Để tên lửa nước rơi xuống an toàn thì cần có dù
Many students have trouble with their nosecone getting stuck on the top of the rocket and not coming off. This can be prevented by making a pedestal for the cone to sit on. It should be high enough up so that there is space between the cone and the top of the parachute compartment. You can make a pedestal out of the same material you will make the fins, the manila folder. Make three mini-fins, invert them and tape them on the rocket where the cone should sit.
Making the Parachute
Don't forget a good parachute has shroud lines that are at least as long as the diameter of the canopy.
Lay your garbage bag out flat. Cut off the closed end. It should look like a large rectangle and be open at both ends. Lay down the bag on a flat surface and smooth it out.
The bag has a long side and a short side and is open at both ends. Fold it in two so that the short side is half as long as it was originally.
Make sure the edges are perfectly lined up during each fold. Now fold it in half along the long axis.
Make a triangle with the base of the triangle being the closed end of the previous fold.
Now fold it again. Fold the hypotenuse so that it lines up with the right side of the triangle in the above drawing.
Examine the base of the triangle and find the shortest length from the tip to the base. This is the limiting factor for chute size. The most pointed end will end up being the middle of the canopy.
Fold the canopy in half, then into quarters, then into eighths. Carefully crease the folds each time. Crease it well and fold it again. Now the canopy is divided into 16ths. Unfold the parachute. Notice the crease marks. Get masking tape and put a piece around the edge at each fold mark. You may also use Avery reinforcement tabs. Place one on both the inside and outside of every crease, making sure that they are overlaid on top of each other.
Punch holes through every piece of masking tape or Avery tab pairs and use these to attach the kite-string shroud lines.
As mentioned earlier the minimum length of the shroud line should be the same length as the diameter of the canopy.
After punching the holes fold the canopy in half. Pick four holes and tie the shroud lines to the holes. After doing this tie the four lines together at the end most distant from the canopy.
Repeat this four times until the chute is completed.
Once you have it complete attach it inside the fuselage. Generally a couple of pieces of duct tape will hold the parachute to the rocket. Pack the parachute loosely and put the nosecone on the rocket.
You are now ready to launch your rocket.
Carefully read the safety instructions. Fill the rocket half full of water, place on the launch pad, pressurize, and launch.ư
Nguồn:
http://www.lnhs.org
* Bài gửi của aiHung_Champion tại diễn đàn cũ PAC trên phobachkhoa.com