3 ms·

This doesn't make sense to me. The detached portion would be subject to radiation pressure from the ground-based propulsion lasers, and would quickly be pushed

• falcolas 11y ago
  Yes, but it's reflecting the light back at the spacecraft. So, even though it would accelerate quickly away from the spacecraft, the light reflected back at the spacecraft would be used to decelerate the spacecraft. So long as the daughter sail never hits C (thanks, physics), it's always reflecting back photons back at the spacecraft (though red-shifted). You'd still have to account for the light coming from the source as well as from the daughter sail, but a black coating on the back of the spacecraft's reflector would take care of that; it would give you n force pushing you away from the original light source, and 2n pushing you towards the source. The coordination and planning required for such a device would not be trivial, but it would be possible.