S34E5: Journey to the Centre of the Tardis

[Broomstick]

I'd think the rooms would always exist but the corridors between them are variable and constructed as needed.

[Batman]

That's one theory.

And it was never meant to be anything more.

Except we know that the internal space (or least least large chunks of it) exists whether or not someone is there to use it. For instance, way back in Catrovalva, the 5th Doctor has 25% of the TARDIS interior burned up for more power - that 25% must already exist and be sitting there empty to be burned up.

I don't see why. Sure, they have to exist once they start burning up, but not before.

Likewise, the 4th Doctor wandered through parts of the TARDIS that hadn't "been used for centuries".

Doesn't mean they actually existed for all those centuries in-between. They existed once, and they existed again when the Doctor wandered through them, nothing more. The TARDIS could just have recreated them for the Doctor to wander through.

[Parallax]

That doesn't make any sense.
You can burn up TARDIS interior to create more power, so to get more power the ship would spend power to create interior space just so it could burn it up to get more power? No. Especially since we see that it was interior facilities that the crew had just used which happened to fall within the 25% that was burned up (Zero Room etc).

Though it is interesting to note that back then, the Doctor explicitly states that there's a big risk that the primary control room (which they're all in at the time) could be part of that 25% of the interior, a risk with manual over-ride on/safeties off. The same trick is employed in The Doctor's Wife but by then the primary control room can't be jettisoned in such a way...

[Eternal_Freedom]

Actually that was Nyssa and Tegan that were worried about jettisoning the Console Room. While they asked the Doctor and he didn't mention any failsafe he wasn't exactly with it at the time, so it could be the failsafe system simply slipped his mind.

Or, he, I dunno, added it afterwards to avoid the problem recurring. And it wasn't just the console room that couldn't be jettisioned, it was that any life-forms within a jettisoned room are sent to the console room so they aren't killed.

[Batman]

That doesn't make any sense.
You can burn up TARDIS interior to create more power, so to get more power the ship would spend power to create interior space just so it could burn it up to get more power?

Presupposes it takes more power to create them than you get from burning them up. Especially as the TARDIS may simply be taking them out of storage again rather than recreating them all anew from scratch.

[Broomstick]

Or "burning up rooms" provides a temporary power boost. You don't create rooms to burn them, but if you need a sudden burst of "speed" or "power" you can convert the matter in the rooms into energy.

[Batman]

You absolutely DO create rooms to burn them if and when that's less power intensive than keeping them around for centuries with nobody using them.
Which is all I was saying. I'm not saying that's the way the TARDIS must do it, I'm saying it might. Room not used for, I dunno, a week, a month, a year? Into the pattern buffer it goes until it's needed again.

[Parallax]

I'd suggest that it not only keeps rooms around that aren't used, it also (according to The Doctor's Wife) seems to store rooms that the Doctor hasn't even designed/created yet (there was a line about future control rooms, I believe).

[The Imperator]

I loved the episode, probably in my top five for season 7 so far. Loved the interior shots, the acting was all fairly good, and I felt the pacing wasn't as rushed as some of the episodes have been.