In this example we will investigate the viability of using radiation pressure to

Question

In this example we will investigate the viability of using radiation pressure to propel a spacecraft. Suppose a spacecraft with a mass of 2.50×104kg has a solar sail made of perfectly reflective aluminized film with an area of 2.59×106m2 (about 1 square mile). If the spacecraft is launched into earth orbit and then deploys its sail at right angles to the sunlight, what is the acceleration due to sunlight? (At the earth’s distance from the sun, the pressure exerted by sunlight on an absorbing surface is 4.70×106Pa .)

a) A communications satellite has solar-energy-collecting panels with a total area of 3.2 m2 . What is the average magnitude of total force on these panels associated with radiation pressure, if the radiation is completely absorbed?

Express your answer to two significant figures and include appropriate units.

Explanation / Answer

Recall that Pressure = Force/Area.  We can use this and F=ma to get our formula:

P=F/A

F=PxA

F=Mxa

a=F/M=PxA/M

Now for the tricky part:  When the pressure number was given above, that was for an absorbing surface.  What happens when the sunlight reflects instead?

Twice as much momentum is transferred!!!

acceleration due to sunlight a=2x(4.70×106 N/m2 )x2.59×106m2 /(2.50×104kg )

=9.7 x10-4m/s2

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