Mach how fast

And when it comes to breaking this barrier, scientists use what is known as a Mach Number to represent the flow boundary past the local speed of sound.

In other words, pushing past the sound barrier is defined as Mach 1. So how fast do you have to be going to do that? However this term is more loaded than you might think. The truth is that a Mach Number is a ratio rather than an actual direct measurement of speed. And this ratio is due to the fact that the speed of sound varies from one location to the next, owing to differences in temperature and air density. This is the loud, cracking sound that is associated with the shock waves that are created by an object traveling faster than the local speed of sound.

Examples range an aircraft breaking the sound barrier to miniature booms caused by bullets flying by, or the crack of a bullwhip. Basically, the speed of sound is the distance traveled in a certain amount of time by a sound wave as it propagates through an elastic medium.

As already noted, this is not a universal value, but comes down to the composition of the medium and the conditions of that medium. But even that is subject to variation.

However, scientists tend to rely on the speed of sound as measured in dry air i. As with most ratios, there are approximations and categories that are used to measure the speed of the object in relation to the sound barrier.

This gives us the categories of subsonic, transonic, supersonic, and hypersonic. This categorization system is often used to classify aircraft or spacecraft, the minimum requirement being that most of the craft classified have the ability to approach or exceed the speed of sound. For aircraft or any object that flies at a speed below the sound barrier, the classification of subsonic applies.

This category includes most commuter jets and small commercial aircraft, though some exceptions have been noted i. Since these craft never meet or exceed the speed of sound, they will have a Mach number that is less than one and therefore expressed in decimal form — i. Typically, these aircraft are propeller-driven and tend to have high aspect-ratio slender wings and rounded features. If the aircraft passes at a low speed, typically less than mph, the density of the air remains constant.

But for higher speeds, some of the energy of the aircraft goes into compressing the air and locally changing the density of the air. This compressibility effect alters the amount of resulting force on the aircraft.

The effect becomes more important as speed increases. But a sharp disturbance generates a shock wave that affects both the lift and drag of an aircraft. The ratio of the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects. Because of the importance of this speed ratio, aerodynamicists have designated it with a special parameter called the Mach number in honor of Ernst Mach , a late 19th century physicist who studied gas dynamics.

The Mach number M allows us to define flight regimes in which compressibility effects vary. There is no upstream influence in a supersonic flow ; disturbances are only transmitted downstream.

The Mach number appears as a similarity parameter in many of the equations for compressible flows , shock waves , and expansions. When wind tunnel testing, you must closely match the Mach number between the experiment and flight conditions. The compressibility of the air alters the important physics between these two cases. The Mach number depends on the speed of sound in the gas and the speed of sound depends on the type of gas and the temperature of the gas. The speed of sound varies from planet to planet.

On Earth, the atmosphere is composed of mostly diatomic nitrogen and oxygen, and the temperature depends on the altitude in a rather complex way. Scientists and engineers have created a mathematical model of the atmosphere to help them account for the changing effects of temperature with altitude.