What computer programs does ITAR say I can or can not write, or share, or use in the US?

Question

After reading this answer by someone knowledgeable in the field, I realized that I still don't understand even a little bit what International Traffic in Arms Regulations (ITAR) (and its cousins) does and doesn't say what various people can or can't do, and so far I haven't found the ITAR-tl;dr.

edit: I'm getting rid of the hypothetical scenario and adjusting the question to make sure it doesn't read like a request for legal advice.

I've given myself an exercise - launch to orbit in 20 lines of python. It's along the lines of A Neural Network in 11 lines of Python; Part 1 and Part 2. (Part 2 is 13 lines, a clear case of mission creep.)

This is purely a deterministic model. ISP is constant or a simple function, thrust is on or off, Earth's atmosphere rotates as a rigid body, drag coefficient is brontosaurus shaped when plotted vs Mach number, atmosphere is isothermal with scale height behavior, etc. You launch thousands of times and use gradient descent to eventually find an orbit. Only SciPy and NumPy are allowed. I think fifty lines is realistic and probably straightforward, but it could be shorter if made ugly and/or opaque.

Now, if I allow for realistic wind, or engine fluctuations, or mechanical noise in my thrust vectoring, or turbulence, or other things, then I need to add some simulated measurements (e.g. simulated inertial sensors or GPS) and then feedback, and also raise my limit to a few hundred lines of python and/or import other python packages within the Anaconda distribution.

I am wondering if is there any way to tell when a US citizen sitting with their laptop in the US might be starting to cross into potential ITAR territory? Is it when feedback is introduced? Or when Kalman filtering is added? Or is it only when it gets out of the laptop and on to the internet?

I am not asking for nor do I want a legal opinion. But are there any guidelines, rules of thumb, articles in space related magazines, blogs... anything where one could get some kind of gist of where the gray zone begins to darken noticeably?

I see a lot of cautions and warnings peppered in SXSE, but they mostly seemed nuanced for those who should already know but a reminder now an then can't hurt. In this case I'm asking from a responsible noob's point of view.

Answer 1

With the exception of model rockets made of paper, wood, or breakable plastic, that are passively stabilized, that have low thrust and low delta V, and that do not have guidance software, launch vehicles fall under ITAR regulations. The regulations are now much more relaxed once the launch vehicle has achieved its goal and placed its payload into orbit. Certain satellites with limited sensor/effector capabilities fall under the realm of the Export Administration Regulations levied by the Commerce Department rather than the realm of the International Traffic in Arms Regulations levied by the State Department. Satellites with even less capabilities (e.g., some cubesats) are pretty much regulation-free.

Whether simulating a launch vehicle of interest might trigger the interest of the State Department (ITAR), the Commerce Department (EAR), or the Transportation Department (FAA regulations) -- I am not a lawyer. It's important to keep in mind that F = ma would be classified TS/NOFORN (top secret / no foreign nationals) if the DoD had its druthers.

From what I've seen, the boundary is rather fuzzy. NASA has publicly released some parts of it's core Flight Executive, some parts of it's core Flight System, and all of it's Trick Simulation Environment as open source. These are highly capable tools. On the other hand, some NASA software that kinda-sorta provides the ability to simulate trajectories and perturbations to those trajectories remains subject to ITAR.

Full disclosure: I've written a good chunk of the software used at the NASA Johnson Space Center to model trajectories and perturbations thereof. Much of the software that I have written has been deemed to fall under ITAR. On the other hand, I've written what is to me significantly more complex software that apparently is not subject to ITAR. I am not a lawyer, so I'm rather clueless with regard to the distinction.