ESA Document - Emits - ESA
Share Embed Flag
Download ePaper

ESA Document - Emits - ESA

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

emits.esa.int
from emits.esa.int More from this publisher
06.02.2013 Views

s 4.3.4.3.2 Primary loop air 630 m3/hr at 27C max 12.3 kW mean + 660W metabolic cold plates assembly liquid/air HX N acquisition system Figure 4-35: SHM radiator and location to MAV thermal bus (secondary loop) 13/18 C liquid/liquid HX thermostatic coils (hull, propulsion, ...) 0 W worst case 1/6 C where high plume density, local protection with titanium foils (lateral, bottom) N 950 kg/hr at 3.5b, 18C pump assembly accumulator Figure 4-36: Surface Habitation Module / primary loop principles 4.3.4.3.3 The insulating system and thermal protection Ascent vehicle primary loop HMM Assessment Study Report: CDF-20(A) February 2004 page 286 of 422 The thermal design for landed vehicles differs considerably from other space applications in that Mars has an atmosphere (7 mb), which plays an important role in the thermal insulation. The choice of insulation and structures must be traded off against each other. The vacuum compatible foams such as Basotect and Rohacell not only have different thermal properties but also are structurally different. Rohacell (a closed-cell rigid foam plastic) is stiff, impact resistant and self-supporting, whereas Basotect (an open-cell foam), a better insulator, is fibrous and lacks any structural integrity. Used on the Pathfinder and MER rovers, Aerogel (Silica gel with carbon black) is an excellent thermal insulator, but has no structural integrity. The different thermal conductivities are shown in Figure 4-37.

s HMM Assessment Study Report: CDF-20(A) February 2004 page 287 of 422 Figure 4-37: CLRC Beagle2 study (L), Aerogel thermal conductivity versus pressure (R) The low density of Aerogel combined with its good thermal insulation makes it an ideal candidate but would need an encapsulation (honeycomb cells for example). If a monolithic structure (aluminium) is retained, insulation materials can be added in a multi-layer design combining radiative (goldenized layer) to conductive insulation (foams). The double requirement to perform in vacuum and in pressurised environment can be answered by installing different type of foams (closed cell inside, open cell outside). goldised foil betacloth int. foam structure ext. foam Figure 4-38: Insulation layout The choice of external layer results as a compromise between the different constraints brought by the Martian and vacuum environment. The principle of a cold radiative skin completed by heat input when necessary is preferred for its simplicity, providing the existing resources of energy (released heat from units and metabolic). Betacloth is retained as the external layer of the SHM to avoid undesirable heating from the Sun during the transfer phase. Its high emittance (high energy exchanged during nights) is somewhat counterbalanced by the high thermal inertia of the vehicle. Its strength is also seen as an advantage. 4.3.4.3.4 The thermostatic system Certain surfaces that cannot be protected by insulating means (interface between MAV and ascent vehicle) are treated (oxidation anodic, alodine) to minimise heat transfer. On the internal face, coils (circulating fluid from primary loop) thermostatically control the temperature (condensation avoidance) and the heat exchanges (control of the heat losses). An adequate redistribution of the rejected heat (thermostatic coils) therefore reduces the use of heater power to the minimum. When not directly accessible to fluid lines, externally mounted elements will require the use of strip heaters combined to an adequate insulation.

s<br />

4.3.4.3.2 Primary loop<br />

air 630 m3/hr<br />

at 27C max<br />

12.3 kW mean + 660W metabolic<br />

cold plates<br />

assembly<br />

liquid/air HX<br />

N<br />

acquisition system<br />

Figure 4-35: SHM radiator and location<br />

to MAV thermal bus<br />

(secondary loop)<br />

13/18 C<br />

liquid/liquid HX<br />

thermostatic coils<br />

(hull, propulsion, ...)<br />

0 W worst case<br />

1/6 C<br />

where high plume density, local protection<br />

with titanium foils (lateral, bottom)<br />

N<br />

950 kg/hr<br />

at 3.5b, 18C<br />

pump assembly<br />

accumulator<br />

Figure 4-36: Surface Habitation Module / primary loop principles<br />

4.3.4.3.3 The insulating system and thermal protection<br />

Ascent vehicle<br />

primary loop<br />

HMM<br />

Assessment Study<br />

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

February 2004<br />

page 286 of 422<br />

The thermal design for landed vehicles differs considerably from other space applications in that<br />

Mars has an atmosphere (7 mb), which plays an important role in the thermal insulation.<br />

The choice of insulation and structures must be traded off against each other. The vacuum<br />

compatible foams such as Basotect and Rohacell not only have different thermal properties but<br />

also are structurally different. Rohacell (a closed-cell rigid foam plastic) is stiff, impact resistant<br />

and self-supporting, whereas Basotect (an open-cell foam), a better insulator, is fibrous and lacks<br />

any structural integrity.<br />

Used on the Pathfinder and MER rovers, Aerogel (Silica gel with carbon black) is an excellent<br />

thermal insulator, but has no structural integrity. The different thermal conductivities are shown<br />

in Figure 4-37.

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!