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42 feet per gallon

nasa.gov

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Re: 42 feet per gallon

#11

Post by spc476 »

drv wrote: post #10
ck2 wrote: post #8

Article doesn't say how far it typically has to travel. Traveling quarter mile, no big deal. Traveling 10 miles, much more expensive.

Seems to be about 3 miles from most of the launch pads to the VAB, so about 377 gallons for a one-way trip ( http://www-pao.ksc.nasa.gov/nasafact/count3teaf.htm ) The crawler can travel about 1 MPH loaded; the tour guide at KSC (at least when I was there several years ago) made a big deal about the blazing 2 MPH it can do when unloaded. :)

The closest observation point is three miles from the launch pads, so yes, the VAB (Vehicle Assembly Building; it's insanely large) is probably around three miles as well.

Why the three mile distance? Back during the Apollo program, engineers determined that if the Saturn V were to explode on the launch pad, the resulting fireball would be around four or file miles in diameter. I think it's a similar radius for the Shuttle as well.

Re: 42 feet per gallon

#13

Post by axod »

rue wrote: post #12

So, 12,8m/3,78541178l or EU standard combined: 29573,53l/100km? I wish at least sciency articles used SI.

The numbers you just put above mean nothing to me. Feet per Gallon is something humans can visualize.

I'm sure I'll get downmodded to hell for expressing this opinion here, but I really do prefer imperial measurements.

Re: 42 feet per gallon

#14

Post by b_emery »

sosuke wrote: post #3
javanix wrote: post #2

You know, 42 feet per gallon sounds pretty terrible, but I'd say moving 5.5 million pounds of equipment 42 feet with one gallon of gas is pretty damn impressive.

The weight of the crawler is 5.5 million pounds, it carries 12 million pounds on top for the trip. I'm not sure if the FPG calculation includes the cargo

Very cool. I had to compare it with the Airbus A380-800: 1,300,000 lbs max takeoff weight, using 85472 us gal max fuel capacity, and 6400 mi max range

= 395 ft/gal or 513.5e6 ft-lbs/gal

Re: 42 feet per gallon

#15

Post by tocomment »

xxpor wrote: post #9
oiuyftgrghjk wrote: post #7

Earlier quoted context omitted.

Interesting comparison. A container ship does about 24knots = 40feet/second It uses around 350tons of fuel/day = 4.5 l/s = 1.2USgall/s So it does a very similar consumption - around 35feet/gallon While carrying 150,000tons of cargo = 320million pounds.

The low speed (90 rpm) diesels in those ships are by far and away the most thermally efficient internal combustion engines on the planet. The biggest ones approach 50% efficient. http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96...

Why is that? Why don't they use these to generate electri ity?

Re: 42 feet per gallon

#16

Post by jmillikin »

axod wrote: post #13
rue wrote: post #12

So, 12,8m/3,78541178l or EU standard combined: 29573,53l/100km? I wish at least sciency articles used SI.

The numbers you just put above mean nothing to me. Feet per Gallon is something humans can visualize. I'm sure I'll get downmodded to hell for expressing this opinion here, but I really do prefer imperial measurements.

It's only something you can visualise if you grew up with imperial units; "42 feet per gallon" is not inherently easier than "3.4 meters per liter", nor "125.7 gallons per mile" than "296 liters per km".

Re: 42 feet per gallon

#17

Post by oiuyftgrghjk »

tocomment wrote: post #15
xxpor wrote: post #9

Earlier quoted context omitted.

The low speed (90 rpm) diesels in those ships are by far and away the most thermally efficient internal combustion engines on the planet. The biggest ones approach 50% efficient. http://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA96...

Why is that? Why don't they use these to generate electri ity?

Because external combustion engines (boiler + turbine) are more efficient and cheaper to build at large scale

Re: 42 feet per gallon

#18

Post by rue »

axod wrote: post #13
rue wrote: post #12

So, 12,8m/3,78541178l or EU standard combined: 29573,53l/100km? I wish at least sciency articles used SI.

The numbers you just put above mean nothing to me. Feet per Gallon is something humans can visualize. I'm sure I'll get downmodded to hell for expressing this opinion here, but I really do prefer imperial measurements.

> The numbers you just put above mean nothing to me.

And they will continue to mean nothing because not even sciency articles bother to use SI. Save a concerted effort to learn, obviously. A meter is about 3 feet or one yard and a litre is about a quart, if that helps.

> Feet per Gallon is something humans can visualize.

Kind of a broad statement, no? Humans who are used to imperial units, sure. To folks not accustomed to them it seems at times that "imperialists" measure everything in football fields…

> […] but I really do prefer imperial measurements.

Do you prefer them in an objective comparison or out of habit? SI units are, I think, easier to use because of the decimal-basedness and simpler conversions.

Re: 42 feet per gallon

#20

Post by wtallis »

jmillikin wrote: post #16
axod wrote: post #13

Earlier quoted context omitted.

The numbers you just put above mean nothing to me. Feet per Gallon is something humans can visualize. I'm sure I'll get downmodded to hell for expressing this opinion here, but I really do prefer imperial measurements.

It's only something you can visualise if you grew up with imperial units; "42 feet per gallon" is not inherently easier than "3.4 meters per liter", nor "125.7 gallons per mile" than "296 liters per km".

But all of those are far more accessible than 29573.53L/100km, which most people would just round up to "a hell of a lot". Using conventional units doesn't really help when the magnitude is so high.
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