Is There a Limit to Timelord “Bigger on the Inside” Technology?

Question

In a previous question about the side of the TARDIS interior no actual answer to the size of the interior of the TARDIS could be found. And at the Battle of Canary Wharf we see the Genesis Ark as what looks like at least several thousand Daleks emerge from it, even though it doesn't look big enough to hold more than one Dalek.

I know we can't answer this question on our own, but there's decades of Doctor Who canon, so I'm wondering if someone may have heard something about this somewhere along the line.

Is there a limit, in Timelord technology, to how large an interior of a container can be compared to the exterior size of the container? If there isn't an absolute limit, is there any kind of practical limit, such as how much power it takes to create the larger interior or to maintain the connection between the interior and the exterior?

Answer 1

The interior of the Tardis is a pocket universe which may require energy to initially to create.

However, in "Rise of the Cybermen", the Tardis (almost) completely loses power. Implying that there is no energy requirement to sustain the pocket universe, or to keep the exterior door of the Tardis bound to the pocket universe.

There has never been a mention of a limit to the interior size, and I think the implication has been that there is none.

However, there may be a maximum size after which the Tardis won't be able to function properly: In "Castrovalva", the Doctor 'jettisons' or 'deletes' 25% of the Tardis's internal structure to provide additional thrust. The implication is that the power required to move the Tardis is tied to the total mass of the interior.

Answer 2

The Doctor also jettisons Romana's room in Logopolis to generate more thrust.

Late 70s, early 80s era stories such as the Invasion of Time (where the Tardis is massive), Logopolis (where Tegan gets lost) suggest that the interior is very very large - making it a bit irrational of the Doctor to home in on Romana's room. Maybe he wanted to jettison the memories as well. I think these stories influenced Neil Gaiman as well in the Doctors Wife where Amy and Rory are running through the Tardis.

In the Doctors Wife it is also suggested that the Tardis keeps an archive of the old control rooms (what a sentimental old thing) Suggesting that some process can add/remove rooms under a control. Perhaps this is a use of Block Transfer Computations alluded to in Logopolis, Castrovalva and the extended media. The Tardis can "store" energy by converting it to rooms like a battery charging only to delete them later and get the energy back

On the other hand in "the impossible planet", the Doctor says that Tardises are grown and then a carving process begins. However if they were carved in the way that we understand it, then concepts such as the Tardis "Desktop theme" wont really apply. Also as we see in the eleventh hour, the Tardis can regenerate herself, suggesting a fluidity where rooms can be added or removed and not a fixed carved structure.

Answer 3

No, there's never been a practical limit given, and the space is theoretically infinite. I would assume that once you've created a gateway to an extra-spatial dimension which has malleable dimensions and reconfigurable geometry there's no real difference between the space being 1 cubic foot or big enough to contain planets.