4 Final Report - Emits - ESA

4 Final
Report
Table 4.5-5: EPS fuel and power consumption and system mass for attitude control over 10 years
Deadzone size Fuel consumption [kg] Power consumption [kW] System mass [kg]
microHEMPT DZ 1/3 0.7 0.2 61
DZ 1/6 3.9 0.2 64
HEMPT 3050 120 2.3 307
Thrusters active [-]
Thrusters active [-]
2
1.5
1
0.5
Thruster activation timeline (DZ: 1/6)
0
1000 1500 2000 2500 3000
Time [s]
3500 4000 4500 5000
Thruster activation timeline (DZ: 1/3)
2
1.5
1
0.5
0
1000 1500 2000 2500 3000
Time [s]
3500 4000 4500 5000
Figure 4.5-9: Thruster activation timelines for dead zone sizes of 1/6 (top) and 1/3 (bottom) of
maximum available torque
The analysed performance values are
• APE 61.1 μrad, AME 11.2 μrad, PDE 0.24 μrad/100ms (all values for 100% probability).
A major issue with the EPS based attitude control system is that it is based upon currently nonexistent
technology which is believed to be available on the European market within the next five to
seven years. No major technological showstoppers are identified for the development of a
microHEMPT system but should such a system prove itself to be infeasible for use on Geo-Oculus,
other technologies such as microHET and FEEPT thrusters can be considered.
4.5.6.5 Manoeuvre performance
One of the key issues for Geo-Oculus is the ability to image multiple locations throughout Europe
several times per day. The limiting factor for manoeuvrability is the available torque to perform the
manoeuvre in the shortest time possible, and the settling time needed after the manoeuvre to reach
the required attitude performance again. Manoeuvrability is only required around the x- and y-axis, to
Page 4-62 Doc. No: GOC-ASG-RP-002
Issue: 2
Astrium GmbH Date: 13.05.2009