ESA Document - Emits - ESA

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Figure 4-70: Dynamic Pressure Over Time (L) and Altitude (R) for Regarded Cases
Figure 4-71: G-Load over Time (L) and Altitude (R) for Regarded Cases
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 334 of 422
As can be seen in the above figures, the duration of the entry phase varies considerably with the
entry angle. Dynamic pressure and g-load increase sharply for steep entries, and also, the
respective peaks shift towards lower altitudes, as shown in the right-hand plots.
It appears that an entry angle of -4º has a particularly well distributed load characteristics and
therefore low structural load peaks. Of course, this feature will have to be investigated in later
analysis. It might be a mere particularity of the given combination of conditions.
A further entity that needs to be investigated is the thermal load. The peak heat flux can be
expected to rise sharply for a steep entry, analogously to the dynamic pressure and g-load.
Conversely, the total integrated heat load can be expected to be slightly, but not dramatically,
larger for shallow entry angles. Details on that analysis are given in the chapter on
aerothermodynamics in this document.
4.4.1.3.1 Budgets
Table 4-37 shows the characteristics of the aerodynamic entry trajectory for the entry angle
corridor with the assumed aerodynamic reference area of 490.87 m 2 . Parachute deployment takes
place at Mach 2, which is reached at an altitude of 13-15 km above the surface.
The entry velocity is about 10% larger at the shallowest end of the range, where also the longest
phase duration is obtained. Conversely, for the steepest entry, the duration is reduced to 227 s.