ESA Document - Emits - ESA

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HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 235 of 422
The MOD shielding, for all the propulsion modules are the same as the one for the THM.
The tanks walls form an integral part of the structure and are designed to withstand the internal
pressure loads as well as the vehicle dynamic loads, without the necessity of a skin, but due to
thermal requirements, an aluminium skin of 1 mm thickness is added to the tanks.
3.4.2.3.1 TMI module
The TMI propulsion module has three stages; each one consists of four stacks attached to a
backbone. The liquid oxygen and liquid hydrogen tanks, connection rings, a skirt, an engine
frame, skin and debris shielding constitute each stack.
The stacks are attached to the backbone through the rings and a three-point connection.
After a preliminary analysis, the first lateral Eigen-frequency for the TMI backbone results in
25.6 Hz. This initially fulfils the Zenit stiffness requirements, for the general launch
environment.
The tanks are arranged in tandem configuration, Figure 3-74, with the liquid oxygen on the top
and the liquid hydrogen tank below, with a common spherical bulkhead. The oxygen tank is a
sphere of 4.3 mm of thickness and the hydrogen tank is a cylinder with spherical domes of 2.9
mm thickness, both with 5 m of diameter.
Figure 3-74: Tandem configuration
Aluminium alloys are recommended for long-term storage of cryogenic propellants, so all mass
calculations were done with pure aluminium in the preliminary analysis.
The engine frame selected is the same as the one used for the main engine of Ariane-5. The
engine frame consists of a cone cap, an attachment ring and cone cap stiffeners.
3.4.2.3.2 MOI module
The MOI propulsion module has two stages; each one consists of two stacks attached to a
backbone. The oxide and fuel tanks, connection rings, a skirt, an engine frame, skin and debris
shielding constitute each stack.
The stacks are attached to the backbone through the rings and a three-point connection.
After a preliminary analysis, the first lateral Eigen-frequency for the MOI backbone results in 71
Hz. This initially fulfils the Zenit stiffness requirements, for the general launch environment.
The tanks are arranged in tandem configuration, with the oxidizer tank on the top and the fuel
tank below, with a common spherical bulkhead. The oxidizer tank is a sphere of 1.2 mm
thickness and the fuel tank is a cylinder with spherical domes and 2.8 mm thickness, both with 4
m diameter.
For long-term storable propulsion, it is recommended to use titanium instead of aluminium for
material skin of the tanks.