Common cold plasma source
mattm's picture
Posted on:
Wednesday, October 25, 2017 - 19:17

An option I think is worth pursuing is a shared cold plasma generator between the reactor and the impulse engines.

The reactor uses much hotter plasma than the engines, but they both start with cold plasma, which is just heating the hydrogen fuel to a point where it ionises so that it can be magnetically contained for further heating. Why duplicate this equipment?

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Alfisti's picture

I think my first question here would be just how mass/volume intensive is the cold plasma generator likely to be? Personally, I think using the same generator system to feed both engines and reactor is an excellent idea, and personally I see absolutely no reason to have discreet systems for both. However, the thought of having only one of any critical system makes me nervous. Sometimes that's unavoidable for mass/volume/physics reasons (eg. the reactor itself), but I would almost be tempted to take a small mass/volume hit if it meant being able to run, say, a pair of lower output cold plasma generators sharing feed duties to both reactor and engines. It might well be that one generator on its own would not be capable of providing sufficient cold plasma to run both engines and reactor at maximum output, but even 50% would be better than nothing.

On a slighty more mundane note: having two lower-output generators would also allow the staggering or maintainence cycles, so one could be left running whilst the other was shut down to have work done.

mattm's picture

They'd be fairly large. And yes, critical systems. Plasma needs to be produced on a continuous basis for the engines but only on startup for the reactor. Each engine could have its own plasma generator with the ability to divert plasma to the other engine in the event of failure of one of them. One of them could also be used for reactor startup when needed (rarely).

The other difference is that reactor plasma requires a mix of two hydrogen isotopes inlcuding tritium. The engines don't need a mix. So use of an enginer cold plasma generator for the reactor would be on a "purge and restart" basis each time.

Alfisti's picture

If a plasma generator is only requied intermittently for the reactor then I would defnitely be considering just utilising one of those for the engines instead of giving it a dedicated unit. It currently sounds like we'll be doing a cruciform array for the drive units. Depending on how well the generators scale (eg. if a lower output = a similarly smaller unit, and there's no machinery/plumbing that doesn't scale proportionally) it could be worth running one per engine, or even integrating them into the drive module so the whole thing can be removed in one hit. Otherwise, one generator per-pair might be the way to go with a plasma line running back to the reactor for the times it is needed.

robh's picture

Yes, the reactor would only need it during it's starup phase. And if the reactor is starting up, there will be no power for the MIE's anyway.

So looks like a good fit.

robh's picture

The reactor uses a combination of deuterium and tritium. I'm not sure if the engines have need for particular isotopes?

In any event, the process of genereting cold plasma shouldn't be too different across different hydrogen isotopes.

paulm's picture

Actually we're still evaluating propellants for the MIE's. Hydrogen is one option and has the advantage of being lighter for storage purposes. Argon and xenon are also being evaluated. If it was to be hydrogen there'd be no real advantage to using an isotope like deuterium in the engines - the advantage it offers (increased reactivity in combination with tritium) is only beneficial to fusion.