Attraction of light sails
To my very dumb bunny non engineering mind the big problem with space flight is reaction mass. Something has to app!y a force to make your spacecraft move.
The attraction of light sails is that you have a constant (though diminishing) supply of light to push you along so you don't have to carry and burn your own reaction mass.
However the solar supply may be effectively constant but inverse square law means that the amount available gets less and less the further you are from the sun.
Lasers are an attempt to tinker with the basic fact that free but diffuse energy implies a very long time span for any interstellar mission which you want to be able to stop at the destination and then return.
Beyond a certain time span the mission starts to become pointless.
So what is the likelihood of improving the efficiency of the conversion of matter to energy?
Beyond a certain point you can presumably generate enough energy to slowly accelerate and decelerate a very large mass. Thinking Footfall style of interstellar travel, and refueling at a gas giant.
Solar energy is effectively free and constant but of limited magnitude. So in, say, 70 years time will we be able to efficiently burn rock or gas for energy and have effectively unlimited reaction mass within the solar system and other star systems?
Also, my dodgy ScFi memory suggests that you may need a force field to clear all the matter in you flight path to avoid high energy impacts. This in turn can be sucked up to provide reaction mass.
Given that we have interstellar visitors shaped like huge rocky turds might we be better off tooling up to hitch a ride on one of these? Or perhaps create our own and keep pouring energy into it as it orbits the sun until we can slingshot it towards a distant star?
I love the idea of light sails but it feels as though they are only one part of a complete solution.