Instead of the old concept of nuclear thermal steam rocket, could we use spin in a pill shaped rocket to provide structural integrity, flight stability, energy storage, artificial gravity, and improved shielding?

Structural integrity. Spin could pull outward stiffening ultra low weight fibers with high tensile strength. It's much cheaper, lighter, and stronger to use materials of high tensile and use spin to convert the tensile to compression strength.

Flight Stability. It doesn't take much spin velocity to weight ratio to force extreme stability in the way of a frisbee. Water as propellant has high mass making this even better.

Energy Storage. If the spin is also used to generate electrical power through magnets and coils and the water is preheated, you should have plenty of potential to convert the hot water to steam, I'd think.

Artificial Gravity. Remaining spin once orbital velocity and altitude are reached could be used as spin gravity. The large pill shaped vessel now with far less water inside, could be easily habitable since water is not toxic.

Improved Shielding. Of course, any remaining water can be used as shielding under the floor. However, a rate of spin should also provide an angle to micrometeor impacts, increasing the material it has to go through a bit.

I would probably use a thin aluminum cavity under the floors wrapped with kevlar, some insulation, and then more kevlar... Use cables to the center, like a bicycle wheel.

This is a concept for launching as premade space station or deep space voyager ..

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    $\begingroup$ I'm not an expert, or even a competent amateur, but I wonder if the problems you are solving are not the big problems that need solving in rocketry. Is it possible that the overwhelming problem is something along the lines of how to stuff more delta-v into the same mass of rocket? $\endgroup$ Commented Nov 18, 2022 at 20:50

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This problems this solves are well down the priority list and it adds some new ones.

There are few cases where the passive spin stability is useful for a large vehicle. It is used in small solid stages because it is simpler than having a vectorable nozzle and/or RCS system to handle any off axis forces during the burn at that scale but for anything doing multiple burns or just a gravity turn it makes changing orientation much harder for no gain. For anything with a nuclear thermal reactor adding thrust vectoring is a relatively minor additional design complication.

The amount of useful energy that can be stored in a spinning assembly is quite small. Flywheel storage certainly exists but is used as a buffer rather than a bulk storage because of low density. The detail depends a lot on design, but mathing a 10 tonne tank at 10 meters @ 10 RPM gives an energy of 12 M joules, which is a big number but 10 tonnes of AA batteries is 3.9 G joules and actual hydrocarbons up around half a T Joule. And this is at around 5G, so our structure needs to be at least 5 times stronger and heavier. Note that just saying 'use layers of kevlar' is not a magic bullet here - we already design using optimal materials so a 5G spin is at least five times heavier.

It is also hard to see how a spacecraft can extract that energy, without having two spinning elements in opposite directions which seems like a terrible failure point to have in a rocket. A useful reference point here is that children's toy helicopters that use a string to spin up a rotor have a flight time in seconds and peak altitude in meters, while similarly size and weight electric drones can fly for minutes.

An additional wrinkle is inertia change during the burn. the rocket is presumably in the middle, so unless plumbing design is clever we are doing the reverse of a yo-yo despin and increasing RPM during the burn (no magic energy gain since the spun mass is decreasing).

The primary constraint on all space craft is weight, in generally boosting performance by getting heavier is not a good idea. Ideally you want no mass in your final stage that is not doing something useful when the burn ends (ie people or science payload), hence staging to drop tank mass. This craft would appear to end up with a large and heavy structure that does nothing once burn completes. Living space is nice, but this will be massively overbuilt for that and have a lot of useless hub structure.

A potential use case for spin is where things need to be pumped or moved, so it is quite possible that large thermal reactor craft will spin, but it would be just enough to give tanks a single suction point and allow convection rather than a system in and of itself.


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