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ESA Document - Emits - ESA

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3.3.9.4 Budgets<br />

The structural mass composition is show in Table 3-56:<br />

Item Nr. Mass [kg] Margin [%] Mass with Margin [kg]<br />

THM Skin 1 2921.99 5 3068.9<br />

Nodes_Skin 2 834.58 5 876.31<br />

EVA 1 254.84 5 267.58<br />

Total Stiffening 1 2005.71 5 2105.99<br />

THM_Debris<br />

Shielding<br />

1 964.94 5 1013.19<br />

Nodes_Debris<br />

Shielding<br />

2 302.73 5 317.86<br />

Fixtures_large<br />

1 1000 5 1050<br />

Tools_gloveboxes<br />

Racks 1 2146 20 2575.20<br />

TOTAL 12468.39<br />

3.4 Propulsion module<br />

3.4.1 Propulsion<br />

3.4.1.1 Trans Mars Injection (TMI)<br />

Table 3-56: THM Structural Mass budget<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 230 of 422<br />

3.4.1.1.1 Requirements and design drivers<br />

This propulsive module performs the transfer from a Low Earth Orbit to Martian orbit by three<br />

impulsive burns<br />

The TMI is composed of several stacks that are injected in LEO by a heavy launcher (Energia)<br />

and have to be assembled in orbit. Each stack contains an autonomous propulsion system with<br />

engines, and relevant tanks fully loaded.<br />

The TMI is composed of three stages each composed of four stacks. The four stacks in a stage<br />

will be fired together to provide the thrust to mass ratio required to avoid gravitational losses.<br />

The inertia forces generated on the solar arrays will be high, so the arrays will have to be folded.<br />

3.4.1.1.2 Assumptions and trade-offs<br />

The TMI module uses LH2-LOX propellant at cryogenic storage conditions. The low Isp of the<br />

storable propellants resulted in prohibitive mass penalty for the TMI.<br />

A model to estimate the dry mass of each stack has been made including thermal protection<br />

system of the tanks, resulting in an inert dry mass of 11.5 % (9.2 tonne) for each stack.<br />

3.4.1.1.3 Baseline design

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