In nature, anything that flies has symmetry. And in the early days of
human flight, mimicking nature made sense. But as we pushed on to ever higher speeds,
our stubborn insistence on symmetry might’ve been a mistake. In the 1950's, a brilliant NASA
engineer began to push for a radical new approach. Proving theoretically and with prototypes,
that aircraft didn't have to be symmetrical. The implications of his work are profound. It
suggests we should be flying a lot faster and more efficiently than we are today.
Since the dawn of flight, aircraft had been getting faster. In 1920, the fastest plane
could barely reach 300 kilometers an hour. By the 1940's, they were already flying
three times as fast. But there seemed to be a limit beyond which they simply couldn't go.
Pilots called it "the sound barrier". Above a certain speed, aircraft stopped
accelerating, control became increasingly difficult, and stress forces could even cause
an aircraft to break apart in mid-air. But in 1947, a daring test pilot flew an experimental
plane beyond the speed of sound. Proving that the sound barrier wasn't a barrier at all.
It’s just that supersonic flight revolved around a different set of aerodynamic principles.
In the decades that followed, engineers mastered the physics of flying supersonic,
pushing speeds ever higher. But a new challenge emerged. Designing an aircraft that would perform
well in both flight regimes. Any aircraft optimized for supersonic flight, would by
definition, fly poorly at subsonic speeds. Because the ideal wing at lower speeds was long
and straight. But for supersonic flight, it was thin or sharply swept. A shape that
struggled to generate lift at lower speeds. Engineers struggled to find a solution.
Eventually coming up with a kind of wing that could transform in mid air. Functioning
more like a straight wing at subsonic speeds and sweeping back for supersonic flight.
But variable sweep wings created their own set of problems. Pivot mechanisms had to bear immense
lift, rotational, and bending forces. Shifts in the center of lift had to be compensated for
with larger stabilizers or other systems. All of which added weight and complexity, largely
undoing performance gains. Variable sweep wings were only successfully applied to a small number
of military aircraft. None of which are still produced today. The sound barrier might not have
been an actual barrier, but it seemed that flying faster would always involve serious trade offs.
By 1955, Robert Jones had made a name for himself as one of NASA’s top aeronautical
engineers. His groundbreaking work on the delta wing, once met with skepticism,
had led to the greatest aerodynamic transformation since the very invention
of the airplane. But his life-long passion lay in an entirely different kind of design.
It was called an oblique wing. A radical concept consisting of a single wing that rotated on a
center pivot. Intuitively, it looks all wrong. As if it would simply corkscrew its way through
the sky. But through wind tunnel tests and with radio-controlled prototypes, Jones proved that
they were surprisingly stable and controllable. Because when it comes to generating lift,
the air doesn't really care whether a wing is swept forward or backwards. So it can
fly. But why build an aircraft like this? Intuitively a highly swept arrow shape seems like
the correct way to minimize drag. But that’s simply not the case. Jones demonstrated that
at transonic and supersonic speeds, the same wing when arranged asymmetrically,
had a much lower predicted wave drag. And so there was no rational reason to favor
bilateral symmetry, when it was actually less efficient. But Jones’s oblique wing
had another important advantage. It could also perform optimally at lower speeds by
transforming itself back into the ideal straight wing. And compared to variable-sweep wings,
oblique wings would be easier to build. With a single pivot mechanism handling just one force,
it would be lighter and less complex. And the center of lift would remain virtually unchanged
regardless of the wing’s position. Secret German documents uncovered after
World War Two suggest that oblique wings were even studied as far back as 1942,
although no prototypes were ever built. On the verge of an aeronautical breakthrough,
Jones and NASA engineers were about to change aircraft design forever.
This is not an ordinary plane. It has a scissor-like design. By the mid-1970’s,
NASA moved beyond wind tunnel tests to develop a large-scale,
remotely operated model that could evaluate the oblique wing’s real-world performance
and handling characteristics. Meanwhile, leading aircraft designers
Boeing and Lockheed were also asked to study oblique wings and evaluate
their potential for future commercial aircraft. Both concluded that they could lead to faster,
more efficient air travel. But it was Boeing’s study that really caught NASA’s attention.
Because by 1975, the dream of mass supersonic air travel had all but faded as Concorde looked
set to become a commercial failure. And it had everything to do with the wing.
Engineers had spent more time developing Concorde’s advanced delta wing than any
other part of the aircraft. But it was still hopelessly inefficient at low speeds,
producing so little lift that Concorde needed fuel-thirsty afterburners to take off.
And when countries banned supersonic flights over their airspace due to concerns over loud
sonic booms, flying slower wasn’t really an option. Concorde wasn't designed to
cruise at subsonic speeds, where its operating economics were terrible.
But Boeing concluded that an oblique wing airliner would have none of these problems.
Because it would be capable of flying efficiently at a range of speeds and cruise at up to Mach 1.2
without even generating a sonic boom that could be heard on the ground. And that would allow for
transcontinental flights over populated areas 50 percent faster than existing airliners.
Power requirements for takeoff, landing, and holding around busy airports would
also be a lot lower, dramatically cutting noise and pollution around airports.
NASA was impressed enough to take the next leap forward. In 1976, development began on a scaled
down version of Boeing’s design. Not a remotely operated model, but the world’s first human
piloted oblique wing aircraft. NASA’s objectives were ambitious,
but the AD-1 was modest in design, built mostly from fiberglass-reinforced-plastic and foam core.
Two tiny jet engines provided less than five hundred pounds of thrust for motivation. The
cockpit had only the bare essentials. No fly by wire or computer assistance, it would be flown
entirely by the skilled hands of a test pilot. Built on a shoestring budget, many at NASA were
cautious about investing huge resources into a still unproven concept. But the AD-1 would back up
NASA’s research with real-world data. In a total of 79 test flights, the AD-1’s wing was gradually
pivoted from zero all the way to 60 degrees. Even flown entirely by hand, control was fairly
straightforward. And at lower pivot angles, any reasonably skilled pilot could manage. But above
45 degrees, maneuvering was more challenging, with a phenomenon called cross coupling
becoming an issue. Pitching the AD-1 up or down caused it to roll left or right. While rolling
left or right caused it to pitch up or down. At a full 60 degrees, pilots had to continually
bank and yaw to the right to keep the aircraft flying straight and level.
None of these issues were all that surprising, and data gathered showed that the AD-1 would
have handled significantly better with an improved wing structure and the help
of a computerized flight control system. But the AD-1 maxed out at just 320 kilometers
an hour, nowhere near the transonic speeds, where oblique wings could begin to show their
potential. For that, NASA would have to turn to a renowned Navy fighter jet.
By the 1980's, the U.S. Navy had also taken an interest in oblique wings. Because an oblique wing
fighter could offer superior take-off performance from a carrier and increased loiter time. Both
were prized capabilities for a next generation fleet defense fighter to replace the F-14.
In 1984, the Navy and NASA signed a joint partnership to develop the first supersonic
oblique test-bed. And the F-8 Crusader was an ideal place to start. Its high wing could be
modified to accommodate an oblique wing and NASA had already experimented with the F-8
to develop fly by wire technologies. A modest thirty six million dollars were
allocated to the project. Design work was to finish by 1986, construction by 1990,
and the first flight was planned for May 1991. But after a successful design phase, the aircraft
never got off the ground. By 1986 the Navy, caught up in deep budget deficits and cost overruns on
other experimental programs, suddenly pulled funding. NASA couldn't carry the program alone,
nor could it find a new partner. In 1987, the project was officially canceled.
After nearly half a century, intensive research into oblique
wing aircraft largely came to an end. Jones never gave up on the oblique wing. He
continued his research into the 1990’s, even at the age of 80. Eventually shifting his
attention to the development of a pure oblique flying wing, a concept that promised to be the
pinnacle of aerodynamic efficiency and fly at Mach 1.5 with operating economics approaching
that of a modern subsonic transport. Over the years, dozens of studies have
demonstrated the potential of the oblique wing. And in NASA’s own words, it remains
a viable concept for large transports. But real-world advantages at transonic and
supersonic speeds have yet to be tested in flight, and the challenges of flying at
extreme wing pivots remain. Modern flight control technologies would go a long way to help realize
the advantages. But the aviation industry is conservative by nature. Aircraft today
look strikingly similar to those designed over a half century ago. The reality is,
it’s less risky for the industry to spend billions eking out single-digit gains in efficiency with a
proven design, than it is to start from scratch with a radical concept like the oblique wing.
That’s why well funded research programs like NASA's AD-1 are invaluable to the advancement
of aerospace. Jones passed away in 1999, having made some of the most important discoveries in the
history of aerodynamics. And his groundbreaking research has left many convinced that despite
obstacles, it’s only a matter of time before oblique wings take to the skies.
Aviation is full of big ideas. But some of them are a little bigger than others. In 1969,
Lockheed set out to determine just how large an aircraft could get, and what it
would mean for U.S. airpower. Lockheed's six thousand ton nuclear powered flying aircraft
carriers are some of the most fascinating and bizarre aircraft ever imagined.
You can learn about the incredible CL-1201 in my latest video, now on Nebula.
Nebula is where you’ll find hours of exclusive Mustard videos that aren’t available anywhere
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concepts. It's also where I experiment with new formats. To help explain the CL-1201,
I hired a former BBC news reporter. Engineers are confident that the reactor
will be fail-safe, even in a head-on impact with a granite mountain.
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