Radiation Design by CG Modeling

This is a radiation simulation created in Blender, designed to test placement of the radiation shadow shield relative to the source of radiation emissions, in this case an open cycle gas core nuclear thermal rocket. For illustration of the full vehicle see my post Open Cycle Gas Core Nuclear Thermal Rocket

By replacing the programmed shaders applied to the gas core reactor with a light emitting shader and stripping all other lighting out of the scene, the gas core reactor becomes the sole source of light in the scene, and one can see the effect of the radiation shadow, since the shadow shield blocks light rays just as it would block radiation. So, everything within the radiation shadow should receive no illumination at all, any spill-over will illuminate the model and reveal where radiation would impinge on the vehicle.

Over the past month Dogmatic Pyrrhonist and I have been working out the design of our gas core rockets and sharing the results across numerous discussion threads. A number of talented and insightful individuals joined in these discussions adding their expertise to this project. One of these is Ron Fischer, who offered the following insight:

Ron Fischer

You can use lighting and shadows in your CG rendering program to analyze your shadow shield, this is where the original math for lighting simulation came from: radiation studies on tanks in the 60s. This is (oddly enough) where computer graphics lighting began. I cannot find an exact reference but believe it was Lawrence Livermore Labs. Might as well go "Back to the Future" on that one!

I found this to be a compelling proposition, an opportunity to test out the validity of my design.

Dogmatic Pyrrhonist and I both set about individually setting up a radiation simulation by CG lighting; his results are to be found at links in this thread November 6, 2015

Initially, for purposes of approximation, I used a cone, which you strip out of the scene once it has served its purpose, this is used to insure the radiators panels (and everything else forward of the shadow shield) are completely within the shadow region. It is a matter of placing the cone so to intersect the aft-most edge of the radiation shadow shield, if all components forward of the shadow shield are properly placed nothing should protrude through the surface of the cone.

I realized the technique can be used not only to optimize the shadow shield in terms of placement, but also in terms of diameter. Previously, using the cone I had realized that increasing the distance between the aft edge of the radiator panels and shadow shield allows a smaller diameter shadow shield.  Using this technique allowed me to test that theory, and it in fact worked exactly as anticipated. Truss segments mass less than the 5% Borated Polyethylene of the shadow shield, so there is a savings on structural mass, which is important because, as we all know, every gram counts.

I rendered the scene against a gray background, then a second time against a completely black background.

I made an attempt (which may be laughable) to model the plume. I used a bright blue emission shader. I was curious in regards to how much blue emission, representing radiation from the plume, would show up on the structure of the vehicle. Lacking data on the physical characteristics of plume expansion immediately after leaving the nozzle, this may be an insufficient test, so I’m not sure this adds anything, but darn, it looks nifty.

Ron Fischer suggested I attempt this again with volumetric lighting, and I intend to do so at a future date.

H/T Ron Fischer, Virtual Production Engineer

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