The large 600-m-long, 100-m-diameter, cigar-shaped dirigible is planned for crui

Question

The large 600-m-long, 100-m-diameter, cigar-shaped dirigible is planned for cruises for retired engineers. As a first estimate the drag (resistance force) is calculated assuming it to be a flat plate with zero pressure gradient, with the drag on the nose and rear areas neglected, Estimate the power required of each of four engines if it is to cruise at 15m/s. Estimate the payload if one half of its volume is filled with helium, and its engines, equipment, and structure have a mass of 1.2 Times 10 6 kg.

Explanation / Answer

reynolds number re=v1l/=5.75x10^8 > 5x10^5 so flow is turbulent

cf=0.455/(ln 0.06*re)^2=0.0015

drag force=0.5cf**v1^2*A(area)

=38415N

Power P=F.v=38415*15=576228 Watt=576.23 kW

(a)power required by each engine=576.23/4=144.06 kW

(b)mass=density*volume=0.179*(pi/4*100^2*600/2)=421545 kg

total payload=1.2x10^6+421545=16215451.62x10^6 kg

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