So they started playing around with using electromagnetic containment fields to suspend exo-thermal chemical reactions (high temp combustion) some distance away from the walls of the engine body. Along the way, they determined manipulation of the containment field can control the direction of the exhaust…. ie., precision control of directional thrust with no mechanical/moving parts.
In parallel, experiments with “cold plasmas” (yup, think neon lights and plasma televisions) have proven the ability to absorb, deflect, or repel various forms of energy (such as radio waves, heat, lasers, sound, etc.,). At the risk of over simplifying it…. find the energy frequency of the thing you want to block… tune your plasma generator to that frequency… and power the plasma field with more energy than the thing your trying to block…. To really over simplify it…. wave cancellation (if you’ve a 220 volt stove, dryer, or water heater in your house… the ground circuit relies on wave cancellation).
By combining various version of these technologies… the entire exterior of a craft + the interior of the propulsion system could be coated in a skin capable of generating precisely measured plasmas tuned to various temperatures, frequencies, and densities. The result would be a craft which never makes direct contact with contaminates, corrosives, etc.,
The same principles which allow us to use a flat microwave antennae to emit precise narrow beam transmissions to any angle relative to the antennae surface (except negative angles, unless ya want to heat the transmitter) are used to control the plasma field.
other folks/applications working on plasma fields include:
the thermo nuclear power generators are looking for containment fields
the interplanetary and deep space life sciences folks are looking to shield humans from highly charged particles (radiation)
the military stealth and black ops folks want anti-radar, anti-sonar, anti-laser fields
the aviation industry wants:
noise mitigating “cushions” to make peace with the urban planning folks
friction reducing (or rather displacing) “cushions” to reduce friction and debris impact related maintenance
directional thrust with no moving parts to reduce the aircraft assembly and maintenance complexities and costs
the high energy shielding to reduce risks related to EMF, EMP, and Lightning
on orbit satellite operators would like to shield from solar flares (seems the public gets testy when HBO goes offline)
launch operators would like to use the plasma fields:
to reduce friction and provide directional control during launch and insertion (while under chemical thrust)
and then use the plasma fields for propulsion during on orbit operations
This stuff has evolved beyond the questions of “is it possible” and has moved on to the questions of:
what energy frequencies need to be manipulated ?
do you want to absorb, deflect, cancel, or repel the energy ?
what power output level is require to absorb, deflect, cancel, or repel ?
can you afford the onboard power generation for that output level ?
is the cost of onboard power generation and field emitters less than alternatives ?
alternatives would be things like: larger fuel tanks, exotic alloys, maintenance schedules, moving parts,
multi-stage rocket assemblies,
Variable Specific Impulse Magnetoplasma Rocket (VASIMR)
Mini-Magnetospheric Plasma Propulsion (M2P2)
High Power Helicon (HPH) Plasma Thruster