Oct. 1, 2009 -- Bullets. Artillery. Horse whips.
For a time, they all could do something humans only dreamed of: travel faster than the speed of sound.
But in the mid-1940s, developments in aviation technology soared. And in 1947, fighter pilot Chuck Yeager became the first man to ever exceed Mach 1.
After Yeager's most famous flight, the military continued to break records in airspeed, even developing an aircraft that could travel six times the speed of sound. But it wasn't until years later that Mach-breaking technology moved beyond the military.
On Oct. 1, 1969, the Concorde 001, a joint British-French venture, traveled faster than the speed of sound for the very first time. It was the aircraft's 45th test flight and it held Mach 1.05 for 9 minutes at 36,000 feet and 75 miles from Toulouse, France.
It wasn't the first commercial aircraft to break the so-called "sound barrier." A few months earlier, the Russian Tupolev Tu-144 became the first commercial airliner to exceed the speed of sound. But unlike its competitor, the Concorde went on to have a relatively long life, carrying passengers across the Atlantic Ocean until it was retired in 2003.
'Sound Barrier' Hype Started in Lead-Up to WWII
"It was terrific," said Bob van der Linden, chairman of the aeronautics division at the Smithsonian's Air and Space Museum, who was a passenger aboard the Concorde's final flight.
Flying at Mach 1 is a little loud, he said, but otherwise it doesn't feel especially different from flying typical airliners.
And as for the entertainment?
"There is no movie," he said. Watching the plane pick up speed is thrilling enough.
"Everyone's eyes are glued to the Mach meter. As soon as it turns Mach 1, everyone applauds. At Mach 2, everyone applauds again," he said. "[Traveling] twice the speed of sound. That's just cool."
The hype surrounding Mach speeds and breaking the "sound barrier" started in the lead-up to and during World War II, said Peter Coen, principal investigator of the Supersonics Project at NASA's Langley Research Center.
The Myth of the 'Sound Barrier'
As pilots approached the speed of sound (which varies depending on the type of medium and the temperature of the medium), they would encounter control issues, he said.
"There were a lot of near crashes and incidents associated with flying near the speed of sound," he said. "It developed a mythology that there was a sound barrier that caused airplanes to crash when they approached the speed of sound."
But though the Concorde was retired for economic reasons, Coen said he thinks there might be a day in the far future when supersonic travel goes commercial again.
"The goal of our project is to overcome some of the barriers that made things like the Concorde ... not successful as commercial vehicles," he said.
Two of the major barriers are sonic booms and the considerable amount of fuel required to achieve and maintain Mach speed.
Because they generate sonic booms, which cause incredibly loud explosions and could even shatter windows depending on how low the aircraft is flying, commercial supersonic flights are prohibited from flying over land.
The Smithsonian's van der Linden said about one ton of fuel per seat was needed for each of the Concorde's trans-Atlantic flights.
Still, Coen said that by 2020, it's possible that small 50-person supersonic commercial aircraft could become the Concorde's successors.
But the Concorde has had some supersonic company. Here are a few other Mach-breaking machines.
Sound Barrier Broken for the First Time
On October 14, 1947, Air Force Captain Charles E. "Chuck" Yeager became the first to break the sound barrier while flying the Bell XS-1. According to NASA, the event was so significant that the fact that Mach 1 had been exceeded was declared "top secret." The government didn't acknowledge the feat until reports were leaked to the press.
Blackbird Designed to Travel at Three Times the Speed of Sound
The SR-71 Blackbird, which was developed in secrecy for the U.S. military during the late 1950s, is considered the fastest turbo jet powered plane. Developed for reconnaissance missions by Lockheed, the planes were designed to cruise at Mach 3.2 at altitudes up to 85,000 feet. The maiden Blackbird flight was Dec. 22, 1964. But it was retired in 1991, Coen said, as satellites overtook the Blackbirds' reconnaissance capabilities.
Rocket-Powered X-15 Flies at Mach 6.7
On Nov. 9, 1961, the X-15, a joint program between NASA, the Air Force, the Navy and North American Aviation Inc., became the first aircraft to travel an astounding six times the speed of sound. The experimental rocket-powered aircraft's first test flight was in 1959 and over the years it picked up speed. It was meant to help engineers explore control, guidance and navigation issues and took its last flight in 1968.
Thrust SSC Breaks Sound Barrier on Land
The sound barrier hasn't only been broken in the sky. On Oct. 13, 1997, Andy Green became the first to achieve an officially timed supersonic drive through a measured mile. The British jet car ThrustSSC made two Mach-breaking runs across Nevada's Black Rock desert at 759.333 mph and 766.109 mph respectively, according to CNN. The speed of sound was calculated that morning at 748.111 mph.