An aerospace platform includes a structure having a cavity and a light-transmissive portion that exposes the cavity to sunlight. The aerospace platform further includes a fluid heating system. The fluid heating system includes a fluid-carrying, thermally absorptive structure within the cavity, and a solar collector for collecting light transmitted through the light-transmissive portion and focusing the collected light onto the absorptive structure. The thermally absorptive structure has a high surface absorptivity that retains thermal energy when exposed to solar irradiance and heats fluid contained therein.