Can you imagine flying from New York to Los Angeles in less than 15 minutes? Although it seems incredible, there is an aircraft capable of this feat: meet NASA’s X-43A Hyper-X, an experimental vehicle that does not look like a normal airplane and does not yet carry commercial passengers.
This NASA engineering marvel holds the record for speed in the atmosphere. It also features a type of aircraft engine (the “scramjet”) that had never before been tested outside of a laboratory.
Fastest atmospheric combustion-engine air vehicle
The problem with developing such an absurdly fast vehicle does not lie in aerodynamics. The problem is that conventional jet engines fail at this type of hypersonic speed: the compressor blades melt and the air chokes when reduced to subsonic speed.
In general, an aircraft that flies too fast reaches a point where its engine runs empty and burns out… or stalls. Developing an alternative engine was the key to the problem. Scientists and engineers developed an engine with no moving parts, which uses the aircraft’s extreme speed and the shape of its structure to compress the air naturally.
How does it work? Well, air enters and combustion occurs while the air continues to travel at supersonic speed (i.e., faster than even sound), all through the engine. It has its merits, since it’s like keeping a match lit in the middle of a hurricane.
Unlike traditional rockets, a scrambled engine “breathes” oxygen from the atmosphere, which reduces weight because it does not need to carry heavy oxidizer tanks like other aircraft.
The Hyper-X Program: NASA’s Odyssey
This engineering process did not happen overnight, but took decades: the X-43A was created as part of the Hyper-X program. Conceptual development began as early as 1996. The total investment cost is estimated to have been approximately US$230-250 million over eight years.
The X-43A was initially conceived as a disposable proof of concept; in fact, after the first flight test, they planned to let it crash into the Pacific Ocean. This aircraft obviously had some failed attempts: in the first test on June 2, 2001, the rocket booster veered off course and the vehicle was destroyed.
However, the first success came three years later: on March 27, 2004, the aircraft reached Mach 6.83. In the context of aviation and speed, Mach is not a fixed speed unit like “kilometers per hour.” Mach is a relative measure that indicates the ratio between the speed of an object and the speed of sound in that same environment.
When we say that the X-43A reached Mach 9.6, it means that it was flying 9.6 times faster than the speed of sound in the air at that moment and place. It is listed as the first scramjet-powered flight in history.
What is Mach 9.6 technology really for?
Believe it or not, the X-43A was not designed to be a commercial passenger aircraft or a military vehicle. It was simply devised to obtain real-life data on how materials interact with high-speed aerodynamics and to study combustion control. We’re not going to pretend that NASA technology isn’t fundamental to the development of modern military hypersonic systems.
Thanks to NASA projects, we now have a vast knowledge of the ability to use atmospheric oxygen to save weight in aircraft. Ultimately, NASA provided the data for follow-on military programs, such as the Boeing X-51 WaveRider.
The X-43A was a small machine ($250 million and only 3.7 meters long, almost as expensive as a LEGO set /s) with a giant impact, moving scramjets from theory to reality. We might not be able to travel this fast in our daily lives, but we can only hope that some day we don’t need to huddle for more than 12 hours during a Transatlantic flight.