T Haiku #atozchallenge

Time is relative;
So are dimensions in space.
It’s bigger inside!

We now begin the final push in the A to Z blogging challenge. One more week! Today’s puzzle should be an easy one for anyone who is connected to the science fiction/fantasy world. This one’s not about a character or a place but a vehicle. It’s not a word, actually, but an acronym. Know what I’m talking about? Tell us in the comments!