ESA Document - Emits - ESA

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Body-mounted radiator
facing sky
Lateral body mounted
radiator
Bottom body mounted
radiator
Advantage Disadvantage
Low sink temperatures (max is -120C) and
good stability (20K variation max over one
sol) => high performance radiator when not
illuminated
Possible combination with the ascent vehicle
radiator necessary during RdV
Partial viewing to the sky increases the
radiator performance when not illuminated
Adequate to a close location with the confined
compartment (secondary loop system) if
chosen on the lower part of the SHM
Permanently shadowed by the SHM body =>
the amplitude of the sink remains low and the
sink close to the night temperatures (high
sensitivity to sun illumination)
Adequate to a close location with the confined
compartment (secondary loop system)
The radiator view factor is closed when
docked to the transfer vehicle (low activity of
the SHM during transfer, the heating budget is
therefore minimised)
Deployable radiator Possibility to implement a tracking of the Sun
to minimise illumination of the radiator
Table 4-11: Radiator options
HMM
Assessment Study
Report: CDF-20(A)
February 2004
page 284 of 422
Only location is on top of the ascent vehicle
already occupied by the solar cells necessary
during rendezvous.
Radiator Sun illumination is maximal over one
day
Possible dust deposits
Sink temperature depends on the viewing with
sky and ground => instability of the sink
(large amplitude of the ground sink)
Possible illumination during a few hours
Viewing of the sky degrades when too close to
the ground
The dust density is higher close to the ground
(possible electrostatic adhesion)
Conflicts with the heating from braking
thrusters => requires specific protection
Gravity and wind pressure penalize mass
4.3.4.3.1.3 Radiator sizing
Figures here below indicate the relative penalty of the radiative surface to the daily variation of
the environment, this if the cooling capability is to be maintained.
In the case of a bottom radiator, how much the ground can heat up with convection and the SHM
rejection will depend on the nature of the ground. The rather low thermal inertia in general does
not make this option attractive, in particular when considering that the ground has little means to
cool down itself if the two surfaces are parallel (so the ground will tend to the mean daily
radiator temperature).
In the case of a lateral cylindrical radiator, assuming a view factor of 0.5 to sky and ground,
equinox, latitude 0, at noon the penalty is a ratio of 2.4 against the same heat rejection at
–120C (end of night). The negative impact of the Sun remains acceptable when considering its
angle of incidence (left figure). Increasing the view factor to the sky increases the rejection but
also increases the Sun illumination (intensity and duration), however at a much lower rate.