## Maximum Aircraft speed on the Earth

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The invention of Aircraft speeded up human life. First successful aircraft Wright flyer developed by Wright brothers had a speed of approx. 28.9 Mph (48 Km/h). Then in world war I & world war II there was a revolutionary development in the field of aviation.

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In 1947 Chuck Yeager was first human to break the sound barrier with Bell X 1. That is Bell X 1 was the first aircraft to travel faster than the speed of sound [ Speed of sound is  767.2 Mph (1234.8 Km/h) ]. The speed of Bell X 1 was approx. 957.5 Mph (1,541 Km/h).

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In 1969 passenger Supersonic Aircraft Concorde took its first flight. The top speed of Concorde was 1354.58 Mph (2180 Km/h). It was twice the speed of sound. Tupolev TU-144 was also the supersonic passenger Aircraft.

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At present time Lockheed SR-71 Blackbird holds a record of world's fastest flown aircraft.  Top speed of Lockheed SR-71  Blackbird is approx. 2200 Mph (3540 Km/h). It is approx. 3 times the speed of sound.

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North Americal X-15 is research aircraft with speed of 4,520Mph (7,274 Km/h). William J. Pete Knight flew it with top speed. It was approx. 7 times the speed of sound (6.7 Mach).

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Engineers keep on trying to increase the speed of aircraft. So what is the maximum speed which aircraft can achieve on earth?

As we know from my previous post how lift is produced by the aircraft wing. And also how drag is induced to the aircraft due to lift. Check out this post (Check out lift induced drag).

As we keep on increasing the speed of aircraft first problem we faced is when aircraft reaches near the speed of sound. As Aircraft reaches near the speed of sound aircraft Shockwaves starts forming over a wing of aircraft. And when aircraft crosses sound barrier drag produced due to shock waves will make it difficult for a pilot to control aircraft.
But this problem has been solved by making some modifications in aerodynamic shape of the aircraft wing. Aerofoil used for supersonic aircraft are a diamond shaped.

Another problem due to supersonic flight is a Sonic boom. As Aircraft crosses sonic barrier sonic boom forms which have an ability to break glasses on the ground also it can create hearing problems to humans on the ground.The sonic boom is one of the reasons for why at present there are no any functioning supersonic passenger aircraft.  Aircraft industries are trying to solve this problem. NASA was successful in reducing sonic boom up to certain extent using spike cone to F15 Aircraft.

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After this problem is solved we will be able to see supersonic passenger aircraft. So at present speed of sound i.e. 1 mach(767.2 Mph (1234.8 Km/h)) is a limit for the speed of  passenger aircraft. But not for combat aircraft. There are lots of combat aircraft with their top speed greater than a speed of sound.

Let's assume that we solved all the problems due to a high speed of aircraft. Then what will be the maximum speed of aircraft?

If we keep on increasing the speed of aircraft using rocket engines(Rocket propellant) at speed of 24987.26 Mph (11.1705 Km/s) Aircraft will leave earth's atmosphere at a height of 12 km from the surface of the earth.This velocity [24987.26 Mph (11.1705 Km/s)] is known as Escape velocity. Wanna know how? Check out now

But remember that as the height from the surface of the earth increases the density of air keeps on decreasing. so at that height aircraft won't get much lift on the wing. So maneuverability methods of aircraft won't be much effective which we use in a normal air(Ailerons & Rudders). But maneuverability is possible by thrusters. once aircraft is out of the atmosphere there won't be much air resistance, so no need of much power for thrust. This is also a reason for why we use space shuttles for space missions & not aircraft. Space shuttles have wings for re-entry purpose so it can glide & land successfully.

Image from:- Wikimedia

And again even if increase the speed of aircraft hypothetical there is nothing which can travel faster than speed of light!!!