ESA Document - Emits - ESA

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3.3.2.2 Assumptions and trade-offs
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 156 of 422
The data shown in this table refer to an open loop control. It suggests a mass of consumables of
more than 47 tonnes. The life support system would have an approximate power requirement of
6.3kW and a volume of about 136m 3 . Taking into account that consumables need additional
hardware for storage and use, as well as the need to treat and store the metabolic products, the
use of an open loop system seems prohibitive. As a reference, the main parameters for an open
loop life support system are shown in Table 3-13:
CONSUMABLES TO BE LAUNCHED (kg)
OXYGEN 4466.9
NITROGEN 91.0
POTABLE WATER 16457.9
HYGIENE WATER 23160.0
DRY FOOD 3899.4
PACKAGING 1392.3
INORGANIC MATERIAL EXCLUDING PACKAGING 3177.9
TOTAL 52645.4
WASTE PRODUCTION DURING MISSION (kg)
WASTE GASES 6129.2
WASTE WATER 39535.8
SOLID ORGANIC WASTE 1006.2
SOLID INORGANIC WASTE EXCLUDING PACKAGING 3177.9
PACKAGING 1392.3
TOTAL 51241.4
ROUGH ESTIMATE ECLSS MASS (kg)
TOTAL 31162.0
Table 3-13: Open Loop Life Support System Mass, Consumables and Waste production
Generally, two classes of regenerative life support systems are considered:
• Physico-chemical regeneration
• Bio-regenerative systems
These systems may be used to lower the cost for a human mission to Mars by reducing the mass
of the consumables and perhaps life support system hardware. Some regenerative systems have
been successfully flown on MIR and the International Space Station. The result of any trade-off
would have to be measured on the criteria that have been selected. The criteria of equivalent
system mass does not seem appropriate for such missions. The lack of incorporating the
reliability of the system as well as the dynamic efficiency might deliver a less optimal system.
In this study the sole criteria was to reduce system mass, and providing a sufficient level of
redundancy. Less critical items were not increased in their fault tolerance whereas for critical
systems, which would cause a catastrophic failure, a two-fault tolerant system was implemented
in the model. Furthermore, this study projects about 20 years into the future. This causes a
significant uncertainty in the performance and parameters of the subsystems. Therefore, if
possible, the parameters have been selected using the best guess approach or data obtained on
similar systems with lower readiness level. Some systems have not been optimised for
spaceflight applications and some mass savings could be expected in the future. Each item