ESA Document - Emits - ESA

s
45˚ 60˚ 70˚
Figure 4-77: IBD shapes
Half cone angle
45d 60d 70d
Lref m 21.55 33.71 26.7
Sref m2 364.74 892.5 560
Table 4-38: Reference IBD characteristics
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 338 of 422
The aerodynamic coefficients were computed with the Newtonian methods and are shown in the
Figure 4-78:
Figure 4-78: Aerodynamic coefficients comparison
The IBD shape selection is based on three coefficients: the drag and the lift coefficients and the
reference surface. A drag coefficient and a reference surface should be high enough to reduce the
velocity during the entry low enough to open the parachute; a lift coefficient should be enough to
reduce the g-load during the entry according to the requirements for a human mission.
Another requirement to be taken into account is the stability of the vehicle. The stability can be
analysed knowing the distance between the centre of pressure and the centre of gravity.
The module which has to be landed is made up from the bottom to the top by the retro-rockets
needed to land, the habitation module and the MAV. The centre of gravity of this module is