Just a couple of decades ago, aviation had some rules. If you wanted to fly fast within the atmosphere, you used a jet engine. The champion here was the SR-71 Blackbird, designed by Lockheed Martin, but it maxed out at Mach 3. If you wanted to go faster, you needed a rocket. But that also meant carrying its own oxygen and operating more like a spaceship than an airplane. This was before NASA’s X-43A came along.
The Previously, scientists had only crunched the numbers in computer simulations and wind tunnels.
The X-43A could not take off on its own. A massive B-52B bomber would give it that initial boost, taking the X-43A up to about 40,000 feet. From there, he would drop the ship, which was strapped to the nose of a modified Pegasus rocket. The rocket would then fire, lifting the X-43A to its test altitude.
The test was not a great success. The first attempt, in June 2001, failed after the booster failed. This forced the team to spend two years redesigning their approach. They returned with a vengeance in 2004. In March, the craft reached a dizzying speed of Mach 6.8. Then, on November 16, 2004, a second vehicle roared through the sky at an incredible speed of Mach 9.6, or nearly 7,000 miles per hour, at an altitude of about 110,000 feet. The engine only burned for about ten seconds, but in that small window it demonstrated that air-breathing hypersonic flight was possible.
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Why scramjets are so important
To help achieve those impossible speeds there is a technology called scramjet, which basically means “supersonic combustion ramjet.” Unlike a normal jet engine that uses fan blades to crush air, the working principle of a scramjet is that it has no moving parts. Instead, it uses the sheer speed of the plane to compress the incoming air. The cool part is that the air stays supersonic throughout the engine as fuel is injected and burned. This is a great engineering challenge because you have to sustain a flame in an air flow that moves faster than sound. It’s also why scramjets can’t operate at low speeds and need a rocket to run them fast enough to “ignite”.
But all this trouble is not in vain, since the great advantage is that scramjets breathe oxygen from the atmosphere, unlike rockets that have to transport their own heavy oxidizer. This means they can be smaller, lighter, or carry more payload. It’s all really fascinating, but the Hyper-X program was never intended to produce a production aircraft, or even be an ongoing mission. Rather, from the beginning it was planned as a three-part research project. After those two successful flights in 2004, NASA had all the important data it needed and concluded.
How the X-43A is still alive
The Boeing X-51A takes to the skies – Boeing
However, the Hyper-X program never completely died. The baton was passed to the US Air Force, which was tasked with figuring out what would come next. The next step turned out to be the record-breaking Boeing X-51 WaveRider, a direct successor that took what the X-43A started and ran with it. In 2013, the X-51 demonstrated how far the technology had come by achieving a scramjet-powered flight that lasted a whopping 210 seconds.
But the real story is the domino effect that little ship had. The data extracted from their flights became a kind of manual for all subsequent American hypersonic programs. Engineers learned some important lessons, such as the fact that the entire vehicle must be designed as a single piece with the engine, and gained a treasure trove of information on how to handle the heat of hypersonic flight.
Even today, that 20-year-old flight data remains the “answer key” that engineers use to verify their modern computer simulations to design new vehicles. It is also what prevents the dream of putting a plane directly into orbit from being pure fantasy.
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Read the original article on SlashGear.