Hi Ron, I'd recommend Joe Armstrong's thesis https://erlang.org/download/armstrong_thesis_2003.pdf to get an idea what's special about Erlang. Briefly, it's designed around keeping systems running live even when they have bugs and other faults. Straight Lisp with single-dispatch wouldn't isolate effects, though of course you could build something in Lisp that did. Initially Erlang was built on top of Prolog.

(This is Darius. I never really learned your system with related goals for robots -- as you know, I didn't stick around at JPL. About 10 years later I did a bit of Erlang for Yahoo.)