Water rocket
Water rocket is also called a pneumatic water jet rocket and a water propulsion rocket. It uses discarded beverage bottles to make power cabins, rocket bodies, arrows, tail fins, and parachutes. Pour in one-third of the water, use a pump to inflate air to a certain pressure and then launch. It uses the mass ratio of water and air (the density of water is 771 times that of air). The compressed air sprays water downwards from the nozzle at the tail of the rocket at high speed. Under the reaction, the water rocket rises rapidly, gliding in the air with acceleration and inertia. The rocket model has a flight trajectory like a missile, and finally reaches a certain height, opens a parachute in the air and slowly lands.
Water Rocket is a hands-on and brain-based science popularization textbook that is entertaining and has high scientific and technological content. It is very popular among teenagers. It allows students to intuitively understand the launch and recovery process of missiles and carrier rockets, as well as the principles and differences between missile flight and aircraft flight. Explain Newton's first, second and third laws (action and reaction, inertia, conservation of energy) and understand some basic aerodynamics and flight mechanics. Let the majority of young people understand and love aerospace technology, and cultivate, cultivate and deliver outstanding talents for the national aerospace industry. (Competitions have been held many times across the country~~)
Launching Principle
Use a rubber-stoppered bottle to form a sealed space. Pour the gas into a closed container, causing the air pressure in the container to increase. When it exceeds the maximum degree of joint between the rubber stopper and the bottle mouth, the bottle mouth and rubber stopper are free to separate, and the water in the arrow spurts out backward, gaining reaction force and shooting out. ． The biggest difference between a water rocket and a rocket is that the propulsion medium changes from high-temperature air to water. Before launching a water rocket, air will be poured into it to reach a certain pressure. Since high pressure will naturally flow to low pressure, when the nozzle is opened, the air will naturally flow to the nozzle. However, since the water is blocked in front, the water will be pushed out of the rocket by the air. , and the rocket also gains forward speed.
Reaction force
Material preparation
2 to 6 2.25L Coke bottles, scissors, single-sided blade, cork, ball air needle, ballpoint pen Core, stapler, double-sided tape, colored decorative paper. Light and airtight materials such as tablecloths
Production process
1. Making the pressure plug: Use a knife to cut off the thicker end of the rubber plug. The diameter of the incision is 2.3cm, and pass it through the small Install the valve core, hose, and nut into the hole, and force the rubber stopper into the bottle mouth so that the part exposed outside the bottle mouth does not exceed about 2mm; use scissors to dig a hole with a diameter of about 12mm in the middle of the beverage bottle cap so that it can be used When tightening the bottle cap, only the valve core is exposed.
2. Production of side wings: Cut out four side wings with pieces of cardboard. In order to make the rocket have better stability during flight, the side wings must have higher hardness. If the paper pieces are not hard enough, It can be made by gluing two or three pieces together. After cutting the side wings, alternately fold the "sticking claws" back on both sides and stick them symmetrically on the lower side of the rocket with transparent tape.
3. Take out one of the Coke bottles and cut it into three equal parts at approximately 1/3 intervals. As shown in Figure 2, leave the mouth and middle part of the bottle, and turn the second Coke bottle upside down. As shown in Figure 3, cover the mouth of the first bottle with the bottom of the second Coke bottle, and then cover the middle section of the first bottle with the mouth of the second Coke bottle. After covering it, stick it tightly with double-sided tape. Find another piece of cardboard and cut out balance wings. The number of balance wings is 4. Balance wings that are too big are heavy, and balance wings that are too small cannot play a balancing role.
4. To make a parachute, fold a square tablecloth in half, then fold it in half again, taking the midpoint as the center, fold it in half twice, and use scissors to cut off the excess part to make it round. , stick the line. 1 Prepare materials. Three or four 2.5-liter Jianlibao bottles or Coke bottles, some X-ray films, a few No. 3 and No. 4 soft rubber stoppers for chemical equipment, a complete set of bicycle valve cores, one pair of scissors and a knife, transparent tape, double-sided Glue and insulating tape, one stick of 502 glue.
5. (1) Wing production. Use scissors to cut the X-ray film into 28 right-angled trapezoids of the same size. The trapezoid is 12cm long and 6cm high. The angle between the oblique waist and the long base is about 45 degrees.
Cut another 4 trapezoids with the same specifications as above but with a height of 8cm and a short base connecting the two overlapping sides (to be used as the surface of the wings). Use double-sided tape to tightly glue 7 small trapezoids into a thick trapezoid, making it straight and flat, and then wrap it tightly with a large double-sided trapezoid and glue it tightly. To make the thick surface of the wing flat, you can use scissors or a knife to straighten it, and then seal the thick surface of the wing with insulating glue. Finally, fold the extensions on both sides of the wing outward to 90 degrees. In this way, the remaining X-ray films are made into three machines according to the above method. (2) Airframe production. Take a Jianlibao bottle (the excessive arc of the bottle head is more natural, and it can be used as a rocket head to reduce air resistance), cut it in cross section 11cm from the lower end, and use insulating glue to glue the part with the bottle mouth to the other bottle At the bottom, use insulating glue to wrap a few more turns around the joint to make it secure. (3) Air plug production. Take a No. 4 soft rubber plug, use a hole-drilling tool to make a straight hole slightly smaller than the valve core sleeve in the middle of the bottom of the rubber plug, and then use a knife to cut off the thin end about 0.6cm; cut the valve core Put a larger "ring" on the sleeve (available in hardware stores), install the valve core from the thin end of the soft rubber plug upwards, put on a similar "ring", and tighten the screws, just a little tight. . Finally, use a whetstone to grind the air plug into a cylinder until it can fully enter the mouth of the Coke bottle or be slightly tighter. Install the valve core and it can be used. (4) Cannon head production. Take a No. 3 soft rubber plug and use a knife to sharpen it and make it smooth. (5) Assemble the wings. Take a Jianlibao bottle and cut a cylinder with two connected sides slightly longer than the length of the wings. Then use transparent glue and insulating glue to glue the four wings into four equal parts. Finally, place the cylinder with the wing glued on it on the bottom of the water rocket so that it is level with the mouth of the bottle (this is not necessarily the best position, you can adjust it up and down during flight practice to find out), and wrap it with insulating glue and glue it tightly. (6) Others. In order to increase the contact surface between the air plug and the bottle mouth and increase the air pressure inside the bottle, you can use a knife to thin the big end of the air plug and make it round, flat and rough. Since the fuselage has a section added to make the rocket head, the rocket head is light and unbalanced. Paper can be stuffed inside to achieve balance. In order to reduce air resistance as much as possible, glue the cannon head made of soft rubber stopper to the mouth of the rocket head bottle with 502 glue. Follow the above method to make a simple water rocket. According to the water rocket we developed, through practical improvements, it can fly up to about 160 meters in the horizontal direction and 40 to 50 meters in the vertical direction.
Water rocket launch method: 1. Water volume control. There is a certain ratio between the water consumption of a water rocket and the rocket's air holding space. It cannot be too much or too little. The optimal water consumption is about 1/4 to 2/5 of the rocket's air holding space (2.5 liters of space can hold about 600 milliliter or so, you can try several times to find out).
2. Launch angle. When flying horizontally, due to air resistance, the optimal launch angle is between 50 and 55 degrees. Different water rockets may be different and can be determined experimentally by controlling variables. (The best angle for the water rocket we made is about 53 degrees). When flying vertically, it is 90 degrees.
3. Use air lock. The principle of using the air plug is to adjust the tightness of the air plug by compressing the volume of the soft rubber plug and expanding it. The greater the compression, the greater the volume expansion, the tighter the air plug, and the greater the air pressure required to flush out the air plug, which is what the rocket obtains. The greater the power. The specific usage method is as follows: first remove the valve core of the air plug, insert the air plug into the bottle mouth of the rocket in its original shape, and then use a sleeve (a tool specially used to tighten screws, available in hardware stores) to tighten the air plug. screws, and finally install the valve core and it can be filled with air. (Note: The tightening degree can be adjusted as needed.)
4. Launch stability control. Only horizontal emission is discussed. A launch pad needs to be made. The launch pad must be equipped with a navigation track. The navigation track should not be too long or too short. It is generally 60cm long (it can be made up of three large triangle plates for teaching and two broom handles. In order to reduce the number of broom handles) For the friction of the water rocket when making the navigation track, transparent glue can be used to paste the broom handle or the model as shown in the illustration). In calm weather, launch directly at the target at the optimal launch angle (referring to the angle between the launch track and the ground). In windy weather, the direction of the launch target should be appropriately adjusted depending on the wind strength and direction to maintain the best launch angle.
5. Things to note. When launching, make sure that the rocket and the track are straight and consistent. Any deviation of 1 to 2 degrees will affect the stability of the flight and cause it to fly in an "8" shape. When inflating with a pump, make sure it is as smooth as possible, and the pumping frequency should not be too slow but should be faster. To plug the air plug as tightly as possible, you can adjust it by tightening the screw of the air plug. The tighter the air plug is, the greater the air pressure in the bottle will be and the greater the power of the rocket will be. Take the first bottle and call it bottle A. Draw a line at positions 1-1 and 2-2 above and below the bottle. The position of the two lines is determined as follows. 1-1: Select the place where the arc curvature on the bottle is similar to the curvature of the rocket foam head. 2-2: Select a point about 0.5cm below the straightening point of the curve below the bottle.
Cut (cut) with a utility knife (or scissors) about 0.5cm above line 1-1 and below line 2-2.
Use scissors to slowly trim to the drawing line, trying to make it as flat as possible so that it can be more closely connected to bottle B. Place the rocket foam head on top of bottle A and check whether the foam head is aligned with the center of the bottle from directly above. If it has been placed correctly, use electrical tape to wrap around the connection and secure it. Take another bottle and call it bottle B, remove the bottle cap, and then tighten the nozzle through the opening of the bottle. Connect bottles A and B. Then roll it on a flat tabletop or the ground to see if the connection is flat and the rolling is smooth. If so, secure it with electrical tape. Take the third bottle and call it bottle C. Draw a line at positions 3-3 and 4-4 on the bottles. 3-3: Select about 0.5cm below the turning point of the curve above the bottle. 4-4: Select about 0.5cm below the turning point of the curve below the bottle. Cut (cut) with a utility knife (scissors) about 0.5cm above line 3-3 and below line 4-4. Fold the cardboard in half and draw four trapezoids with a pencil. Then cut along the line with scissors. Note: The size and shape of the tail can be changed in different ways to test its impact on flight. Also use the slide to make a trapezoid with the same specifications as the thick cardboard. Wrap the prepared transparencies around the outside of the thick cardboard trapezoid. You can first use double-sided tape to join the transparencies and thick cardboard together, and then use electrical tape to tape them on three sides. Apply double-sided tape to the bottom of the folded part. This step is to attach the four completed tail fins to the C bottle. Completed picture of the four tail fins. Attach the four tail wings to the C bottle and make sure they are cross-symmetrical so that they can be balanced. First, use electrical tape to stick to both sides of the tail fin. When sticking, please note that the length of the electrical tape must be long enough. The top part should be about one tape height higher than the tail fin. The bottom part should be folded into the C bottle to increase the firmness. Then wrap the electrical tape around the top of the tail wing about two times. Use electrical tape to connect bottles C and B. Note: You must also pay attention to keeping the water rocket body straight to ensure the accuracy of the flight direction.