[Kaoru Chujo]

Originally Posted by Seska

dont forget the trainie ship, at the end of Episode 02.... It have only 1 ring... Mfg, Seska

In Yui's Q&A, it says that the single-ringed ships are just for training, but that they can attack other ships with a sonic boom.

Spoiler for ep2:

Maybe that's how Aer (Yui transliterates it Arel) was able to destroy the enemy ships. I couldn't figure that out when I watched it.

I like the idea that the time- and space-rings interact to produce the special power of the Simoun, but maybe the training ship just has the space-ring. I'm sure we will learn more gradually. That appears to be how this show works.