What are Water Rockets?

Water rocket is a toy designed by using mass ratio and air pressure. It is also one of the famous cases in physics teaching. It can cultivate students' interest in physics learning, and the physics principles contained in it are an important basis for understanding mechanics in physics. .

Close the bottle with a rubber stopper to form a closed space. Push the gas into the closed container, so that the pressure of the air in the container increases. When the maximum degree of the rubber stopper and the mouth of the bottle is exceeded, the mouth of the bottle and the rubber stopper are freely separated, and the water in the arrow is ejected backward to obtain a reaction force The biggest difference between a water rocket and a rocket is that the medium it propels from hot air to water. Before launching the water rocket, the air will be filled to a certain pressure. Because the high pressure will naturally flow to the low pressure, when the nozzle is opened, the air will naturally flow to the nozzle, but because the water is blocked in front, the water will be pushed out of the rocket by the air. , And the rocket also used this to gain forward speed.

At an altitude of 830 meters, it was created by several students at the University of Cape Town. The rocket has a strange shape and looks like a chopstick from a distance. Designed by a professional team after several data collection and analysis calculations, the exterior is made of special materials. It is quite different from the traditional water rocket manufacturing process and concept.

The relationship between the vertical height of the water rocket and the water level in the bottle:

The relationship between the vertical height of the water rocket and the water level in the bottle can be obtained through experiments: through experiments, when the water volume is 1/3, the water rocket flies the highest. From the experimental results, it can be seen that the pressure is proportional to the range. This is because the greater the air pressure, the greater the power of the water jet, the greater the impulse of the water rocket, and the water rocket does a recoil motion. When the launch water volume is more than 1000ml, the water in the water rocket has not been sprayed, and the acceleration stops due to the decrease in air pressure. The weight of the water rocket is increased, and the water rocket falls under the influence of gravity. The greater the mass, the greater the momentum that needs to be provided. When the mass is constant, the greater the velocity, the greater the momentum. The method to increase the speed is to increase the amount of water spray per unit time. Therefore, only when the air pressure and the amount of water in the water rocket are appropriate can the enclave be farther and higher. It was found in the experiment that if the amount of water is greater than the upper limit that can be sprayed by a fixed air pressure, the water in the water rocket will not be sprayed out. How to avoid the situation where the spraying is not complete? According to PV = nRT, the upper limit of the amount of water that can be ejected at a certain pressure can be obtained. If the amount of water is not enough, the amount of water that can be ejected is sprayed earlier. According to the theory, when launching, we first measure the maximum value that can be filled into the water rocket, and then calculate the maximum amount of water that can be sprayed by this air pressure. × Mmax).

Improve the stability of water rockets:

During the ascent process, the water rocket does not rise vertically, and often rises sideways or sideways. This requires us to improve its stability and make it rise vertically. To improve its stability, we must consider the role of atmospheric resistance. First, the top of the water rocket should be sharp,

There are many types of water rockets, including single-stage single-throw (first-stage rocket, one thruster nozzle), single-stage multi-thrust (first-stage rocket, multiple thruster nozzles), and multi-stage multi-thrust (multi-stage rocket, multiple thrust) Device nozzle) and so on, few multi-stage single push. Single-stage multi-thrust is generally a passive separation of the thruster (made by one or several bottles in series) and the arrow body and the thruster are launched at the same time. Therefore, although the thruster is thrown away, it is generally not considered a multi-stage water rocket. The multi-stage multi-propelled water rocket adopts the "active separation" technology of the thruster and the arrow body and replaces the launcher of the thruster arrow body. The technical interests of water rocket production mainly include: nozzle technology, active separation technology and recycling technology.

The domestic popular method of making a bicycle inner tube and a gas port for a bottle stopper, but since this method cannot control the launch time well, multiple pushes cannot be perfectly realized. The launcher ring was pulled down with a pulley and a line to achieve a good control of the launch time.

Generally speaking, single-stage multi-propelled water rockets involve the thrust difference between the thruster and the arrow body. Because it is a passive separation naturally achieved by gravity, the thrust of the thruster must be greater than the thrust of the arrow body to ensure that when the water rocket is lifted off, the thrust of the two is the largest and integrated. When the thrust of the thruster is exhausted, due to the effect of gravity Fall off naturally. The main arrow body continued to fly. The advantage of this rocket is that it does not involve complex multi-stage separation technology, but also has a large thrust and is relatively simple to make. It should be noted that the diameter of the arrow nozzle is smaller than the diameter of the thruster nozzle to achieve the thrust difference. The arrow body generally uses parachute recovery technology.

Let's talk about multi-stage multi-propelled water rockets. This water rocket is huge and can even exceed 200 meters in height. The currently known maximum launch altitude is 864 feet, or 263 meters, created by foreign water rocket enthusiasts on October 30, 2010. Although the launch height of this rocket is not very high, it is more challenging and more popular with water rocket enthusiasts because it involves "staggered jet" technology, "active separation" technology, and "stage recovery" technology of arrows and thrusters. Favor. There are different types of active separation technology in foreign countries, but the basic principles are the same. Using the gravity when the thrust of the thruster is exhausted, the spring force in the pre-buried separator, and the second-stage arrow body ejection thrust at the beginning of the separation, the first and second-stage active separation is quickly achieved. The propeller part enters the falling stage to open the parachute, and the second stage continues to rise until the thrust is exhausted and drops to open the second stage parachute. If there is a third level, proceed in order.

Both single-stage multi-propelled water rockets and multi-stage multi-propelled water rockets can be very large, but it is not difficult to distinguish between the two, and it can be distinguished from the appearance. The single-stage multi-propelled water rocket (can be called a fake second-stage) arrow body and thruster nozzle are on the same plane, because only then can it be easiest to achieve simultaneous launch. Multi-stage multi-propelled water rockets are not. The second-stage nozzle must be connected to the thruster, because the second stage is not working at the beginning of the launch. So just look at the position of the nozzle and you can tell.

1. After you are familiar with the basic production of water rockets, you can try to make large and multi-stage water rockets. Made of lighter weight metal, air pressure is provided by the air pump.

2. Production of multi-stage rocket:

Tie several water rockets together and provide air pressure through an air inlet. At the same time, the water column is ejected to improve the flying capability of the water rocket.

After half a semester of exploration, research, and experimentation, we have initially completed the research and development of water rockets, from which we have improved in many aspects. By looking for information, we have a deep understanding of the development history of rockets, especially the history of the development of rocket technology in China. Knowing that rockets are the necessary means of delivery for modern aerospace, China is the birthplace of rocket technology. However, due to lack of funds and technical shortcomings, the development of aerospace has been slow, but with the comprehensive national strength, it has been launched in cooperation with foreign countries. A number of "Long March Series" rockets.

2. Divide one of the special bottles into three parts; leave the bottle mouth and middle section

3. Put the remaining bottle mouth and the middle section on the bottom and the mouth of another bottle, respectively, apply adhesive and fix it with insulating tape.

ps: The arrow body of the rocket must be kept in a straight line

4. Use thick transparent film or pearl plate to make four tail wings, and distribute them evenly in the second half of the rocket.

Magic water rocket experiment

PS: Apply adhesive and secure with tape. Not evenly distributed or fixed will affect the direction of the rocket

5. Put on the rocket and nozzle, and prepare to fly high

6, ready to launch on the launch pad