TWR Problems...

[Shadow Wolf56]

So umm, a couple months ago I was lazy and used mods like Kerbal Engineer for data readings. Soon I became interested in collecting those data values myself. Soooo I headed to the cheat sheat in the KSP wiki. I learn’t ‘The Rocket Equation’ quite easily and then moved onto TWR. But whenever I plugged in the numbers it would turn out wrong. So I spent hourrs
trying to solve this problem with no results. Here is the formula off the wiki:

Where 

Ft is thrust 

m is mass

g is the gravitational acceleration 

I’m also using a scientific calculator for these calculations. Any help would be appreciated whatsoever!!!

Edited January 9, 2018 by Shadow Wolf56

[Steel]

1 hour ago, Shadow Wolf56 said:

So umm, a couple months ago I was lazy and used mods like Kerbal Engineer for data readings. Soon I became interested in collecting those data values myself. Soooo I headed to the cheat sheat in the KSP wiki. I learn’t ‘The Rocket Equation’ quite easily and then moved onto TWR. But whenever I plugged in the numbers it would turn out wrong. So I spent hourrs
trying to solve this problem with no results. Here is the formula off the wiki:

Where 

Ft is thrust 

m is mass

g is the gravitational constant

I’m also using a scientific calculator for these calculations. Any help would be appreciated whatsoever!!!

Can you give an example of a calculation that has gone wrong? 

Seems wierd that you'd get stuck on TWR if you can manage the rocket equation.

 

EDIT: wait, g is the acceleration due to gravity at sea level (i.e 9.81 ms^-2), are you using that or the gravitational constant, G?

Edited January 9, 2018 by Steel

[Shadow Wolf56]

Yeah I can in a couple of minutes...

[Steel]

See the edit to my previous post ^^^

[Lukaszenko]

As Steel said, g is 9.81, and NOT the gravitational constant. 

[Shadow Wolf56]

Yeah i put 9.81 into it @Steel @Lukaszenko

Here is what my calculator calculates

6*200(this is for Kerbal X)+1500/130.94*9.81= 1312.3797

???

I couldn’t get pics because I forgot how to

 

Edited January 9, 2018 by Shadow Wolf56

[Steel]

43 minutes ago, Shadow Wolf56 said:

Yeah i put 9.81 into it @Steel @Lukaszenko

Here is what my calculator calculates

6*200(this is for Kerbal X)+1500/130.94*9.81= 1312.3797

???

I couldn’t get pics because I forgot how to

 

Make sure you're putting brackets around everything to make sure the operations are being carried out in the correct order.

(6*200+1500)/(130.94*9.81) = 2.10

 

The way you have input it, the calculator is doing

(6*200) + (1500/130.94) *9.81 = 1312...

because of BIDMAS (or sometimes PIDMAS).

Edited January 9, 2018 by Steel

[Streetwind]

Tip: instead of doing thrust / (mass * gravity), you can do thrust / mass / gravity. It's easier to memorize, easier to enter into a calculator, and gives the exact same result.

But you still need to correctly set brackets around the addition of individual thrust values, just as @Steel said. IMHO, just do the addition first and then use the result from that as a single number for thrust. Troubleshooting math problems is all about reducing unnecessary complexity.

[Delay]

I think I know what happened. Your calculator cares about order of operations. Make sure to put brackets where required.

Your calculator is doing is this: (6*200)+(1500/130.94*9.81), which equals 1312.37971...

What you really want to do is this: (6*200+1500)/(130.94*9.81), which equals 2.10195.

[Shadow Wolf56]

10 hours ago, Steel said:

Make sure you're putting brackets around everything to make sure the operations are being carried out in the correct order.

(6*200+1500)/(130.94*9.81) = 2.10

 

The way you have input it, the calculator is doing

(6*200) + (1500/130.94) *9.81 = 1312...

because of BIDMAS (or sometimes PIDMAS).

Ok, this might work!!!

EDIT: Thanks guys, my calculator now is doing the right thing!

 

 

 

 

Edited January 9, 2018 by Shadow Wolf56

[Steel]

17 minutes ago, Shadow Wolf56 said:

Ok, this might work!!!

EDIT: Thanks guys, my calculator now is doing the right thing!

 

 

 

 

What I've found over the years is that it's good practice, whenever you do a fraction, to put the top and bottom halves into their own brackets, even if it's not necessary. Avoids a lot of annoying mistakes