Reply To: General thought on old coal mines.

[zapkitty]

Brian H wrote: I wonder if MHD can be used for jet transport. FF seems like a natural for this; I’ve seen designs for SSTO spacecraft that use it in atmosphere, and ion drive thereafter.

Still just not enough power, it seems. FF units, as currently described, are just too heavy

The currently proposed uses of MHD in aerospace propulsion are decelerating incoming air and using the power extracted from that to accelerate the outgoing exhaust (more of a power transfer than actual propulsion) and for external airflow control at supersonic and hypersonic speeds…

These uses alone have power overhead requirements measured in 10’s of MWs.

This would seem to indicate that MHD just can’t be used for primary propulsion at the notional ~50 MW power levels I’ve floated in this thread and that any MHD enhancements to the primary propulsion would eat the entire power supply… including the power that was budgeted for the primary propulsion.

A wild-ass guess says that we’re looking at 400 MW or more in excess of primary power needs to enable a switch to jet-style propulsion.

But once that raw power plateau has been reached (whatever the actual numbers may be) then the entire panoply of MHD tricks should be available and fusion-powered craft will occupy all niches of the aerospace ecology…

… and…

… and what everybody and their dog keeps insisting on jamming sideways into all fusion flight discussions…

…flying to orbit…

… becomes theoretically possible 🙂