AAWSAP DIRD, MHD Air Breathing Propulsion and Power for Aerospace Applications, November 2010

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MHD Air-Breathing Propulsion and Power for
Aerospace Applications
Summary
The paper reviews novel propulsion concepts utilizing plasmas (ionized
gases) and magnetohydrodynamics (MHD). These concepts are shown to
be attractive due to their potential to achieve propulsion and
aerodynamic performance far beyond current conventional technologies.
However, significant difficulties impede the development and application
of these technologies; these include weight, complexity, higher power,
and the need for complex and energy-consuming artificial ionization in
"cold" air (at Mach <12).
A well-publicized Ajax concept of MHD energy bypass has been shown to
be meaningless below at least Mach 12. In contrast, a new "reverse
energy bypass" with Virtual Cowl is potentially practical for air­
breathing hypersonic vehicles.
Applications of the Virtual Cowl and other plasma/MHD devices to
reentry, global-strike hypersonic gliders, and aeroassisted orbital
maneuvering are identified as promising in the near future. The ability of
a plasma/MHD system to generate high power onboard and to provide
L/D (lift-to-drag ratio) far beyond that possible conventionally makes
these applications both feasible and desirable for national defense.
However, these applications are also likely to be implemented by
nations such as China, Japan, and Russia.
The outlook for uses and applications of MHD propulsion could increase
dramatically if high-speed (hypersonic) vehicles begin to carry powerful
onboard electricity sources, such as nuclear (fission or fusion) reactors.
For spacecraft, the current trend of replacing chemical rockets with
electric propulsion systems will continue and is likely to become the
standard. Electric systems can provide a much wider range of operation
(e.g., low-thrust fine positioning/pointing, more frequent or
nontraditional maneuvers, and longer times on station) than chemical
systems can.
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