2949775337

Comparison of Liąuid Propellant Rocket Engine Feed Systems - 1 - 4

current from the battery to altemative current with a freąuency suitable enough to drive the electric motor at the reąuired speed.

H. ANALYTICAL DEVELOPMENT

To realize comparisons it is necessary to estimate the total mass of each feed system described in the previous section. To simplify this analysis, only the mass of the principal components of each system will be considered. That is, the masses of the plumbing system, the mounting system, the valves and the electronics Controls will be assumed as negligible.

Hence, giving denominations to the diverse masses of the components of each feed system yields:

m,_p\ total mass ofthe turbo-pump feed system.

m_ep: total mass of the electric-pump feed system.

mpg\ total mass of the pressurized-gas feed system.

m_g: pressurizing gas mass.

m,_g\ pressurizing gas propellant tank mass.

m,₀: oxidizer tank mass.

m,/. fuel tank mass.

m_pu. pumps mass.

m,„: turbinę mass.

/Wgg! gas generator mass. m_ee\ electric engine mass. m_inv: inverters mass. mbai. batteries mass. m_Q\ oxidizer mass. m/. fuel mass.

m_p m₀ + mf. propellant total mass. m_p,_u\ turbinę driven propellant mass.

Thereby, and taking into account the figurę 1 schemes, the total masses of each feed system respond to the following eąuations:

m,_p = m_g + m,_g + m_lo + m_lf + m_pu + m_tu + m_gg + m_plu m_ep = m_g + m_lg + m_l0 + m_tf + m_pu + m_ee + m_inv + m_hat m_pg - m_g + m_t + m_l0 + m_lf

The comparisons presented in this report, deal with engines primarily intended to be applied in vehicles operating far above of the sea level, where the atmospheric pressure is very Iow. Therefore, in the following calculations the atmospheric pressure will be neglected.

2.1. Pressurizing gas mass

From the analysis done in [1], about the propellant tank pressurization, using the energy conservation principle, the next expression can be obtained:

"I,

g

eZł j*

RJo _x_p^

, Po,

(2.1.1)