Reply To: General thought on old coal mines.

[nemmart]

jamesr wrote:

Is it silly me or is the 0.282 kN = 0.282 MW?
Edit:
Boeng output is probably per second
Where FF is per hour, in that case we need ~203 modules with electrical output
or 102 with full output in case efficiency is similar.

1W = 1Nm/s so 0.282MN/s is equivalent to 0.282MW

another way of looking at it is: Power = (force *distance) / time = force *speed

So if we take the maximum speed (rather than the cruising speed) then this should be where the maximum force the engines can produce is just maintaining the speed and not accelerating it.

We have max speed (from the same wiki link above) = mach 0.92 @35000ft = 988km/h = 274m/s
Force = 4*262kN = 1048kN

Therefore Power of 747 at full thrust = 1048000*274 = 287152000W ~300MW

or 60 5MW FF generators!

Something is fishy though. According to http://www.howstuffworks.com/question192.htm, a 747 burns 36,000 gal over a 10 hr flight, or about a gallon a second.
A gallon of Jet A has ~121 MJ. 121 MJ delivered in 1 second is 121 MW. Therefore, averaged over a 10 hour flight, you need 120 MW, or 24 FF’s. The difference
might be explained as a peak vs. average output.