Engineering is a wonderful branch of science. It allows one to analyze, design, and create things that might seem impossible. Engineering is in everything, ranging from children’s toys to the huge spacecraft and rovers. Basically, anything that is fun and exciting has some engineering concept applied in it. Not all engineering concepts are as straight forward as Newton’s Third Law of Motion. Some are so mind-boggling that most people would refuse to even acknowledge them. Here, in this article, we have listed 10 such engineering concepts that most people will refuse to believe.

1 A rocket can transport astronauts into space in less than ten minutes, but it takes hours, and even days, to dock it with the International Space Station.

In space, the International Space Station (ISS) is moving at a speed of 27,576 km/h. On Earth, even the fastest aircraft can only move at the speed of around 2,550 km/h. Catching up to an object moving as fast as the ISS is an incredible feat. The spaceship or rocket sent to ISS would have to get to the same height and be at the same velocity. This is quite hard to achieve. So, instead of chasing it, the astronauts let the ISS chase the spacecraft. Even though it may sound simple, it is a very complicated process.

Traveling at an incredible speed, a spacecraft can leave the Earth’s atmosphere within minutes. Once it reaches space, astronauts fire the rockets parallel to Earth. This makes the spacecraft go into an orbit around Earth, but it’s lower than the orbit of ISS. Then the astronauts perform a “Hohmann Transfer,” which makes the spacecraft take a higher, circular orbit. Surprisingly, no one can predict perfectly where the second circular orbit will be. So, the astronauts perform a series of short, brief, correction burns so that the spacecraft can reach the right place in orbit. During this period, the spacecraft orbits once around the Earth every 86 minutes – 4 minutes faster than ISS. This small timing difference is the key to reach ISS.

After a series of correction burns comes the final step – a second Hohmann Transfer just as the spacecraft surpasses the ISS. The spacecraft would be now 408 km above the Earth’s surface, in the same circular orbit as the ISS, and right in front of it. Then the spacecraft makes a U-turn and the astronauts fire its engines one last time to slow it down to let the ISS catch up. Then both the spacecraft line up, and the mission can be completed. This whole process might take anywhere from a few hours to even days to complete. (1, 2)

2 Running a fridge makes the room hotter, and if the fridge door is left open, the room will warm up even faster.

Imagine being cooped up in a room during the summer. What will you do if the room has no windows but one perfectly working refrigerator? Most people will open the fridge door so that it can cool the whole room. If you do this, then the cool air from inside the fridge will be released and give you relief, but that is only temporary. After some time, you will sense that instead of cooling down, the room is actually getting warmer. Believe it or not, it actually happens. Opening a fridge door will never lower down the room temperature in the long run, rather it will make the room warmer.

To understand why you need to understand that the refrigerator can’t actually produce cold. A fridge is basically a heat engine in reverse. What it does is move the heat from one place to another. When we place food inside the fridge, the temperature increases. The fridge starts cooling itself and the heat is released outside in the room. So, even when the fridge door is closed, it heats up the room. When the fridge door is open, the cold air instantly goes out and brings the temperature down a bit, but as the heat inside the fridge increases, it draws in more energy in the form of electricity. After some time, the heat transferred from the cooling coils of the fridge to the room becomes greater than the heat removed from inside the fridge. Thus, we end up with a warmer room. If you are wondering how air conditioners cool your house, then take note that a part of the unit is always installed out of the house. This part has the cooling system takes the heat from inside the air conditioner and releases it outdoors. (1, 2)

3 Suction is actually an illusion. During suction, the object doesn’t get pulled in, rather, the air pressure around the edges and the internal pressure of the object pushes it in. Also, suction does not exist in space because space has no air.

What is a vacuum? People who have a basic idea about it will reply that it is a space that is completely devoid of matter and it sucks any object into it. Most people believe that this is how a vacuum cleaner works, by creating a vacuum which sucks the dirt, dust, and grime inside it. Wrong. This is not how vacuum and suction works. We all have simply got the basic concept of suction wrong.

Suction occurs only when there is a difference in air pressure. To understand it, let’s perform an experiment. Take a straw and put a finger on one of its ends. Taking the other end in your mouth, suck out the air. You will feel the skin of your finger being pulled inside the straw. Usually, people think that sucking out the air creates a vacuum inside the straw, and this vacuum sucks in the skin. But this is not what happens. Actually, when we suck out the air from the straw, the pressure inside it drops. The air pressure around the edge of the other end and our internal body pressure pushes the skin inside the straw.

Now about the suction in space – suction doesn’t occur in space. Actually, it cannot occur as there is no air in space. No air means no air pressure, and so, no air pressure difference. Space doesn’t suck anything. (source)

4 The internal operating temperature of airplane engines is higher than the melting point of the turbine blades. They are just very efficiently cooled.

In a typical commercial jet engine, fuel burns in the combustion chamber producing temperatures of up to 2,000 degrees Celsius. The metal in this part of the engine begins to melt at 1,300 degrees Celsius which is a lot lower than the temperature produced during combustion. So, ultimately, every time fuel burns in the combustion chamber, all the metal parts including the turbine blades should just melt away and the engine would fail. But this doesn’t happen thanks to an advanced cooling technique installed in the plane’s engine.

For high engine efficiency, airplanes must have turbine blades that could work at high turbine inlet temperatures. The most efficient metal that can demonstrate those properties at such high temperatures is nickel alloys. That’s why turbine blades are made of nickel alloys, but still, their melting point is lower than the temperature to which it is subjected. That’s why turbine blades have multiple, small holes. To prevent the blades from melting, cool air is forced out of these small holes onto the blade. The cool air prevents the metal from melting without detracting from the overall performance of the airplane’s engine. (source)

5 Contrary to popular belief, using a smaller pipe does not increase water pressure. However, restricting the opening size increases the speed of water as the same volume of water per second passes through the smaller hole.

A misconception that often persists in the lawn sprinkler industry is that using progressively smaller pipe sizes will help keep the water pressure high. It is believed that as water moves through the pipes with progressively smaller sizes, the pipes squeeze the water increasing the pressure high enough to operate the sprinklers. It would be really nice if the sprinklers worked this way as it would eliminate the need for pumps, but unfortunately, it doesn’t work.

This misconception prevails because when we press our thumb over a pipe’s end, the water comes out at a greater speed. To understand this, think about Bernoulli’s Principle which states that as the speed of a fluid increases, the pressure of that fluid decreases. So, according to this principle, as the water comes out at greater speed when we place a thumb over the pipe, the pressure must decrease! This is called the “Venturi effect,” and this is the reason why using progressively smaller pipes would actually decrease the pressure instead of increasing it.

When we put a thumb over the end of the pipe, the speed of water increases. Restricting the opening size restricts the flow of water throughout the pipe. As the water flows more slowly, pressure loss due to friction from the pipe surface decreases. Since less pressure is lost, the pressure at the end, where the thumb is pressing, increases and causes the water to come out at greater velocity. Ultimately, pressing a thumb doesn’t create any new pressure, it just trades reduced flow for increased pressure. (source)