Regional Final - Parachute
For our parachute prototype in the regionals we looked for a simple solution which was using an umbrella which gave us an hexagonal shaped parachute. We initially ignored our teachers advice regarding calculations and went straight into design. We simply took the fabric off of the umbrella, and attached several pieces of strings which later on held a can. The can was filled with stones to be 320g, and was dropped from a certain height. The descent speed was 5 m/s, which was far from the optimal velocity of 8m/s ~ 11m/s. This hexagonal parachute needed to be trimmed.
We went back to the drawing board and read the section on parachute design. The optimal surface area was found out using the formula FD = ½ r Cd A v2 , where Fd is the drag force, p is the density of air, Cd is the drag coefficient, A is the area of the parachute, and v is the velocity through the air. |
National Final - Parachute
For the Nationals we wanted to keep our parachute, because it worked very well. To make it tangleproof we added a little net between the strings.
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To test our parachute we dropped it several time from different windows on schools ground. As soon as we were happy with our parachute we did a few drone tests to reach a higher altitude and see the impact of wind better.
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European Parachute
For the European Final we are looking at completely redesigning our parachute. We have a GPS system in place that tells us its current coordinates of the can. The can we hope will self guide itself towards a inputted destination using coordinates. This is achieved through automatically controlling the parachute with an internal motor (180 degree servo).
The new design is similar to that which many skydivers use. It is a 14-cell Ram Air Canopy parachute. The material used is ripstop which is slightly more expensive than other sources however it’s waterproof, durable, air resistent, and very light. The pieces were cut from 4 templates that we made. There are a total of 17 pieces. 13 inner ribs which include holes in the centre to allow air flow within the canopy, 2 outer ribs which are longer, a top and a bottom sheet. We made calculations using the parachute formula which worked out that we needed an area of roughly 541.5cm^2. However we soon realised that this formula won’t work for us because our parachute is tilted. This means instead of fully resisting the air it pushes it through it giving us a forward push. |
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