MHD Discoid 2.0 Quantitative Feasibility Study of a 22-m Radial Air-Breathing Vehicle Using Potassium-Seeded Magnetohydrodynamic Propulsion and Atmospheric Ejector Augmentation

AbstractMurtazin Ilgiz FaritovichThispaperdevelopsaquantitativelyclosedreduced-ordermodelforapotassium-seeded,atmospheric-airversion oftheMHDDiscoid 2.0concept. Itisdeliberatelyretainedasaseparate companion architecture to the author’s cesium-seeded argon study. The objective isto determinewhetheranair-breathingprimaryMHDstreamcanremovethelargecarriedworking-fluid penalty of the Cs/Ar architecture while remaining consistent with momentum conservation, MHD electrodynamics, electron attachment in oxygen-containing gas,potassium vapor constraints, and pulse-power requirements.The baseline vehicle has diameter 22 m and mass 132 t. At a target initial thrust-toweight ratio of 1.10, total static thrust is 1.424 MN. Ideal actuator-disk theory gives a strictlower bound of 55.7 MW and an induced mass flow of 18.2 t/s. An experimental ejectorbenchmark of 1.8 thrust augmentation is retained only as a design reference, giving arequired primaryMHD force of791kN.Theoriginalannularchannelarea,82.944m2,andactive volume, 111.41 m3, are retained. A reduced-order optimization is then performedover primary-channel pressure at a conservative 700 K gas temperature and 0.1 mol%potassium seeding.Theresultingoptimisticminimumoccursnear3.02kPa. Theself-consistentprimaryairflow is0.703t/s,theexitspeedis1.13km/s,andtheprimarykineticpoweris446MW.Ageneralized crossed-field conductivity argument gives an optimum effective force-producingconductivity near 3.50 S/m. At the most favorable Hall/Pedersen mobility point, this requires at least 2.62e20 free electrons per cubic metre and approximately 84% ionizationof the available 0.1 mol% K seed. The corresponding Joule loss is 44.6 MW. Scaling themeasured atmospheric-air electron lifetime of roughly 20 ns by the three-body densitylaw gives an attachment time near 122 microseconds at the referencestate. Thequantumlimit power to recycle attached electrons by photodetachment at 1064 nm is then another44.6 MW, while the minimum 266 nm power required to ionize the charge populationconvected through the channel is approximately 9.1 MW. Heating the reference primaryair from 300 K to 700 K requires approximately 295 MW. The resulting lower-bound systempower is therefore approximately 839 MW,or8.39GJfora10spulse,beforereallaserefficiency, optical absorption, compressors, cryogenics, inverter losses, magnet mass, electrode losses, and ejector losses are included.Theconclusion isasymmetric. Potassium-seededaireliminatesthetens-of-tonnesstoredargon burden of the Cs/Ar architecture and requires only about 9.5 kg of potassium for a10 s reference pulse. However, oxygen electron attachment and the thermal/chemical requirements of sustaining atomic potassium in the gas create a severe additional powerburden. No conservation law forbids the concept, but the present model does not establish practical feasibility. Its principal value is that it identifies explicit experimental thresholds for conductivity, electron recycling, seed chemistry, ejector thrust augmentation, andmagnet/pulse-power technology.