Power and Energy Budget for a Controlled Plasma Envelope

No, and assuming it does is the fastest way to make the power budget look impossible. Useful magnetohydrodynamic interaction depends on electrical conductivity, and conductivity rises steeply with only fractional ionization. An entry flow is already partially ionized at no cost to the vehicle; the research question is how much additional ionization must be purchased, and where, to move the interaction parameter into a useful range.

For an entry application, from stored energy — the envelope is required for minutes, not months, so batteries or a capacitor bank sized to the heating pulse are the honest baseline. For a sustained propulsive application, from a nuclear electric or high-power solar electric source. NASA's fission surface power and nuclear electric propulsion studies define the realistic near-term power classes, and any envelope concept requiring more than those deliver should be stated as out of reach rather than assumed away.

Flight-proven Hall and gridded ion systems operate in the single-kilowatt to tens-of-kilowatts class, with the 12.5 kW Advanced Electric Propulsion System representing a high-power flight article. Laboratory magnetoplasmadynamic thrusters run in the hundreds of kilowatts. An envelope concept that lands in that same band is engineerable; one that requires megawatts on a small vehicle is a power-source problem before it is a plasma problem, and we say so.

Partly, and this is the most interesting part of the budget. A fast entry deposits enormous power into the flow, and magnetohydrodynamic energy extraction from an entry plasma has a published literature. The optimistic case is a partly self-powered envelope that taxes the flow it is already fighting. The pessimistic case is that extraction efficiency, added conductivity requirements, and mass penalties consume the benefit. That balance is unresolved and we do not claim it either way.

Energy cost per sustained electron in a flowing, non-equilibrium, partially ionized gas at flight enthalpies. Laboratory values exist for static discharges and for specific tunnel conditions, but the extrapolation to a flight density and velocity profile is not well constrained. Every downstream number in this page inherits that uncertainty.

Because a page that only publishes the favorable case is not research. The purpose of the budget is to identify the regime boundary — the combination of vehicle scale, envelope density, and duration where the concept closes — so that effort is spent inside it. Finding a hard boundary is a result.