ESA Document - Emits - ESA

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3.4.1.2.4 Budgets
Element Mass
Propellant mass 76 324 kg
Propulsion Dry mass (including margins)
This mass includes the following estimation:
3776 kg
Structure 1643 kg
Engines, tanks, actuators feed lines, valves 1903 kg
and regulators
Thermal 95 kg
Mechanisms 36 kg
Table 3-60: MOI/TEI stack mass budget
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 234 of 422
3.4.1.2.5 Options
For the TEI, four YUZHNOYE RD 861-G gas generator bi-propellant NTO-UDMH thrusters
have been proposed instead of the RD 0212 engine. However, the final choice was dictated by
thrust-to-mass ratio constraints.
Overall thrust of the module in this case is around 305 kN whereas overall mass of the
propulsion system remains unchanged.
3.4.2 Structures
3.4.2.1 Requirements and design drivers
For the design of the propulsion module the following set of general requirements were taken
into account:
• Maximum of a 6 m diameter for the propulsion structural elements, due to
compatibility with Energia fairing.
• Compatibility with the vehicle launcher Energia induced mechanical loads.
All structures shall provide the mechanical support to the propulsion stacks.
3.4.2.2 Assumptions and trade-offs
Given information regarding the longitudinal and lateral frequencies requirements of the
launcher Energia, the verification of these requirements was based in the correspondent values
for the Zenit rocket. Which implies the following requirements: lateral frequency higher than 8
Hz and longitudinal frequency higher than 20 Hz.
The wall thickness of the propellant tanks will first be calculated from stresses caused by internal
pressure loads, and then checked for other loads.
For strength calculations a safety factor of 1.5 was considered.
3.4.2.3 Baseline design
Each propulsion stage is composed of a number of stacks attached to an aluminium backbone, of
5 m diameter and 4 mm thick. The difference between the backbones of the TMI and MOI
modules is the length, due to the size differences of the tanks and engines.