Impractical and pointless engineering challenges

What are some things that could be built, ie, they don’t violate any laws of science, but the engineering challenge would be way higher than any possible benefit?

I ask because I just had a brainstorm for a REALLY stupid thing: a doppler musical instrument. It would be a very long magnetic track of some sort, with the ability to zip a tiny little car back and forth at very high speeds. Mounted on the car would be a sound emitter that generates a single tone. The volume of the tone can be changed, but not the pitch.

Then you can play music by zipping the little car either towards or away from the audience at extremely high speeds, thus generating whatever actual pitch you want via the doppler effect.
I’m fairly sure this would be INCREDIBLY difficult to engineer… as you’d need the “track” to be very high speed, and have incredible acceleration/deceleration, but also nearly silent, so that you could hear the music over it. But… it’s not like it’s time travel or something.

Wow, that one’s clever but a real thread-kill. Gonna be hard to top. But I’d love to see/hear a performance of your invention. :slight_smile:

We’ve had threads and threads of folks arguing for dirigibles filled with vacuum which they say is *so *much lighter than hydrogen or even helium. As an idea its an epic fail. Not due to impossible physics in the narrow sense, but due to impossible materials requirements.

IF we had a way to materials-engineer something with the strength of armor plate steel several feet thick and the mass of 0.01" mylar film we *could *build one. Which would lift about (IIRC) 10% more mass than a conventional dirigible the same size made of conventional aluminum and filled with conventional helium.

That’s a whoppin’ great load of way, way, way concentrated unobtanium for darn little practical effect. OTOH, we’re in the middle of a materials engineering breakthrough nowadays that’s as profound as when we first went from stone to metal.
Whether you want to score materials challenges as out of bounds or not is up to you. I agree it’s a marginal case at best. OTOH, we’re in the middle of a materials engineering revolution as profound as when we went from stone to metal. If that’s not engineering, I’m not sure what is.

The idea of a tunnel across the Bering Strait (or a bridge) is a perennial favorite (see post #8 of that thread).

(And would be:

  1. An engineering challenge.
  2. Mostly impractical and pointless.)

Hamburger earmuffs!

There have been speculations about a transcontinental pneumatic subway that would take you coast to coast faster then a jet. Engineering challenges aside, I’d think that the cost of building it would be prohibitive.

How about a mile-high building?

The original Reagan “Star Wars” SDI probably fell into that same category. Doable, sorta, for way silly money and not very good at its intended mission when it’s done. And in the specific case of SDI, which like any armament is a competitive situation, it would be trivially outflanked by the competition.

Which IMO is also the problem with hyperloops, Chunnels, and Bering Strait tunnels. Fixed transportation infrastructure’s biggest Achilles heel is that it’s fixed. Ships and aircraft are so vastly more flexible.
Many of Robert Munroe’s what-ifs contain silly engineering challenges he hand-waves away in the interest of keeping the physics story moving. e.g. How about we (re-)move the moon using laser beams? https://what-if.xkcd.com/13/. That’s definitely doing something the hard way.

Space elevator.

A variant on the davidm idea.

Subway systems linking major cities along straight line chords rather than following the curvature of the Earth.

Challenge stage 2: Intercontinental.

ETA: Let’s get some of those underwater cities off the drawing board.

There’s currently an effort to build Babbage’s Analytical Engine, based on his original designs.

Currently, they’re at the “deciphering Babbage’s extensive, intricate, and systemically esoteric 150 year old manuscripts” stage. This has been going on for several years, now.

I kinda think we (including me) lost the point the OP was aiming for. It wasn’t “civil engineering white elephants for $300, Alex”.

It was doing something sorta sensible and completely doable, but doing it utterly the hard way. Just because. Think of it more like Rube Goldberg in the 21st Century. No bowling balls and cats and ceiling fans, but lasers and computers and ???

Okay. An ice cream making system. You mix the ingredients, then launch them in a missile aimed at the Arctic. Automated systems then retrieve the missile, whip the ingredients in the Arctic cold, pack the resulting ice cream in an insulated compartment in another missile, and send it back to you. You get fresh ice cream without requiring refrigeration equipment.

Pfft. Amateurs, the lot of you. If you want a real engineering challenge, try building an experiment to detect an individual graviton.

I’ve long speculated that this experiment is how Type III civilizations show off to each other, because it’d be tough even for them.

A performance of the 1812 Overture, but with atomic bombs instead of cannons. Little ones are ok, like the Davy Crockett.

Outstanding post/user name combo.

Have the Rockettes perform live, on the moon. It should be just a matter of money.

Interesting, but of course the car would have to spend half its time travelling away from the audience, with the resulting lower pitch.

How 'bout this? You have a large, horizontal disk, spun at high speed by a motor (like a centrifuge). Around the edge of the disk are 100 speakers that can each emit the same steady tone. A computer on the disk controls which speakers are activated at any time. It plays music by turning on those speakers that are advancing or receding to produce the correct tone. You’d need to be sitting in just the right place for it to work.

Is not this already done? The machine is on display at the Computer History Museum in Mountain View, CA. It’s an actual working replica based on his original designs, but built with modern materials. I believe there is another one somewhere – I think it was mentioned that there are two of them.

Every so often, a docent demonstrates and operates the machine.

No - the replicas you mention (one was built in London in 2002 and the other in California in 2008) are of Babbage’s Difference Engine #2, not his Analytical Engine.

The distinction is that the Difference Engine was basically a calculator for a single task (computing mathematical tables), and the Analytical Engine would have been a truly programmable general-purpose computer. This is the one mentioned by Ranchoth as being in the process of being constructed.

The Difference Engine replicas work as intended, but they are not general-purpose.

I was thinking something quite similar, but mechanical - you sit facing a row of conveyor belts that are all running at different speeds, the conveyors have bells fitted to them (all tuned to the same note) at intervals - when a ‘note’ is played, the machine chooses the belt that is running at the speed necessary to transform the bell’s tone, and strikes the bell on that belt (that is, the bell that’s coming toward you along the top of the belt).

The advantage of this machine is that when it goes wrong, it kills the audience by hurling metal bells at them.