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of an annual Premium subscription. [ ♪ Intro ] A lot of us probably share a pretty common
idea of what planes look like. But there have been some strange aircraft
over the last century, too. For example, the fastest piloted plane ever
was so loosely constructed that fuel leaked out of it before takeoff. And a crucial member of the Apollo program
was so bulky that people doubted it could even fly. Sometimes, for extraordinary missions, researchers
have to get creative and push the boundaries of engineering. And while doing so, they’ve built some weirdos. Here are five of the most bizarre, impressive
aircraft throughout history, ones that, despite what you might think, still managed to fly. In the early 1960s, a couple of American U-2
spy planes were shot down by missiles. To keep that from happening again, the U.S. government wanted a new spy plane that could outrun any missile fired at it from the ground. So they reached out to the company Lockheed
(now Lockheed Martin) who had already begun work on an extra fast aircraft. And ultimately, Lockheed delivered the fastest
piloted plane ever: the SR-71 Blackbird, one of the most famous aircraft out there. This thing could cruise at more than three
times the speed of sound, some 3900 kilometers per hour. So fast that many pilots got to see the sun
rise in the west. But like you might guess, building this thing
wasn’t easy. During flight, air friction heated the Blackbird
to over 350°C, and there aren’t many metals that can withstand that much heat for hours without losing strength. To overcome that, the plane had to be made
out of a special titanium alloy that was both lightweight and especially strong. But that still only solved one side of the
heating problem. See, hot metals aren’t just weaker; they
also expand. And if the pieces of the Blackbird expanded
too much mid-flight, they could grow into each other and break. To prevent that catastrophe, the plane’s
engineers came up with an extreme solution: They built the SR-71 so that, when it was
on the ground, its pieces didn’t fit together snugly. And there were some gaps that parts expanded
into as the plane flew and heated up. But on the ground, those gaps were big enough
that fuel could actually leak out of the aircraft’s tanks. Thankfully, that wasn’t actually very dangerous. On the runway, Blackbirds only held enough
fuel to take off and fly for a little bit. Later, they had to link up with another plane
that filled them up in the air. And even if a lot of fuel did leak before
flight, it could only ignite at a super-high temperature. So it wasn’t like a bunch of Blackbirds
were explosions waiting to happen. The Air Force retired the SR-71 back in 1990, as satellites and improved defense systems slowly made it outdated. But it did retire in style: Its last flight
was a record-setting 64-minute streak from LA to Washington, DC, so that it could become part of the collection at the Smithsonian Air & Space Museum. Now, at least the Blackbird looked like a
plane. The Grumman X-29 looks like someone building
a model airplane got distracted and put the wings on backwards. Except the X-29 was no model. It was almost 15 meters long, nearly 8000
kilograms at takeoff, and could fly at more than 1.7 times the speed of sound. Its wings were just on the wrong way. But there was good reason for that. Years before this plane was built, engineers had wondered what the benefits and drawbacks of different wing designs were. They could get all kinds of data about standard wings, but backward ones were a lot harder to test at supersonic speeds. That’s because, while standard wings sweep
air away from a plane’s body, backwards wings do the opposite: They move air toward
the body. And that leads to all kinds of new, large
forces. We didn’t have materials strong enough to
withstand those forces on a supersonic plane until the 1970s. But once we did, the X-29 wasn’t far behind. NASA and the U.S. Air Force used the plane
to study the advantages and disadvantages of the new air path and the results were
mixed. The plane’s big advantage was maneuverability, especially at steep angles where most planes would have stalled or started losing the lift
that keeps them in the air. Conventional planes stall when the front of
their wings blocks too much air from moving over the wings and providing lift. But since the X-29 had backwards wings, any
air they blocked got moved toward the plane’s body, so it had to go over the aircraft in
one way or another. That meant it didn’t stall as easily. But those extra-steep climbs came with a pretty
big disadvantage: Air constantly twisted the wings as it went by, and the slightest wrong move or unexpected bump could send the plane completely out of control. It could go from perfectly stable to torn
apart in less than two-tenths of a second, far faster than any pilot could respond. To counter that, the X-29 was designed with
three redundant computer systems, which looked for hints of disaster and corrected course
before the pilot noticed. And thanks to them, the X-29 was able to fly
422 times between 1984 and 1992. Ultimately, though, the backward-wing design
didn’t have enough benefits to make it worth using for many more aircraft. But the X-29’s odd shape lives on in aviation
history as a very successful experiment. In the 1960s, the Space Race was just shifting
into high gear. NASA kept building bigger and bigger rockets, but they had to ship large pieces of them from where they were made in California to
the assembly building in Florida. That’s a long sea voyage, and parts could
crack or break along the way. So two men, Jack Conroy and aircraft salesman
Lee Mansdorf, came up with a solution: Why not build a gigantic cargo plane and fly the
pieces to Florida? The two helped start the company Aero Spacelines, and eventually, they produced the Aero Spacelines 377PG, more fondly known as the Pregnant Guppy. It’s a larger version of another plane,
called the Boeing Stratocruiser, which Mansdorf just happened to own a couple of. As you do. At the time, the Guppy was the largest plane
in the world. Its cabin was almost 6 meters across and 12
meters long, big enough to hold an entire rocket stage inside of it. Some people were skeptical that such a bulbous,
45,000-kilogram plane could really fly, especially hauling 24,000 extra kilograms of cargo. But the Pregnant Guppy worked, and a series of dramatic demonstrations convinced NASA it was worth using. Yeah. I said convinced NASA. Because they didn’t actually ask Aero Spacelines
to build the Guppy. Instead, Conroy and Mansdorf just thought
it was a great idea and went ahead building it. But boy, was NASA glad they did. The Guppy cut down NASA’s trip time from
18 days to 18 hours, and it performed a crucial role throughout the heart of the Space Race until it was taken apart in 1979. But even once it was gone, its legacy lived
on. After it came the Super Guppy: 7 meters wide
and a full 28 meters long. And today, we have the Airbus Beluga. It’s also pretty weird-looking, but its
job is similar to the original Guppy’s: It carries parts of other planes around the
world in a gargantuan cargo area. But no matter how sophisticated and shiny
they look, the Beluga and other modern cargo planes are all, in one way or another, children of the original Pregnant Guppy. Because it didn’t fly due to how air moved
past its wings, the North American X-15 isn’ttechnically an airplane. Instead, it’s an air-craft, which includes
planes and everything else that flies through the sky. But it’s not just any aircraft. The X-15 was the fastest piloted aircraft
in history, with a rocket engine that blasted it to over six times the speed of sound, twice
that of the SR-71 Blackbird. What might be even more interesting, though, is that this aircraft was never built to touch a runway. It didn’t land on one, and it didn’t take
off from one. In fact, it never really took off at all. The X-15 was built in the 1950s to help us
research conditions at high speeds and high altitudes, but it only carried about 80 to
120 seconds’ worth of fuel. Using fuel to speed up, take off, and get
high in the air would have been a waste, so the X-15 was carried up on a much larger plane: The B-52, also known as the “Mothership”. The B-52 would fly way into the air with the
X-15 under its wing, then drop its rocket-powered cargo. The X-15’s rocket would fire, and it would
speed out of the Mothership’s sight. Then, the engine would go until the aircraft
ran out of fuel, and the X-15 would glide down to a dry lakebed, skidding to a stop 10 minutes or so after leaving the B-52. The aircraft flew from 1959 to 1968, repeatedly getting so high above the ground up that its pilots officially count as astronauts. And in that decade of research, we learned
a lot. The X-15 showed NASA the kinds of conditions
rockets experience during launches into space, and it taught engineers how to make reliable,
pressurized spacesuits. It also taught physicists about fluid dynamics
at supersonic speeds, and it gave doctors valuable data about how humans respond to extreme flight conditions. All while setting unofficial records for the
fastest aircraft in history. So it might not be a true plane, and it might
not have ever actually taken off, but the rocket-powered North American X-15 is still
pretty impressive. You know, sometimes you just don’t know
where to put your plane once you’re done with it. Planes are just so big and wide; they don’t
stack together very neatly. If only there were an aircraft whose huge,
rigid wings folded up for storage. #PlaneOwnerProblems, am I right? Well, never fear. The Bell Boeing V-22 Osprey is here. And it folds. The U.S. Military uses the V-22 for transporting
troops and cargo, up to 24 troops or about 10,000 kilograms of cargo in one trip. But the Osprey has another special talent,
too: It’s a shapeshifter. And it takes off and lands vertically like
a helicopter, with propellers facing up toward the sky. Then, once it’s in the air, the engines
and propellers start to turn. In as little as twelve seconds, they’re
completely horizontal, just like on an airplane. These two modes give the Osprey the advantages
of both helicopters and planes in the same machine. They don’t need the long runways of a conventional
airplane because they can land and take off completely vertically, making them good in
forests or other dense environments where planes would be helpless. But in the air, they can fly about twice as
fast as an average helicopter could. Then there’s possibly the best part: The
Osprey has one more contortionist trick up its sleeve. When it lands at a safe base and won’t be
flying for a while, the Osprey’s rotor blades fold completely flat against each other. Like some kind of weird, mechanical dragonfly. Then, the entire wing turns until it’s flat
along the top of the Osprey’s body. The whole process takes about a minute, and it allows the aircraft to take up far less space between flights. It’s awesome. Once, people said it was impossible to fly
in something heavier than air. A century and a half later, a plane lands
somewhere in the world every couple of seconds. We also have enormous Guppies and folding
half-helicopter/half-planes performing special tasks and helping researchers throughout the
world. Which is pretty amazing progress, if you ask
me. Thanks for watching this episode of SciShow! There have been plenty of cool planes in the
past, but engineers also have a few surprises up their sleeve for the future. Maybe you do, too. If you think you might be a future engineer,
or just like learning new things and testing your knowledge, check out Brilliant.org. This course on classical mechanics is particularly
cool if you liked this episode. The whole course is fun, but the sections
on energy and momentum are an awesome way to learn more about flight. All this week, we’re partnering with Brilliant.org to share science quizzes and lessons we think you’ll like. And right now, Brilliant is offering the SciShow
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