Thermal Management Question in Spacecraft

[Tanzim Kawnine]

Hello guys,

Below I am presenting a question related to thermal management in spacecraft . Perhaps many of you might find it interesting! And this could be a real-life problem for thermal engineering in a spacecraft . So, the question is following:

An instrument dissipates 10W and, in order for its detector to operate effectively, must be kept below -20°C. Its baseplate has a contact area of 175mm by 125mm and is bolted to a radiator with a chotherm interface. If the spacecraft is orbiting Mars (at a sun distance of 1.5 AU) and the radiator is facing the planet, estimate the size of radiator required. Assume the following :
• Albedo of Mars is 0.29 and its temperature is -60°C. The solar constant is
1369 W/m2
• The interface conductance between the unit and the radiator is 250 W/(m^2)*K
• Emissivity of the radiator is 0.8, absorptivity is 0.08

Also, An uncertainty margin of 10°C is to be used!

I found out the size of the radiator should be about 0.105 m^2.
What about yours? I would appreciate your help here. Thanks in advance.

Regards
TK

 

[berkeman]

Thread closed temporarily for Moderation...

 

[NatSusan]

Hi TK,

Interesting question! To calculate the size of the radiator required, we can use the following formula:

Q = A * (T_h - T_c) / (1/ε - 1/α)

Where:
Q = heat dissipated by the instrument (10W)
A = contact area of the baseplate (175mm * 125mm = 0.021875m^2)
T_h = temperature of the baseplate (assumed to be -20°C)
T_c = temperature of the radiator (assumed to be the same as Mars' temperature, so -60°C)
ε = emissivity of the radiator (0.8)
α = absorptivity of the radiator (0.08)

Plugging in these values, we get:

10 = 0.021875 * (-20 - (-60)) / (1/0.8 - 1/0.08)

Solving for A, we get A = 0.105m^2.

So, it looks like your calculation is correct! Good job. It's important to also consider the uncertainty margin of 10°C, so the actual size of the radiator may need to be slightly larger to account for this.

Does anyone else have a different approach or calculation? Let's discuss!