Traveling at Supersonic Speeds: How Fast Is Mach 5?

How fast is Mach 5, really… Goose, Maverick, and Rooster know it — do you? 

The “Top Gun” franchise popularized the term “Mach speeds,” but they’re a real unit of measurement used in aviation to describe the ratio of the speed of an object to the speed of sound. In an era of global aviation races, it’s important to know what Mach speeds are and how they affect travel around the world.

Most passenger planes fly below Mach speeds; in other words, they don’t break the sound barrier when they fly. Breaking the sound barrier is usually reserved for pilots in the military or research capacities who need to travel great distances in short amounts of time. Interestingly, though, Mach speeds aren’t a specific miles-per-hour number. Based on air temperature, planes can reach Mach 5 (or any other Mach speed) at a different speed. For example, a plane flying around sea level may break the sound barrier and hit Mach 1 at around 760 miles per hour, while a plane 60,000 feet above sea level can hit Mach 1 flying 660 miles per hour. It’s all about the ratio.

Learn more about Mach speeds; specifically, how fast is Mach 5, how to break down the speed of sound, and what speed in miles per hour the other Mach speeds reach.

How Fast is Mach 5? 

Mach 5 is approximately 3,836.35 miles per hour. Mach measures the speed of sound, so the exact number of Mach 5 will vary depending on the medium an aircraft flies through when it measures its Mach speed. 

Understanding Mach Speed

Mach speed, named after the Austrian physicist and philosopher Ernst Mach, describes the ratio between the speed of sound and the relative speed of an object. It’s used in aeronautics as a dimensionless quantity for pilots to communicate their true airspeed.

The levels of Mach speed relate to the speed of sound, though there isn’t a direct relationship like there is for temperatures on different scales. Instead, Machs use a formula of local flow velocity over the speed of sound in the medium. The medium causes the indirect relationship; depending on the medium in which a plane flies, its miles-per-hour speed will be different to reach a certain Mach speed.

Not every plane can go Mach 5. In fact, very few commercial flights, unless specially designed for those speeds, can travel at Mach 5. A plane’s ability to fly Mach 5 comes down to the construction and material of the plane, as well as the engine it has. Most commercial passenger aircrafts fly between Mach 0.6 and Mach 0.9.

The fastest Mach speed ever recorded was Mach 9.6. This speed, achieved by NASA’s unmanned hypersonic aircraft “NASA X-43” is the fastest Mach recorded as of July 2023. The fastest Mach reached by a manned aircraft is Mach 6.72. 

Finally, understanding Mach speeds comes down to a general regime classification like the following:

• Below Mach 1 travel is subsonic, which most propeller-driven turbofan aircrafts travel at. 
• Mach 1.2 is the top speed to transonic.
• Between Mach 1.2 and Mach 5 is supersonic travel.
• Hypersonic travel is any travel between Mach 5.0 and 10.0.

No craft has hit a Mach speed of over 9.6, and no human has traveled faster than Mach 6.7.

How Fast Is Mach 5 Compared to Other Machs?

Breaking Down the Speed of Sound

What exactly is the speed of sound?

The speed of sound describes how fast the wave or vibrations of sound pass through a certain medium,  or more broadly, matter. If in dry air at 30 degrees Celsius, the speed of sound is 343 meters per second. Sound travels much slower than light, which is why you see lightning strike before you hear the crack of thunder that heat makes. Sound can also travel through a vacuum, and it travels faster through materials like steel than air because the particles are closer together and more stable.

Ultimately, the speed of sound depends on the elasticity, temperature, humidity, and density of its medium. For example:

• Sound travels slower when a medium is dense because the particles are larger and it takes more time to vibrate larger particles.
• Particles at a higher temperature have more energy and allow sound waves to travel faster, so sound travels faster at higher temperatures.
• Sound travels faster in humid air. The more humid the air is, the less dense it is, and as mentioned above, the less dense a medium is, the faster sound can travel. 

“Top Gun” often references the speed of sound and Mach speeds in its movies. Any movie or pop culture media that has something to do with jets, pilots, and flying aircraft around the sound barrier will discuss the speed of sound in their movies and television shows. However, they’re not always accurate with the science they use. 

Achieving Mach 5: Technological Challenges

The technology required for supersonic flight differs from aircrafts traveling at subsonic or transonic speeds. Most of the time, titanium or titanium alloys create these crafts’ fuselages. In addition, because these crafts need to break through the sound barrier, they need an aerodynamic design and powerful engines.

Several startups have a passion for revolutionizing air travel to make supersonic and hypersonic flights a commercial product, but the reality of the market lies at least five years away. Hermeus, a start-up in Atlanta, Georgia, even created a new business model for the commercial flight they want to create. 

Serving business and first-class travelers, Hermeus’ main jet would ferry passengers from New York to London in about an hour and a half. That saves nearly a half day of travel; as the usual flight time between the two cities averages around seven hours. 

Today, start-ups invest millions in research and development to create engines and designs of aircrafts that can support air-breathing planes at a speed of Mach 5, as the current fastest air-breathing plane only reached Mach 3.3. 

Beyond Mach 5: Hypersonic Speeds

Beyond Mach 5, hypersonic speeds propel unmanned crafts further to test the limits of the physical and engineering worlds. While humans remain unable to travel at hypersonic speeds, leaders in aeronautic industries discuss the many applications these speeds could have for trade, exploration, and more. 

The Future of Supersonic Travel

What does the future of supersonic space travel look like?

While the flights will cost a pretty penny, public demand exists for supersonic travel. According to 2023 research, 97% of global premium passengers would fly on a supersonic airplane for an international trip; a percentage up from 81% in 2021. 

As the world makes a foray into supersonic travel, several agencies caution the innovation based on environmental impacts like the depletion of stratospheric ozone and jet fuel controversies.

Faster Than the Speed of Sound

At Mach 5, humans would travel 3,836.35 miles per hour — or over a mile a second. As technology continues to evolve, Mach speeds will grow in popularity and demand. In fact, several hypersonic startup tech companies already plan Mach 5 passenger travel, with plans to have physical aircrafts built by 2029.

The photo featured at the top of this post is © agsaz/Shutterstock.com