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ESA Document - Emits - ESA ESA Document - Emits - ESA

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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.

s 4.3.6.1 Budgets HMM Assessment Study Report: CDF-20(A) February 2004 page 311 of 422 The mass and power for the avionics systems can be derived using the same mass/power ratio. The result lead to the following budgets, divided per functional module. Element Mass Surface Habitation Module 40 kg Mars Ascent Vehicle 30 kg Table 4-16: Mass budget The above figures have been derived considering a ‘classical’ approach to the DHS, including all the strictly necessary units. No evaluation for the harness has been made (apart from the usual 4% figure). The current assumption is that the Descent Module is ‘free’ of avionics. As a comparison, the power consumption and mass of the avionics core units in Mars Express configuration are : CDMU : 9.1 kg each, 19W (one active, one cold redundant) RTU : 7.7 kg, 6W AIU : 6.2 kg, 8W SSMM : 8.7 kg, 17W (TBC) Total : 40.8 kg, 50W 4.3.7 Communications 4.3.7.1 Requirements and design drivers • Tracking, Telemetry and Command (TT&C) communications will be supported without any interruption longer than 1 hour. • The maximum range that shall be supported is 1.37 AU and the minimum one 1.1 AU (maximum and minimum Earth / Mars distance respectively during surface operations) • The telecommand (TC) and telemetry (TM) data rates shall be selectable to improve the data rate depending on the distance. • Data rates should be optimised by giving realistic assumption of on-board equipment and ground segment availability. • Data consists of housekeeping, high quality audio and video channels, and any additional data (for example internet access). • Communications during EVAs shall be provided, for simultaneously two astronauts and for a maximum distance of 1 km from SHM. • During EVAs, communications shall be possible even without direct visibility astronaut – SHM. 4.3.7.2 Assumptions and trade-offs 4.3.7.2.1 Communications availability from SHM: relay satellite

s<br />

4.3.6.1 Budgets<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 311 of 422<br />

The mass and power for the avionics systems can be derived using the same mass/power ratio.<br />

The result lead to the following budgets, divided per functional module.<br />

Element Mass<br />

Surface Habitation Module 40 kg<br />

Mars Ascent Vehicle 30 kg<br />

Table 4-16: Mass budget<br />

The above figures have been derived considering a ‘classical’ approach to the DHS, including all<br />

the strictly necessary units. No evaluation for the harness has been made (apart from the usual<br />

4% figure). The current assumption is that the Descent Module is ‘free’ of avionics.<br />

As a comparison, the power consumption and mass of the avionics core units in Mars Express<br />

configuration are :<br />

CDMU : 9.1 kg each, 19W (one active, one cold redundant)<br />

RTU : 7.7 kg, 6W<br />

AIU : 6.2 kg, 8W<br />

SSMM : 8.7 kg, 17W (TBC)<br />

Total : 40.8 kg, 50W<br />

4.3.7 Communications<br />

4.3.7.1 Requirements and design drivers<br />

• Tracking, Telemetry and Command (TT&C) communications will be supported<br />

without any interruption longer than 1 hour.<br />

• The maximum range that shall be supported is 1.37 AU and the minimum one 1.1<br />

AU (maximum and minimum Earth / Mars distance respectively during surface<br />

operations)<br />

• The telecommand (TC) and telemetry (TM) data rates shall be selectable to improve<br />

the data rate depending on the distance.<br />

• Data rates should be optimised by giving realistic assumption of on-board equipment<br />

and ground segment availability.<br />

• Data consists of housekeeping, high quality audio and video channels, and any<br />

additional data (for example internet access).<br />

• Communications during EVAs shall be provided, for simultaneously two astronauts<br />

and for a maximum distance of 1 km from SHM.<br />

• During EVAs, communications shall be possible even without direct visibility<br />

astronaut – SHM.<br />

4.3.7.2 Assumptions and trade-offs<br />

4.3.7.2.1 Communications availability from SHM: relay satellite

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