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## Homework Statement

- 4.18

With reference to Example 4.21, consider the design of a solar sail

intended to reach escape velocity from the Earth 2gRe = 11.2 km/s using only the pressure due to sunlight. The sail is made of a Kapton⃝R film 0.0025 cm thick with a density 1.4 g/cm3. Take the solar constant to be 1370 watts/m2, assumed to be constant during the acceleration.

(a) What is the acceleration near the Earth due to sunlight pres- sure alone?

(b) How far from the Earth, as measured in units of the Earth’s radius, Re, would the sail have to be launched so that it could es- cape from the Earth?

## Homework Equations

attached

## The Attempt at a Solution

Solution attached

no issues with part a

part b: I am getting the wrong answer as solution come up with r ≥ 194*R

_{E}

Help is greatly appreciated as solutions suggest a due to sun photon influx in towards the sun as my understanding should be away!