Why The Air Force, NASA?
by Paul McGoldrick
The theory of the ramjet has been around since the notion of jet engines
was conjured in the 1930s; to say that the rite of passage for the technology
has been long in coming would be putting it mildly, but the very notion
of having to lift an aircraft off the ground before the technology can work
is a rather daunting "oops." Getting rid of the pieces of a jet
engine that move -- the bits that break spectacularly, when they do -- is
a dream we should perpetuate. Unfortunately, the ramjet has really been
confined to missiles.
Taking the technology of compression-by-design to new heights by increasing the speed of combustion in the scramjet (supersonic compression ramjet) using the atmosphere as the oxidizer was a remarkable development, and NASA stepped into the breach with a test bed in the form of the X-43A, a vehicle dropped at altitude from a modified B-52B, and then boosted up into the atmosphere where it would fly unaided. Three vehicles were to be built, each with a slightly different air intake configuration.
The first flight in 2001 was a disaster when the Pegasus booster had to be destroyed, along with its scramjet payload, after it veered off course. That allowed the first successful flight of a scramjet -- although not free-flying -- by the University of Queensland (Australia) on August 16, 2002,when their vehicle reached Mach 7. The second NASA flight was sweet, with the vehicle reaching Mach 7 on March 24, 2004. NASA announced the third flight was to take place on November 15 or 16, 2004 in the test range over the Pacific, just northwest of Los Angeles. And, indeed, on November 16 the vehicle reached Mach 9.8, very close to the target Mach 10.
NASA was extremely pleased with itself, and rightly so. The planned way to go beyond the X-43A was the X-43C, a vehicle that would use its solid hydro-carbon fuel as a coolant for the engine and would specifically demonstrate transitioning from supersonic (>Mach 1) to hypersonic (>Mach 5) velocities. But the agency quietly pulled the plug on that further program even before the second flight. Why?
The official line was that the search for a practical hypersonic transport was not related to the agency's needs for space exploration, particularly as called for by the imagination of the country's chief executive. What happened to the "Aeronautics" in the NASA acronym?
There is still a slight mystery about whether the X-43B, a larger version of the X-43A and X-43C, and which was due to follow the "C" (logical, right?) or the combined flight cycle X-43D were also officially cancelled, but with the budget priority changes they almost certainly have been taken off the table.
Remember that all the equipment used in this NASA testing has also been
marked "U.S. Air Force." We're not likely to see hypersonic passenger
transportation anytime soon. We will, however, see weapons like cruise missiles
dropped from aircraft that are safely outside a theater of war, to reach
their targets within a few minutes instead of thirty or forty minutes. Boy,
we'll be able to kill so much faster! So much for the peaceful uses of science.