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Minimum thrust of engines at liftoff 
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#1
Feb2810, 02:18 AM

P: 107

1. The problem statement, all variables and given/known data
Hi there Rocket has a total mass of 3.4 x 10^6 kg at liftoff. The first stage contains 2.0 x 10^6 kg of propellants which is consumed at a rate of 1.4 x 10^4 kg s Find the minimum thrust of the engines at liftoff? I would have thought that you needed one more variable to be able to solve this? 2. Relevant equations 3. The attempt at a solution I used the mass flow x escape velocity and ended up with 15.7 x 10^6 N. It takes 142 sec for the first stage to finish its burn. I just dont think that this is right  as the next part states that if this thrust is sustained  find the time over which the first stage operates and the acceleration of the vehicle at that time. (Neglect air friction  and suume whole flight is vertical. Help needed please. Cheers 


#2
Mar110, 06:43 PM

P: 107

Any thoughts?
Cheers 


#3
Sep1510, 12:29 PM

P: 69

Wouldn't the minimum thrust just be m*g? In order to get the rocket moving, you would need at least 3.3*10^7 N of force.



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