ESA Document - Emits - ESA

s
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 310 of 422
Option 2 (high pressure storage) has several advantages: the mass and the volume of the tanks
are amazingly high, but also, the transportation of very high pressure tanks located close to the
crew is a large risk in case of failure.
On the other hand, the use of regenerative system (here performed with solar cells) in the best
case cannot be designed with a solar panel smaller than 100 m². Given the difficulties that the
astronauts will have to face with the gravity just after the landing, it is not possible to assume a
manual deployment of the panels within at least 2 days. Deployment mechanisms have to be
mounted on the Habitation Module.
These mechanisms are expected to be heavy since they have to cope with the gravity on Martian
surface and the huge solar array areas that need to be deployed.
In conclusion, the architecture that fits the requirements the best is Option 1: Primary
hydrogen/oxygen fuel cells stored in cryogenic tanks. Another benefit of this topology is the
possibility to combine the life support oxygen tanks with the ones of the power subsystem.
Figure 4-60 shows the mass budget of the selected option. The tank optimal shapes have not
been studied. In this budget, they were spherical with diameters of 1.1 m. The oxygen tank
includes also the part allocated for life support. The empty water tank is included in the mass
budget of the life support subsystem. To avoid the boil-off during the cruise to Mars, a constant
power consumption of 1800W is allocated to the thermal regulation of the tanks for the design of
the TV.
The hydrogen tank mass is computed with the data given in [RD60]. For example, it is assumed
that a cryogenic container can store 20 wt.% hydrogen. This value seems optimistic.
Other aspects that require closer investigation are:
• the estimation of the boil-off
• the power estimation of the tanks thermal regulation
• the gravimetric capacity of the tanks
• the shape of the tanks
Element 2: Surface Habitation Module
MASS [kg]
Unit Element 2 Unit Name Quantity Mass per Maturity Level Margin Total Mass
Click on button below to insert new
quantity excl.
incl. margin
unit
margin
1 Fuel Cells 1 35.8 To be developed 20 43.0
2 Tank O2 (Spheric) 2 733.1 To be developed 20 1759.4
3 Tank H2 (Spheric) 4 149.4 To be developed 20 717.3
4 PCDU 1 114.8 To be developed 20 137.8
5 Fully developed 5 0.0
- Click on button below to insert new unit
To be developed 20 0.0
ELEMENT 2 SUBSYSTEM TOTAL 4 2214.5 20.0 2657.4
4.3.6 Data handling
Figure 4-60: Mass budget of Option 1 SHM power subsystem
The excursion vehicle’s module integrated avionics shall be seen as a small subset of the one
already described for THM.