We know solar sailing works anyway- some satellites use it for attitude control, and the size of the effect is consistent with photonic pressure. Solar particles are a much smaller effect it turns out.
Rocket engines can definitely be constructed with aluminum. There are some big advantages from doing so:
a) aluminum has great thermal conductivity (not *quite* as good as copper, but way up there)
b) aluminum is very light, 2.7 g/cm^3
c) aluminum is easy to work
The downsides are the low...