ESA Document - Emits - ESA

s
Term Value Unit
Radius of equator 3393.94 Km
Radius of polar 3376.78 Km
Gravity constant 4.28228E+13 M 3 /s 2
Rotational rate 7.088218E-5 Rad/s
C2,0 (J2) -8.75977E-4 ND
Table 4-50: Mars Reference Ellipsoid Parameter
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 365 of 422
4.5.1.2.2 Trajectory strategy and results
The most efficient way to reach the orbit is shown in Figure 4-102. The objective is to minimise
the lift-off mass. The sequence is as follows:
1) 1 st stage engine burn out (depletion)
2) 2 nd stage engine first burn
3) Coastal arc
4) 2 nd stage engine second burn, injecting the MAV into the target orbitThe coastal arc is
flown along an orbit 100km x 500 km. Nevertheless, the minimum lift-off mass is achieved if
that transfer orbit has a negative altitude of the perigee. This option was discarded due to safety
reasons: in case of a failure in the restart of the 2 nd stage, if the altitude of the perigee were
negative the MAV would crash onto the surface of Mars.
10 seconds delay between the separation of the 1 st stage and the ignition of the 2 nd stage were
assumed.
1 st Stage
2 nd Stage 1 st burn
Figure 4-102: Baseline trajectory strategy
Coastal arc
(100km x 500km orbit)
2 nd Stage 2 nd burn
With this type of trajectory and with the input data shown above, the minimum lift-off mass is
21896 kg (Table 4-47). A detailed sequence of events can be seen in Table 4-51, and some plots
with the most relevant parameters of the trajectory are shown in Figure 4-103.