The hidden chemical attack that forced the Northern line’s extraordinary repair
"Thirty years ago, an entire section of the Northern line had to be replaced because it was under attack from acid, and all the work was done without the public ever noticing. Even today, it’s a little-known feat of very clever engineering that was needed to fix a problem that had been set in motion some 50 million years ago."
Designing Moon Trains
"In rail engineering, lateral acceleration is usually measured not in units of acceleration, but in units of distance...
a = (e/k)g
The upshot is that a standard-gauge railway on the Moon can expect to have a maximum total equivalent cant of 300 mm or somewhat more, same as on Earth – but that is compatible with a value of a of 0.33 m/s^2. In effect, curve radii have to be six times wider, assuming equal technology."
