ESA Document - Emits - ESA

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3.3.8.4 Options
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 226 of 422
As regards the power generation system, other systems are currently in study phases:
• Concentrator solar arrays- Use of concentrator surfaces to increase solar energy on to
the cells- Potential to decrease the physical size of arrays, however mass influence is
unclear.
• Flexible arrays- the power versus mass or watt/kilogram ratio of flexible arrays will
increase and become greater than the W/kg of conventional fixed panel arrays,
however the size capability and mass of such arrays is unclear.
3.3.9 Structures
3.3.9.1 Requirements and design drivers
For the design of the TV the following set of general requirements were taken into account:
• Habitation Module, with a diameter limitation of 6 m for compatibility with Energia
fairing.
• Compatibility with the vehicle launcher Energia induced mechanical loads.
• THM shall provide a stormshelter to protect the crew in case of a solar particle event.
All module structures shall provide the mechanical support to ensure mission success.
3.3.9.2 Assumptions and trade-offs
Due to lack of information regarding the longitudinal and lateral frequencies requirements of the
Energia, launcher the verification of these requirements was based on the correspondent values
for the rocket Zenit. This implies the following requirements: lateral frequency > 8 Hz and
longitudinal frequency > 20 Hz.
For strength calculations a safety factor of 1.5 was considered.
3.3.9.3 Baseline design
3.3.9.3.1 Habitation module skin
The Habitation Module is the main load-carrying structureIt is a 6-m diameter and 14-m long
pressurised cylinder of 4 mm thick aluminium. This structure needs local framing structure
around windows and other penetrations and discontinuities.
Aluminium was selected due to its low density and high strength.
The first eigen-frequency, for the THM, results in 35.6 Hz, which initially fulfils the Zenit
requirements.
3.3.9.3.2 Meteoroid and debris shielding
The safety of the spacecraft in long-term space flights requires a special protection from damage
by meteoroids and orbital debris.
For the spacecraft meteoroid and orbital debris protection two options were considered: a
“default shielding”- monolithic shield of aluminium and a multi-shock shield, the solution
proposed for the Mars Trans Habitat design study, [RD55], with Nextel and Kevlar as bumper
materials.