Dispersal of heat generated by onboard systems is a critical issue for a ship. If it cannot deal with heat, the crew may be cooked within the hull.
Radiation is the only way to shed heat in a vacuum. Civilian vessels utilize large, fragile radiator panels that are impossible to armor. Warships use Diffuse Radiator Arrays (DRA), ceramic strips along the exterior of the armored hull. These make the ship appear striped to thermographic sensors. Since the arrangement of the strips depends on the internal configuration of the ship, the patterns for each vessel are unique and striking. On older ships, the DRA strips could become red- or white-hot. Dubbed "tiger stripes" or "war paint" by humans, the glowing DRA had a psychological impact on pirates and irregular forces.
Strip radiators are not as efficient as panels, but if damaged by enemy fire, the ship only loses a small portion of its total radiation capacity. In most cases, a vessel's DRA alone allows it to cruise with no difficulties. Operations deep within solar systems can cause problems.
A ship engaged in combat can produce titanic amounts of heat from maneuvering burns and weapons fire. When fighting in a high heat environment, warships employ high-efficiency "droplet" heat sinks.
In a droplet system, tanks of liquid sodium or lithium absorb heat within the ship. The liquid is vented from spray nozzles near the bow as a thin sheet of millions of micrometer-scale droplets. The droplets are caught at the stern and recycled into the system. A droplet system can sink 10-100 times as much heat as DRA strips.
Droplet sheets resemble a surface ship's wake through water. The wake peels out in sharp turns, spreading a fan of droplets as the ship changes vectors and leaves the coolant behind.