It has been mentioned in the advanced customization thread:
here and
here.
If there is anything else not mentioned in the thread, please post and I'll be happy to answer (to the best of my knowledge).
I can't rule out creating ERA for Spacemaster. The thing is that I would need a comprehensive list of the changes required. For that, I would need those who know enough of its rules to try ERA out and let me know what is missing.
I know that it would at least imply creating a special list of skills, professions, "spells"(psionics), weapon tables, critical tables, fumble tables. If it were only that, then I can assure you that it is doable, and I would happily prepare it.
But I seem to remember from reading the base book once that there were other changes, such as the measures using a different system, round taking less time, and such. Those changes worry me more, because they would require changing a lot that is fixed into stuff that would change depending on the ruleset (RM vs SM).