The Georgetown Rail inspection system doesn't appear to be the same type of system because it isn't able to inspect the rails for cracks. It looks like a image-recognition system that throws a red flag if it looks like a tie/spike/etc. is not where it should be.

It sounds like UCSD system is a "laser sonar", effectively pinging the metal rails with photons and "listening" the echo photons. If this is true, it works because the operating wavelength of lasers is massively smaller than that of sound or physical vibrations and can be discrimiated.

Ralph,

If what you're saying is true and I'm exactly right, wouldn't that make you exactly drunk?

It's 5 PM, I'll be joining you shortly.

I think (caveat: it's a Friday) in this case, you don't want the CG to be low on dynamically stable system, i.e., a system that requires motion to be stable.

Think of this way: hold a broom upside-down on your hand and try balancing it. Pretty easy. Now flip it around and try the same. Not so easy.

We all know that when the CG is high on a statically stable system, it is more susceptible to perturbations and vice versa, e.g., tall SUVs are more likely to rollover than low sports cars, and low CGs on sports cars make them transition quicker, i.e., better handling.

However, A high CG "slows" things down to where "something", like your hand/brain or computer, can react, for both statically and dynamically stable systems. So in this case, the high CG is good because it gives the computers and control algorithms a chance to react so the beers the professors and grad students put on it don't end up on the floor.

Like I said, I think I'm right but ask me after 5PM when the number of beers consumed becomes proportional to how confident I am that I am right.

You in the back of the classroom, stop giggling, I said PER-terbation.

An "incorrect" answer will get you fired; a "wrong" answer will get you (and probably other people) killed.