Do I need to integrate twice for calculating velocity in Kerbal Space Program?

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Discussion Overview

The discussion revolves around the calculation of maximum velocity in the game Kerbal Space Program, specifically addressing whether it is necessary to integrate twice to derive velocity from acceleration, which is influenced by changing mass and thrust. The scope includes theoretical reasoning and mathematical formulation related to physics concepts.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant presents an equation for fuel mass over time and derives an expression for acceleration based on thrust and mass change.
  • Another participant confirms the need to integrate to find velocity, referencing a linked paper for further details.
  • A subsequent post reiterates the need for integration and poses a question about whether one or two integrations are necessary to transition from jerk to acceleration and then to velocity.

Areas of Agreement / Disagreement

There is agreement among some participants that integration is necessary, but there is uncertainty regarding the number of integrations required to obtain velocity from acceleration.

Contextual Notes

The discussion includes assumptions about the relationship between mass, thrust, and acceleration, but does not resolve the mathematical steps or clarify the dependency on specific definitions or conditions in the game mechanics.

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So i was playing Kerbal Space Program and decided i wanted to calculate the maximum velocity of my ship. First, I formed this equation. A(t) = M - dm/dt (t) Where A is the amount of fuel at a given time, M is the total mass of the fuel, Dm/dt is the rate of change of the mass of the fuel, and t is time. As far as experiments in game show this equation works. The problem occurs when i want to calculate the maximum velocity. First i differentiated F = MA and solved for da/dt which gave me -F(dm/dt)/m^2 = da/dt. This gives me the jerk and i believe by multiplying it by t I can get the acceleration at a given time. (-F(dm/dt)/m^2 )(t) = a(t) .
From here I'm stuck. I can conceptualize how to obtain the velocity from this point. I started thinking of summation and that lead me take the integral. So my question is could I get the velocity at a given time by integrating this equation (-F(dm/dt)/m^2 )(t) = a(t)? Not sure if i provided enough information but thanks to anyone who can help.
 
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Dr. Courtney said:
Yes, you need to integrate. One approach is described in the linked paper:

http://arxiv.org/ftp/arxiv/papers/0903/0903.1555.pdf
I actually have one more question. Would I need to integrate twice to go from jerk to acceleration then from acceleration to velocity or could I just take the integral of the equation I posted of acceleration as a function of time. Still reading through paper it might answer this.
 

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