ESA Document - Emits - ESA

s
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 364 of 422
Figure 4-101 shows the drag coefficient data. The drag coefficient was defined by linear
interpolation from a table of drag coefficients as function of Mach number. To make the model
simple, CL was supposed to 0 for any Mach number.
Drag coefficient
1.8
1.75
1.7
1.65
1.6
1.55
1.5
1.45
1.4
1.35
Drag coefficients vs Velocity
Shape : Cone-angle 70d
Assumption--> Speed_sound=175 m/s
0.00 5.00 10.00 15.00 20.00
Mach
25.00 30.00 35.00 40.00
Figure 4-101: Cd Data
The reference area used for computing the aerodynamic force is 15.9 m^2, equivalent to a circle
of 4.5 m of diameter.
Heat Flux Coefficients
The formula and coefficients used for the heat flux computation are the following:
Heat flux = C x (density) N x (Velocity) M W/m 2
Components Value Unit
C 1.5588 e-4 W/m2 /((kg/m3) N /(m/s) M )
N 0.5 ND
M 3.04 ND
Table 4-49: Reference data to calculate heat flux
Atmosphere Model
The atmosphere data used in this study is the Mars-GRAM 2001. Winds profiles were not taken
into account. The density, temperature and sonic velocity profiles correspond to latitude of 15
degrees. This is conservative, since the Mars-GRAM 2001 provides higher density profiles for
higher latitudes.
Planetary Model of Mars
The Table 4-50 shows the planetary model of the Mars. The gravitational acceleration was
derived from the gravitational potential expressed in spherical harmonics. The main term and the
C2,0 (J2) terms were taken into account, as well as the rotation of Mars.