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# Jim Riggs

### Missile Defense Agency - Advanced Technology Group

248 total contributions since 2017

Developing simulations for the Missile Defense Agency - Advanced Technology group
30+ years experience in missiles, smart munitions and other aerodynamic systems. Specializing in systems engineering, aerospace systems design, simulation and modeling, aerodynamics, and numerical analysis.

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help fixing the Heuns method
Heun's method is otherwise known as "explicit trapezoidal method", "improved Euler's method" or "modified Euler's method". Th...

7 days ago | 0

I need help coding a human cannonball ignoring air resistance
Assuming zero drag and relatively low muzzle velocity ( acceleration due to gravity = constant), the point-mass trajectory can b...

23 days ago | 1

Runge Kutta 4th Order Method
I think the problem is the T argument. in k1 you have a capital T, which is a 3-vector in k2, k3, and k4 it is a lower case t,...

30 days ago | 0

Matlab Homework that im struggling with
To prompt a user to enter a value, try: x = input('Enter the number of equations (from 2 to 5): \n')

30 days ago | 0

I need help with this script
Try this: T = input('Enter your temperature') if T<=96 disp('You are either hypothermic or a zombie') elseif T<99 d...

30 days ago | 0

Ballstic Impact of Bullets on armor
I don't know af any specific ballistics tools. You should browse the a list of Matlab products at this link: Matlab Products

1 month ago | 0

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How to find theta and theta dot in a simple pendulum simulation in MATLAB.
I'm not sure at all what your system equations are. The first rule of dynamics is where you have translational modes of motion ...

2 months ago | 0

What is a "system variable" in a Simulink model?
In this context, the "system" is the device that you are modelling. Therefore, a "system variable" is one of the variables in y...

2 months ago | 1

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Undefined function 'simset' for input arguments of type 'char'.
simset is an obsolete function. See documentation here. It says to use the Configuration Parameters dialog box.

2 months ago | 0

Newtons method for finding minimum of a function.
Here is another variation; function [f,g,h] = myfunction(x) f1 = @(z) exp(2*sin(z))-z; %function dx ...

2 months ago | 0

help me in trying to solve the secant method
Try preallocating x, right after you define n: n = 100; x = nan(1,n); ...

2 months ago | 0

trying to calculate the central diff approximation
There is a Matlab function "diff" which will do this. Otherwise, your subscripts must all match (2:end-1) Adi_1 = diff(Vdi_1...

2 months ago | 0

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Performing calculations (Newton's method) over values in loop
Yes, your loop is not quite right. Notice your placement of the three lines i=1; converge = false; po = p_init(1); These t...

2 months ago | 0

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Draw a circle for arbitrary orientation on spherical surface
My approach is to define the circle around the X-axis, then rotate it into the desired position through a Yaw-Pitch rotation. ...

2 months ago | 1

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the meaning of basic matlab words
an argument is a constant or variable that you provide to a function; e.g. sin(x) % here x is the argument to the function sin...

2 months ago | 0

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How to alter Comet Speed
I don't see a way to control the speed of the comet function. There is a discussion of controlling the speed of an animated lin...

2 months ago | 0

Incorrect Answer Calculated For Force Calculation
It is assumed that you want to find F3 and y such that the system is in equilibrium (this is not stated) (and I disagree with D...

2 months ago | 0

Transformation Matrix Between Two Cartesian Systems
This is a very generic question and there are many ways to answer. It depends on what information you have about the two coordi...

2 months ago | 0

Why is ode45 changing the value of the state variable between calls to my dynamics function?
ode45 implements the Dormand-Prince method which is an embedded 4th / 5th order Runge-Kutta method. For every "step" in the sol...

2 months ago | 0

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Implement friction into a model, related to the velocity. (Missile Launch)
This question is familiar. look here.

2 months ago | 0

How to make a marker circle bold?
plot(x, y, 'ro', 'linewidth',2);

2 months ago | 0

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how can i resolve this equation Runge kutta method
Ths is the equation for a parabola. y'' = -1 y' = -y y = -1/2 y^2 No need for a numerical approximation.

2 months ago | 0

Step 1: Draw a free body diagram that shows the body with all of the forces that act on it and the coordinate frame(s) that are...

2 months ago | 0

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How to calculate the slope from geopraphical coordinates?
First of all, you should consider the relationship between the WGS84 lat/lon/alt and the ECEF frame. Altitude is perpendicular ...

3 months ago | 1

calculate rotation matrix in 3D
I'll assume that we make the reference frame right-handed by negating the axis_3 vector such that axis_1 = [2.7239 -0.2014 -...

3 months ago | 1

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Translational motion of a rotating object.
To begin, Chasles' theorem states that translational motion and rotational motion obey the law of superposition. Therefore, you...

3 months ago | 0

change variable value based on other variable in if loop
Your input command is requesting a string input: in1 = input('first: ','s'); in2 = input('second: ','s'); This results in in1...

3 months ago | 1

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I don't know the problem involved Backward difference.
I am assuming that your question is that you don't understand Simpson's rule. Below is an exerpt from Wikipedia: Simoson'...

3 months ago | 0

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1-2-1 or X-Y-X rotation matrix not supported
I recently cataloged all of the permutations of the 2 and 3 axis planar rotations. It is easy to write your own functions. See...

3 months ago | 0