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Comparison of Liąuid Propellant Rocket Engine Feed Systems - 1 - 10

^mee

p_opllc

1

S_LV

(2.4.3)

Replacing the powers, with the help of preceding eąuations, finally yields:

Pc^mp

(2.4.4)

It is necessary to denote that a similar expression can be obtained by the same procedurę, considering a system where each pump is driven by individual motors.

2.5. Inverter mass

As above, beginning with defming the electric motor efficiency, with the same approach applied for the pumps case, will allow relating the inverter output power with the power consumed by the pumps:

(2.5.1)

In the same way, the inverter power density relates its output power with its mass:

S_inv =

P_oinv

m_jnv

(2.5.2)

In this way, from the two above eąuations, from 2.4.1 and with the same arguments that in the preceding paragraph the inverter mass is estimated in the following way:

m_it|v

= (! + *„

Pc^mr f ^ai

(2.5.3)

2.6. Batteries mass

The batteries are limited in both their energy and power capacity; therefore, the mass must be estimated accordingly with the most restricting factor. Then, two batteries merit factors are defined:

^mHa

where, S_bap: Batteries power density (W/kg). Show: Batteries energy density’ (J/kg).