Question: Why do you want to produce a very small rocket engine for mini spacecraft?

Charlie Ryan answered on 14 Mar 2011:

well these mini spacecraft are ok for basic science and earth observation, but currently there isn’t too much way to control them. Simply put the normal rockets (like on the space shuttle) are too big for these tiny ~1kg satellites. This means that these ‘cubesats’ can’t be pointed in one direction very easily. So if you want to take images of the earth, then you need a bigger more expensive satellite. Also if you want to go to the moon say with these tiny spacecraft, then you need tiny rockets!!
So summing up, big spacecraft=big rockets, small spacecraft=small rockets!!!!! There is quite a bit more to it than this, but that’s the gist of it!