1 00:00:00,000 --> 00:00:07,120 So, how do you think you did? Well, your mathematical computations and reasoning are important skills to answering the last questions. 2 00:00:07,440 --> 00:00:10,380 Also, are you ready with your own questions? 3 00:00:10,640 --> 00:00:14,960 Here we are now. With me to fill my questions are Mike and Zach, and 4 00:00:15,160 --> 00:00:17,840 shown on your set are the numbers to use. Now, 5 00:00:17,840 --> 00:00:23,880 please note that the telephone numbers are good only for today's November 10th broadcast. All right, let me begin. 6 00:00:23,880 --> 00:00:28,340 I've got a number of email questions that have come in, so I'm going to start with the email questions. 7 00:00:28,340 --> 00:00:34,900 My first question, if you take a look at it, is what is glide ratio? Mike or Zach, who'd like to answer that? 8 00:00:34,900 --> 00:00:36,240 I'll go ahead. 9 00:00:36,240 --> 00:00:42,880 The glide ratio, as you saw earlier, is the ratio of the horizontal distance flown to the altitude drop. 10 00:00:43,200 --> 00:00:45,200 Now, from a design standpoint, 11 00:00:45,480 --> 00:00:50,460 we look at the glide ratio as the result of the aerodynamic efficiency, 12 00:00:50,600 --> 00:00:55,160 which is basically the lift versus the drag ratio, or L over D. 13 00:00:55,460 --> 00:00:58,260 So when we design an airplane, glide ratio is important. 14 00:00:58,460 --> 00:01:02,860 That's a measure of the aerodynamic efficiency and how good the airplane is. All right, 15 00:01:02,860 --> 00:01:09,580 we had a question that was related to that. If we look at our second email question, someone wants to know, does weather affect 16 00:01:09,740 --> 00:01:13,660 glide ratio? It certainly can. In fact, when you 17 00:01:14,300 --> 00:01:19,800 earlier you saw the wind and the rain, those are two factors that very heavily, in fact, impact the glide ratio. 18 00:01:20,180 --> 00:01:26,860 The more wind that you have and the higher the rainfall, the more likely you are to have not as good a glide ratio. 19 00:01:27,060 --> 00:01:32,380 Okay, so wind speed could be a factor here, then. All right. Well, I know that we have a caller out there, 20 00:01:32,380 --> 00:01:35,780 so caller, how about giving us your name, please, and your question? 21 00:01:41,660 --> 00:01:43,660 Michael Williams, Lightning Note. 22 00:01:44,660 --> 00:01:46,660 Lightning Note, how far could the first 23 00:01:47,640 --> 00:01:49,640 airplane in your show go? 24 00:01:50,960 --> 00:01:55,080 If you could turn down your set and ask the question again, 25 00:01:55,080 --> 00:01:59,600 I think we would hear a little bit more clearly. Could you repeat that again, please? That's the fun doing that. 26 00:02:00,160 --> 00:02:02,680 Could you ask the question one more time, then, please? 27 00:02:03,240 --> 00:02:05,840 How far did the first model go? 28 00:02:06,440 --> 00:02:08,440 How far did 29 00:02:09,220 --> 00:02:14,760 the model go? Are you referring to the students' model? Yeah. 30 00:02:15,140 --> 00:02:19,760 Well, you saw there on the data that they collected that it went, 31 00:02:19,760 --> 00:02:25,820 they tried it ten times, and we saw their data for five times, and you saw the distance for five of those flights. 32 00:02:25,820 --> 00:02:29,420 So, your challenge is to go back and look at that data, 33 00:02:29,420 --> 00:02:36,220 and you could calculate the mean and the median for those five flights, and then you'll have that answer. Good question. 34 00:02:36,260 --> 00:02:41,700 All right. Well, let me go back to my email, because I know I've got several questions that have come in here. 35 00:02:41,700 --> 00:02:48,500 Here's a question. How do researchers, in designing an airplane, decide what its wingspan should be? 36 00:02:48,560 --> 00:02:50,440 It's a good question, Shelley. 37 00:02:50,440 --> 00:02:57,960 It really depends on the aircraft mission. Typically, transport aircraft have very long wingspans where they need high fuel efficiency. 38 00:02:58,620 --> 00:03:05,160 For fighter-type aircraft, you typically have shorter spans. You require a lot more structural strength out of the airplane. 39 00:03:05,760 --> 00:03:09,580 So, you typically have a short span on fighter-type configurations. Okay. 40 00:03:10,160 --> 00:03:14,040 All right. We've got another email question that's kind of related to this. All right. 41 00:03:14,040 --> 00:03:21,080 And maybe you've answered this already. How important is the width of a wingspan in an airplane's performance? 42 00:03:21,840 --> 00:03:28,260 In a very simple sense, I guess the longer the span, typically the more fuel-efficient an airplane configuration would be. 43 00:03:28,720 --> 00:03:32,280 That's why you see long spans on commercial transport airplanes. 44 00:03:32,280 --> 00:03:34,160 All right. Well, I know we've got another caller out there. 45 00:03:34,160 --> 00:03:39,360 So, let's go ahead and go back to the phones. And, caller, could you give us your name, please, and your question? 46 00:03:39,880 --> 00:03:42,240 Yes. My name is Eric Morgan. I have a question for them. 47 00:03:42,760 --> 00:03:44,240 My question is, 48 00:03:44,240 --> 00:03:46,000 the little 49 00:03:46,000 --> 00:03:49,240 perforated holes, or the little holes in a golf ball, that help break down 50 00:03:50,000 --> 00:03:54,200 wind turbulence for the golf ball, will that help on a plane's wing to reduce drag? 51 00:03:55,120 --> 00:03:57,480 Good question. Who wants to take that one? Mike, Zach? 52 00:03:57,480 --> 00:03:59,200 I can do that one. 53 00:03:59,200 --> 00:04:05,880 As you know, though, the little dimples on a golf ball helps change the drag of the golf ball by creating turbulence. 54 00:04:05,980 --> 00:04:13,260 Now, in fact, there's a similar system that can be applied to transport configurations called hybrid laminar flow control, 55 00:04:13,340 --> 00:04:19,420 where, in fact, there's little holes that can either suck air in or blow air out that helps to create a 56 00:04:19,580 --> 00:04:26,820 smooth layer of air near the surface of the skin. That actually can reduce the drag of the airplane as much as 15 to 16 percent. 57 00:04:26,980 --> 00:04:29,300 All right. Good question. Did you want to add something else? 58 00:04:29,300 --> 00:04:33,060 Yes. And, actually, a very similar application that's developed here at NASA Langley is 59 00:04:33,280 --> 00:04:39,280 a turbulent drag reduction in the form of what we call rivulets, which are fairly rough surfaces along the airplane, 60 00:04:39,400 --> 00:04:45,200 which actually reduce the overall drag of the wing. All right. Well, that's about all the time we have. 61 00:04:45,440 --> 00:04:52,560 So, I'd like to thank all the guests that contributed to this program, including Mike and Zach, Paul, Karen, and Sharon. 62 00:04:52,560 --> 00:04:56,240 I'd also like to thank Jones Magnet Middle School, Deer County Airport, 63 00:04:56,740 --> 00:05:04,100 AirVenture 98, and Hoot Gibson, who did win his race. And, finally, the Smithsonian National Air and Space Museum. 64 00:05:05,780 --> 00:05:12,340 Just a final reminder to check out the Shapes of Flight website, where you will see, hear, and learn more about today's topic. 65 00:05:12,740 --> 00:05:17,620 Also, we invite you to camp out with like-minded students in our special virtual aeronautics camp. 66 00:05:17,940 --> 00:05:22,340 No sleeping bags required. Just some creativity and mathematics and science know-how. 67 00:05:22,340 --> 00:05:31,120 Videotape copies of this show, along with the lesson plan, may be obtained from NASA's Central Operation of Resources for Educators, or CORE.