The X-51: making aeronautical engineering sexy again (Photo credit: United States Air Force.)
The space shuttle Atlantis landed for the last time yesterday while the hypersonic X-51 test aircraft flew for the first time. The X-51 "Waverider" flew for a little more than three minutes, hitting a top speed of Mach 5. The X-51 is not a replacement for the shuttle, but in contrast to the poor progress on ways to get into space, hypersonics are scorching a path forward in aeronautics.
Research on hypersonics has been going on for four decades, but it took until the 21st century for the first hypersonic vehicles to fly. The math gets extremely tricky. It's only been pretty recently that computing power has been overwhelming enough to begin replacing wind tunnel and flight testing for much slower moving objects like commercial passenger jets. Hypersonic flight presents a brand new set of modeling challenges. The extreme speed and temperatures mean you have to model the effects of, for instance, knocking oxygen atoms off nitrogen atoms.
However, actual hypersonic flight appears to be more a matter of grit than a product of particular advances. Michael Smart, head of the pioneering Hyshot Group in Australia says:
Computers have definitely given us more confidence in our predictions of scramjet performance, and CAD based manufacturing has also helped. I actually think it's more to do with different personalities pushing to “fly stuff” rather than just testing on the ground that has really moved things forward. As an engine guy who mainly tests on the ground, having to adapt my engines to a real flight vehicle has actually changed the way I design engines.
There are also interesting engineering parallels with synthetic biology. In both, elements of the design are highly interdependent in very complicated ways. Also (and perhaps consequently), design elements perform more than one function. The Waverider is in a sense, a flying engine, the interdependence of airframe and propulsion becoming extreme with the speed of the aircraft. Fuel serves not only to propel but to cool the X-51.
It's unlikely hypersonics will solve our space launch problem and right now the applications imagined are military. However, technologically, it's real deal, genuine gee-whiz stuff.
----------------------------------------------------
Related:
The future of spaceflight: “social welfare for nerds”
Human Space Exploration: Scaled Back to Vanishing