DeltaV wrote:If Polywell is ready before Mach-effect, then:
Superconducting electric lift fans (VTVL) from ground to low atmosphere,
transitioning to superconducting electric turbines from low to medium atmosphere,
transitioning to ram-air arc-jet from medium to high atmosphere,
transitioning to onboard propellant arc-jet from upper atmosphere to orbit.
Modes blended where appropriate.
All powered by direct-converted alphas.
Instead of "
arc-jet", which is low-voltage, high-current, ohmic resistive, I should have written "Quiet Electric Discharge (QED) All Regeneratively Cooled (ARC) engine", as with a Relativistic Electron Beam aimed into a high-density working fluid, with magnets surrounding, per Bussard.
So, if light weight, high power, high-to-low voltage convertors are just wishware (MSimon?), let's (ignoring neutron/radiation shielding for now) keep the above high altitude modes and rethink the low altitude modes to somehow use either the alphas directly or the high-voltage REB (without venting any ozone).
93143 wrote:You'd have to be careful to design it so it didn't destroy itself, but that's true of a reusable QED rocket too. You could use it either as a heat source for a high-efficiency thermal power cycle, or as a way to heat incoming air without generating ozone
93143 wrote:Now all we need is a heat exchanger that can handle the required temperature without being too heavy...
It would be nice to keep the Polywell/direct-conversion system sealed (as far as possible) and simply use it in all flight modes as a high-voltage "battery" driving the REB. To avoid ozone at low altitude we need a heat exchanger that keeps the REB and air/propellant separated. Maybe a sealed, REB-scanned, "channellized" heat exchanger made out of thin-walled metal and ceramic, that heats the air/propellant without ozone and is moved out of the "combustion chamber" when QED-ARC kicks in at higher altitude. A conical or cylindrical heat exchanger might work, with the REB entering through a single, sealed tube and being either scanned via a rotating magnetic field or circularly fanned-out to the channels via a static field. A rectangular geometry would require some fancy ductwork.
The simplicity is appealing (practical is another matter)... REB heating of air/propellant for all four modes (I'm not giving up on VTVL!), with no intermediate closed-cycle thermal loops as it seems would be needed for low-voltage superconducting motors.