Whatever happened to....?

[John Bentley]

I was just wondering about several technological achievements that were touted as "revolutionary" not so long ago, and I realized that I haven't heard anything about them in quite some time. So here is a partial list, and I am hoping that someone can help me find out what's going on in these areas.

1. Room temperature superconductors - a few years ago, some ceramic compounds were said to show great promise in their ability to act as superconductors at temperatures far above the standard liquid He ranges. Haven't heard anything since then.

2. Automatic piloting system for cars - Not very long ago, a couple of university computer gurus developed a system that could actually navigate your car, even in light traffic. They drove across the country in a car piloted by their system to prove it. I don't remember what University they were from. Nada since then.

3. About a decade(?) ago, Carver Mead at CalTech pioneered a technique whereby he reproduced the human retina and the human cochlea in CMOS VLSI computer chips. Very successfully, I might add. I have his textbook that explains his designs and "how he did it". He bragged that he was going to attempt to copy the hardwired portions of the brain in the same fashion. Nothing since then.

Well that's enough for now. Feel free to add to the list, but please tell me what's going on in these areas if you know.

[Zombified]

Originally posted by John Bentley
1. Room temperature superconductors - a few years ago, some ceramic compounds were said to show great promise in their ability to act as superconductors at temperatures far above the standard liquid He ranges. Haven't heard anything since then.
Superconductors have managed to claw their way up to liquid nitrogen temperatures, but not much higher. If you can manage having liquid nitrogen cooling your circuits, high-temp superconductors work great. But for most applications, that's not very practical. Incidentally, even liquid nitrogen is far above liquid helium temperatures...

I'm guessing the computer-piloted car will be a very long time coming. The potential liability issues may very well make it uneconomic.

A couple of other fun things I've been waiting for: Fuel cell electical generation in the home or car.

I was also rooting for LEO satellites for Internet, although this failed for economic reasons rather than technological ones (Teledesic was supposed to be live next year).

[John Bentley]

Zombified,
I had heard about the liquid nitrogen temperature range superconductors. I'm still wondering why they aren't in extensive use. Liquid nitrogen is fairly easy to contain, and readily available. I used to keep some at my veterinary clinic for use in cryosurgery. Properly insulated containers that are rarely opened will keep the nitrogen liquified for quite some time. Surely some practical use could be made for such a superconductor, given the almost "miraculous" properties of true superconductors. I'm no physicist, but I can think of several practical devices -- from superconducting magnets to batteries, and they would simply require "topping off" the coolant before use. What's stopping these ideas from becoming reality? Cost of manufacture, etc?

[BillC]

My understanding was that as Tc (the critical temperature for superconductivity) went up, Jc (the maximum sustainable current density) tended to go down. The higher temperature superconductors are generally unable to take a high current density without reverting to a normal resistive state.