HEAT AND COLD

Mars planet has a very thin atmosphere, but it is sufficient to induce on a spaceship, during the atmosphere entry phase, very harsh mechanical (vibrations, shocks) and thermal (temperature on the shield above 1300°C) environmental conditions.

Once the landing "trial" passed, the probe will be on a relatively inhospitable planet, notably the climatic conditions (maximal temperature 20°C, minimal temperature -120°C, mean diurnal-nocturnal difference 70°C).

Due to the functionalities and environmental constraints inherent to each phase, the lander is constituted of two distinct sub-systems in regard to their function and dimensioning:

The EDLS (Entry Descent and Landing System),
The Surface Module.

EDLS - A HIGHLY RISKY SEQUENCE

The EDLS must protect the surface module during all the mission phases before its installation on Mars surface.

Thus, it is mainly composed of:

a thermal shield with a double function: to assure by its shape, the stabilisation of the probe during the entry phase in the martian atmosphere and to reduce at the most the heating of the surface module during this slowing down phase (step 6),
a primary chute which inflate when the probe reach the speed of about mach 1.5 (step 7), then a main chute which take over when the speed is of 0.8 mach (step 8 to 10). These chutes reduce the descent speed down to about 25 m/s at the impact time
an "airbag" system which allow to limit the impact crash to about 200 g / 20 ms (step 13).

EDLS section

Surface module in the inflated airbag

SURFACE MODULE - A MAXIMAL COMPACTNESS

The surface module is composed of a cylindrical mechano-thermal structure in carbon composite. The lower part is divided in two compartments of equal volumes, of which one is regulated in temperature (± 40°C) by an insulating cocoon in compressed silicate (SEC System Electronic Compartment) and a loop heat pipe. This compartment holds all the sensible electronics as well as the batteries.

The second compartment accommodates the deployable elements of the scientific payload (meteorological boom, camera, magnetometer, seismometer), the UHF antenna as well as the hood opening mechanism. This last one must be able to flip the surface module if necessary. Indeed, after the airbag ejection, the surface module can land upside down and thus needs to be fliped.

The electrical power are exclusively supplied by the solar generators on the "petals" (about 1m² surface). The mean power required for a surface module was specified at 50 Wh/sol (1 sol = 1 martian day that is 24 h 40 min).