How a Nuclear Thermal Rocket Engine Works (NERVA Expander Cycle)

This explanatory 3D printed model was created to illustrate the principles of operation of an expander cycle solid-core nuclear rocket engine. As it draws inspiration from multiple nuclear thermal rocket engine (NTRE) designs, especially those from the NERVA program, it is not an exact replication of any one design, but the essential NTRE components are present.

Due to a number of external factors, this project was rather rushed towards the end. If I have made any major mistakes I'll remove the video until they're corrected, and if I get time to refine the design and/or record a more detailed explanation I'll upload that too/instead.

The model and this video are intended for informational and scientific purposes, and for use in the Space Nuclear Propulsion course in the University of North Dakota Space Studies program. This is only a model - it does not contain any radioactive elements, and the individual system components are not shown to scale.

[Retinetin]

That is so fascinating. I studied this in my class but this video is much more intuitive. Do you happen to have the model files available? I'd love to 3D print my own

[artems_ud]

I've been trying to learn about NTP and struggling, but this video made it so simple and easy to understand! +1 sub, extremely underrated!

[maseratidyce]

Kinda inspired by the nuclear lightbulb but would it be possible to use an extremely high purity UF6 gas inside of fused quartz tubes surrounded by ideal neutron reflectors (with a propellant channel in between) such that the UF6 could be confined inside the fused quartz tube by a rotating cyclone of inert, or better yet neutron reflecting gas, if such a thing exists, basically ‘assembling’ a sub-critical UF6 gas, compressing it and keeping it off the walls of the quartz tube until it reaches supercriticality? It would release much more energy than a typical nuclear lightbulb NTR? Could the fused quartz contain this pressure? Could fused quartz, with its low cross section of radiation absorption survive this for very long?

Is this just the hardest way to take advantage of criticality? The hardest matter phase to use for criticality? It’s not a bomb, cuz supercritical masses quickly go subcritical unless certain very hard to achieve conditions are met. This would quickly go subcritical and would need frequent recharging from a tank of subtitula UF6?

Could this be done with another nuclide like plutonium or a trans-Uranic, or thorium? It seems like criticality is this awesome, very interesting and energetic nuclear reaction that’s slept on, but because aside from the atom bomb, it doesn’t really have a use. And if this enhanced nuclear lightbulb, the nuclear flashbulb, doesn’t work just because the material engineering and nature of gaseous UF6 and density required for criticality makes it impossible rather than the nuclear physics making it impossible I would be peeved. I thought I remember hearing about a criticality incident involving a liquid UF6 and an accidental increase of nuclei density until it flashed and killed some Japanese guys. Am I crazy?

So build one of those please and let me know how that part works. When it’s ready I’ll get the 99.5% U-235F6 gas for you. Don’t even worry about that I know some people.