Problem 4.177[Difficulty: 3]Given:Data on "jet pack" rocketFind:Initial exhaust mass flow rate; mass flow rate at end; maximum time of flightSolution:Basic equation: Momentum flux in y directionAssumptions: 1) Jet pack just hovers 2) Steady flow 3) Uniform flow 4) Use relative velocitiesGiven dataVe3000ms⋅=M0200 kg⋅=Mfuel100 kg⋅=gmoon0.17 g⋅=gmoon1.67ms2=At all instants, the momentum becomesM−gmoon⋅v1−mrate⋅=Ve−mrate⋅=ormrateMgmoon⋅Ve=Hence, initiallymrateinitM0gmoon⋅Ve=mrateinit0.111kgs=Finally, when all the fuel is just used up, the mass isMfM0Mfuel−=Mf100 kg
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This note was uploaded on 10/19/2011 for the course EGN 3353C taught by Professor Lear during the Fall '07 term at University of Florida.