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Comparison ofLiguid Pr opel font Rocket Engine Feed Systems - 1 - 14

For each calculation routine, it will be necessary to adopt a combustion chamber pressure value and a propellants mixture ratio value. With this parameters established, both the specific heat ratio and the molar mass of the combustion gasses can be estimated from the data presented in [2],

3.2. Pressurizing gas

Helium is chosen as pressurizing gas and the necessary data are obtained from [3]:

Table 2: Characteristics of the pressurizing gas.
Gas	Temperaturę [K]	Specific heat ratio	Molar Mass [kR/kmoll
Helium	288.15	1.667	4.0026

The gas is initially pressurized (unless the calculation routine suggests another thing) to: \p₀ =200Bai]

3.3. Propellants and gas tanks

The propellant tanks are pressurized to a higher or lower pressure depending on the employed feed system. In that way, is convenient to number the Systems as follows:

1.    Pressure-gas feed system.

2.    Electric-pump feed system.

3.    Turbo-pump feed system.

It is assumed that both fuel and oxidizer pressures are the same.

3.4. Propellant pumps

From the mass estimation done in section 2.3 it is evident that two parameters are necessary: the pump power density and the pump efficiency. It is assumed identical fuel and oxidizer pumps. In this way, the following values are adopted for the parameters of the two propellant pumps [14]:

<5, = S„ = W^kw ,

^p/ _te

\n„ = 'te = H

3.5. Turbinę

It is assumed that a single one-stage impulse turbinę will be employed. The inlet gas temperaturę should not be too higher to avoid complicating the turbinę blades design. However, it must be as higher as possible to increase the turbinę efficiency. Depending on the materiał from the blades are madę the maximum temperaturę should vary between 850K and 900K (Stated that no exotic alloys will be employed). So, the following optimistic limit is adopted: