zapkitty wrote:If you're using air augmentation then, while you may use the vortex to keep the plasma from eating your nozzles, you are still going to be moving a lot of air that while hotter than jet exhaust won't be heated to anywhere near plasma temperatures... so could that cooler air be used to cool the nozzle walls instead while the plasma is heating the air?:)
The basic idea of VCCW is a reversed-flow vortex, and it's more about keeping the thrust chamber cool than keeping the nozzle cool. In Orbitec's version the cold outer vortex is mostly oxidizer and the hot inner vortex, moving axially in the opposite direction, is where the combustion takes place after fuel is injected at the top. It works so well that for some tests involving H and O combustion they were able to use a clear acrylic cylinder for the outer wall without melting it, so they could photograph the combustion zone. This behavior is opposite that of the well-known Ranque-Hilsch vortex tube, which has a hot outer vortex and a cold reverse-flow inner vortex.
After reading more about segmented arc heaters being the most efficient type, I think that heater design considerations should overrule VCCW design considerations, but there might be some potential there for combining the two concepts, say, to eliminate the water cooling typically needed for arc heaters.
zapkitty wrote:And outside of the nozzles is the ducting. The primary drawback to air augmentation is the weight of the ducting but designers were willing to work with that even for the chemically-powered Nova rockets...
Now, this design is oversized for the task, 500 tons to LEO, but it's a VTVL design that I think, in a smaller version with 2 polywells stacked where the LH2 tank is, might be closer to the results you want:
That's another possible arc heating application.
The vehicle configuration I'm considering here (another Plan B... Plan A is still Mach Effect) is more along the lines of a slightly flattened, more rounded X-33, maybe intermediate between X-33 and Lenticular Reentry Vehicle. The flattened, large-planform shape makes VTVL a little easier when you consider Polywell cusp locations, and provides lots of area for thermal radiators as well as making the vehicle fluffier for reentry (lower ballistic coefficient) so that metallic TPS might be used. It would operate as VTVL for lighter payloads, but could also do HTHL for heavy payloads. In either case, vertical and horizontal thrust would be obtained by electric arc heating of airflow at low to medium altitudes (no additives, unless something is absolutely needed to reduce ozone near the ground), transitioning to heating onboard propellant as the air thins out on the way to orbit. Able to cruise indefinitely in atmosphere prior to orbit boost and after reentry, since the main consumables in that mode are small amounts of H and B11. Intakes and exhausts generally within the aeroshell envelope if possible (maybe pivoting or retractable for VTVL like Excalibur
, but with all of the lower surface sealed for reentry).