Fuel consumption formula

[Dr. Alex]

I've been trying to calculate this for a while, but I can't do it.
Here's my process:
Thrust = 100,000 kgf = 980.665 kN
Isp = 240 s
g0 = 9.80665 m/s²

Wikipedia tells me that Isp in seconds is by weight and for that the thrust-specific fuel consumption is 101,972/Isp to get it in g/kN*s.
If I do this to 240 s, I get 424 + 53/60 g/kN*s.
Logic would follow that since thrust-specific fuel consumption is fuel consumption per unit thrust, and I require fuel consumption in kg/s:
424 + 53/60 g/kN*s = 424,883 + 1/3 kg/kN*s
If you then multiply by unit thrust, the number does not seem to change.

424,883 kg/s cannot be accurate however, because that is over 3 times the largest fuel tank's mass.

Please tell me what I did wrong!

 

[Axiom]

Yeah it's wrong, I don't follow what's wrong with your method but here's an easier way to do it
Edit: This is what you did wrong

424 + 53/60 g/kN*s = 424,883 + 1/3 kg/kN*s

Kilograms are 1000 times larger than grams, so you need to make the value 1000 times smaller to get the correct value. you should get around 0.42488kg/Kn s
then you multiply by 980.665 (the engines thrust in kilonewtons) to get around 416.67 kg/s for fuel consumption.
In future I think it would be easier to use the forumula below as your method seems very roundabout and complicated

Fuel Consumption (kg/s) = Thrust (N)/(g (will always be 9.80665) x Isp (s)

So in your case the values would be 980665/(9.80665*240), which gives you 416.67 kg/s for fuel consumption

 

[Dr. Alex]

Thank you, I knew something was wrong.

 

[Axiom]

That's why in engineering we have sanity checks, to make sure your equations at least slightly make sense

 

[Dr. Alex]

Thrust in N / g * Isp would be Thrust / g divided by Isp, so Thrust in kgf divided by Isp?

 

[Axiom]

You can do that aswell, or do it in tons force to get in tons per second (I prefer to do that as everything in this game is measured in tons)