and included in French and British national airline fleets. Yet, it was in service cruising at twice the speed of sound, in intercontinental travel between 1976 and 2003. The only rival of the “Concorde” was from the east block by the Russian made Tupolev TU-144. Although it was not as successful as Concorde, this aircraft made about 100 flights in the Siberian sky and then was removed from the Aeroflot fleet in 1983.