Would Or Could A Nuclear Saltwater Rocket Be Converted Into A Plasma Rocket With A Magnetic Nozzle?

[Spacescifi]

Yes or no?

Would this extend it's travel range greatly?

[AckSed]

Someone's been watching For All Mankind...

Okay, "plasma" is characterised by the presence of a significant portion of charged particles in any combination of ions or electrons.

A NSWR rides a continuous nuclear explosion held at bay by the flow rate, but the peak neutron flux should happen outside the craft and in the nozzle. Should.

A nuclear explosion contains some charged particles due to how hot it is, and maybe some alpha and beta particles. The magnetic nozzle will be able to corral them. So the advantage is that the ISP will rise. Slightly. But now you are stuck designing a superconducting nozzle that will withstand a constant barrage of neutrons, gamma rays and heat. I wouldn't want that challenge.

Edited May 18 by AckSed

[Spacescifi]

6 hours ago, AckSed said:

Someone's been watching For All Mankind...

Okay, "plasma" is characterised by the presence of a significant portion of charged particles in any combination of ions or electrons.

A NSWR rides a continuous nuclear explosion held at bay by the flow rate, but the peak neutron flux should happen outside the craft and in the nozzle. Should.

A nuclear explosion contains some charged particles due to how hot it is, and maybe some alpha and beta particles. The magnetic nozzle will be able to corral them. So the advantage is that the ISP will rise. Slightly. But now you are stuck designing a superconducting nozzle that will withstand a constant barrage of neutrons, gamma rays and heat. I wouldn't want that challenge.

I would say pulse fire it, but something tells me doing that with a nuclear reaction only limited by flow rate would be a challenge, albeit not an impossible one.

So the plasma drive version of a nuclear saltwater rocket would be designed to pulse fire rather than for continous exhaust and with a magnetic nozzle.

[AckSed]

Pulsing... wouldn't be a good idea either. The inventor, Dr. Robert Zubrin, the one who came up with Project Orion in the first place, said that this concept depends upon a steady stream of constantly-fissioning propellant, and water to shield the reaction chamber/nozzle.

For the why, read on.

From what I have read, a lot of the engineering and startup/shutdown processes in any rocket engine are attempts to mitigate/eliminate transient events.

Transient events, or transients for short, are the bane of any system in spacecraft, most often fluid-carrying systems. They happen when you turn something on and things are in the process of starting, or the opposite, when things are in the process of stopping. Sometimes it's when you have almost reached full power, but have to literally wait for the pumps to catch up.

We find this on Earth with normal plumbing. Closing or opening a tap/valve suddenly will cause a bang as the speed of a mass of an incompressible liquid (water) is reduced to zero, and the energy is dissipated at shockwaves ringing through your pipes. This is hydraulic shock AKA "water hammer".  If the system isn't engineered to mitigate it, such shockwaves can cause pipes to crack from the strain and bubbles of vacuum or vapour to form.

That's like a couple kilograms per minute in a good water system.

In a rocket engine pumping hundreds of kilograms of propellant per second, suddenly closing a valve that's feeding the propellant from the tanks is Bad. And explodey.

Citation: "Treatment of Transient Pressure Events in Space Flight Pressurized Systems"

It gets worse, though.

"Hard starts" are generally caused by fuel or oxidiser left in the engine or pipes meeting up with new oxidiser or fuel being fed in when you restart the engine. Certain mixture ratios or allotropes or frozen/semi-frozen mixtures of fuels explode. You must run the engine lop-sidedly by feeding in one part of the propellant to wash away any trace of the other, and  in the case of cryogenic fuel/oxidiser, do not boil when entering the pumps, causing vapour bubbles that the pumps will ingest, overspeed and then tear themselves to shreds. (This is what "engine chilldown" is prior to a Falcon 9 second stage engine igniting.) See here: https://space.stackexchange.com/questions/41473/how-does-lox-lead-startup-prevent-hard-starts

A NSWR, when the propellant is dissolved nuclear salts of a certain concentration that can boil off the water and become more concentrated, will need to be really, really, absolutely certain it is not leaving a crust of uranium tetrabromide on the reaction chamber walls that will not detonate when more nuclear fuel is fed in. Because water (which we are using to cool the chamber walls) is a good way to slow down highly energetic neutrons so that they can split fissile uranium i.e. it is a moderator. So if a restart doesn't feed multiple swimming pools of water into it beforehand, it's going to suddenly produce much more radiation and then blow up in a very dirty explosion.