Minimum thrust of engines at lift-off

In summary, the conversation is discussing the minimum thrust needed for a rocket at lift-off with a total mass of 3.4 x 10^6 kg and a first stage containing 2.0 x 10^6 kg of propellants. The suggested solution involves calculating the mass flow and escape velocity, but the question of the time and acceleration of the rocket's first stage is raised. Another suggestion is that the minimum thrust could simply be the mass of the rocket multiplied by the acceleration due to gravity.
  • #1
zebra1707
107
0

Homework Statement



Hi there

Rocket has a total mass of 3.4 x 10^6 kg at lift-off. 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 lift-off?

I would have thought that you needed one more variable to be able to solve this?

Homework Equations





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 don't 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
 
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  • #2
Any thoughts?

Cheers
 
  • #3
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.
 

What is the minimum thrust required for a rocket to lift off?

The minimum thrust required for a rocket to lift off depends on various factors such as the weight of the rocket, atmospheric conditions, and the desired velocity. Generally, the thrust must be equal to or greater than the weight of the rocket for it to lift off.

How is the minimum thrust calculated for a rocket?

The minimum thrust for a rocket is calculated by considering the weight of the rocket and the desired acceleration. It can be calculated using the formula: Thrust = Mass x Acceleration. The acceleration required is usually based on the desired velocity and the time taken to reach that velocity.

Why is the minimum thrust important for lift-off?

The minimum thrust is important for lift-off as it determines whether the rocket will have enough force to overcome the Earth's gravity and achieve the desired velocity. If the thrust is too low, the rocket may not be able to lift off, and if it is too high, it may lead to instability or damage to the rocket.

How do scientists determine the minimum thrust for a specific rocket?

To determine the minimum thrust for a specific rocket, scientists consider various factors such as the weight and size of the rocket, the desired velocity, and the atmospheric conditions. They also conduct simulations and tests to ensure that the rocket has enough thrust to successfully lift off.

Can the minimum thrust be adjusted during lift-off?

Yes, the minimum thrust can be adjusted during lift-off. This is usually done to control the acceleration and ensure a smooth and stable lift-off. The thrust can be adjusted using the rocket's engines or through additional boosters that can be ignited during lift-off.

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