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Designing Aircraft - Contenido educativo

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Connect segment explaining the tools, techniques, and requirements of designing an aircraft. The segment also explains the importance in wind tunnels and model planes.

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So, have you ever wondered what goes into designing an experimental plane, such as the 00:00:00
HyperX? 00:00:07
I know I have. 00:00:08
I'm here at NASA Langley Research Center in Hampton, Virginia to talk to Dr. Scott Hull. 00:00:09
What are the steps in designing an aircraft? 00:00:15
How does the mission requirements of an aircraft determine its shape? 00:00:19
Why are wind tunnels important in testing aircraft designs? 00:00:26
Why? 00:00:29
Hi, Dan. 00:00:32
Hey. 00:00:33
HyperX is definitely a very exciting program. 00:00:34
My job, I use wind tunnels to determine the flying characteristics of a variety of different 00:00:36
vehicles that fly many times faster than the speed of sound, like the HyperX. 00:00:40
The exciting part of the HyperX program is that it's truly pioneering. 00:00:44
That means no one's ever done it before, so we have to blaze the trail. 00:00:47
NASA sure has blazed many trails. 00:00:51
How do they do it? 00:00:53
The first thing you have to do when blazing a trail is to determine a mission or where 00:00:54
you want to go. 00:00:57
We develop a set of requirements for the vehicle, and then we begin a process of designing a 00:00:59
vehicle to meet that mission. 00:01:03
Have you ever been to an air show to see a bunch of different airplanes? 00:01:04
Yeah. 00:01:07
Some planes are short, some are long and slender, some fly slow, and some fly fast. 00:01:08
You're right. 00:01:12
They look and perform differently because they were designed to satisfy different missions. 00:01:13
For the HyperX program, our mission is to have it fly very fast. 00:01:17
We also want to be able to control it, and we want it to be able to propel itself. 00:01:20
You see, NASA has many years of experience testing fundamental shapes to understand and 00:01:24
document how those shapes, we call them geometries, respond to the airflow at various speeds. 00:01:29
Let me show you. 00:01:34
The Apollo capsules used to bring the astronauts back to Earth after their trips to the moon 00:01:38
were designed as blunt bodies. 00:01:42
This is because this particular shape has high drag, a force that slows an object down. 00:01:44
The blunt body creates the drag needed to deploy the drogue parachute, 00:01:55
followed by the main parachutes. 00:02:01
The force of drag, then, gently lowers the vehicle safely to the Earth. 00:02:04
NASA had to design a vehicle that would slow down to speeds where it was safe to deploy 00:02:10
the parachute for landing in the ocean. 00:02:14
Okay, I get it. 00:02:16
But what about other shapes? 00:02:18
Well, we know that slender shapes, like the Concorde, have less drag. 00:02:20
A vehicle that has to propel itself, like the Concorde or the HyperX, 00:02:23
has to have an engine with enough power to overcome the vehicle's drag. 00:02:27
So if you were designing the HyperX to propel itself and fly really fast, 00:02:30
would you want a blunt body or a slender body? 00:02:34
I'd want a slender body. 00:02:36
That's right. 00:02:38
The HyperX is designed as a slender body because it has less drag for the engine to overcome. 00:02:42
You're well on your way to becoming a conceptual designer, Dan. 00:02:46
I am? Sweet. 00:02:49
So, once you've decided on a mission, what's next? 00:02:51
Detailed design. 00:02:55
A conceptual designer makes decisions, like the one you just made, 00:02:57
to find a geometry that will meet the mission requirements. 00:03:00
The detailed designer uses tools such as CAD or computer-aided drafting 00:03:03
to turn ideas into drawings. 00:03:07
These drawings help us work out the details of how to design parts of the HyperX, 00:03:09
like the engines, the control surfaces, the fuel tanks, and so forth. 00:03:12
Once we have an initial design, we begin a process to improve it. 00:03:16
We compare the design of the HyperX to other vehicles with similar characteristics. 00:03:19
We may need to make changes to the geometry to improve the performance. 00:03:23
How do you know if you need to change the shape? 00:03:27
One way is conducting wind tunnel tests. 00:03:29
You see, during the design and computer modeling stages, 00:03:32
we extensively used our wind tunnels to quickly screen our HyperX designs. 00:03:35
And then, the wind tunnel tests helped us to determine the best design 00:03:38
and to understand how the vehicle will fly. 00:03:42
Okay, so what is a wind tunnel? 00:03:45
Wind tunnels are devices that allow us to move air over a scale model of a flight vehicle, 00:03:48
like the HyperX. 00:03:52
We use models instead of the real vehicle because they're smaller, 00:03:54
less expensive, and easier to change if needed. 00:03:57
This is NASA Langley's 31-inch Mach 10 wind tunnel. 00:04:00
This tunnel can get the air moving up to 10 times the speed of sound. 00:04:03
Once we place the model of the HyperX in the wind tunnel, 00:04:07
we make measurements to determine how the air interacts with the model. 00:04:10
At the nose of the vehicle, the flow near the surface is very smooth. 00:04:13
We call it laminar. 00:04:16
But as the air moves down the length of the body, it changes and becomes turbulent. 00:04:18
You can see this natural process by looking at the smoke after you blow out a candle. 00:04:22
After you've blown out a candle, you'll notice that the smoke near the candle rises smoothly. 00:04:26
That's laminar flow. 00:04:30
But farther away from the candle, you'll notice it becomes rough and irregular. 00:04:32
That's turbulent flow. 00:04:35
Normally, we think of laminar flow when designing aerodynamic shapes. 00:04:37
We want the air to flow smoothly around them. 00:04:40
However, for the HyperX geometry, we require turbulent flow. 00:04:42
Why would you want turbulent flow on the HyperX? 00:04:45
In order for the scramjet engine to work properly. 00:04:48
You see, turbulent airflow enhances the mixing of the air with the hydrogen fuel for better engine performance. 00:04:51
Turbulent airflow is created by a device called a trip located underneath the belly of the HyperX. 00:04:57
Using the wind tunnel, we tested several trips with different shapes or geometries 00:05:02
to see which one worked best to change the airflow from laminar to turbulent. 00:05:06
Our wind tunnel test determined that this triangular-shaped trip was the best design 00:05:10
for creating turbulent flow for the scramjet engine on this vehicle. 00:05:14
How do you test the scramjet engine? 00:05:17
We have specialized wind tunnels capable of testing scramjets, 00:05:19
but the ultimate proof of the HyperX is flight testing. 00:05:22
That's the last phase in designing an aircraft. 00:05:25
NASA conducts all of its flight tests on aircraft at the NASA Dryden Flight Research Center in Edwards, California. 00:05:28
Thanks, Scott. 00:05:33
We'll visit NASA Dryden Flight Research Center later in the show. 00:05:35
But first, join me at Dan's Domain, where we'll use technology to prepare for today's math-based, hands-on activity. 00:05:39
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Idioma/s:
en
Materias:
Matemáticas
Niveles educativos:
▼ Mostrar / ocultar niveles
      • Nivel Intermedio
Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
166
Fecha:
28 de mayo de 2007 - 16:53
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
05′ 46″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
Resolución:
480x360 píxeles
Tamaño:
34.60 MBytes

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