Hello all, I am slightly confused as to how emitters produce the thrust to move the actors around, if say you had a rocket MK1, it produces 8500 particles per minute at an average velocity of 16 m/s all weighing 9 kg, but how does this produce the thrust?
If I had an object weight 7200 kgs then is it simply (8500/60)(16*9) = 7200(velocity)
ie, the rocket would have a velocity of 2.833 m/s? But that doesnt make sense, since I cant simply have a velocity, I need an acceleration.
Another problem I can think of with this is the spread, since not all particles are traveling down I would only get a percentage of the thrust up, the other would make it more stable...

im not that into rocket science or something but the more weight the particle its emitting has and the faster it emitts to more thrust you get

and the more spread it has to more likely it will give thrust to different directions and it will change the object flight course

Alright I thought as much, but how do I figure it out mathmatically? With say a spread of 0.2 then i can assume that 80 % of the normal thrust is going into lift, but how do i find this normal thrust?

umm.. if i understood correctly

you want to find out the ammount of thrust that i emitting at a spread of 0.0

you said 20 percent

so..

lets say 7500 PPM

7500 x 20
_________ = 1500 (20%) than 6000 (mathamatically) are the 80% that emitt straight
100

but, since the spreading methond of CC is random (dont know the exact percent) percent is actually based on infinite numbers and out of 7500 its is highlt unlikley that it will be exactly 1500 particles every 7500 particles emitted. unless CC is coded that way so it takes out the percent of the 7500
(i thought of this theory but i dont know if its really like that.. thus making it a theory.)

That doesnt help me get the force though, Im trying to figure out the force it creates so I can better understand the rockets, but I dont happen to know how to compute the thrust produced, the spread is easy, but finding the full thrust is what I dont know how to get.

umm.. i think the equation should consists of these variables:
The gravity of the Current scene
the weight of the particle
its speed
and some how find out how much thrust the object loses between particle emissions

Edit:

Try this

V = particle velocity
W = particle weight
R = Particle emission ratio
G = Scene gravity (or how fast the object loses its velocity) (youll have to find out how)
S = The percent of the particles that emitt at 0.0 spread

V x W x R x S
____________ Equals the 0.0 spread thrust ammount /and than divide by 60 so it turns to thrust per second
100

7500 per minute. that would be

7500/60=125 per second. and i have no idea on how to calculate the delay between each emission (no time actually)

and when you find out the amount of delay calculated each 7500 particles, i think you need to multiply it by the amount of velocity the object loses per second and subtract it from the equation made above (the V x W x R x S one, after its been divided by 60)


Im not sure this will work

And instead of speed im pretty sure you want velocity, speed is scalar and so would not indicate the direction, velocity would tell us which direction the rocket is traveling in.

well in real life the recoil of a gun can be equated as (mass of the bullet)(speed of the bullet) = (mass of the gun)(speed of the gun) so if you had a .02 kg bullet traveling 120 m/s and the gun weighed 2 kg. (0.02)(120) = (2)(x) the gun would recoil at a velocity of 1.2 m/s
So would each particle add to the velocity?

If I had a rocket of 7200 kg it would weigh 142704 newtons, ie. it has a force pointing towards the center of the planet with a magnitude of 142704, F=ma so 142704 / 7200 = 19.82 m/s/s
For every second its velocity decreases by 19.82, I need to produce a force greater than 142704 in order to accelerate up and fly away.
The equations i know are:

• Momentum = Mass * Velocity | F=MV
• Force = Mass * Acceleration | F=MA
• Change in position = Velocity * Time + 1/2(Acceleration)(Time^2)
• Final Velocity = Velocity + Acceleration * Time | Vf = Vo + aT
• Final Velocity^2 = Velocity^2 + 2*Acceleration*(change in position)

I just cant seem to get this to work out right, those stupid finals always fry my brain...

Perhaps I can use the momentum equation like this:
F = (8500/60)(9*16)
20400 = ma
20400/7200 = a
so then the acceleration is 2.833 m/s/s

any thoughts?

Simply because random numbers are involved, I don't think there's really any reliable way to say "This rocket will accelerate at this rate" just by eyeballing the numbers going in. I dunno if anyone else actually calculates things, but I just tweaked the weight and such of my particles until they do what I want. Of course, this is probably a bad way to go if you want hyperrealism instead of just messing around with things until they look cool.

As an aside, Steve, I think your acceleration due to gravity there is a touch off.

I dont have any idea what equations you would want to do but I know that the spread is calculated in radians but not how you would expect - 3.14 (Pi) radians is normally 180 degrees but for the spread in CC 3.14 is 360 degrees for some reason i'm not really sure why, the chance of the emission being straight down are equal to thoose of it being at any of the other angles it could be at given its spread

TL,DR;

the spread is calculated in half radians and is completely random in where it goes in that spread's range

Whoa that was long

Pi in both directions = 2Pi spread. If you want a total of 0.2 rad spread, you want to put 0.1 in there.

I fixed the acceleration, it is double in CC, most likely due to the fact that in most physics games 10 looks too slow, in any case, is that acceleration correct? and if so if I had a spread of .2 then that means that it can go anywhere from vertical to 22.9183118 degrees off, which means that on average that 12.73 % of the thrust goes into stability, so the acceleration is the slightly less 2.47 m/s/s

that sound right?

.2 spread = .4 rad
.4 rad = 22.9183118 degrees
22.9183118/180 = 12.73 %
2.833 m/s/s * 87.27 % = 2.47 m/s/s

But now that I think about it my earlier acceleration makes no sense, I could have the original force limit towards infinity and still get a positive thrust, but to fix it:

F = (((8500/60)(9*16))*(180-(todeg(2*spread)/180)) - (mass of the main object)(gravity)


that all sound right?
That physics final drained my head today....

there are at least 2 things wrong with the origional formula.

First, you did not account for gravity. the force exerted only gives that speed in zero gravity. To begin moving you must be able to overcome gravity AND add that speed, or it will just hover.

This is what a burst is for. when you start a rocket/jetpack there is a constant stream for flight, but there is a burst to get it off the ground. the jetpack cancels out gravity, letting it hover, but the burst gives it its momentum, making it move in such and such a direction.


second you didn't account for spread. if you have all the particles moving in one direction you get 100% the force, but if half is going at a 45 degree angle from that, your only getting, 50% of that thrust upwards, and your also getting 50% horizontal force, at that point, making it flip, then you need more going the other way to cancel that out.

you literally ARE getting into rocket science with this, so I can't help other than the obvious problems.

I think I accounted for the gravity in the second equation, my post above yours, also the jetpack more then cancels out, you accelerate when using the jetpack and as such burst isnt the only momentum getter.

Right now im trying to get the equations to work out on paper for the Rocket MK1, if it works then i'll post the finished equation, if not then it back to the brain breaking.


Edit:

Alright I think I got it now:
For rocket MK1

• Mass of 943.14
• Emitter
  
  • Emission 1
    
    • Main Thruster Blast Ball 1
      
      • Mass of 9
    • 4500 particles per minute
    • Spread of 0.2
      
      • 0.4 radians
        
        • 23 degrees
        • 12.7% off
        • 87.3% down
    • Max velocity = 18
    • Min velocity = 14
  • Emission 2
    
    • Main Thruster Blast Ball 2
      
      • Mass of 9
    • 4000 particles per minute
    • Spread of 0.1
      
      • 0.2 radians
        
        • 11.5 degrees
        • 6.38% off
        • 93.62% down
    • Max velocity = 20
    • Min velocity = 12

F = (((4500/60)(9*18))*0.873)+(((4000/60)(9*20))*0.9362) - (943.14*19.82)
F = 3148.3152
F/m = a
3148.3152/943.14 = a
3.34 m/s/s

Any thoughts? did i do something wrong? I think so, only being able to carry 314 kg seems way to small...

For the record, this should be something that is on the wiki.

One major and helpful difference, you can make fully straight thrust with useless eyecandy to cover it.

The spread is not the major problem, getting the thrust equated is, so do the acceleratio/equations look correct?