Proposals have been made to ?sail? spacecraft to the outer solar system using the pressure of sunlight, or even to propel interstellar spacecraft with high-powered, Earth-based lasers. Sailing spacecraft would need no fuel a great advantage because fuel constitutes much of the initial weight of any space mission. NASA?s Sunjammer, launched in 2015, is the first sailing spacecraft deployed beyond Earth orbit. Figure 29.15 shows what a similar solar sail might look like in space.

One spacecraft has a sail that absorbs all light incident on it; the other has a perfectly reflective sail. How do their accelerations compare in light with the same intensity?a. The absorptive sail gives twice the acceleration.b. The reflective sail gives twice the acceleration.c. The absorptive sail gives greater acceleration, but not twice as much.d. The reflective sail gives greater acceleration, but not twice as much.