ESA Document - Emits - ESA

s
flux [W/m2]
250
200
150
100
50
0
energy on 2 face radiator (alp=0.2, eps=0.8)
rad.
0 15 30 45 60 75 90 105 120 135 150 165 180
angle (normal rad. to center planet) [deg.]
receiv ed inf rared receiv ed albedo (sun coplanar to rad.) absorbed total
Radiator area [m2]
2 faces WP radiator (eff. 0.8), biphasic, P=12kW
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 177 of 422
100
90
80
70
60
50
40
1 face radiato r (no heat load, other face adiabatic)
2 face radiato r
(no heat load)
30
20
10
0
-60 -40 -20 0 20 40 60 80 100 120
temp. fluid [C]
0 30 60 90 deg.
Figure 3-36: Total energy on radiator (L), Radiator size versus angle and temp. fluid (R)
Figure 3-36 (L) shows the total absorbed energy from Earth as a function of the angle it normal
makes with the centre of the planet (the Sun being considered in the radiator plane) Figure 3-36
(R) shows the impact of this parasitic heat load on the radiator size. Despite planetary heat loads
and the prize of the rotation angle, the size of a two-face radiator design remains inferior to a
single-face (as long the radiator temperature remains superior to the planet temperature). The
cost of a full tolerance of planetary heat load decreases with the fluid temperature increase (at
5C, the ratio is 1.17). The option of a fixed radiator could be therefore tolerated at this expense
and with an adequate spacecraft attitude (no Sun on the radiators).
The technology to rotate a biphasic radiator is not available in Europe (nor is there a
development plan), so a fixed radiator is retained with an adequate tolerance to planetary heat
loads.
Out of the influence of the planet, the system performs optimally and the heat rejection
capability is naturally increased (by a ratio 1.37). The flexibility of the secondary loop is
provided by the bypass valve regulating the mass flow and therefore the sink temperature
provided to the users.
The minimum set point (high heat load) for the primary loop is set to 4/7C (inlet 13/18C), which
gives a minimum of 0/4C required from the secondary loop inlet at the heat exchanger level.
Setting the bypass inlet at -5/-1C provides a possible solution, and drives a radiator area of 56.6
m 2 .
The Lockheed-Martin PVR assembly mounted on the ISS truss is taken as a baseline (see last
picture in Table 3-26). The following configuration is chosen: 8 panels, each 2.1 x 3.4 m 2 ,
deployable by an electric motor ‘scissor’ mechanism. Total weight is 849 kg per assembly (x 2).
White paint coating (type PSG121FD) is applied on both sides. Its degradation over time is well
known and can be controlled through a careful illumination from solar UV.
Two identical systems are mounted symmetrically on the spacecraft body.
3.3.3.4.5 Insulating system and thermal protection
sun