(no subject)

[zwol]

http://www.withouthotair.com/ is a book (full text online in html and pdf, or you can buy a paper copy) which breaks down the per capita energy consumption of Great Britain and lays out what exactly would be required for that country to stop using fossil fuels altogether. It's written for a general audience and is intensely practical. Well worth reading, particularly the first two segments.

One of the I-didn't-know-that observations is that airplanes are already right up against their efficiency limits - any heavier-than-air craft must continuously push air downward and backward, so you can derive the minimum energy to go from point A to B from Newton's laws of motion; it turns out we're already within 20% of that. Being I put up the mad science icon for this, you can probably guess that I'm thinking, what about dirigibles? It's buried in Appendix C with all the math, but they do very nicely indeed; an idealized 400-meter dirigible could do about as well as high speed rail, energy-wise, assuming it traveled at 80 km/h (three days to cross the Atlantic, which is not ridiculous) If we want to get there faster and still be more efficient than airplanes it looks like we're going to have to figure out some way to build intercontinental railways.

Comments

[kaolinfire.livejournal.com]

intercontinental railways sound AWESOME. I can just picture bullet trains withstanding 200ft waves, lightning racing down sinks just off the monorail...

[zwol.livejournal.com]

I actually have a design in my head. It involves sealed, vacuum-filled tubes, weighted down to float about a hundred feet below the surface of the water, with the train magnetically levitated inside. Ideally made of some transparent material, so the trip isn't too boring.

[kaolinfire.livejournal.com]

I hereby submit someone should start a contest (the U-Prize) and... hmm. that still doesn't give you the funding to create it. Next lottery winner, take note!

(I first (and second) read the line as "with the train magically levitated inside")

[zwol.livejournal.com]

Magic, magnets, whatever works, really!

[aldren.livejournal.com]

I've often thought about building a dirigible. I'd want to use hydrogen rather than helium, as it seems easier to get, and theoretically you'd be able to refuel mid-flight. Provided you could safely contain it, perhaps by running water over the shell of the balloon, you could keep static discharge down, preventing it from sparking.

I did all the calculations for it a couple of years ago. It's very doable.

[zwol.livejournal.com]

Yeah, hydrogen got a bad rap because of the Hindenburg, but I've read that the real problem there was that the skin was made of thermite. Eejits.

[kaolinfire.livejournal.com]

ROFL@thermite. Though some back-of-the-napkin internet reading suggests that was not a significant factor.