Water Rocket

Water rocket is a simple rocket that can be made by everyone. We can make it by 1.5 L plastic bottle (mineral water or soda).  There are  4 components of water rocket, it is nosecone, body, fins, and launcher. The best design for each component:

- nosecone : the shape is hemisphere

- fins : actually the most important is the distance between one fin and the others. The distance of one fin and another fin should be the same. Then, the best shape is parallelogram, and the fins should be four.

- launcher : the launcher should be fit with the nozzle of bottle, it is to minimize the leakage of fuel when it is launched.

 The fuel for this water rocket can be water, soda, or soapy water.  If the fuel is water, the water rocket should be filled by water 1/3 of it’s volume. It is the best comparison to make the water rocket fly as high as possible. Why we should use water/soda/soapy water as the fuel of our water rocket? Can’t it just the air as the fuel? >>>

the fuel can’t just the air, because air is compressible and water is incompressible. Compressible fluid is the condition if the density of the fluid changes with respect to pressure. Incompressible fluid is the condition if the density of the fluid does not changes with respect to pressure. Compressibility  is defined as the change in volume due to change in pressure. It is inversely proportional to its volume modulus of elasticity, also known as bulk modulus.

                To calculate the maximum altitude that can be reached by our water rocket, we can use:

1.       Parabolic motion formula (if the motion of water rocket launching is parabolic).

t =                   

 = 2V0

V0 =  x

Then,

y =

information: t = time (s)          g = gravity (9.8 m/s²)              V0 = initial velocity (m/s)

                     y = maximum high (m)

2.      Mass Flow Rate

Mass Flow rate is a measure of the amount of mass (Fluid) passing through

a given area with respect to time. 

The mass flow rate of a given fluid can be determined with the

following equation:

ṁ = A x Cd x  

information: ṁ = mass flow rate (kg/sec)      Cd = discharge coefficient (0.98)

                      A = area of nozzle (m²)              = density (kg/mᵌ)

                         = Pi – Pf (psi)

Then,

ft = ṁ × v                             v = velocity (m/s)

then,

R =

Where:      V = a×t

t = Time when all of the water is expelled from the Rocket.

θ = angle Rocket is being launched

so, to make a good water rocket, we have to

Ò  Maximize thrust : pressure from the pump has to maximum

Ò  Maximize lift : the fuel can be water or soda or soapy water, The loader in the peak of nosecone shouldn’t be too heavy or too light

Ò  Minimize drag : hemisphere nosecone; parallelogram fins, with the same distance between one fins and another.

Ò  Minimize weight : water rocket as light as possible, but still balance.

(^-^)9