re: As far as I remember there was plenty of activity at sci.space.tech
Among the more notable frequent message postings were those from Geoffrey Landis. But besides him, there was nothing new there. More of the same topics, over and over again, until anyone browsing them could take in the entire list at a glance and know if there is anything noteworthy there. Persons like myself could do this for several months before discovering something worth reading. That's how repetitive it was. It was however one of the most active space-related message boards, so I have no idea why it's gone.