1. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page1 of 7
AIR-BREATHING MAGNETOHYDRODYNAMIC JET PROPULSION (MAGNETOJET)
Referenced Patent
4,852,529 Laser Energy Ignition System, Robert W. Vowles
Referenced Literature
Rosa, Richard J. Magnetohydrodynamic Energy Conversion (Washington: Hemisphere
Pub. Corp., 1987)
Cramer, Kenneth R. Magnetofluid Dynamics for Engineers and Applied Physicists
(Washington: Script Pub. Co. 1973)
Brogan, T.R., Electrical Properties of Seeded Combustion Gases, "Progress in
Astronautics and Aeronautics", vol. 12, pp. 319-345, (Academic Press Inc., New York,
1963)
FIELD OF THE INVENTION
The proposed Magnetojet is an airbreathing laser combustion-based engine which uses
a MHD device instead of a turbine to convert mechanical energy into electrical energy
without thermally-stressed rotating parts. This allows higher jet engine temperatures
and results in improved propulsive efficiency. Where propulsive efficiency(ηp) is defined
as the portion of available energy usefully applied in propelling the vehicle relative to
total energy of the local jet stream,
ηp = [ 2Vo / (Vj + Vo)]
where
Vj = exhaust velocity
Vo = local velocity).
Simplified Description of the Magnetohydrodynamic Conversion of Energy
Fig 1. MHD conduction generator—Diagram and direction of vectors of principal quantities
BACKGROUND OF THE INVENTION
Magnetohydrodynamics (also known as magneto-hydro-mechanics, magneto-gas-
dynamics, magneto-plasma-dynamics, or hydromagnetics) is the study of the interaction
of electrically conducting fluids (such as ionized gases) in the presence of electric and
magnetic fields. The mechanism of energy transfer from the flowing plasma into the
external load is the result of a complex interaction between charged particles and the

2. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page2 of 7
external electromagnetic field. Neutral particles transfer energy to charged gas particles
by collisions.
Electromotive force v x β, induced in a plasma that flows perpendicularly to the direction
of a magnetic field, E, causes an electric current, J, to flow through an external closed
circuit. Figure 1 reveals the elementary configuration of a conduction generator and the
direction vectors of the principal quantities. For the sake of simplicity, assume in this
study that the magnetic field strength β, the velocity v of the plasma and the electric field
strength E in the gap between the electrode array lie along the axes of an orthogonal
coordinate system.
Electrical energy in ordinary generators is obtained through the motion of metal
conductors in a magnetic field. Similarly, in a magnetogasdynamic generator, the
electrical power is generated as a result of the passing of a gaseous conductor--
plasma--through a magnetic field. The simplest linear generator consists of a channel
through which the plasma is flowing, of an electromagnet which creates a transverse
magnetic field, and of electrodes situated on the two opposite sides of the channel.
When plasma moves through the magnetic field, an electromotive force is produced.
This force generates current flow through the plasma, the electrodes, and the external
load. Magnetogasdynamic generators are divided into generators with open and closed
cycles. An open cycle uses products of combustion which are continuously supplied
directly to the generator. In closed cycle generators, the same working gas is
constantly recirculated.
The losses inherent in this scheme are the result of heat transferred from the plasma to
the walls of the generator channel; corrosion of the electrodes; and magnetic viscosity.
SUMMARY OF THE INVENTION
At supersonic mach numbers, thrust specific fuel consumption (TSFC) for turbojets and
ramjets are somewhat comparable. Moreover, the TSFC curve for turbojets is
terminated at mach number 3 because a turbojet or turbofan must increase its
combustion temperature to a level where materials limitations restrict sustained
operation. Although ramjets produce high thrust, their subsonic efficiency is very low--
typically, TSFC of approximately 3 to 4lb of fuel/(lb of thrust) (hr) for ramjets at subsonic
speeds; decreasing to 2 or less at supersonic speeds.
0 1 2 3 4

3. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page3 of 7
By replacing the turbine stage with a MHD duct to power a electrically-controlled
compressor, the material limitations of turbo engines can be avoided. More importantly,
as turbine blades must typically withstand temperatures over 2000°R, these blades
often consist of exotic metal or crystal substances, often fabricated using sophisticated
manufacturing processes. As a result, the turbine stage is by far, the most expensive
component of a conventional jet engine.
In addition, since compressor rotation in the proposed magnetojet is electrically
controlled, engine stall is not possible with a magnetojet (as long as electrical power is
available). Finally, a magnetojet consisting of a compressor driven by an electric motor,
laser combustor, and a MHD duct would require a of minimum lubricants—increasing
reliability while greatly reducing operating costs and maintenance.
DESCRIPTION OF AN “IDEAL” MAGNETOJET CYCLE
The thermodynamic cycle for an "ideal" magnetojet is similar to that of an ideal turbojet
engine. The ideal magnetojet engine cycle ignores the effects of friction and heat
losses. Here, the airflow pressure is isentropically compressed from Pi to Po in the inlet,
and the pressure is then isentropically increased to P1 by the electric compressor. The
process follows the isentrope pvs
=c1, where s is the ratio of specific heats, and c1 is a
constant. In the laser-initiated combustor (as in US Patent 5, 404,712), fuel is injected
into the airstream and ignited to a plasma at essentially constant pressure. Since the
temperature is increased by combustion and the pressure is constant, the equation of
state, pv=RT, dictates that v must increased from v1 to v2 in the laser combustor.
Energy conversion throughout the MHD generator duct isentropically drops the pressure
to P3, and further isentropic expansion through the nozzle decreases the pressure to P4.
The MHD generator and nozzle expansions follows through the isentrope pvs=c2, where
c2 is a constant different from c1. The ideal engine process further assumes that the
nozzle expands the gas to ambient pressure, so that Pe=P4=Pi=Po.
In a real magnetojet process, there would obviously be frictional, conductivity and heat
losses; the diffuser, electric compressor, MHD generator, and nozzle processes will not
be exactly isentropic, the laser combustion process is not precisely at constant
pressure, and the nozzle exit pressure pe will be slightly different from po. However, the
ideal magnetojet cycle is a reasonable preliminary estimation of a real system. The
accounting of nonisentropic processes in the magnetojet is left for a working prototype.
The fundamental equations that describe a magnetojet propulsion system are the
following:
(1) Equation of conservation of mass, which is analogous to ordinary fluid
mechanics.
Mair = doVoAi

4. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page4 of 7
The thrust of a magnetojet is calculated as in a turbojet. Here the jet engine takes in a
mass flow of cool air, Mair at velocity essentially equal to Vo and exhausts a mass flow of
hot air and combustion products, (Mair + Mfuel), at velocity Ve.
Thrust = (Mair + Mfuel)Ve - MairVo+peAe-poAi+[po(Ai-Ae)]
As in turbojet, the mass of fuel added is usually small in relation to the mass of air;
Mfuel/Mair (approx 0.05). Thus, the thrust equation can be simplified by neglecting Mfuel.
Thrust =Mair (Ve-Vo)+(pe-po)Ae
(2) Equation of conservation of momentum, which is altered by the forces of
fluid mechanics. The ponderomotive force (Lorentz Force) per unit
volume is given by J x β where J is the vector current density and β the
magnetic induction.
(3) Equation of energy conservation; identical to ordinary fluid mechanics with
the addition of Joulean dissipation.
(4) Equations describing the thermodynamic state.
Physically, in the magneto-fluid-mechanic system, a velocity field, q perpendicular to the
magnetic lines of flux β gives rise to an induced current whose magnitude is given by
J=c(qxβ).
Simplified Description of MHD Energy Conversion Duct
Electromotive force v x β, induced in a plasma that flows perpendicularly to the direction
of a magnetic field, causes an electric current to flow through an external closed circuit.
For simplicity, this proposal assumes that the electric field strength β, the velocity is v of
the plasma, and the electric field is E. The electrical conductivity, c, of the plasma, is
considered a scalar quantity. Magnetic permittivity µ is equal to unity and magnetic
induction β and magnetic field strength H are indistinguishable. It is also assumed that
the permittivity and permeability of the plasma to be constant and their numerical values
to agree with those of a vacuum. The plasma consists of electrons and singly charged
ions (simple plasma) and that electron and ion temperatures are the same (isothermal
plasma).
Neglect all dissipative effects, such as viscosity, thermal conductivity, or electrical
resistivity.
The electric power supplied by the generator is drawn from the energy of the plasma,
either its kinetic energy or potential energy. In the first alternative, the gas is
decelerated as in an impulse turbine, while in the second case the gas temperature is
reduced as in a reaction turbine. This deceleration force in the unit volume of plasma is
known as the Lorentz force, and is converted to power v x (P2-P1)=v x (Jxβ)= j(vxβ).
The resulting pressure gradient is converted to a current density, J, in the plasma
flowing pass the electrodes; where P1 and P2 represent the pressure in the inlet and
outlet sections of the MHD generator. (P2-P1)=Jxβ

5. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page5 of 7
Electric Axial-Flow Compressor Stage
Ambient air with a velocity Vo, enters from the engine inlet at atmospheric pressure (Po),
density (do), and temperature (To) is compressed isentropically to a selected
compression point (P1).
Where the ratio of specific heats, s, equals 1.4 for air, the compressor exit temperature
(T1), and density d1 can be calculated from
P1 T1
s/(s-1)
Po To
and
P1 d1
Po do
The power input required (W) to compress a mass flow (M) with a electric compressor
drive motor equals the following (this ignores the negligible work required to power the
laser combustor, electromagnets, and engine accessories);
P1 - Po
W M
do
Laser Initiated Combustor
At constant pressure (P2=P1), a laser combustor raises the mass flow temperature
exiting the combustor (T2) to a minimum of 3000°K( for plasma creation). With specific
heat at constant pressure (Cp) for air equal to 1008 J/(kg)(k), the energy equation for
frictionless, adiabatic flow can be used to calculate the mass flow velocity (V2) exiting
the combustion stage;
V2 = 2Cp(T2-T1)
From the equation of state, mass flow post-combustion density d2 can be calculated;
P2
d2
RT2

6. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page6 of 7
MHD Generator Duct
Where T2 and T3 are the entrance and exit static temperatures, the static temperature
change is calculated from the work output required for the compression stage (Wg) per
mole of working plasma
Wg = Cp (T2-T3)
The power generated by the entire channel is simply the mass flow rate multiplied by
the static enthalpy change through the MHD duct
Pg = M Cp (T2-T3)
At a temperature of 3000°K, conductivity (c) of JP-4 and O2 combustion products
entering the MHD duct approaches 80 mhos/m.
The current per unit area induced by the plasma mass flow through a magnetic field of
strength β is J= c (V2 β - E); where V2 is velocity, and E is the internal electric field due
to the load.
KMHD is the ratio of the external load resistance to the total resistance of the MHD
generator
Rext
KMH
D
Rext+Rint
The pressure drop occurring through the MHD channel is
P3 T3
S/ [K(S-1)]
P2 T2
The area increase through the MHD duct is
P3 A3
1-S/ [K(S-1)]
P2 A2
Since the expression (1-KMHD)KMHD attains its maximum value at KMHD=0.5, the highest
specific output power obtainable from the generator is
Pmax =1/4 [cV2
β A L] ; where A is the cross-sectional area of the generator chamber in a
plane which is perpendicular to the gas velocity, and L is the length of the chamber.

7. Proposal
J. Rollan, Radical Tek; Las Vegas, NV, USA
Magnetohydrodynamic Jet Engine (Magnetojet) Page7 of 7
Therefore, the length and output of the entire MHD generator depends on the pressure
gradient
(P3-P2)
L
c V β2
(1-KMHD)
Nozzle
As the nozzle isentropically expands flow to atmospheric pressure (P4=Po), exit
temperature (T4) is calculated from
T4 P4
(s-1)/s
T3 P3
Assuming air to be an ideal gas, exit velocity (V4) can be calculated from
V4 - V3
Cp (T3-T4)
2
Finally, with an exit area Ae, thrust can be calculated from
Thrust = M (V4 - Vo) + (P4 - Po) Ae