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0 pointsdredmorbius12y ago0 comments

I ran my math several times, and the values seemed, literally, incredible. The first time I did this I got something on the order of 4x the power of the original engines of the Hindenberg / Zeppelin. I'm still trying to figure out where I went wrong this time.

Units: dimensions in feet multiplied to give surface area. Convert to meters. Insolation at 1 kW/m^2, PV efficiency of 20%. Oh. I got kW and MW confused. Wups.

I'm actually getting 1900 HP now, which is closer to my original results. Brain damage....

mW == megawatt.

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ars12y ago· 2 in thread

For quick calculations like these I use http://www.wolframalpha.com/

Also, the dimensions for the zeppelin are diameter (not radius) and length, so multiply by Pi - and then divide by 3 since not all of it will be visible to the sun at once.

Converting feet^3 to meter^3 is non obvious because of the ^3 - that would be my guess for where you had an error.

> mW == megawatt.

1.4 MW is not 1.8 million HP, it's 1.8 thousand hp.

dredmorbiusOP12y ago

For quick calculations like these I've found that the GNU 'unit's command is actually very useful. Keep your prefixes straight and it will confirm your units as well:

https://plus.google.com/104092656004159577193/posts/CEq8xTH3...

You have: 117.075 peta watt hours / (325 days * 8 hours/day * 1 kilo watt/meter^2) You want: km^2 * 45028.846

ars12y ago

GNU units is very nice, I used to use it a lot, but wolfram is easier because it's less picky about getting the spelling of each unit correct.

<ribbing>So if it's so great why did you get your calculations wrong? :)</ribbing>

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