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William-Black's avatar

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

Related Art

The R.A. Heinlein

Open-Cycle Gas-Core Nuclear Thermal Rocket

Mars Courier Mission, Earth-Orbit Escape Burn With Radiator SFX

Mars Courier Mission, Earth-Orbit Escape Burn

Mars Courier Mission, Earth-Escape Tank Jettison

Open Cycle Gas Core Nuclear Thermal Rocket

Gas Core Rocket New Radiation Simulation
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NyrathWiz's avatar
And I think that the more one gets the details correct, the closer to reality the design is, the more "real" it is. This just happens to be Hard SF.
If one wants these sorts of things to come to pass, getting the details correct is helping the process along.
William-Black's avatar

I’ve re-posted this really to give my response to Winchell Chung some additional exposure.


There is a population of SF fandom that doesn’t really know what Hard SF is, or why getting the details right might matter. Then there are some who, oddly, think Hard SF is some kind of threat, or something they should oppose. Then there are the malicious few who suffer from a self-limiting paranoia and conspiracy oriented mind-set, misleading others into a dark fearful anti-intellectualism and self-imposed ignorance.


I’m just a creative guy with a life-long passionate interest in human spaceflight, and a belief that humanity has the capacity to dare great things, that we will not be bound to this one tiny world forever, that what we have accomplished with our science and technology is amazing, but it is only the beginning, and that one day we will build a civilization that spans the solar system, and eventually, perhaps, we will go to the stars.

NyrathWiz's avatar
You have made the jump from artist to full engineer. Bravo!
William-Black's avatar

Thanks Winchell, you know, really I consider myself a student. I just care a great deal about the integrity of my work, about getting the details right.


Many years ago Robert A. Heinlein offered a statement which serves as a good definition of Hard SF: "realistic speculation about possible future events, based solidly on adequate knowledge of the real world, past and present, and on a thorough understanding of the nature and significance of the scientific method."


I am not an engineer, nor am I a scientist, but I make the effort to research thoroughly, and I look for advisement and input from other insightful and knowledgeable people, learning as much as I can, because the details are important. I am merely someone who cares a great deal about the kind of work I produce. I invest a great deal of time in research because the facts matter and accuracy matters.


Heinlein once spent three days working out orbital mechanics on butcher paper by hand in 1947 for one line of dialogue in "Space Cadet".  Apollo astronauts quoted his work (Green Hills of Earth) while over the Moon because he was such an inspiration to the space program.


Of course you know all of this, Winchell, I’m mostly speaking to the benefit of others who might not understand what Hard SF is about, or why anyone would bother.


It’s about integrity. Knowing the work is right because you’ve made the effort to understand the scientific and engineering principles, and tested those ideas.


There is an abundance of artwork produced by artists who are happy to repeat the well-worn television tropes, and that’s fine. I think those who want science-fantasy deserve science-fantasy. And I get it, some people feel a certain amount of loyalty to their media product of choice. But that’s just not my core interest as an artist, and, not everyone can fit their mind in the limitations of that box.


You never know who you are influencing, or where that will take them in the future. The details are important because one day humanity is going out there, and it’s the real stuff that will take us there.