WEBVTT - It Is, In Fact, Rocket Science 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:13.680 stuff works dot com. Hey there, and welcome to tech Stuff. 0:00:13.720 --> 0:00:17.200 I'm your host, Jonathan Strickland. I'm an executive producer at 0:00:17.200 --> 0:00:20.239 how Stuff Works and I love all things tech. And 0:00:20.280 --> 0:00:27.000 we are continuing our epic series about space and space travel. 0:00:27.240 --> 0:00:30.280 And I've covered the various spacecraft involved during the actual 0:00:30.360 --> 0:00:33.240 space race, from the vast Stock to the saw Us, 0:00:33.400 --> 0:00:36.440 from the Mercury to the Apollo, but I didn't really 0:00:36.440 --> 0:00:39.680 go into much detail about the launch vehicles or what 0:00:39.840 --> 0:00:43.360 we would more casually refer to as the rockets. So 0:00:43.400 --> 0:00:46.320 today we're gonna talk about rockets and the science behind 0:00:46.440 --> 0:00:48.280 them and some of the ones that have been used 0:00:48.320 --> 0:00:51.239 to put stuff what was once on Earth out in 0:00:51.360 --> 0:00:54.440 space somewhere. And don't worry, I'm not going to cover 0:00:54.520 --> 0:00:56.920 every single rocket that ever was put to such use. 0:00:57.400 --> 0:00:58.959 That would sound like I was reading off a very 0:00:58.960 --> 0:01:02.440 weird phone book, because it would involve not just all 0:01:02.520 --> 0:01:07.160 these odd names that we as Americans we asn't I'm 0:01:07.160 --> 0:01:11.120 saying myself here the Americans created, but also all the 0:01:11.200 --> 0:01:14.720 different designations that have been made by various countries around 0:01:14.720 --> 0:01:18.119 the world. Lots of countries have made launch vehicles. So 0:01:18.360 --> 0:01:20.240 I'm just gonna focus on some of the ones from 0:01:20.280 --> 0:01:23.880 the space race period because I think, uh, you know, 0:01:24.000 --> 0:01:27.120 it relates to the episodes I just did mainly, and 0:01:27.160 --> 0:01:30.360 also it has a nice narrow focus. The history of 0:01:30.440 --> 0:01:34.880 rockets stretches far back before there was ever a space race, 0:01:35.200 --> 0:01:37.560 or before there was a Soviet Union, or before there 0:01:37.600 --> 0:01:40.280 was a United States of America. And of course by 0:01:40.280 --> 0:01:43.000 that I mean before there were those nations. Obviously the 0:01:43.120 --> 0:01:45.520 land masses were there and there were people living on them. 0:01:45.560 --> 0:01:47.720 But you know what I mean. The origins of the 0:01:47.800 --> 0:01:51.200 rocket are closely tied to that of fireworks, and I've 0:01:51.240 --> 0:01:55.520 covered fireworks in previous episodes. Scholars have nailed down the 0:01:55.560 --> 0:02:01.279 emergence of rockets in Chinese alchemy sometime during the dynasty 0:02:01.520 --> 0:02:05.320 that stretched from nine sixty Common era to twelve seventy 0:02:05.400 --> 0:02:09.240 nine Common Era. The former curator of rockets for the 0:02:09.280 --> 0:02:12.880 Smithsonian National Air and Space Museum, a guy named Frank Winter, 0:02:13.280 --> 0:02:16.120 attempted to narrow that down a bit, and his work 0:02:16.200 --> 0:02:20.480 suggested that during the eleventh century, Chinese alchemists were trying 0:02:20.520 --> 0:02:23.280 to suss out a formula that would lead to eternal life. 0:02:23.919 --> 0:02:26.880 They were attempting to make practical use of the Chinese 0:02:26.880 --> 0:02:30.280 philosophy that all the universe is divided into passive and 0:02:30.400 --> 0:02:36.200 active forces, and that mixing your yin and yang materials 0:02:36.320 --> 0:02:40.680 in a proper way would create various amazing results, such 0:02:40.680 --> 0:02:44.920 as presumably never dying. So they never landed on a 0:02:44.960 --> 0:02:48.040 mixture that would preserve life indefinitely, but some of the 0:02:48.080 --> 0:02:52.359 mixtures did up having other interesting properties, like blowing up 0:02:52.480 --> 0:02:56.200 if you lit them, so they effectively invented an early 0:02:56.280 --> 0:02:59.800 form of gun powder. By twelve thirty two, the Chinese 0:02:59.840 --> 0:03:02.760 were using rockets in warfare. They had a weapon that 0:03:02.840 --> 0:03:06.440 they called the fai Ju san Uh. And I know 0:03:06.480 --> 0:03:09.880 I'm mispronouncing that. I apologize my Chinese is terrible, but 0:03:09.960 --> 0:03:14.359 it means flying fire lances. And if you listen to 0:03:14.440 --> 0:03:17.800 the fireworks episodes that we did on text of years ago, 0:03:18.240 --> 0:03:20.960 you know there are various myths and legends about Chinese 0:03:20.960 --> 0:03:24.880 thinkers who tried to use rockets for flight and the 0:03:24.960 --> 0:03:27.400 various results of those experiments. So I'm not going to 0:03:27.480 --> 0:03:30.240 go into those here. Instead, we're just gonna skip ahead 0:03:30.240 --> 0:03:33.520 a few centuries. In the fifteen nineties, in Germany, there 0:03:33.560 --> 0:03:37.800 was a fireworks maker named Johann schmid Lap, who attempted 0:03:37.840 --> 0:03:41.080 to create fireworks that could reach much higher altitudes through 0:03:41.080 --> 0:03:45.440 a process called staging. Staging is where you divide up 0:03:45.480 --> 0:03:49.760 a rocket into two or more stages, and each stage 0:03:50.120 --> 0:03:54.080 contains its own propellant. So when the first stage burns out, 0:03:54.520 --> 0:03:57.600 it ignites the second stage, which in schmid Lab's case 0:03:57.720 --> 0:04:00.640 was a smaller rocket that was carried by a larger 0:04:00.920 --> 0:04:05.080 first stage rocket. So the first stage rocket ignites launches 0:04:05.520 --> 0:04:08.480 as it gets towards the end of its fuel, it 0:04:08.560 --> 0:04:12.800 ignites the fuel inside the second rocket, which then continues 0:04:12.840 --> 0:04:15.920 to launch and go even higher into the sky and 0:04:15.960 --> 0:04:19.080 deliver the payload way up in there, and you get 0:04:19.080 --> 0:04:22.200 a really impressive firework. While schmid Lap made a practical, 0:04:22.320 --> 0:04:26.840 practical multi stage rocket, the idea had previously been theorized 0:04:26.880 --> 0:04:31.159 by an Austrian military engineer named Conrad hass hass wrote 0:04:31.200 --> 0:04:35.480 a manuscript about his ideas that predated schmid Laps designs 0:04:35.600 --> 0:04:39.279 by a few decades, including multi stage rockets. Even talked 0:04:39.279 --> 0:04:42.279 about the possibility of using liquid fuels as propellant, although 0:04:42.320 --> 0:04:45.720 that would take quite some time to come true. Now, 0:04:45.720 --> 0:04:48.880 whether schmid Lap knew of Hassa's work or not. I 0:04:48.920 --> 0:04:51.960 don't know. Maybe he did. It's possible that this was 0:04:52.000 --> 0:04:54.599 a case of two people coming up with essentially the 0:04:54.640 --> 0:04:57.560 same idea around the same time that has happened before. 0:04:58.000 --> 0:04:59.680 Or it could be that schmid Lap had heard of 0:04:59.720 --> 0:05:01.960 Hassa his ideas and that schmid Lap was the one 0:05:02.000 --> 0:05:05.040 who was able to make practical use of them. Either way, 0:05:05.120 --> 0:05:07.119 whether he came up with the idea or not, schmid 0:05:07.160 --> 0:05:09.560 Lap was the one who actually made it work. In 0:05:09.720 --> 0:05:14.520 seven Sir Isaac Newton published his work Principia, which included 0:05:14.560 --> 0:05:17.640 his three Laws of motion. So we see that the 0:05:17.680 --> 0:05:23.080 practical understanding of rocketry preceded a more nuanced scientific understanding 0:05:23.120 --> 0:05:26.520 of what was going on by several centuries, which is 0:05:26.560 --> 0:05:30.720 often the case where we notice something, we observe something interesting, 0:05:31.120 --> 0:05:33.880 and we even make use of that something for some time, 0:05:33.880 --> 0:05:35.720 but we don't have a full understanding of what's really 0:05:35.720 --> 0:05:38.880 going on until much later. That has happened on numerous 0:05:38.920 --> 0:05:42.640 occasions throughout human history. So what are the three laws 0:05:42.680 --> 0:05:44.880 of motion and why are they important? Well, the first 0:05:44.960 --> 0:05:48.320 law is every object in a state of uniform motion 0:05:48.520 --> 0:05:51.320 tends to remain in that state of motion unless an 0:05:51.360 --> 0:05:54.320 external force is applied to it. We also call this 0:05:54.480 --> 0:05:57.840 the law of inertia. So, for example, if there is 0:05:57.880 --> 0:06:01.479 a rock sitting on a level section of ground, we 0:06:01.520 --> 0:06:04.000 would expect that rock to just sit there, to remain 0:06:04.040 --> 0:06:07.440 in that position, to stay still, unless some external force 0:06:07.520 --> 0:06:10.440 like someone's foot were to come in and be applied 0:06:10.480 --> 0:06:12.240 to the rock. So soone kicks the rock, then we 0:06:12.240 --> 0:06:14.640 would expect it to move. But we wouldn't expect the 0:06:14.720 --> 0:06:17.279 rock to move on its own. It wouldn't just spontaneously 0:06:17.320 --> 0:06:20.800 start rolling around. That would be in violation of the 0:06:20.800 --> 0:06:24.840 first law of motion. The second law of motion is 0:06:24.880 --> 0:06:29.440 that the relationship between an objects mass, it's acceleration and 0:06:29.480 --> 0:06:35.120 the applied force is force equals mass times acceleration. Acceleration 0:06:35.120 --> 0:06:39.280 and force are vectors, meaning they don't just have a magnitude. 0:06:39.279 --> 0:06:43.000 They also have a direction, so you have to describe 0:06:43.080 --> 0:06:46.640 them as having a direction while you're working with them. 0:06:46.800 --> 0:06:50.280 You can't just give, you know, just a unit and 0:06:50.360 --> 0:06:56.560 be accurate and this law. In this law, the direction 0:06:56.600 --> 0:06:58.799 of the force vector is the same as the direction 0:06:58.880 --> 0:07:02.200 of the acceleration victor, so you can't have an acceleration 0:07:02.320 --> 0:07:05.560 vector that's an opposite direction of the force vector. The 0:07:05.560 --> 0:07:08.680 equation lets us understand how velocities change when we apply 0:07:08.839 --> 0:07:11.640 different forces to the system. And a change in velocity 0:07:12.240 --> 0:07:17.520 is acceleration, right, Velocity itself is uh is speed and direction, 0:07:17.760 --> 0:07:20.520 So acceleration is when you change something about that. You 0:07:20.600 --> 0:07:23.320 either change the speed, so you make it speed up, 0:07:23.400 --> 0:07:26.480 or you make it slow down, or you change the direction, 0:07:27.160 --> 0:07:30.440 which you know because velocity is a vector, and either 0:07:30.480 --> 0:07:34.200 one of those would be considered a change in acceleration, 0:07:34.320 --> 0:07:38.760 or rather it would be acceleration itself. And the third 0:07:38.800 --> 0:07:41.560 law of motion is for every action, there is an 0:07:41.600 --> 0:07:46.360 equal and opposite reaction. So you've probably heard this before, 0:07:46.520 --> 0:07:48.520 and I'm sure you have a decent understanding of it, 0:07:48.560 --> 0:07:51.000 but just in case, here's a way of thinking about. 0:07:51.040 --> 0:07:54.280 Imagine that you're standing on a platform that's suspended by ropes, 0:07:54.440 --> 0:07:57.640 right like it's a square platform. There are four ropes, 0:07:57.680 --> 0:08:00.640 one at each corner, and there's a second platform on 0:08:00.720 --> 0:08:02.600 a column that's in front of you. But in order 0:08:02.600 --> 0:08:03.920 to get there, you're gonna have to take a pretty 0:08:03.920 --> 0:08:06.600 big step. Not not a huge step, but a decent one. 0:08:07.040 --> 0:08:09.720 As you take that step, if there were another observer 0:08:09.920 --> 0:08:13.320 watching all this, they would notice that the platform you 0:08:13.360 --> 0:08:16.560 stand on would move the opposite direction of where you 0:08:16.560 --> 0:08:20.600 were stepping. This is that equal but opposite reaction. That's 0:08:20.600 --> 0:08:23.600 an exemplification of Newton's third law of motion. It's also 0:08:23.720 --> 0:08:27.480 ultimately what explains the phenomenon of a rocket flying into 0:08:27.520 --> 0:08:30.000 the air. When it's blasting what appears to just be 0:08:30.120 --> 0:08:33.160 fire and smoke out of its business end, the rocket 0:08:33.200 --> 0:08:36.800 is actually throwing mass in one direction in the form 0:08:37.000 --> 0:08:41.080 of very high pressured gas. The rocket itself moves in 0:08:41.160 --> 0:08:43.720 the opposite direction because of this. If you were to 0:08:43.800 --> 0:08:46.800 sit in an office chair that has wheels on it, 0:08:47.200 --> 0:08:49.120 and then you had a mess and ball in your hands, 0:08:49.120 --> 0:08:51.200 and you threw the mess and ball straight ahead of you, 0:08:51.679 --> 0:08:54.440 that you and the chair would roll backward. Because of 0:08:54.480 --> 0:08:57.920 this principle, rockets work the same way. It's just that 0:08:58.000 --> 0:09:00.120 the rocket is throwing up mass in the form of 0:09:00.160 --> 0:09:05.520 that high pressure gas an incredible rate. So remember that 0:09:05.640 --> 0:09:09.360 second law forces equal to mass times acceleration. That's also 0:09:09.480 --> 0:09:13.880 very important. The rocket has a lot of mass, particularly 0:09:13.880 --> 0:09:16.080 when it's full of fuel. You have the mass of 0:09:16.120 --> 0:09:18.120 the rocket structure and you have the mass of all 0:09:18.160 --> 0:09:21.720 the fuel inside of it. When a rockets engine, which 0:09:21.760 --> 0:09:25.880 is a reaction engine, It's important to note because when 0:09:25.880 --> 0:09:27.600 we hear the word engine. I don't know about you, 0:09:28.040 --> 0:09:30.360 but when I hear the word engine, I'm usually thinking 0:09:30.400 --> 0:09:36.720 about a mechanical device that forms some form of rotational power, right, 0:09:36.760 --> 0:09:39.920 a rotational force, like a reciprocating gasolene engine. That's kind 0:09:39.920 --> 0:09:42.640 of what I think about. But a rocket engine is 0:09:42.679 --> 0:09:47.720 a reaction engine. Rocket engines fling mass in that form 0:09:47.840 --> 0:09:51.319 of hot gas uh at a very high rate of acceleration, 0:09:51.760 --> 0:09:54.840 and the combination creates a lot of force. Right. So, 0:09:55.720 --> 0:09:58.679 however much mass it is times that acceleration that equals 0:09:58.720 --> 0:10:02.040 the force. Well, the equal and obvious that reaction means, 0:10:02.400 --> 0:10:05.960 if you're pushing that much mass downward at a very 0:10:06.000 --> 0:10:11.840 fast rate, then you're moving upward. Uh. And the speed 0:10:11.880 --> 0:10:14.880 at which you move is based upon how fast and 0:10:14.920 --> 0:10:19.360 how much stuff you're pushing down That that equation tells 0:10:19.440 --> 0:10:22.240 us all of this stuff, and we can actually figure 0:10:22.280 --> 0:10:25.320 out how much acceleration the rocket will experience if we 0:10:25.400 --> 0:10:29.040 know the mass and the acceleration of the hot gases 0:10:29.080 --> 0:10:31.040 coming out of its engine. The two sides of the 0:10:31.040 --> 0:10:33.560 equation have to balance out. It has to be equal 0:10:33.559 --> 0:10:36.760 and opposite, right, So rocket science is hard But let's 0:10:36.800 --> 0:10:39.240 go back to that office chair and medicine ball example, 0:10:39.320 --> 0:10:42.720 because that makes it way easier to understand. So practical example, 0:10:43.000 --> 0:10:45.520 let's say I'm sitting in an office chair and I 0:10:45.600 --> 0:10:49.240 have a mass of about sixty eight ms. The chair 0:10:49.320 --> 0:10:52.479 has a mass of about twenty two kilograms, so collectively 0:10:52.679 --> 0:10:55.920 the chair and I are nine DRAMs. The medicine ball 0:10:56.000 --> 0:10:59.240 I have has a mass of four point five rams. 0:10:59.600 --> 0:11:02.520 So at the very beginning of this I have a 0:11:02.559 --> 0:11:05.520 total mass of ninety four point five ms because I'm 0:11:05.559 --> 0:11:08.680 holding the medicine ball right, and then I also have 0:11:08.720 --> 0:11:13.240 a velocity of zero. I'm not moving, so I'm staying still. 0:11:13.760 --> 0:11:15.600 I've got this messin ball in my hands, and then 0:11:15.640 --> 0:11:18.000 I throw the mess and ball straight out in front 0:11:18.040 --> 0:11:21.679 of me at fifteen per second. That's about thirty three 0:11:21.720 --> 0:11:24.000 and a half miles per hour, and that's probably way 0:11:24.040 --> 0:11:25.840 faster than I could actually throw a messin ball. But 0:11:25.840 --> 0:11:28.480 forget that for now. How fast am I going to 0:11:28.520 --> 0:11:32.000 travel back in my chair? How fast will the chair 0:11:32.160 --> 0:11:36.480 roll backward in opposite direction from my throw? Well, to 0:11:36.600 --> 0:11:39.080 understand that, we take the velocity of the messin ball 0:11:39.160 --> 0:11:43.240 times it's mass, So we take that fifteen per second 0:11:43.679 --> 0:11:47.320 times four point five ms, which gives us sixty seven 0:11:47.360 --> 0:11:51.520 point five Newton's technically that represents the force of the 0:11:51.640 --> 0:11:54.280 medicine ball flying away from me. There must be an 0:11:54.320 --> 0:11:58.679 equal and opposite reaction, So that means the product of 0:11:58.720 --> 0:12:03.120 my mass and vela city has to equal negative sixty 0:12:03.160 --> 0:12:07.320 seven point five. It's equal and opposite of the original. 0:12:07.640 --> 0:12:10.720 Now it's negative because we're looking at velocity in the 0:12:10.720 --> 0:12:14.440 opposite direction of the medicine ball's flight, so it's it's 0:12:14.480 --> 0:12:17.839 from the perspective of medicine ball's flight being positive. Mine 0:12:17.960 --> 0:12:20.240 has to be negative. So it doesn't mean that I 0:12:20.320 --> 0:12:25.160 have some sort of weird negative unit of measurement. Instead 0:12:25.240 --> 0:12:28.800 is referring to it being a different direction and opposite direction. 0:12:29.640 --> 0:12:32.520 So again forces mass times acceleration, and we know what 0:12:32.600 --> 0:12:36.160 my mass is with the chair right, it's nine. And 0:12:36.200 --> 0:12:40.199 we know that the force is equal and opposite of 0:12:40.240 --> 0:12:42.199 the force that was in the medicine ball side of 0:12:42.240 --> 0:12:45.560 the equation, so we know it's the forces minus sixty 0:12:45.600 --> 0:12:49.680 seven point five. So that means we have to divide 0:12:49.679 --> 0:12:53.720 both sides by my mass. We divide minus sixty seven 0:12:53.720 --> 0:12:56.120 point five by my mass of ninety kilograms and we 0:12:56.240 --> 0:13:00.360 end up getting minus point seven five meters per second, 0:13:01.440 --> 0:13:04.800 So that means I'm traveling backward in my chair at 0:13:04.960 --> 0:13:09.360 point seven five per second initially before friction slows me down. 0:13:10.160 --> 0:13:13.800 Rocket science is exactly like that, only of course, way 0:13:13.800 --> 0:13:16.679 more difficult. We'll get into why it gets way more 0:13:16.720 --> 0:13:20.160 difficult in just a second, but first, y'all, I need 0:13:20.200 --> 0:13:23.000 to take a quick break. I'm gonna thank my sponsor. 0:13:30.480 --> 0:13:34.559 The science of rocketry continued in large part because rockets 0:13:34.559 --> 0:13:39.560 could be effective weapons of war. In four engineers discovered 0:13:39.600 --> 0:13:43.280 that by designing jet vents on an angle so they're 0:13:43.320 --> 0:13:46.800 not coming just straight out, a rocket would spin when 0:13:46.800 --> 0:13:49.720 it was ignited, and that spinning motion would actually create 0:13:49.720 --> 0:13:52.600 a stabilization in the rockets flight path, kind of like 0:13:52.760 --> 0:13:56.000 a bullet experience when it emerges from a gun, It 0:13:56.120 --> 0:14:00.320 spins and that produces stability. Uh. The st to ability 0:14:00.320 --> 0:14:03.520 of spinning objects would become a very important component, not 0:14:03.640 --> 0:14:06.080 just in space travel, but in technology in general. It's 0:14:06.480 --> 0:14:10.440 you know, I've talked about that with gyroscopes in Constantine. 0:14:10.440 --> 0:14:13.120 Soolkov Sky, who I talked about in the first episode 0:14:13.120 --> 0:14:16.040 of this whole series, proposed the possibility of space travel 0:14:16.120 --> 0:14:20.000 through rocketry. Moreover, he theorized that a liquid propellant would 0:14:20.040 --> 0:14:23.920 be a more suitable fuel source to provide the energy 0:14:24.040 --> 0:14:26.640 necessary to push a rocket into space, but had not 0:14:26.800 --> 0:14:32.000 quite worked out how that would actually happen. Solkovski worked 0:14:32.040 --> 0:14:34.880 on some really important details about the relationship between a 0:14:35.000 --> 0:14:38.000 rocket's mass and its speed and what it would take 0:14:38.000 --> 0:14:40.320 to get a rocket into space. So let's take a 0:14:40.320 --> 0:14:43.360 few moments to understand the calculations that are necessary. Now 0:14:43.400 --> 0:14:47.200 we've already covered the equal and opposite reaction. We understand 0:14:47.240 --> 0:14:50.000 that that whatever we want the rocket to do is 0:14:50.040 --> 0:14:53.080 going to be based upon the amount of mass it's 0:14:53.120 --> 0:14:56.560 throwing out through its engine and how fast it's throwing 0:14:56.600 --> 0:14:58.880 that mass out. But now we have to consider some 0:14:58.960 --> 0:15:02.640 other complicating fact. There's first, a rockets mass when it's 0:15:02.680 --> 0:15:06.280 fully fueled is different than the rockets mass one second 0:15:06.320 --> 0:15:09.520 before all the fuel burns up. That mass is decreasing. 0:15:10.320 --> 0:15:12.320 Now the mass is not being destroyed, it's just being 0:15:12.360 --> 0:15:15.600 thrown out of the engine. Because you cannot create or 0:15:15.680 --> 0:15:19.640 destroy matter. You can't convert it from one form to another, 0:15:20.600 --> 0:15:23.800 but you can't destroy it, So that mass isn't being destroyed. 0:15:23.840 --> 0:15:26.840 If you talk about a rocket that has, you know, 0:15:26.960 --> 0:15:30.720 twenty thousand tons of fuel aboard it. That twenty thousand 0:15:30.760 --> 0:15:33.480 tons of fuel gets turned into twenty thousand tons of 0:15:33.560 --> 0:15:36.880 high pressured gas during the process of being shot out 0:15:36.880 --> 0:15:40.160 of the engine. So burning fuel means you're ejecting mass 0:15:40.200 --> 0:15:43.600 through the rocket engine. So the rockets mass decreases throughout 0:15:43.640 --> 0:15:46.600 the engine burn and that affects the equations. And if 0:15:46.600 --> 0:15:49.120 you want that rocket to actually carry something into space, 0:15:49.480 --> 0:15:52.440 the payloads mass has to be taken into account along 0:15:52.440 --> 0:15:55.360 with the rocket in the fuel. Sometimes that can seem 0:15:55.400 --> 0:15:58.360 like it's negligible, but it's still really important. So getting 0:15:58.360 --> 0:16:00.320 a payload into space as a matter of the earning, 0:16:00.400 --> 0:16:03.040 how much force you will need to escape Earth's gravity, 0:16:03.480 --> 0:16:05.680 how large your rocket will need to be to do that, 0:16:05.840 --> 0:16:08.280 how much fuel you're gonna need to move that rocket, 0:16:08.480 --> 0:16:10.240 which in turn might mean that you have to make 0:16:10.320 --> 0:16:14.280 changes to how big the rocket is. And as this continues, 0:16:14.360 --> 0:16:16.200 you can easily see it get away from you. Right, 0:16:16.280 --> 0:16:18.720 you could say, well, to move something of this mass, 0:16:18.720 --> 0:16:21.280 i'm gonna need x amount of fuel. But if you 0:16:21.360 --> 0:16:23.320 have X amount of fuel, that's too much fuel for 0:16:23.360 --> 0:16:25.400 this rocket. So the rockets gonna have to be bigger, 0:16:25.640 --> 0:16:29.400 but the rockets bigger than the mass is greater, which 0:16:29.440 --> 0:16:31.440 means I'm actually gonna need more fuel than what I 0:16:31.480 --> 0:16:34.760 thought before, and that can quickly run away from you. 0:16:34.920 --> 0:16:38.200 So that's another complication. Any changed the design of the 0:16:38.280 --> 0:16:40.160 rocket or the payload is going to affect the amount 0:16:40.200 --> 0:16:42.520 of fuel you're gonna need to use. And of course, 0:16:42.520 --> 0:16:44.800 when you add more fuel, you add more mass, so 0:16:45.400 --> 0:16:49.560 it's really slippery slope. When you burn the fuel, you 0:16:49.600 --> 0:16:52.640 create this high pressure gas, and releasing that gas in 0:16:52.680 --> 0:16:56.200 a specific direction provides the thrust to push a rocket. 0:16:56.760 --> 0:16:58.880 The weight of fuel you burn is equal to the 0:16:58.880 --> 0:17:00.960 weight of the gas that is generated, So if you 0:17:00.960 --> 0:17:02.960 burn a ton of fuel, you have created a ton 0:17:03.040 --> 0:17:06.359 of high pressure gas. The burning process is what actually 0:17:06.359 --> 0:17:10.000 accelerates the mass with the release through the nozzle that 0:17:10.040 --> 0:17:14.119 provides thrust, and the nozzle also can increase the the 0:17:14.160 --> 0:17:18.080 acceleration or it accelerates. Rather, I shouldn't say increases the acceleration, 0:17:18.119 --> 0:17:23.120 it accelerates the mass further. And by this incredible acceleration 0:17:23.760 --> 0:17:27.560 multiplied by the mass of the high pressure gas that 0:17:27.600 --> 0:17:30.680 you're shooting out of this rocket engine, that's what creates 0:17:30.680 --> 0:17:34.200 the force that allows a rocket to lift off the ground, 0:17:34.680 --> 0:17:37.560 and we measured thrust in either Newton's as I mentioned earlier, 0:17:37.680 --> 0:17:39.320 or in the good old us of A. Because we 0:17:39.720 --> 0:17:42.560 obviously refuse to do things the way the rest of 0:17:42.560 --> 0:17:45.520 the world does it, we refer to it as pounds 0:17:45.560 --> 0:17:48.120 of thrust. One pound of thrust is equal to four 0:17:48.160 --> 0:17:51.359 point four or five Newton's of thrust, and one pound 0:17:51.359 --> 0:17:53.320 of thrust is what would take to keep a one 0:17:53.320 --> 0:17:56.720 pound object stationary against the force of gravity on Earth. 0:17:57.359 --> 0:18:00.440 One Newton is the amount of force necessary to make 0:18:00.520 --> 0:18:03.879 one mass of one kilogram accelerate at a rate of 0:18:03.960 --> 0:18:08.280 one m per second squared. This means on Earth, a 0:18:08.320 --> 0:18:11.920 mass of one kilogram pushes against whatever it is resting 0:18:11.960 --> 0:18:15.720 on with a force of nine point eight Newton's on average. 0:18:15.840 --> 0:18:20.080 So if you have a kilogram weight on a table, 0:18:20.400 --> 0:18:24.720 that kilogram is effectively pushing against the table with nine 0:18:24.720 --> 0:18:27.879 point eight newtons of force, the tables pushing back with 0:18:28.080 --> 0:18:31.760 nine point eight newtons, a force equal and opposite. And 0:18:31.840 --> 0:18:34.560 the reason why it's nine point eight Newton's it's because 0:18:34.600 --> 0:18:40.120 Earth's gravity, at least at mean sea level, is nine 0:18:40.160 --> 0:18:44.399 point eight meters per second squared. To get space to 0:18:44.480 --> 0:18:46.400 get up to space. You have to travel fast enough 0:18:46.400 --> 0:18:48.400 to break free of the gravitational force of the Earth. 0:18:49.200 --> 0:18:51.240 We actually figured out exactly what speed we need to 0:18:51.240 --> 0:18:54.840 do that, so that speed would be eleven kilometers per 0:18:54.880 --> 0:18:58.120 second or seven miles per second. You gotta get at 0:18:58.359 --> 0:19:02.840 at that speed in order to breakthrough an escape Earth's gravity. 0:19:02.880 --> 0:19:07.280 On March sixteenth, ninety, Robert Goddard, whom I also mentioned 0:19:07.280 --> 0:19:10.439 in that earlier episode, created a rocket that used liquid 0:19:10.560 --> 0:19:15.119 oxygen and gasoline as propellant. Liquid oxygen was used as 0:19:15.119 --> 0:19:18.040 the oxidizer. He also got to work developing multi stage 0:19:18.119 --> 0:19:20.960 rockets and liquid fuel rockets. This was a big deal. 0:19:20.960 --> 0:19:23.720 It was the first liquid fuel rockets. They're very important, 0:19:24.040 --> 0:19:26.719 but up until Goddard, no one had figured out how 0:19:26.760 --> 0:19:29.360 to do them. They had been using solid fuel rockets, 0:19:29.359 --> 0:19:31.880 like the gunpowder rockets that the Chinese had created way 0:19:31.920 --> 0:19:36.919 back in the Sum dynasty. Uh. Solid fuel rockets burned quickly, 0:19:37.920 --> 0:19:41.680 and if they're designed properly, they do not explode. It's 0:19:41.680 --> 0:19:45.679 easier said than done. It requires finding the right mixture 0:19:45.720 --> 0:19:47.879 of components so as you can have a rapid but 0:19:48.040 --> 0:19:51.719 controlled burn, and uncontrolled burn turns into an explosion. So 0:19:51.760 --> 0:19:55.479 typically solid fuel rockets have a whole kind of down 0:19:55.520 --> 0:19:58.240 the center think of think of a solid fuel rocket. 0:19:58.720 --> 0:20:00.960 Think of it as taking the case of the rocket 0:20:01.040 --> 0:20:05.399 off and you have a a solid cylinder of fuel. 0:20:06.359 --> 0:20:11.880 Down the center of that cylinder is a tube or 0:20:11.920 --> 0:20:17.080 a hole, and you ignite the fuel in the center 0:20:17.119 --> 0:20:20.480 of this tube and it burns from the center out 0:20:20.560 --> 0:20:25.560 towards the edge where it's making contact with the casing 0:20:25.600 --> 0:20:28.800 of the rocket, and then the fuel is spent. The 0:20:28.840 --> 0:20:32.080 thing about it is, once you ignite a solid fuel rocket, 0:20:32.800 --> 0:20:36.280 it burns until all the fuel's gone. There's no stopping 0:20:36.320 --> 0:20:40.119 the engine once you start. Liquid rockets, however, offer up 0:20:40.160 --> 0:20:43.480 more control. You can actually turn on or turn off 0:20:43.560 --> 0:20:46.600 the burn process, so you can control the rocket engine 0:20:46.640 --> 0:20:49.560 that way. But they also come with other challenges. So 0:20:49.640 --> 0:20:52.520 to burn stuff, you need three things. We all remember 0:20:52.520 --> 0:20:55.479 the triangle, right, You need heat, you need fuel, and 0:20:55.520 --> 0:20:58.120 you need an oxidizer. And here on Earth we tend 0:20:58.160 --> 0:21:02.000 to just rely on oxygen. Right, that's our oxidizer. We 0:21:02.040 --> 0:21:03.879 also don't have to do anything special with it if 0:21:03.880 --> 0:21:06.000 we're on the surface of the planet. But in liquid 0:21:06.080 --> 0:21:09.080 rocket design, you need to have an oxidizer incorporated into 0:21:09.160 --> 0:21:12.600 the design of the propulsion system in order to create 0:21:12.600 --> 0:21:15.359 an environment in which fuel can actually burn. You cannot 0:21:15.359 --> 0:21:20.400 burn fuel without an oxidizer. Liquid oxygen is a frequent oxidizer, 0:21:20.480 --> 0:21:23.160 or at least in the early rockets, that was frequently used, 0:21:23.600 --> 0:21:26.600 and that's what Goddard did. The oxidizer and fuel end 0:21:26.640 --> 0:21:31.600 up being pumped into a combustion chamber and it's mixed there, 0:21:31.640 --> 0:21:35.240 so you get a fine mix of oxidizer and fuel 0:21:35.680 --> 0:21:38.880 which can then be ignited that ends up burning off 0:21:38.880 --> 0:21:42.199 and creating this high pressure gas that then can be 0:21:42.240 --> 0:21:45.359 directed through a nozzle to create the thrust. The combustion 0:21:45.440 --> 0:21:48.399 chamber and the nozzle can get really really hot, like 0:21:48.560 --> 0:21:51.639 hot enough to break down if the heat goes unchecked. 0:21:51.920 --> 0:21:56.000 So typically a liquid fueled rocket design will include either 0:21:56.080 --> 0:22:00.800 the oxidizer or the fuel as a super cold cryogenic 0:22:00.960 --> 0:22:04.359 liquid like liquid oxygen obviously has to be a cryogenic liquid, 0:22:04.400 --> 0:22:07.320 or liquid hydrogen has to be a cryogenic liquid. You 0:22:07.359 --> 0:22:10.000 have to get them at very very cold temperatures in 0:22:10.080 --> 0:22:13.600 order to keep that stuff in liquid form. Typically those 0:22:13.600 --> 0:22:17.240 cryogenic liquids would pass through lines that are adjacent to 0:22:17.280 --> 0:22:21.520 the combustion chamber and nozzle and transfer heat away from 0:22:21.560 --> 0:22:24.600 those parts of the rocket engine and the pumps that 0:22:24.680 --> 0:22:27.320 provide the oxidizer in the fuel to the combustion chamber 0:22:27.520 --> 0:22:32.359 have to be incredibly strong because inside that combustion chamber 0:22:32.359 --> 0:22:35.280 you're generating that high pressured gas. If the pumps are 0:22:35.280 --> 0:22:39.040 not strong enough to overcome that high pressure, then the 0:22:39.080 --> 0:22:42.800 gas is gonna go up those pump lines instead of 0:22:42.800 --> 0:22:45.720 out the nozzle, or they'll go up the pump lines 0:22:45.760 --> 0:22:48.280 and out the nozzle, and you don't want that. So 0:22:48.320 --> 0:22:50.080 you have to have very very strong pumps in a 0:22:50.160 --> 0:22:54.920 liquid fuel rocket, which is why, uh, it's a complicated process. 0:22:55.000 --> 0:22:57.600 Is a complicated technology, and it's why it took a 0:22:57.680 --> 0:22:59.880