1 00:00:00,000 --> 00:00:09,800 Hi, I'm Jennifer Pulley, your host, along with Dan Jarreau, who's joining us remotely 2 00:00:09,800 --> 00:00:13,160 from the NASA Langley Research Center in Hampton, Virginia. 3 00:00:13,160 --> 00:00:16,880 You know, we're real excited to be here at the U.S. Space and Rocket Center in Huntsville, 4 00:00:16,880 --> 00:00:19,840 Alabama, for part of this NASA Connect. 5 00:00:19,840 --> 00:00:23,560 Teachers, make sure you have the educator guide for today's program. 6 00:00:23,560 --> 00:00:25,800 It can be downloaded from the NASA Connect website. 7 00:00:26,360 --> 00:00:32,160 In it, you'll find great math-based, hands-on activities and information on our instructional 8 00:00:32,160 --> 00:00:34,400 technology components. 9 00:00:34,400 --> 00:00:39,400 On this episode of NASA Connect, we're visiting NASA Marshall Space Flight Center in Huntsville, 10 00:00:39,400 --> 00:00:40,400 Alabama. 11 00:00:40,400 --> 00:00:45,840 There, we'll meet NASA scientists and engineers who are exploring the challenges of building 12 00:00:45,840 --> 00:00:49,040 the next generation of reusable spacecraft. 13 00:00:49,040 --> 00:00:52,800 My friends here are going to help me figure out what it takes to get into orbit. 14 00:00:52,800 --> 00:00:53,880 How can we do that? 15 00:00:53,880 --> 00:00:58,760 By learning how NASA is getting spacecraft into orbit more safely and less expensively. 16 00:00:58,760 --> 00:01:00,880 Can't we just keep doing it the way we always have? 17 00:01:00,880 --> 00:01:06,040 Well, you know, things change, and we need to change in order to continue our journey 18 00:01:06,040 --> 00:01:07,520 of exploration. 19 00:01:07,520 --> 00:01:14,320 Just think, we went from the Wright brothers' first flight in 1903 to landing on the moon 20 00:01:14,320 --> 00:01:16,160 in 1969. 21 00:01:16,160 --> 00:01:20,720 As you can see, people have been dreaming of flight for ages. 22 00:01:20,720 --> 00:01:26,760 One of those dreamers was American Robert Goddard, an early experimenter with rockets. 23 00:01:26,760 --> 00:01:31,320 His work continues to inspire generations of scientists. 24 00:01:31,320 --> 00:01:37,720 These rockets are the results of Goddard's and other pioneers' imagination and hard work. 25 00:01:37,720 --> 00:01:39,800 Now it's your turn. 26 00:01:39,800 --> 00:01:42,000 You are the next generation of space explorers. 27 00:01:42,000 --> 00:01:43,320 Whoa, that's way cool. 28 00:01:43,320 --> 00:01:45,000 I know, it really is, Zach. 29 00:01:45,280 --> 00:01:50,680 And you know, just as the early space programs of NASA like Mercury, Gemini, and Apollo led 30 00:01:50,680 --> 00:01:55,080 us to the shuttle, the shuttle leads us to the next generation of spacecraft. 31 00:01:55,080 --> 00:01:56,280 What's that? 32 00:01:56,280 --> 00:01:58,160 That's what this show is all about, Seema. 33 00:01:58,160 --> 00:02:02,000 All right, okay, I'm pumped, but how do we get these heavy rockets off the ground? 34 00:02:02,000 --> 00:02:06,000 You know, Zach, that's a really good question, and what do we mean by the word heavy? 35 00:02:06,000 --> 00:02:10,720 Well, what we call heavy is just a way of measuring gravity. 36 00:02:10,720 --> 00:02:13,920 Gravity is a force of attraction between objects. 37 00:02:13,920 --> 00:02:17,280 Everything in the universe is attracted to everything else. 38 00:02:17,280 --> 00:02:19,760 Sometimes it's powerful, but sometimes it's weak. 39 00:02:19,760 --> 00:02:23,320 The amount of attraction really depends on the mass of the objects. 40 00:02:23,320 --> 00:02:24,320 Mass? 41 00:02:24,320 --> 00:02:27,320 James, what do you want me to say? 42 00:02:27,320 --> 00:02:30,360 Hey, Zach, pick Cassie and I up one, too. 43 00:02:30,360 --> 00:02:32,400 Mass is not the same as weight. 44 00:02:32,400 --> 00:02:36,200 Think about how astronauts become nearly weightless in space. 45 00:02:36,200 --> 00:02:40,960 When they are on the moon, they weigh only one-sixth of their weight on Earth. 46 00:02:40,960 --> 00:02:46,880 For example, a man who weighs 180 pounds on Earth would weigh 30 pounds on the moon. 47 00:02:46,880 --> 00:02:48,400 They didn't shrink, did they? 48 00:02:48,400 --> 00:02:51,360 Their mass is the same, so what causes their weight to change? 49 00:02:51,360 --> 00:02:52,480 Gravity. 50 00:02:52,480 --> 00:02:55,000 The force of attraction between objects. 51 00:02:55,000 --> 00:02:59,200 On Earth, we feel gravity because of Earth's mass. 52 00:02:59,200 --> 00:03:02,640 Weight is just how we measure gravity's pull on things. 53 00:03:02,640 --> 00:03:07,400 In space, gravity is less because we are further away from the Earth's mass. 54 00:03:07,400 --> 00:03:12,320 The further away from a large mass like our Earth, the less gravity, and therefore, the 55 00:03:12,320 --> 00:03:13,320 less weight. 56 00:03:13,320 --> 00:03:16,120 What does this have to do with building a spacecraft? 57 00:03:16,120 --> 00:03:17,120 Everything, Zach. 58 00:03:17,120 --> 00:03:21,880 The mass of a spacecraft determines its weight, and the more a spacecraft weighs, the more 59 00:03:21,880 --> 00:03:23,680 force is needed to reach orbit. 60 00:03:23,680 --> 00:03:24,680 Force? 61 00:03:24,680 --> 00:03:26,120 I thought we were talking about gravity. 62 00:03:26,120 --> 00:03:29,400 Hmm, okay, I think we need to talk about some basics here. 63 00:03:29,400 --> 00:03:35,120 Lucky for us, 17th century English scientist Sir Isaac Newton explained the relationship 64 00:03:35,120 --> 00:03:36,920 of mass to gravity. 65 00:03:36,920 --> 00:03:41,000 He said we need force to overcome gravity. 66 00:03:41,000 --> 00:03:44,560 Newton described this relationship as a series of laws. 67 00:03:44,560 --> 00:03:47,840 Newton helped our understanding of gravity with his first law. 68 00:03:47,840 --> 00:03:50,160 What Newton said is easy to understand. 69 00:03:50,160 --> 00:03:54,600 An object at rest will stay at rest unless a force moves it. 70 00:03:54,600 --> 00:03:58,520 With a spacecraft, we need to come up with the force to move it. 71 00:03:58,520 --> 00:04:01,880 So we need to keep the weight, I mean, mass, low, right? 72 00:04:01,880 --> 00:04:02,880 Correct. 73 00:04:02,880 --> 00:04:05,560 Keeping the mass low will mean less weight at launch. 74 00:04:05,560 --> 00:04:09,960 The force of gravity on the spacecraft is equal to the force of the launch pad holding 75 00:04:09,960 --> 00:04:13,680 it up, what Newton called balanced forces. 76 00:04:13,680 --> 00:04:17,040 We have to unbalance these forces to move the spacecraft. 77 00:04:17,040 --> 00:04:18,040 How do we do that? 78 00:04:18,040 --> 00:04:22,160 Well, Cassie, Newton explained in his second law that if a force is applied to a body of 79 00:04:22,160 --> 00:04:26,200 mass, the body will move in the direction of the force. 80 00:04:26,200 --> 00:04:30,800 Newton also described in his third law that for every action, there is an equal and opposite 81 00:04:30,800 --> 00:04:32,160 reaction. 82 00:04:32,160 --> 00:04:35,000 The thrust of a rocket motor is the action. 83 00:04:35,000 --> 00:04:38,760 The reaction is the spacecraft leaving the pad. 84 00:04:38,760 --> 00:04:41,200 Thrust measures the power of a rocket engine. 85 00:04:41,200 --> 00:04:45,440 The thrust must be greater than the force of gravity that keeps a rocket on the launch 86 00:04:45,440 --> 00:04:46,440 pad. 87 00:04:46,440 --> 00:04:53,600 For example, if the thrust, T, of a rocket is 75 kilograms and the weight of the rocket, 88 00:04:53,600 --> 00:05:02,200 W, is 50 kilograms, then subtracting 50 from 75 would equal 25 kilograms of upward force, 89 00:05:02,200 --> 00:05:03,200 F. 90 00:05:03,200 --> 00:05:07,960 To get into orbit, you need to keep the upward force greater than the force of gravity. 91 00:05:07,960 --> 00:05:14,880 When you ride an amusement park ride like the Space Shot here at the Space and Rocket 92 00:05:14,880 --> 00:05:18,920 Center, you are overcoming gravity as you rise up. 93 00:05:18,920 --> 00:05:24,120 At the top, you experience free fall or microgravity, just like the astronauts. 94 00:05:24,120 --> 00:05:29,200 You just don't stay in free fall very long because you drop back downward as the downward 95 00:05:29,200 --> 00:05:32,720 force of gravity becomes greater than the upward force. 96 00:05:32,720 --> 00:05:34,600 That was awesome! 97 00:05:34,600 --> 00:05:39,360 The force of gravity is measured in units called Gs. 98 00:05:39,360 --> 00:05:42,520 At sea level, that force equals 1G. 99 00:05:42,520 --> 00:05:46,280 So we need more than 1G of force to move the rocket? 100 00:05:46,280 --> 00:05:49,000 Pretty much, Seema, but, you know, it's not as easy as it sounds. 101 00:05:49,000 --> 00:05:51,920 Let's take the Saturn V rocket of the Apollo program. 102 00:05:51,920 --> 00:05:55,960 Now, how much do you think that rocket weighed at launch? 103 00:05:55,960 --> 00:05:59,960 Remember how fast a spacecraft needs to travel in order to reach orbit. 104 00:05:59,960 --> 00:06:02,960 Yes, 17,500 miles per hour. 105 00:06:02,960 --> 00:06:03,960 Correct! 106 00:06:03,960 --> 00:06:06,760 And that's over 28,000 kilometers per hour. 107 00:06:06,760 --> 00:06:11,960 The Saturn V is taller than the Statue of Liberty and weighed over 6 million pounds 108 00:06:11,960 --> 00:06:12,960 at launch. 109 00:06:12,960 --> 00:06:18,920 The Saturn V's engines had to produce over 7.5 million pounds of thrust to have enough 110 00:06:18,920 --> 00:06:22,960 upward force to overcome the downward force of gravity. 111 00:06:22,960 --> 00:06:24,480 Okay, I get it. 112 00:06:24,480 --> 00:06:27,480 If we keep the weight of the rocket down, we won't need as much engine thrust to move 113 00:06:27,480 --> 00:06:28,480 it. 114 00:06:28,480 --> 00:06:29,480 Right! 115 00:06:29,480 --> 00:06:30,480 You guys are so smart. 116 00:06:30,480 --> 00:06:32,000 You know, engineers deal with this all the time. 117 00:06:32,000 --> 00:06:36,480 They use math to compare the vehicle weight to the thrust of the engines. 118 00:06:36,480 --> 00:06:40,840 Now, this can be written as a ratio, and a ratio is just a simple way of comparing one 119 00:06:40,840 --> 00:06:41,840 thing to another. 120 00:06:41,840 --> 00:06:45,160 In this case, vehicle weight compared to thrust. 121 00:06:45,160 --> 00:06:50,200 So let's talk about the Saturn V. Let's say it weighs a million pounds and it produces 122 00:06:50,200 --> 00:06:52,020 a million pounds of thrust. 123 00:06:52,020 --> 00:06:55,020 The ratio for that would then be 1 to 1 and wouldn't go anywhere. 124 00:06:55,020 --> 00:07:00,660 But the Saturn V's engines created 7.5 million pounds of thrust and the vehicle weighed 6 125 00:07:00,660 --> 00:07:01,660 million pounds. 126 00:07:01,660 --> 00:07:08,020 Yeah, so that's a ratio of 7.5 to 6, or let's see, 5 to 4. 127 00:07:08,020 --> 00:07:09,020 Exactly. 128 00:07:09,020 --> 00:07:12,020 Now you see how important it is to build rockets more lightweight. 129 00:07:12,020 --> 00:07:18,020 A couple of ways NASA scientists and engineers tackle this problem is by using lightweight 130 00:07:18,020 --> 00:07:21,260 materials and designing more efficient engines. 131 00:07:21,500 --> 00:07:26,900 Today, NASA is working on the next generation of reusable spacecraft, or Launch Vehicle 132 00:07:26,900 --> 00:07:27,900 System. 133 00:07:27,900 --> 00:07:31,060 We call it the Space Launch Initiative, or SLI for short.