1 00:00:00,000 --> 00:00:06,589 Welcome to CANSAT EVA 2 00:00:11,589 --> 00:00:17,120 Let's talk about parachute design. 3 00:00:17,120 --> 00:00:24,140 Parachutes are vital parts of any CANSAT mission. 4 00:00:24,140 --> 00:00:34,140 They are often regarded as simple pieces of public compared to the complex electronics that lies within the CANSAT. 5 00:00:34,140 --> 00:00:36,140 But that's a big mistake. 6 00:00:36,140 --> 00:00:44,740 Without a well-designed parachute, your concept might not have time to complete its scientific 7 00:00:44,740 --> 00:00:50,179 objective, or rather yet, it could crash land. 8 00:00:50,179 --> 00:00:59,380 As in any other engineering project, our concept must meet some specific requirements, such 9 00:00:59,380 --> 00:01:09,079 such as the size, mass and even more important, the concept's design speed must not be lower 10 00:01:09,079 --> 00:01:18,659 than 5 ms or higher than 12 ms for safety reasons. 11 00:01:18,659 --> 00:01:25,939 For recovery reasons, a maximum flight time of 120 seconds is recommended. 12 00:01:25,939 --> 00:01:35,739 Without a well-designed parachute, these requirements cannot be met. 13 00:01:35,739 --> 00:01:39,680 Let's try to understand our design equation. 14 00:01:39,680 --> 00:01:47,180 First, we are going to draw the free-body diagram to analyse all the forces acting on 15 00:01:47,180 --> 00:01:49,219 our contact. 16 00:01:49,219 --> 00:01:58,260 The two main forces acting on it are the weight due to gravity and the drag force due to the 17 00:01:58,260 --> 00:02:05,760 resistance. Combining these equations and considering Newton's laws, we can get to 18 00:02:05,760 --> 00:02:13,300 the design equation. In the fall, the cansat is dropped, then the initial 19 00:02:13,300 --> 00:02:19,919 velocity is zero and the only force acting on it is gravity. As it falls, the 20 00:02:19,919 --> 00:02:28,509 velocity increases and the drag force increases as well. Finally, both forces 21 00:02:28,509 --> 00:02:35,710 are balanced and the terminal velocity is reached. From this point on the cancels 22 00:02:35,710 --> 00:02:45,159 will form at a steady rate. Combining these forces we reach to the design 23 00:02:45,159 --> 00:02:55,000 equation where A is the canopy surface area equals 2 times the mass times the 24 00:02:55,000 --> 00:03:03,860 acceleration of gravity divided by the product of the air density, zv, the drag 25 00:03:03,860 --> 00:03:09,960 coefficient and the square terminal velocity. Canopy surface area can be 26 00:03:09,960 --> 00:03:16,900 changed by making the parachute smaller or larger and the drag coefficient can be 27 00:03:16,900 --> 00:03:23,620 changed using a different style of parachute. Drag coefficients are 28 00:03:23,620 --> 00:03:34,180 are determined experimentally. We are going to design a flat octagon parachute. 29 00:03:34,180 --> 00:03:43,259 Applying several geometric equations, we can reach to the length and the height needed 30 00:03:43,259 --> 00:03:52,919 to draw a template of the triangles. With the 8 triangles joined together, the complete 31 00:03:52,919 --> 00:04:01,979 template of the flat octagon is ready to be used but there is an easier way to 32 00:04:01,979 --> 00:04:13,919 get our parachute ready. We will show you how to do it using a little bag. The first 33 00:04:13,919 --> 00:04:22,980 step is to fold it in half so that you will make a square. Cut the remaining 34 00:04:22,980 --> 00:04:38,949 part to get a complete triangle so with a square fold it in twice in half fold it again and again 35 00:04:41,970 --> 00:04:55,959 and then cut it so you have a triangle cut the tip to make the spill and there it is your canopy 36 00:04:55,959 --> 00:05:06,800 is ready. Cut a piece of thread. Join the thread to the corners of the canopy using 37 00:05:06,800 --> 00:05:18,370 fellow tape. Do the same with the other three pieces of thread. Congratulations! 38 00:05:18,370 --> 00:05:34,029 your parachute is now ready