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Routine Hypersonic Flight: The Final Frontier of Aeronautics | Kevin Bowcutt | TEDxSnoIsleLibraries


Translator: Geoff Jensen
Reviewer: Denise RQ What if you could wake up
anywhere on the West Coast, go to work for a few hours,
and at about lunchtime, head to the airport and catch
a two-hour flight to Tokyo? (Laughter) Arriving morning their time,
afternoon our time, you could have a business meeting and return home in time to sleep
in your own bed the same day. Or what if you could order sushi on Amazon Fresh one afternoon from Tokyo chef Jiro Ono
and receive it in time for dinner? Yes, that would be an expensive dinner (Laughter) but it would be good. Or perhaps most exciting of all, what if you could hop
on a space plane, not on a rocket, and fly into orbit for a space vacation or to catch a connecting flight to Mars? This has been my dream for 30 years,
but for me it’s been more than a dream. For the same 30 years,
I’ve enjoyed working on things that will transform
this dream into reality. My dream was born in 1986. I had a couple months to go before finishing my PhD research
in hypersonic aerodynamics, when I heard President Reagan in his State of the Union address
talk about the Orient Express, a project to develop a hypersonic airplane that could take off from Dulles Airport,
accelerate to Mach 25, and attain Earth orbit
or fly to Tokyo in two hours. I was hooked. The roots of my dream extend
back farther to the sixth grade. This is when I started to learn
about technology in school. Not content to just read about it
in a textbook or look at pretty pictures, I would go home after school
and make working models of these things from scrap materials
in my father’s workshop, and then take them to school the next day and show the kids,
my fellow classmates, how they worked. This led to an extreme curiosity,
interest, and fascination with flight and how things flew, and this passion drove me, before long,
to college to study aerospace engineering, which leads me back to the Orient Express. The Orient Express was actually
the National Aero-Space Plane, a national project to develop
a single-stage-to-orbit space plane. But it was too technologically ambitious. We spent eight years on it;
we did not succeed. Even today, with today’s technology, we still can’t get to orbit
in a single stage without dropping empty fuel tanks
along the way, called staging. But despite it not achieving
its full goals, it did three very important things: it developed and matured
scramjet engine technology, advanced design tools,
and high-temperature materials. I’m going to talk to you
briefly about the first two. The key to routine hypersonic flight is the supersonic combustion
ramjet, or scramjet. This was an idea that was actually
conceived almost 60 years ago, but it hasn’t been until recently
that it’s been proven in flight. Unlike a turbojet or a turbofan
that uses propeller-like blades to compress the air before burning it, a scramjet, like its slower-speed
cousin, the ramjet, uses shock waves
to compress and slow the air, created by flying faster
than the speed of sound. if you try to use a turbojet
or a turbofan above about Mach 3, air friction would make the blades
so hot they would melt, so you can’t use it. Switch to a ramjet,
but if you go above about Mach 5, the air has gone through
so many shock waves, the airflow has actually gotten subsonic
in the combustor, where you burn it, and the pressure and temperature
are too high for it to work properly. So we solve that
by pushing the air through, processing it through fewer shock waves. We let it stay supersonic, and we burn
the air in a supersonic flow. If you’ve ever tried to light a match
in a breeze, you know how hard that is. Imagine trying to light a match
in a supersonic hurricane. That is our challenge. A scramjet is fundamentally simple:
it’s just a shaped pipe. But the details of that shape
are very, very important. We have to shape the inlet to compress the flow just enough
but not too much, through shock waves. The air is in the engine
for only one brief millisecond. In that one millisecond,
a thousandth of a second, we have to inject fuel,
get it to mix completely, ignite, and burn to completion. That’s incredibly difficult to do. We do it through flow turbulence, and turbulence is fundamentally difficult
to understand and even predict using advanced computational
methods with computers. So even though the scramjet
is fundamentally simple in its shape, the physics behind it are very complex. It’s little wonder that it’s taken
almost 60 years to prove that they work. What’s the benefit of a scramjet? For high-speed flight, the benefit
of a scramjet over a rocket is a rocket has to carry its own oxygen. A scramjet, like any jet engine,
just uses the air; it breathes air. So, that fuel economy benefit
is illustrated in this plot. It’s a plot of specific impulse
as a function of speed or Mach number. It sounds complicated,
but it’s really not. Specific impulse is just the thrust
that the engine produces divided by the fuel flow rate; the fuel that’s used
to generate the thrust. So you want high thrust,
low fuel flow rate. You can see in the green,
that’s turbofans. That powers our commercial airplane. Way high fuel economy
compared to the red band, which is rocket engines. As you go up in speed,
you go to a ramjet and a scramjet, the specific impulse decreases. It’s because thrust decays
as you go to higher speed, but it’s still everywhere
higher than a rocket, and that’s the benefit. The first time a scramjet
was proven in flight was in 2004, on NASA’s X-43A experimental vehicle. This test vehicle, 12-feet long,
was carried aloft by a B-52 bomber. It was attached to a huge rocket booster, carried out over the Pacific Ocean,
and it was dropped. The booster boosted it
to almost Mach 7 in one flight and almost Mach 10 in the second flight. After the booster burned out,
it was pushed off, the engine was lit, and it burned hydrogen
for about ten seconds, which was all it could fit, and the vehicle accelerated as predicted. After almost a half a century, the theory of scramjets
was finally proven. Let’s jump forward to 2013. And if you would, for a moment,
imagine you’re on the team trying to create this next giant leap
in hypersonics, in hypersonic flight. So we’re in the control room,
at Edwards Air Force Base. The tension is palpable. You’re very excited, incredibly nervous. The anxiety is almost excruciating.
You’ve been here before three times. In 2010, you tried
and partially succeeded, but not completely;
the next two times, you failed. This is the last vehicle you have, the last chance you have
to do this mission. You’ve been in the control room for hours
waiting for the right conditions, which just added
to the stress and the anxiety. Let me take you to the cockpit
of an F-18 fighter jet at 50,000 feet over the Pacific Ocean. We’re going to watch this flight
unfold together from that cockpit. So this is the U.S. Air Force X-51
WaveRider scramjet engine demonstrator. You see it drop off the B-52;
it’s attached to a booster. The booster accelerates it from 50,000 feet Mach 0.8
to 60,000 feet Mach 4.8. If you look carefully,
you’ll see it ascending. Eventually, you’ll see
a little white pigtail come off the back. That is the booster being ejected
off of the scramjet. Watch carefully. There it goes. What you see is
the world’s first scramjet contrail, the first in history. Success! Cheers! Hurray! High fives in the room! We did it! (Applause) It was awesome. The X-51 continued to accelerate
for three and a half minutes, going from Mach 4.8 to 5.1,
until it ran out of fuel. In that amount of time,
it traveled 200 miles, which is about a mile per second,
or twice as fast as a speeding bullet. At that sped, you could fly from L.A.
to New York in about 45 minutes. What was different
between this and the X-43? The X-43 was heavy;
it was like a flying wind tunnel model. It used hydrogen fuel. But it did break the record;
it was the first flight of a scramjet. This vehicle was lightweight,
as light as a real airplane; it burned jet fuel not hydrogen fuel,
and it broke a new record, the longest scramjet flight in history. This success was particularly sweet to me,
because the X-51 was my baby. I conceived the concept in 1995
and led the early design team. This was the culmination. The dream of hundreds of people
was finally realized in the flight of this practical scramjet. Scramjets are hard to design, but the vehicles that they power
are equally hard to design. The reason is they’re
what’s called “highly integrated.” A conventional airplane has
distinct wings, body, tails, and engine, but a hypersonic vehicle has to be
blended and highly integrated. Why is that? It’s because the engine
actually has to be so big. Remember that specific impulse plot? Remember as the speed gets up,
the thrust goes down? If the thrust goes down,
the engine has to get bigger, and eventually gets so big
that it’s a flying engine, and that’s depicted in this example here. The whole bottom of this vehicle
is the scramjet engine from the nose to the tail. The blue part up front
we call the forebody. It grabs air and shoves it
through the engine. The red part is part of the nozzle;
it expands flow and creates thrust. So the entire bottom is engine. But not only that, it’s also a wing. You don’t really see distinct wings here. So that engine also generates a large portion
of the lift of the vehicle. It’s a blended wing and engine. Traditional, conventional
aircraft are designed by a conventional design technique
that dates back to the Wright brothers: you design each of the pieces,
the wing, the body, the tails, the engine, you bolt them together. But a highly blended vehicle,
you cannot use that approach. It really doesn’t work very well. That’s because all the parts,
and components, and functions are highly interconnected,
and they interact strongly. One affects the other very strongly. This creates what I call
the “whack-a-mole problem.” So what this is is if I go try
to optimize one of these parts, it could and tends
to make the others worse. So while I’m whacking
on one mole, new moles pop up. So the whole process,
I’m going around whacking moles, and I never converge
in the design process. It requires a new method of design,
and we came up with a method called multidisciplinary
design optimization where we consider
all the disciplines together. We don’t just design or optimize the wing; we do it all together. I used this process to design the X-51,
which as best I know is the first time in history that MDO was used
to design a real flying vehicle. This illustrates the method
that I and my colleagues developed, the MDO method,
to design hypersonic vehicles. It starts by creating a mathematical description
of the airplane. So what does that mean? It’s a model where we use variables
like dimensions – width, length, height – angles, curvatures to define its shape. It typically requires
100 or 200 of these variables to define a complete shape. Since they’re all highly interrelated,
we can’t optimize all of them, but today, we can optimize
about 25 of them. Let’s see what this leads to. If I have 25 variables
I’m trying to optimize, they’re coupled, and I pick
three values of each one, I’ll end up with a combination
of 850 billion vehicles I have to analyze to find the one. I call that the “needle-
– in-the-haystack problem,” finding that one needle. That’s more than twice the number
of stars in our Milky Way Galaxy. That’s an impossible task,
so what we do instead is we use statistical techniques,
– in this case, design of experiments – to search design space and just pick some select points
out of design space. So instead of billions, we’re down to a few hundred
or maybe a couple of thousand. We then automate the analysis process. We take all those disciplines,
link up all the computer tools, and automate that. So we put in a vehicle design
and out pops its performance: how much does it weigh,
how far does it go, how much does it cost, etc. Now we’ve got a sparse representation
of the behavior of design space. We curve fit it; we fill in those dots with mathematical curves
called curve fitting. What this is like is —
so, we do the analysis process. Let’s say we predict cost
for hundreds of vehicles, and then we fit all that. What we now have is,
with 25 variables and one output cost, we have a 26-dimensional mountainscape, and our job is to find the highest peak in
that mountainscape, or the lowest valley, in this case, the lowest cost. We use mathematical optimization tools
to efficiently search that mountain space in multiple dimensions
to find the best vehicle. What’s the result of this? Here’s a great example:
the vehicle labeled “Baseline” here was the result of eight years
of whacking on moles on that National Aero-Space Plane,
essentially. After a month of MDO,
you see the optimized shape. It’s smaller, it looks a little different, and it’s 40% lighter,
which is a huge, significant effect. This technique
can be applied to lots of things. Any kind of an integrated system
can use MDO, whether it’s an automobile, an electronic system that’s integrated,
or even a medical treatment regimen. With all this exciting
hypersonic technology, what might we do with it? There’s been a lot in the press
these days about space travel. NASA and SpaceX tout plans to fly to Mars. Elon Musk of SpaceX has even talked
about colonizing Mars, and Jeff Bezos of Blue Origin wants us
to become a space-faring nation with millions of people
living and working in space. But there are some real challenges
to these dreams and these goals. One of the biggest is the cost
of just getting payload into orbit. Today, with expendable rocket systems, it costs about 10,000 dollars
to put one pound, something you can hold
in your hand, into orbit. Think about it; we’re going to go to Mars. We’re going to take people,
fuel, food, spaceships and everything they need
to go there and come back safely. It’s tons and tons of mass. Just to put that stuff into orbit is going
to cost tens of billions of dollars, not accounting the cost for designing,
building, and operating it. So this is severely limiting. So how do we solve this problem? We’ve studied it, and we’ve learned
that there are two key factors to dramatically reducing
the cost of getting to orbit. We could reduce it by 50 or 100 times. The two factors are:
the system has to be completely reusable. You can’t throw anything away;
kind of makes sense. It has to have a high utilization, which means, after a mission,
you need to be able to come home, turn it around quickly
and use it again at a high rate. It’s not enough
to just reuse the first stage. It’s not enough to refurbish a stage, taking weeks or months
to get it ready for the next flight. It really has to operate
more like an airplane. It has to have
aircraft-like characteristics. What you see here, there’s lots of possible ways
of solving this problem, lots of different design concepts,
and you see a few here. The stages might be powered by rockets, air-breathing engines like scramjets,
or a mix of the two. The ultimate solution is going to be
the design and the technology set that achieves those goals
of complete reusability, 100%, high utility, utilization rate,
at the lowest purchase price. If we master affordable space flight, it could naturally follow
fast global transportation. Conversely, if we design
a hypersonic transport, it could serve as the second stage
of a two-stage-to-orbit vehicle. But there’s challenges to achieving
this goal of high-speed flight. Chief among them are
environmental challenges: emissions, the exhaust,
carbon dioxide, and even water, greenhouse gases, sonic boom – challenges. The solution to these challenges may lie
in the future of energy technology. Let’s look far down the technology road. I believe that harnessing
some form of safe nuclear energy will be the ultimate solution for powering
hypersonic airplanes and even spacecraft. Perhaps a device that can store
a sufficient amount of antimatter and annihilate it in a controlled way
to create pure energy, according to Einstein’s
famous e=mc squared, would be the ultimate
portable power device. It would be similar
to a real-life version of the arc reactor that Tony Stark used to power Iron Man. Amazing, huh? At an energy density
a billion times greater than jet fuel, it would eliminate almost all
the weight of the jet fuel, which for a hypersonic vehicle
can be 65% of the takeoff weight. A hundred thousand pounds
of jet fuel could reduce to a tenth of a gram
of antimatter – amazing. With so much energy available, the extra drag of supersonic
or hypersonic flight would be all but irrelevant. Excess energy that you carry aboard
could actually be beamed ahead of the aircraft to create a thermal spike,
what we call a “thermal aerospike,” that could make the vehicle look
way longer than it actually is, which would mitigate
and maybe even eliminate sonic boom. So this is far out there, but this is
technology people are working on, and I believe it’s the ultimate solution. So, just as the first successful flight
by the Wright brothers led to 100 years of amazing breakthroughs and to affordable global travel
for vast numbers of people, our first air-breathing hypersonic flight
is a preamble to the next age of flight. After decades of failed attempts, we finally succeeded and opened up
the age of hypersonic flight. Routine hypersonic flight
will shrink the globe; it will bridge air and space,
making access to space more affordable; and create a new era of space exploration, space industry,
and even possibly, space colonization. The dreams of faster flight
and space travel are converging
and creating an exciting future where new dreams at the edge of the imaginable
are ready to be realized. Thank you very much. (Applause)

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