1 00:00:00,000 --> 00:00:07,500 So, have you ever wondered what goes into designing an experimental plane, such as the 2 00:00:07,500 --> 00:00:08,500 HyperX? 3 00:00:08,500 --> 00:00:09,960 I know I have. 4 00:00:09,960 --> 00:00:15,000 I'm here at NASA Langley Research Center in Hampton, Virginia to talk to Dr. Scott Hull. 5 00:00:15,000 --> 00:00:19,000 What are the steps in designing an aircraft? 6 00:00:19,000 --> 00:00:26,000 How does the mission requirements of an aircraft determine its shape? 7 00:00:26,000 --> 00:00:29,000 Why are wind tunnels important in testing aircraft designs? 8 00:00:29,000 --> 00:00:32,000 Why? 9 00:00:32,000 --> 00:00:33,000 Hi, Dan. 10 00:00:33,000 --> 00:00:34,000 Hey. 11 00:00:34,000 --> 00:00:36,000 HyperX is definitely a very exciting program. 12 00:00:36,000 --> 00:00:40,000 My job, I use wind tunnels to determine the flying characteristics of a variety of different 13 00:00:40,000 --> 00:00:44,000 vehicles that fly many times faster than the speed of sound, like the HyperX. 14 00:00:44,000 --> 00:00:47,000 The exciting part of the HyperX program is that it's truly pioneering. 15 00:00:47,000 --> 00:00:51,000 That means no one's ever done it before, so we have to blaze the trail. 16 00:00:51,000 --> 00:00:53,000 NASA sure has blazed many trails. 17 00:00:53,000 --> 00:00:54,000 How do they do it? 18 00:00:54,000 --> 00:00:57,000 The first thing you have to do when blazing a trail is to determine a mission or where 19 00:00:57,000 --> 00:00:59,000 you want to go. 20 00:00:59,000 --> 00:01:03,000 We develop a set of requirements for the vehicle, and then we begin a process of designing a 21 00:01:03,000 --> 00:01:04,000 vehicle to meet that mission. 22 00:01:04,000 --> 00:01:07,000 Have you ever been to an air show to see a bunch of different airplanes? 23 00:01:07,000 --> 00:01:08,000 Yeah. 24 00:01:08,000 --> 00:01:12,000 Some planes are short, some are long and slender, some fly slow, and some fly fast. 25 00:01:12,000 --> 00:01:13,000 You're right. 26 00:01:13,000 --> 00:01:17,000 They look and perform differently because they were designed to satisfy different missions. 27 00:01:17,000 --> 00:01:20,000 For the HyperX program, our mission is to have it fly very fast. 28 00:01:20,000 --> 00:01:24,000 We also want to be able to control it, and we want it to be able to propel itself. 29 00:01:24,000 --> 00:01:29,000 You see, NASA has many years of experience testing fundamental shapes to understand and 30 00:01:29,000 --> 00:01:34,000 document how those shapes, we call them geometries, respond to the airflow at various speeds. 31 00:01:34,000 --> 00:01:35,000 Let me show you. 32 00:01:38,000 --> 00:01:42,000 The Apollo capsules used to bring the astronauts back to Earth after their trips to the moon 33 00:01:42,000 --> 00:01:44,000 were designed as blunt bodies. 34 00:01:44,000 --> 00:01:49,000 This is because this particular shape has high drag, a force that slows an object down. 35 00:01:55,000 --> 00:02:01,000 The blunt body creates the drag needed to deploy the drogue parachute, 36 00:02:01,000 --> 00:02:04,000 followed by the main parachutes. 37 00:02:04,000 --> 00:02:09,000 The force of drag, then, gently lowers the vehicle safely to the Earth. 38 00:02:10,000 --> 00:02:14,000 NASA had to design a vehicle that would slow down to speeds where it was safe to deploy 39 00:02:14,000 --> 00:02:16,000 the parachute for landing in the ocean. 40 00:02:16,000 --> 00:02:18,000 Okay, I get it. 41 00:02:18,000 --> 00:02:20,000 But what about other shapes? 42 00:02:20,000 --> 00:02:23,000 Well, we know that slender shapes, like the Concorde, have less drag. 43 00:02:23,000 --> 00:02:27,000 A vehicle that has to propel itself, like the Concorde or the HyperX, 44 00:02:27,000 --> 00:02:30,000 has to have an engine with enough power to overcome the vehicle's drag. 45 00:02:30,000 --> 00:02:34,000 So if you were designing the HyperX to propel itself and fly really fast, 46 00:02:34,000 --> 00:02:36,000 would you want a blunt body or a slender body? 47 00:02:36,000 --> 00:02:38,000 I'd want a slender body. 48 00:02:38,000 --> 00:02:39,000 That's right. 49 00:02:42,000 --> 00:02:46,000 The HyperX is designed as a slender body because it has less drag for the engine to overcome. 50 00:02:46,000 --> 00:02:49,000 You're well on your way to becoming a conceptual designer, Dan. 51 00:02:49,000 --> 00:02:51,000 I am? Sweet. 52 00:02:51,000 --> 00:02:55,000 So, once you've decided on a mission, what's next? 53 00:02:55,000 --> 00:02:57,000 Detailed design. 54 00:02:57,000 --> 00:03:00,000 A conceptual designer makes decisions, like the one you just made, 55 00:03:00,000 --> 00:03:03,000 to find a geometry that will meet the mission requirements. 56 00:03:03,000 --> 00:03:07,000 The detailed designer uses tools such as CAD or computer-aided drafting 57 00:03:07,000 --> 00:03:09,000 to turn ideas into drawings. 58 00:03:09,000 --> 00:03:12,000 These drawings help us work out the details of how to design parts of the HyperX, 59 00:03:12,000 --> 00:03:16,000 like the engines, the control surfaces, the fuel tanks, and so forth. 60 00:03:16,000 --> 00:03:19,000 Once we have an initial design, we begin a process to improve it. 61 00:03:19,000 --> 00:03:23,000 We compare the design of the HyperX to other vehicles with similar characteristics. 62 00:03:23,000 --> 00:03:27,000 We may need to make changes to the geometry to improve the performance. 63 00:03:27,000 --> 00:03:29,000 How do you know if you need to change the shape? 64 00:03:29,000 --> 00:03:32,000 One way is conducting wind tunnel tests. 65 00:03:32,000 --> 00:03:35,000 You see, during the design and computer modeling stages, 66 00:03:35,000 --> 00:03:38,000 we extensively used our wind tunnels to quickly screen our HyperX designs. 67 00:03:38,000 --> 00:03:42,000 And then, the wind tunnel tests helped us to determine the best design 68 00:03:42,000 --> 00:03:45,000 and to understand how the vehicle will fly. 69 00:03:45,000 --> 00:03:48,000 Okay, so what is a wind tunnel? 70 00:03:48,000 --> 00:03:52,000 Wind tunnels are devices that allow us to move air over a scale model of a flight vehicle, 71 00:03:52,000 --> 00:03:54,000 like the HyperX. 72 00:03:54,000 --> 00:03:57,000 We use models instead of the real vehicle because they're smaller, 73 00:03:57,000 --> 00:04:00,000 less expensive, and easier to change if needed. 74 00:04:00,000 --> 00:04:03,000 This is NASA Langley's 31-inch Mach 10 wind tunnel. 75 00:04:03,000 --> 00:04:07,000 This tunnel can get the air moving up to 10 times the speed of sound. 76 00:04:07,000 --> 00:04:10,000 Once we place the model of the HyperX in the wind tunnel, 77 00:04:10,000 --> 00:04:13,000 we make measurements to determine how the air interacts with the model. 78 00:04:13,000 --> 00:04:16,000 At the nose of the vehicle, the flow near the surface is very smooth. 79 00:04:16,000 --> 00:04:18,000 We call it laminar. 80 00:04:18,000 --> 00:04:22,000 But as the air moves down the length of the body, it changes and becomes turbulent. 81 00:04:22,000 --> 00:04:26,000 You can see this natural process by looking at the smoke after you blow out a candle. 82 00:04:26,000 --> 00:04:30,000 After you've blown out a candle, you'll notice that the smoke near the candle rises smoothly. 83 00:04:30,000 --> 00:04:32,000 That's laminar flow. 84 00:04:32,000 --> 00:04:35,000 But farther away from the candle, you'll notice it becomes rough and irregular. 85 00:04:35,000 --> 00:04:37,000 That's turbulent flow. 86 00:04:37,000 --> 00:04:40,000 Normally, we think of laminar flow when designing aerodynamic shapes. 87 00:04:40,000 --> 00:04:42,000 We want the air to flow smoothly around them. 88 00:04:42,000 --> 00:04:45,000 However, for the HyperX geometry, we require turbulent flow. 89 00:04:45,000 --> 00:04:48,000 Why would you want turbulent flow on the HyperX? 90 00:04:48,000 --> 00:04:51,000 In order for the scramjet engine to work properly. 91 00:04:51,000 --> 00:04:57,000 You see, turbulent airflow enhances the mixing of the air with the hydrogen fuel for better engine performance. 92 00:04:57,000 --> 00:05:02,000 Turbulent airflow is created by a device called a trip located underneath the belly of the HyperX. 93 00:05:02,000 --> 00:05:06,000 Using the wind tunnel, we tested several trips with different shapes or geometries 94 00:05:06,000 --> 00:05:10,000 to see which one worked best to change the airflow from laminar to turbulent. 95 00:05:10,000 --> 00:05:14,000 Our wind tunnel test determined that this triangular-shaped trip was the best design 96 00:05:14,000 --> 00:05:17,000 for creating turbulent flow for the scramjet engine on this vehicle. 97 00:05:17,000 --> 00:05:19,000 How do you test the scramjet engine? 98 00:05:19,000 --> 00:05:22,000 We have specialized wind tunnels capable of testing scramjets, 99 00:05:22,000 --> 00:05:25,000 but the ultimate proof of the HyperX is flight testing. 100 00:05:25,000 --> 00:05:28,000 That's the last phase in designing an aircraft. 101 00:05:28,000 --> 00:05:33,000 NASA conducts all of its flight tests on aircraft at the NASA Dryden Flight Research Center in Edwards, California. 102 00:05:33,000 --> 00:05:35,000 Thanks, Scott. 103 00:05:35,000 --> 00:05:39,000 We'll visit NASA Dryden Flight Research Center later in the show. 104 00:05:39,000 --> 00:05:46,000 But first, join me at Dan's Domain, where we'll use technology to prepare for today's math-based, hands-on activity.