I saw this today and it made me very curious.
See page 8 here: https://www.nasa.gov/pdf/167129main_Systems.pdf
Ammonia has a boiling point of -30 C. The ammonia is liquid in these loops, so if ever exposed to sunlight I'd imagine intense expansion as it goes into gas phase. I noted that Ammonia volumetric expansion coef > water expansion coef.
Is the ammonia loop highly pressurized? Would that make the make the risk of leaks higher? (I see there have been several spacewalks due to ammonia coolant loop leaks)
Next point: The specific heat capacity of Ammonia is: 80.8 kJ/kg K Which is much higher than water 4.2 kJ/ kg K
====EDITED APRIL 14TH ============
***I made a mistake the specific heat capacity of ammonia is pretty close to water, at 4.7 kJ/ kg K
So I guess this means that ammonia can exchange substantially more heat energy without changing its temperature. Yet, I dont clearly see the advantage of that since its normal boiling point is at lower temperature than water.
So whats the advantages/ reasoning for using Ammonia for the coolant loop?