2) In 2013, the Kepler spacecraft had a failure of two reaction wheels that help it point properly. Fortunately, some brainiacs at NASA figured out that they could use the radiation pressure of the Sun to stabilize the spacecraft and allow it to continue taking usable science data. If the spacecraft is at the same distance from the Sun as the Earth (cf. Problem 1) and it has cross-sectional area of 15 m², which we'll assume is totally reflective, what total force does the Sun's radiation exert on the craft? (Remember from basic physics that a change in momentum with respect to time is the same as a force, so can you count up the momentum transfer onto the craft from all those photons per second, given that each transfers Ap = 2h/2 as it bounces off the craft?) Assume all photons have wavelength 550 nm.

2) In 2013, the Kepler spacecraft had a failure of two reaction wheels that help it point properly. Fortunately, some brainiacs at NASA figured out that they could use the radiation pressure of the Sun to stabilize the spacecraft and allow it to continue taking usable science data. If the spacecraft is at the same distance from the Sun as the Earth (cf. Problem 1) and it has cross-sectional area of 15 m², which we'll assume is totally reflective, what total force does the Sun's radiation exert on the craft? (Remember from basic physics that a change in momentum with respect to time is the same as a force, so can you count up the momentum transfer onto the craft from all those photons per second, given that each transfers Ap = 2h/2 as it bounces off the craft?) Assume all photons have wavelength 550 nm.