Question: I heard the possibilty of using a light sail as propulsion for space craft, if you had to design a spacecraft with a light sail, how do you think it would have to differ from a normal space craft.

Colin Shirran answered on 2 Mar 2016:

The spacecraft design would change a lot from the typical spacecraft you see at the moment. The main use of the light sail is to use it for the spacecraft to travel large distances. The reason for this is that you will be constantly accelerating from the impact of the Suns photons on the sail. Given enough time, the spacecraft will accelerate to high speeds, although I think it will fall off as it get’s further from the sun, but hopefully by then you have built up a lot of speed.

So straight away we don’t need a propulsion module or propellant tanks. This will leave far more mass for more instruments to do science or to just make the spacecraft smaller and cheaper. Secondly you will need a method of housing the sail and during the launch and a large mechanism to unravel it and possibly steer it. Can you think of anymore possible differences?