Water rocket

A water rocket is a rocket that ejects water and carries its energy in the form of compressed air or hot water.

It is driven by a jet of water is forced under pressure through a nozzle and leaves the rocket with an opposite impulse. Depending on the type of production this pressure, a distinction is cold water and hot water rocket missiles; The latter are also referred to as vapor pressure missiles. Is common to both, that the drive energy is carried in physical form and not, as in most chemical energy missiles.

Cold water rockets are offered in a simple form as a toy, used for demonstration of the rocket principle and found mainly in the leisure industry application. Hot water rockets are mostly to be found in university research and development.

Cold water rocket

A cold water rocket is a water rocket, wherein the partially water-filled missile body with the help of the superjacent compressed air is driven before. Upon release of the nozzle, the water enters by means of compressed air from the missile body at high speed and accelerates it by its recoil.

Cold water rockets are used due to their lower efficiency, especially in the leisure sector as a hobby or in the classroom as a demonstration model to illustrate the recoil drive.

Important in driving the cold water rocket is the ratio of compressed air to water. The largest peak height is reached at a water / air volume ratio of 1: 3

As a model structure and toy products available water rockets are inflated with a bicycle pump and can reach a height of several dozen meters. For beginners and hobby pilots are already half-finished kits mostly Asian manufacturers.

As the pressure hull to the self of cold water rockets, PET beverage bottles are suitable. These hold partly 8 bar ( non-returnable PET bottles) or even up to 20 bar (burst ) ( returnable PET bottles) from overpressure. With more prolonged and combined PET - bottles ( boosters ) heights of over 190 m can be achieved.

The return of such missiles from disposable PET bottles without causing significant damage even without a parachute, unless massive payloads to be transported. Since the pressure in the bottles and the thrust force and the acceleration at the start are significant, the handling still remains dangerous. The launching rocket takes an uncontrollable trajectory and can for example take on viewers. A one-way PET bottle developed without having mounted, constricting nozzle at 6 bar 213 Newton thrust and depending on the payload thus a starting acceleration from about 15 times the acceleration due to gravity, which even increases after a few meters.

There is a worldwide community of friends of the cold water rocket, to which no doubt the worldwide distribution of PET bottles has helped.

Method of construction

A cold water rocket can be built from a PET bottle itself. There are non-returnable bottles, but also uses the thicker-walled returnable PET beverage bottles. As a starting mechanism, a plug-in coupling for garden hoses and its counterpart is often used. In the Internet there are a variety blueprints for missiles and other starting mechanisms. To be described with spacers extended rockets or multistage models.

To increase the compressive strength of the cylindrical portions of the wraps of the PET bottles will be described. To compress the air air hand pumps or compressors are used.

In order to achieve a more stable flight, additional fins / vanes are glued to the rocket, the effect partly by tilting a stabilizing spin.

The forward- flying bottom of the bottle is sometimes (especially in the heavy returnable PET bottles) protected with a tennis ball cut in half compared to hard impact.

Hot water rocket

A hot water rocket (also steam pressure rocket) denotes a water rocket which, with the help of a mostly electric heating the water in the rocket body at high temperature (about 250-500 ° C ) is heated. This due to the pressure in the closed water tank liquid remaining water is discharged to start by duly shared with a valve exhaust nozzle evaporates in this and exits at high velocity from the nozzle. Due to the recoil the rocket is accelerated against the outflow direction. The water tank of water rockets must be able to withstand high pressure and high temperature.

Hot water rockets are occasionally used as a starting aid missiles and for experimental purposes. They are superior to the cold water rockets, since the ejected mass itself contains the power and thrust to the " burnout " remains almost constant. The performance of missiles with solid and liquid fuels, however, is much higher.

Rückhol-/Bergungssysteme

For larger water rockets and their payloads, it is recommended to use a parachute. This is for reasons of safety and the impairment necessary, for example, when electronics (height measurement / Altimeter ), video camera and batteries to be carried.

The triggering of the parachute, for example, with spring plants from Aufziehspielzeugen ( Tommy timer), achieved by timers or a power - tripping by " Flight Computer ".

Of course, all other conventional recovery systems are possible depending on the mass and value, such as, inter alia, swing-wing, rocket glider, streamer.

Records

• The model " X12 " reached on 14 June 2007 630.33 m ( 2,068 feet) altitude. The model belongs to the so-called Class A ( single-stage, cold water rocket, as compressed air medium).