NASA Orion ATCS Glycol-Water vs Ammonia NASA’s choice for Orion’s cooling comes down to safety vs. efficiency. While anhydrous ammonia is an incredible coolant, it’s highly toxic to humans. Since Orion is a crewed capsule, NASA opted for a water-glycol mixture for the internal loops. This keeps the cabin safe from lethal leaks. To handle the heat of deep space, they use a heat exchanger to transfer that energy to an external ammonia loop safely away from the astronauts. Discover why NASA priorit