Nuclear Thermal Rocket questions (riding around space in a uranium powered steamboat)

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I'm pretty sure titanium oxide can't be much more oxidised than it already is. Using a titanium casing is not very difficult either.

About containing the nuclear fuel, an idea I had some time ago is to use electrodynamic levitation to keep it in the middle of the chamber.

It uses a lot of power, which is lost to heat, both in the coil and the fuel, but it should be possible to deal with it. After all, you're building a nuclear reactor. A MHD generator could use the exhaust to get power for example.

The main issue with this technique is that your uranium has to be conductive, and will likely have a spheroid shape, which is not ideal for controlled nuclear reactions.

To keep the uranium metallic, you couldn't use water directly, but one can imagine electrolysing water, injecting hydrogen into the core, and then mixing the two flows.

To reach safe criticality, I have a few ideas, but I don't know enough about nuclear reactors to estimate their value. You could use spherical neutron reflectors, or have several liquid uranium balls with moderators in-between, or maybe find a way to shape the uranium in rods.