Traveling at Supersonic Speeds: How Fast is Mach 9

Faster than the speed of sound, Mach 9 travel is similar to a spacecraft returning to Earth through the atmosphere. It’s fast, it’s hot, and it’s fascinating to learn more about how quickly humans can will their inventions to travel.

Discover more about Mach 9: how fast it is, if humans can travel at that speed, and which aircraft, if any, can travel at that speed. 

What are Mach Numbers?

Mach numbers describe the speed of an object relative to the speed of sound.

Named after the Austrian physicist Ernst Mach, Mach numbers came about in 1929 when Jakob Ackeret proposed it. The aeronautical engineer, widely believed in industry circles to have been the foremost authority on aeronautics in the 1900s, also led the research to calculate the lift and drag on a supersonic airfoil.

Mach regimes follow a basic framework for the speed of flight travel, explained in the following chart:

How Fast Is Mach 9? 

Mach 9 is around 6,905.42 miles per hour in a temperate environment with an average air temperature. It describes roughly nine times the speed of sound.

If something is traveling at Mach 9, you can understand that it’s traveling nine times faster than the speed of sound, or at a hypersonic speed of Mach 9. The actual speed of something traveling at Mach 9 differs based on the air temperature and physical design of the object. 

Compared to other well-known things that travel quickly, the velocity of Mach 9 is nearly incomprehensible. Something traveling this fast is three times faster than a speeding bullet and over nine times faster than a commercial airplane like the Boeing 747.

Can Humans Travel at Mach 9?

No, humans cannot travel at Mach 9. The fastest Mach a human has ever traveled was Mach 6.7 in 1967. At the height and air temperature at which the pilot flew, Mach 6.7 measured about 5,140.7 miles per hour.

In recent years, innovative space technology companies have worked to create an aircraft that will fly passengers at Mach speeds around the globe. This revolutionary travel will enable humans to travel at lower Mach speeds, though. Commercial airliners will travel at supersonic speeds to start, not hypersonic like Mach 9.

Mach 9 travel for humans, based on the current technology on the market, remains a way off.

Aircrafts Flying at Mach 9

In 2004, NASA’s X-43 aircraft, a scramjet, set the Guinness World Record for the fastest speed in a jet-powered aircraft: Mach 9.6. This aircraft actually smashed its own record; in March of 2004, it’d set the record for the fastest flight at Mach 6.8. Only a few months later, it shattered its own world record. Since 2004, physicists and engineers haven’t recreated an aircraft that travels faster than Mach 9.6. Because of this discontinuance of construction, no other aircraft exist in the world that can travel as fast as the X-43. The closest are the North American X-15 with a top speed of Mach 5.8, the Lockheed YF-12 with a speed of Mach 2.9, and the Lockheed SR-71 Blackbird with a top speed of Mach 2.8.

Mach Speed vs. G-Force

When discussing mach speeds and traveling faster than the speed of sound, it’s easy to also think about G-force and travel that makes you feel weightless. However, Mach speed and g-force are very different and not directly convertible. For example, it’s incorrect to ask how fast, in Mach speed, someone is traveling if they’re “pulling 10 Gs.” 

G force stands for “gravitational force equivalent,” so it makes sense instead to ask what the g-force of something traveling at Mach 9 is. If it’s moving at a constant speed, the g-force would be zero. If a starting velocity exists, as well as distance traveled and time frame, you can calculate a rough estimate of the g-force endured to reach a certain Mach speed.

9 Times Faster Than the Speed of Sound: Mach 9

While commercial aircraft and humans can’t travel at Mach 9 yet, we have achieved building an airplane that broke Mach 9.0. As technology continues to evolve, it will be fascinating to discover just how fast we’re able to push the limits of travel.