EP3275291B1

EP3275291B1 - Plasma propulsion system and method

Info

Publication number: EP3275291B1
Application number: EP16726438.1A
Authority: EP
Inventors: Gennaro DI CANTO
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-03-24
Filing date: 2016-03-21
Publication date: 2019-08-21
Anticipated expiration: 2036-03-21
Also published as: EP3275291A1; WO2016151609A1

Description

This invention relates to a plasma propulsion method and system.
Still more specifically, this invention relates to an air plasma propulsion method and system comprising an air turbine plant and a plasma propulsion unit, and the following description relates to this specific field.
Operational embodiments are known as the high-tech VASIMR Rocket Engine and the Helicon Double Layer technology which will be described below. VASIMR = Variable Specific Impulse Rocket Magnetoplasma.
The experimental work on the engine has been in progress for more than 25 years and it is performed by NASA and by the United States department for energy research and development in plasma physics and space propulsion technology. The VASIMR uses an inert gas such as Argon, Xenon Krypton. It does not use electrodes and does not have accessory moving parts. As it enters, the gas is bombarded, that is heated, with microwaves and immediately afterwards with high voltage and radio frequency to pull the electrons away from the atoms thus determining an ionisation of the gas. This determines a passage to the plasma state where ions and electrons, both speeded up, seek an original stability.
In a second step, the magnetic and electrical energy is increased, with radio frequency heating, and a strong outflow speed (thrust) is thus imposed, for example, not less than 10-30 km/seconds before a dangerous thermal diffusion takes place.

Helicon Double Layer

This is a method for circumscribing the flow of gas with helical envelopment which discharges inside it a suitable radiofrequency. The outside is surrounded by crowns of super magnets which energise in combination with the radiofrequency of the helicon, generating the plasma. This all occurs in the VASIMR propulsion system without electrodes and without moving accessories. It does not require cathode-anode grilles since the positive ions and the negative electrons merge together in equilibrium at the outfeed.
F.R. Chang-Diaz "Plasma propulsion for interplanetary flight", Thin Solid Films 506-507 (2006), 449-453, relates to the VASIMIR propulsion system.
Another example of propulsion system is disclosed in WO 2010/096087 A1 , which discloses a Supersonic Magnetic Advanced Generation Jet Electric Turbine (A- MAGJET) together with a subsonic derivative (MAGJET).
US 2014/0305096 A1 discloses a propulsion system for spacecraft wherein plasma particles are selectively accelerated via a pulsed laser that accelerates dominantly the electrons in the plasma.
The propulsion system according to the invention comprises an ionic plasma propulsion unit and it consists of two parts: the fluid dynamic part relative to the turbine and the successive electromagnetic plasma part.
The invention aimed at the improvement of the plasma propulsion technology has different purposes:

Simplicity, compared with the complexity of the prior art solutions.
No fuel, compared with the propensity to pollution of the environment of the prior art solutions.
a high degree of autonomy and, therefore, freedom of movement and consequent safety in its movements.

Advantageously, according to the invention, the thermo-fluid-electrodynamic and ionic-plasma cycle uses a single gas: air.
The plasma of the air is a mass in which in the neutral atoms or molecules (diatomic) are separated into electrons and electrically charged ions.
The aims of this invention are to:

make a plasma propulsion system/method which is easy to make/operate.
make a plasma propulsion system/method as eco-compatible as possible.
make a plasma propulsion system which is as independent and autonomous as possible.

These and other aims are achieved by a propulsion method/system as described in the appended claims.
In a first aspect, the invention defines a plasma propulsion system comprising:

a plant 100 with an air turbine A designed to receive a supply of air from an outside environment, and a plasma propulsion unit 200 designed to increase a speed of the air after a corresponding ionisation and passage of the air into plasma phase,
wherein the plant 100 for the air turbine comprises:
- first compressing means 3 designed for a first compression of the air;
- second compressing means 5 designed for a second compression of the air pre-compressed by the first compressing means 3;
- first heating means 9 designed to heat the air previously compressed by the first 3 and second 5 compressing means;
- a starter electricity generator designed to produce electricity;
- a counter-rotating power turbine 10 which can be operated by the air heated for producing expanded air, wherein the turbine is designed to:
  - perform compression using the first compressing means 3 and the second compressing means 5;
  - produce electricity E;
  - discharge residual expanded air Ar as a function of the air compressed and already heated with part of the electricity E produced.

The plasma propulsion unit 200, associated with the air turbine plant 100, comprises:

a duct 201 for plasma flow designed to receive the residual expanded air Ar discharged by the power turbine 10;
a connecting portion 202 located between the power turbine and the duct 201 for plasma flow, wherein the connecting portion has a decreasing cross-section in the direction of the duct 201 plasma flow and comprises an anode 12 and a cathode 11 configured to generate a thermal arc X by means of an RF oscillator so that the residual air in the connecting portion subjected to the thermal arc becomes an ionised and heated air Ai;
magnetic means (13,14,16) fixed in such a way as to surround the duct for plasma flow in a ring and designed to generate a corresponding magnetic field, wherein said anode, said cathode and said thermal arc are located in said magnetic field, wherein said magnetic means are configured to generate a plasma from said ionised and heated air;
a source of radio frequency or microwaves applied with helical antennas adjacent to and encircling the duct 201 for plasma flow in the magnetic field B generated by the magnetic means 13, 14, 16;
a laser source configured to emit a laser wave which passes linearly along the centre of the duct 201 of plasma flow so as to accelerate said plasma just generated in the magnetic field B generated by the magnetic means 13,14,16;
discharging means 17 for discharging the plasma PL generated in the duct 201 for plasma flow and comprising a divergent supersonic nozzle 17 with an antenna 15 and shaped in the form of a bell where the discharging means 17 in the outlet of the plasma PL create a thrust power PW produced by the propulsion system.

Preferably, the first compressing means 3 comprise a stator 3b and a rotor 3a associated with a fixed shaft 6 of the turbine plant 100.
Preferably, the second compressing means 5 comprise a counter-rotating axial compressor comprising a first plurality of blades pi which rotate inversely relative to a second plurality of blades p2.
Preferably, the starter-electricity generator is designed to produce a three-phase alternating current and is characterised by stator fixed to the axis and an outer magnetic rotor of the Halbach array type fixed to an inner counter-rotating duct 103.
Preferably, the first heating means 9 comprise several series of micro blades counter-rotating relative to each other made of metal alloys which are hard and resistant to heat situated in a circular gap 104 defined by two cylindrical ducts 102 and 103 designed to rotate in a counter-rotation fashion relative to each other with respect to a fixed shaft 6 thus forming, with continuous rotations, a plurality of mini thermal arcs designed to immediately raise the temperature of the compressed air in transit.
Preferably, the annular magnetic means 13, 14, 16 comprise one or more between: magnetic and electromagnetic rings;
two solenoids with central choking of the axial flow of the plasma controlled by a magnetic ring with ortho-radial flow;
accelerator with multi-phase solenoid 16 equipped with further circular magnetic rings of the Halbach array type inside 14.
In a further example, the system comprises a processing unit configured for correlating the radio frequencies by ionisation, by helicon, by discharging nozzle and by magnetic density produced by the magnetic means and by the solenoid.
In a second aspect, the invention defines a plasma propulsion method comprising the steps of:

preparing an air turbine plant (100) designed to receive a supply of air from an outside environment and a plasma propulsion unit 200 equipped with a duct 201 for the plasma flow, associated with the air turbine plant 100 and designed to increase the speed of the air after a corresponding ionisation and passage of the air into plasma phase;
in the air turbine plant (100), performing a first compression of the air A and a second compression of the air previously compressed;
heating by thermal arc the air previously compressed by means of the first and second compression;
expanding the heated air in a power turbine 10 to:
- perform compression using the first compressing means 3 and the second compressing means 5;
- produce electricity E;
- discharging residual expanded air Ar as a function of the air compressed and already heated with part of the electricity (E) produced;
- simultaneously carrying out the steps of:
  - increasing the speed of the residual air Ar in such a way as to reduce the pressure by reducing the transit cross section 202 of the residual air Ar at the outlet from the power turbine 10;
  - applying to the residual air Ar a thermal arc X by a pulsed radio frequency in a magnetic field B wherein the magnetic field B is generated by annular magnetic means 13, or multiphase solenoids 16 fixed in such a way as to surround in a ring the duct for plasma flow (201);
  - where the two steps of increasing the residual air speed Ar and applying to the residual air Ar a thermal arc X, performed simultaneously, determine, starting from the residual air Ar that dropped in temperature at the end of the previous passage in the power turbine 10, a ionised, heated and speeded up air Ai suitable for a passage to the plasma state;
  - receiving the ionised, heated and speeded up air Ai in the duct 201 for the plasma propulsion unit 200;
  - determining a passage to the plasma state and subsequent step of energising and accelerating the plasma, using energising means comprising:
    - a hybrid radio frequency or microwave with one or more helical antennas encircling the duct 201;
    - a laser source which emits a laser wave which passes linearly along the centre of the duct 201 for plasma flow,
  - discharging the plasma PL generated in the duct 201, comprising a divergent supersonic nozzle 17 with radio frequency antenna 15, resulting in an outflow of the plasma PL from the propulsion unit 200 representing a thrust power PW produced by the propulsion method.

In a further example, the pulsed thermal arc X is at the inlet of the duct 201 and at the power turbine 10, and is configured to operate at radio frequency with oscillator in the magnetic field B and is combined with a second radio frequency reflected and distant from the first by 90°- 180°, wherein the pulsed thermal arc X is in association with triggering means 11 and 12 identified as a cathode 11 and an anode 12 positioned in circular order, in ordered coaxial position and immersed in the magnetic field B generated by the magnetic means 14, 16.
Preferably, the magnetic means 14, 16 comprise an accelerator with multiphase solenoid 16 equipped inside with further circular magnetic rings of the Halbach array type wherein the direction of the magnetic field generated by the multiphase solenoid 16 in position parallel to the axis of the propulsion duct substantially determines the longitudinal thrust direction of the plasma PL with a helical movement towards the discharge nozzle 17.
Preferably, the step of energising and accelerating the plasma PL using the excitation means comprises one or more quadruple helical antennas 15 with rectangular cross section to energise and accelerate with radio frequency or microwave the plasma PL wherein the radio frequency applied is 2.45 GHz.
In a further example, the laser source which emits a laser wave which passes linearly along the centre of the duct 201 of plasma flow is characterised by an ultra-short and ultra-dense laser wave with double frequency which is greater than the frequency of the plasma.
Preferably, the method comprises a step carried out using a computer configured for synchronising or correlating the cyclotronic frequencies of resonance and of repetition in the process for generating plasma with magnetic density produced by the solenoid and to facilitate a process of ionisation and acceleration of the plasma at the same radio frequency.
The technical advantages of the invention are described in more detail below in the description of an embodiment illustrated by way of general example in the accompanying drawings.
The description is provided below with reference to the accompanying drawings, which are also non-limiting and provided by way of example only, in which:

Figure 1 is a diagram of a first embodiment of the propulsion system according to the invention.
Figure 1A is a cross-section of Figure 1 along line A-A of Figure 1.
Figure 2 shows a diagram of the propulsion system according to a second embodiment of the invention wherein the parts coinciding with the embodiment in Figure 1 are not numbered to make the specific details of this embodiment in the drawing more easily understood.
Figure 3 shows a diagram of the propulsion system according to a third embodiment of the invention wherein the parts coinciding with the embodiment in Figures 1 and 2 are not numbered to make the specific details of this embodiment in the drawing more easily understood.
Figure 4 to 6 show details of the embodiments shown in Figures 1 to 3. The invention describes a propulsion system comprising an air turbine plant designed to receive infeed air from an outside environment, and a plasma propulsion unit designed to generate a thrust power, and associated to the air turbine plant in such a way as to receive the air discharged from the air turbine plant.

In other words, the propulsion system according to the invention comprises a fluid dynamic stage relative to the turbine and a stage for generating electromagnetic plasma.
According to the invention, in the fluid dynamic stage relative to the turbine, the propulsion gas is air; the following description will always consider air as the gas, in particular a mainly diatomic and neutral gas.
It is well known, in effect, that the air which surrounds us not only helps us to live but is also very useful for a plasma-ion propulsion system in the terrestrial atmosphere. Air mainly consists of two important gases: nitrogen 78.08% and oxygen 20.95%.
Nitrogen is the most abundant gas in our atmosphere; it is diatomic like oxygen, neutral, colourless, odourless, tasteless and plasminogen, and also absorbs heat very quickly.
The excited and de-energised nitrogen, that is, when the electron returns in a position in the atom in a femtosecond, emits a photon with rows of U.V. ray emissions, visible as blue light.
According to a reduction of the pollution of the environment, the nitrogen reacts only with the oxygen of the air in the presence of high temperatures and pressure determining the nitric oxide (NO) and the nitrogen dioxide (N0₂). Nitrogen dioxide can react with water and form nitric acid HN0₃ which soon becomes nitrate. Nitrates are extremely useful for plants as nutrients and fertilisers to promote growth. Every other type of compound which derives from it is always useful to man and the heating of the Earth.
Some components used in the invention and physical phenomena related to them are described in detail below.
According to the invention, the magnets contribute to producing the plasma, limiting and guiding (confining) and accelerating the beam of plasma which gives the thrust. The research is proposing increasingly more powerful permanent magnets without renouncing the advantageous Halbach array system.
The energy saving also prevents possible secondary electrostatic instability effects. After the pre-ionising in order to avoid heat exchanges, which as well as reducing the temperature of the plasma would destroy the duct, it is necessary to thermally insulating the plasma.
A radial or ortho-radial magnetic structure is created, that is, perpendicular to the flow of the plasma which borders the particles of plasma in a reduced space inside the tubular duct 201. The property of charged particles to follow helical paths around the force lines of a magnetic field is the basis of the methods of magnetic confining/insulation of the plasma. The density of the magnetic field ortho-radial to the horizontal flow lines must be less than the same horizontal lines of the magnetic flow applied. The confinement thus created by the magnetic field limits the number of degrees of freedom of the motion to only one in the direction of the force lines towards the outlet.
The electromagnetic accelerators have various embodiments.
For example, according to this invention they are made as multiphase solenoids and as helical antennas as shown in Figures 5 and 6.
The fields applied and the internal currents may be stationary, pulsed, or alternated on a frequency range and various ionisation systems and methods for releasing the electrical power may be used. In reality, there are many effects which alter the situation and play a crucial role in determining the effectiveness of the accelerating process. The alignment of the magnetic field is tangential to the components of the system; for example, according to this invention, these components are the cylindrical ceramic duct 201 and the helical antennas (Figure 6).
Regulating a variety of conditions and approximations of the overall geometries of the magnetic fields and the magnets requires a careful assessment of the thermal and structural problems inside the cylindrical duct.
The magnets must have the density suitable for sufficiently absorbing the R.F. waves of the plasma. The intensity of the magnetic field corresponds to the dimensions of the ionisation chamber. The details on the type of magnetic field have very complex effects on the process. A true neurological network of the electronics.

Ponderomotive force.

This is the force applied on the plasma by the density of the high-frequency electro-magnetic field. It also depends on the quantity of gas ionised and loaded. The duct may be made of material lined internally with radioactive isotopic with rate of emission of secondary electrons: this increases the electronic density and increases the ionisation. In general, the value of the frequency of the electromagnetic field is equal to or just less than 10 - 30% of the frequency where the electromagnetic field, at the start of the ceramic duct 201 is maximum.
The last circular magnet is provided with a radial magnetic density lower than the other previous magnets so as to favour the easy outfeed of the plasma. A radio frequency which strikes the molecules, the atoms, the electrons in the magnetic field creates inelastic impacts (collisions) of the electrons which significantly increase the temperature. The collisions (inelastic impacts) create mini swirling and energetic flows which unbalance any direction of motion. In the presence of magnets with inclination on the axial lines of the flow of plasma and of other successive magnets with a lower ortho-radial magnetic charge, the electrons with gyrokinetic energy are translated into longitudinal kinetic energy favoured and confined by the divergent magnetic fields.
When the waist of the laser beam, for example laser 2 in the drawings, is greater than the plasma wavelength the longitudinal component of the ponderomotive force is the dominant one and determines the formation of positive and negative charge areas, that is, a wakefield electrostatic field.
It should be should be specified that in general the electron beam being more lightweight of the ions (thousand times) are most subject to the effect of a R.F. This greater heating of the electrons activates a phenomenon of collisions with the ions, thereby heating them. Since the electrons are at a much high temperature and since they are lighter than the ions the thermal electron speed is much higher than the thermal ion speed. Since the electrons are originally entrapped by electrostatic charges the ions are able to gain acceleration as they have a positive potential and this phenomenon is optimised until the flows of electrons and ions become equal, reaching an equilibrium.

Supersonic propulsive plasma discharge nozzle 17.

As already mentioned, the system according to the invention comprises a supersonic propulsive plasma discharge nozzle 17 shown in Figures 1, 2 and 3. The discharge of the plasma is almost neutral, meaning that there are an equal number of ions and electrons and more simply that ions-electrons recombine to neutralise the outfeed plume. In this way, there is no longer the need for a hollow cathode/electronic cannon.
Also, the particles passing in a magnetic field which expands decreasing its density accelerate axially to the expense of their rotational movement. During the expansion upon discharge the plasma cools down generating a thrust and it therefore accelerates axially.
Any additional acceleration may be applied to the discharge cone with a radio frequency antenna, for example labelled 15 in Figures 1, 2 and 3.
The detachment from the divergent discharging nozzle is obtained when the density of the kinetic energy, parallel to the magnetic flow, becomes larger the density of the magnetic energy. It is therefore necessary that the gas (plasma) is at the outlet of the duct (necessarily converging) under saturation conditions, that is critical conditions, i.e. at sonic speed (M1). Only afterwards can the gas flow in the channel divergent where the waves of expansion, which generate due to the negative pressure existing in the outlet section of the nozzle and which travel at the speed of sound, spread with small oblique shock waves inside the nozzle and, taking into account the limit layers, are able to rise up the subsonic current present in the divergent nozzle by accelerating the fluid towards the outlet transforming it into a uniform current (axial speed).
There is thus a considerable increase in the supersonic speed since the increase in cross section favours the expansion with reduction of the density and pressure in compliance with the flow rate and the quantities of motion which are constant; this only occurs at supersonic speed in a divergent nozzle or rather, in the form of a duly proportioned bell.
A significant effect is provided by a small laser already mentioned, labelled 2 in Figures 1, 2, and 3, which passes linearly along the entire centre of the duct with a strong plasma-dynamic effect.
The laser is located in the end part of the turbine axis where the ionisation process starts.
The introduction of the laser produces a localised disturbance which causes the moving away of the electrons, which are lighter than the ions, forming electrical fields returning to the starting position, that is, of equilibrium. Due to a strong inertia, oscillations are created at a frequency specifically defined as the plasma frequency; this makes it possible to accelerate at extremely high speeds. To obtain an excitation resonance it is necessary for the laser pulse to be ultra-short and ultra-dense and its wavelength must be commensurate with the wavelength of the "plasma frequency".
The average force of the laser pulse acts on the electrons, separating them spatially from the ions and generating intense electrostatic fields.
As the femtosecond laser (the unit for measuring the duration of the pulse) is characterised by the shortness of the pulse in the transit zone it adopts a very high electromagnetic energy density. Precisely because of this ultra-short and dense pulse, interaction regimes are created which are greatly non-adiabatic, efficiently transferring the energy of the pulse to the plasma. An ultra-short laser pulse creates a plasma wave in the longitudinal electric field of which the electrons can be entrapped and accelerated. If the spatial extension of the pulse is of the same order as the wavelength of the plasma an electronic wave (excitation) is generated behind it with a large amplitude with an oscillation of the electrons of the plasma wave around their position of equilibrium in a time which is precisely the period of oscillation of the plasma wave. Where the electric field is higher, the ponderomotive force expels the electrons creating a density modulation with consequent production of an electronic wave of the plasma and this bond with the intensity of the laser pulse gives it a phase speed step equal to that of the laser pulse.
The characteristic frequencies of the laser pulses are much larger than the plasma frequencies. The actual and ideal regime of the duration of the laser pulse is around a few tens of femtoseconds which corresponds to a plasma density of approximately 10¹⁸ el/cm³ (I = 10¹⁸ W/cm²).
For an optimum embodiment, the intensity of the laser pulse must be greater than the electromagnetic field which links the electron in the atom of the nitrogen. Only in this way is it possible to obtain an instantaneous ionisation of the nitrogen transforming it into plasma which with the ultra-short laser pulse receives an immediate transfer of energy.
The double pulse lasers have a greater potential as they can be collimated in various ways with an optical-acoustic modulator.
In a preferred embodiment of the present invention, the first pulse has an energy equal to 10% of that available to the laser; the second pulse, which is the main and the most powerful pulse, starts from a distance of a period from the first and has an energy of 90%; it also has twice the frequency of the first pulse.
In general, the double pulse laser does not exceed 200 fs. The pulses must be similar as must the relative frequencies in such a way that their sum constitutes the energising frequency of the laser.
The synchronisation of the pulses with the resonant absorption of the plasma must coincide perfectly (auto-correlation).

The air plasma.

It has already been mentioned that air has a dielectric resistivity higher than the other gases, diatomic molecule, medium-high atomic weight, and nitrogen is a neutral gas.
The is composed of nitrogen + oxygen and it is precisely the oxygen which is not neutral and, therefore, having a dielectric resistance and enthalpy lower than the nitrogen, may release free electrons which allow the ionisation to start and therefore drive the start of the plasma in the cycloidal gyrokinetic carousel.
The easier ionisation is obtained by raising the air temperature (standard pressure and temperature) since composites and combinations are created with smaller dielectric resistance and lower effect of emission by recombination. The air is heated using a thermal arc as an ionising source which moves electrons in the air and produces a flow.
According to the invention, the pulsed thermal arc X is located at the infeed of the plasma duct 201 and cathode 11 and anode 12 are located in the magnetic field (see Figures 1, 2 and 3).
The alternating of this electric charge (thermal arc) creates a flow variation favouring an electromotive force due to the few electrons produced previously and there is then a discharge of an increasingly large number of electrons due to the impact between the electrons and the neutral atoms (nitrogen) and the current, determining a significant increase in temperature with consequent passage to the plasma state. This current heats the plasma by the Joule effect.
When a neutral atom (nitrogen) loses an electron, the atom become an ion, transferring high energy to the plasma and will therefore remain almost always positive. Electrons and ions in movement create electric currents and create around them oscillating magnetic fields, that is to say, electromagnetic waves. These electromagnetic waves in combination with microwaves or radio frequencies are absorbed by the plasma and cause new oscillatory phenomena until reaching the magnitude of the frequency applied, becoming a relative resonance energy which transforms into kinetic energy of the particles involved. There are three methods of heating and acceleration in the plasma:

Ion Cyclotron Resonance Heating ICRH.
Electron Cyclotron Resonance Heating ECRH (its frequency comes into resonance if it equal to the electronic one).
Lower hybrid resonance L H R H (1 - 4 GHz).

The frequency of the plasma depends on the square root of its density.
The density also depends on homogeneity requested from the plasma. The critical density forms when the radio frequency applied corresponds to the frequency of the plasma. In the case of the nitrogen, in which binary collisions are obtained, which are therefore not oblique and not homogeneous, the problem remains. This spatial non-uniformity connected to the partial ionisation causes defocussing and the laser pulse focusses until the electronic density is satisfactory.
This problem is resolved by applying characteristic frequencies of the laser pulses which are much greater than the plasma frequency. The quantity of laser energy not only feeds the ponderomotive force but may be varied to alter the force of the magnetic fields. By modifying the wavelength and/or laser energy and the frequency of the pulses, the resulting magnetic wave form may be synchronised on the required harmonics. A double radio frequency (or radio wave) or powerful pulsation and a weaker one applied to an antenna in a magnetic field not only causes cross and self modulating phenomena but also a considerable increase in the intensity of the lateral bands associated with those interacting and the pulsation harmonics of the powerful wave. The greater density of the laser (which is very useful) reduces its power. The electron cyclotron resonance arises from the effect of the Lorenz force which opposes the magnetic field by activating a cycloidal flow movement with an angular frequency.
When an alternating and pulsed electric field is applied, by a RF or microwaves, which is synchronous with the gyrokinetic period of the free electrons, their gyrokinetic energy is increased in such a way as to become greater than the ionisation energy of the diatomic molecule of the air (oxygen + nitrogen).
The collisions which the kinetic energy produces are only binary and there also exists, in our case, a residual pressure (from the expansion turbine, labelled 10 in Figures 1, 2 e 3) which favours and easy recombination. The optimum solution is to create precise conditions of a resonance between the R.F. frequencies, laser frequencies and repetition frequencies, which work in multiphase and pulsed systems.
The solution makes an increase of the magnetic field and the electric field unnecessary.
The problem is not resolved with the increase in the energy costs.
The turbine 10 consists of a fixed shaft 6. It is formed by an outer cylindrical duct which houses two other cylindrical ducts which rotate in counter-rotation. These allow the housing of two rotors which work with the stators fixed inside the outer fixed duct.
The initial compression prepares the air for cooling and for the subsequent entry into the counter-rotating compressor.
The counter-rotating axial compressor consists of six blade rotors which rotate inversely to six other blade rotors. The outermost rotors have the base distributed horizontally (cylindrical surface) and this is ideal for a better fluid dynamic effect. The technical effect achieved is an excellent compression and a better stability and symmetry between the speed triangles: six + six rotors.
The air thus compressed to 10 - 14 etc. Atm (kg/cm²) reaches a temperature of above 400°C and then passes in a gap (circular crown) constituted by the two cylindrical ducts which rotate in counter-rotation.
The two ducts have, in their gap 104, other rotors (Figure 4) with small blades made of metal alloys which are hard and resistant to heat, for example made of HSS3, a very hard special steel resistant to high temperatures.
The pressure conditions, the form of the electrodes, the surfaces in contact with the air, the distance of the electrodes, are all variables which condition the final choice of the type of electric discharge applied. The blades are used mainly for increasing the heating of the air up to 1,000°C. In effect, the continuous counter-rotation cyclically moves one towards the another thereby creating the minimum and useful distances for thermal arc triggering.
In this case, if the counter rotation is referred to 30,000 rpm the respective cylinders (ducts) rotate at a total of 30,000 + 30,000 rpm, that is, 60,000 rpm. There is therefore a continuous series of thermal shocks due to the numerous mini thermal disturbances (30 kV only initially) which occur each time a blade of a duct encounters the other one of the opposite duct in rotation. Also, the arrays of blades-rotors have a further purpose: coordinating the transit of the compressed air which may be defined as a circulation fan or blowing device. The compressed air already partly heated thus reaches the temperature of 1,000°C and is pushed to the discharge turbine where during expansion it produces the power to operate the compressor and the electricity starter.
The speed of transit of the air in the compressor may be selected between 140 and 200 m/second, the inlet flow rate of air for a small project may be of 1.5 - 2 m3/second, the external diameter of the compressor may be 15 - 16 cm. The number of revolutions can be referred to as 30,000 rpm. The increase in speed of transit through the counter-rotating axial compressor may be 10 - 15% from the inlet to the outlet.
The discharging turbine is also counter-rotating and has 3 + 3 rotors of blades. On the fixed shaft, between compressor and turbine, a starter - generator is housed having the magnetic rotor outside the stator, fixed to the inner counter-rotating duct 103, with a diameter smaller by approximately 11 cm, which rotates at 30,000 rpm, and it is wound around by a pack of graphene and Kevlar fibres with inclinations transversal to each other and linked by a resin. This is advantageous in order to have less weight and withstand the centrifugal force. The magnetic rotor is of the array type as it allows a greater magnetic density towards the inside of the rotor and at the boundary with the stator. The starter generator produces an alternating or even three-phase current.
In one embodiment, it is possible to use magnets resistant at a higher temperature so as to avoid cases of demagnetisation.
The stator is fixed to the immovable shaft of the turbine. The electricity production is greater than 12 kW and can produce up to 100 kW; in the case of graphene, stanene and germanene type superconductors there is no need for special cooling. At this point, we are in the presence of pressure + temperature. The air passes through the counter-rotating power turbine which, after expansion, discharges, in fluid communication, in the successive plasma duct and simultaneously activates the counter-rotating compressor and with it the magnetic rotor of the starter-electricity generator. The air discharged in the magnetic duct is still characterised by a residual pressure and a good temperature (500°C can be measured) which is useful and functional for the subsequent ionisation process and for a significant increase in the temperature. In effect, the flow, at the entrance to the plasma duct, transits in a thermal arc (alternating) in magnetic field.
This thermal arc uses a radio frequency with oscillator in the magnetic field and combines with a second radio frequency reflected and distant from the previous one by 90°-180°. The voltage applied is 50 kV - 100 kV and, in any case, not less than 30 kV/cm (the distance in cm is measured between anode and cathode). The pulsed thermal arc X is in association with triggering means 11 and 12 identified as cathode 11 and anode 12 arranged in circular order, in an ordered coaxial position and immersed in the magnetic field B generated by magnetic means 14, 16 and positioned in an arrangement designed to favour the maximum ionising efficiency; the smaller distance between cathode and anode AK - GAP making it possible to increase the frequency. The previous electrical discharges have produced elastic and non-elastic impacts of the electrons with the ions and the neutral atoms with exchange of charge and recombination exceeding the dielectric failure and creating a continuous triggering of small productions of ions. It is known that the ions of the nitrogen atom return to their position in a femtosecond. The duct which constitutes a thrust axis and which is not conductive is wound with permanent annular magnets or electromagnetic coils or solenoids. The air is ionised at the start of this duct. The ionisation of the air allows the conduction of electric current so that the subsequent step is highly magnetised, energised and accelerated by the R.F. frequency of the electromagnetic force. It is also possible to adjust the magnetic charges and it will be easier to apply a same radio frequency for the ionisation and the acceleration. The radio frequency is supplied to a strip of copper, with a rectangular cross section, wound in the form of a helicoid on the ceramic duct with low permittivity or made of materials with a high rate of secondary electron emissions such as BN, alumina AL203, b4C or silicon nitride Si3N4 and it allows the immediate creation of a plasma which can also be defined as a pre-plasma or cold plasma. The supply system is the Helicon Double Layer. In effect, the presence of a magnetic field directed along the axis of the helicon antenna creates a mode of operation with high ionisation efficiency and a greater electronic density than a typical ICP. All the magnets which enclose the "duct" like a crown have important functions in activating the plasma, contributing also to the increase of the ponderomotive force and the confining. The first magnet engaged in the ionisation zone must have a inclination - angle of 20°- 30°, that is, the magnetic flow lines which is are normally parallel to the plasma flow lines are not parallel, but positioned in the form of a cone, with the widest side in the direction of the outlet. This facilitates the confining, the ponderomotive force, the direction of the transit speed. It should be noted that it is not the electro-magnetic field which ionises, but the radio frequency. In the application of the quantity of radio frequency in a magnetic field it is foreseeable to use a range not far from that which may be granted by the magnetic or electromagnetic field applied. The ions are insensitive to the magnetic field even if when it is excessive they are disturbed; and if this is created in the ionising zone - inside the duct - it improves the efficiency the intervention of the radio frequency. It should be noted that the ions are limited radially by the magnetic fields and entrapped longitudinally by the electrical fields.
The configuration of the magnetic elements of the plasma propulsion unit may be of three types as in Figure nos. 1, 2, 3.

1 - Magnetic or electromagnetic rings.
2 - Two solenoids with central choking of the axial flow of the plasma controlled by a magnetic ring with ortho-radial flow.
3 - Accelerator with multiphase solenoid.

According to the invention, a lower hybrid resonance heating LHRH is preferred to an ECR for the heating since the hybrid wave not only has a lower frequency but also does not need the radio frequency to coincide with the magnetic field. The greater, if not double, radio frequency necessary for an ECR system produces a significant loss of energy since the excessive heating of the electrons is such that they no longer comply with the unchanging adiabatic and carry away the greater heat absorbed with an energy which is unnecessary and greater than that necessary for a RF plasma. The microwave adopted is between band X and band S (SHF). In this case, it is preferable to align a lower hybrid wave close or similar to a 2.45 GHz ECR adjusting, possibly reducing (modulating), the intensity of the magnetic field. In this way it is possible to vary the thrust power increasing the ionisation and the RF power.
The preferred embodiment is with a microwave propulsion unit and with a multiphase solenoid.
The constant application of electricity with sequential phase variation produces a more unidirectional thrust. The direction of the magnetic field created by the multiphase solenoid, in a position parallel to the axis of the propulsion duct, is substantially the longitudinal thrust direction with vigorous helical movement. The continuous basic rotation favours a more centred plasma. The multiphase solenoid is characterised by the possibility of varying the magnetic field in relation with the other electronic conditions are present.
The phase displacement may be made by a multiphase solenoid (Fig. 5) composed of six concentric turns axially rotated in reciprocal fashion by 60° from each other and dispensing from progressive R.F. sources with radial influence of 0° - 60° - 120° - 180° - 240° - 300° -, or, remembering that in this case we have a three-phase current, three concentric turns rotated in reciprocal fashion by 120° from each other in progressive radial order of 0° - 120° - 240°.
Moreover, inside the multiphase solenoid, there is a magnetic Halbach array system which is also useful to increase the radial confining of the moving plasma, thus with the presence of a multiphase pulsed magnetic field and with a single direction (one pole per phase is indicated for the neutral gases).
The Array type system of magnets comprises three consecutive stages: 1st stage: 3 poles, 2nd stage: 6 poles, 3rd stage (output): 3 poles. The antenna (Fig. 6) is with helicon, with a rectangular cross section, quadruple and may be double at the correct distance between them at the magnetic fields of greater density.
The plasma duct the may be lined internally with reflective material. In this way, a more powerful quasi-isotropic confinement is granted, without electrostatic acceleration and the charge-mass ratio may be zero, that is, neutral plasma with quasi-isotropic collisions. The multiphase accelerators act with radial and longitudinal frequency which translates into a vigorous helical movement and with correct frequency indication preferred for application to the hot and compressed air applies a (lower hybrid wave) 2.45 GHz microwave (or, alternatively, the nearby waves of the S - X band) suitable for interacting with any gas producing continuous unidirectional thrust. The ultra-short and ultra-dense (SML WFA) double pulse laser (pulsing alternately), excites (as already stated) with a localised disturbance the rotational states of the molecules which are transformed into oscillations known as plasma frequency. The double pulse laser, with a suitable repetition frequency, creates, due to the initial delay of the second pulse (of a period), a harmonic spectrum, which can create, if in resonance, a temporary delocalisation of the electrons positioning them in an atomic orbit without the effect of their electronegativity.
The quantity of laser energy may vary for altering the force of the magnetic fields thus modifying the wavelength and/or the laser energy and the frequency of the pulses. The resulting magnetic wave can be adapted and tuned in to the desired harmonics or in any case offered by the procedure in progress.
The hybrid wavelength resonance frequency is a disturbed cyclotron frequency which has the effect of moving the ion and electronic resonance frequencies in proportion to the electronic density.
The cyclotron resonance frequency is characterised by electrical charges or voltages which are much lower than other resonance methods and are therefore easier to apply and control.
It is understood that a small variation in energy, magnetic and electronic density, pressure, frequency or pulse results in the need for a continuous refining already described with words such as: balancing, tuning, resonance, timing, modelling. For each project it is necessary to set up precisely the characteristics of the parameters present. For this problem use is made of a computational software of the plasma. The range and the extremely high computational complexity of the plasma phenomena force the operations relating to the linear solutions of the system to be parallelised (distributed memory). There is a range of software of the plasma. This software allows the maximum performance to be guaranteed even of complex systems by implementing data acquisition and calculation codes. The application of certain software for controlling and monitoring specific instruments and hardware makes it possible to monitor the operation and set the relative parameters.
This therefore remedies the rheological behaviour of the plasma which has nonlinearity, a large number of degrees of freedom, lack of symmetry. The computational software is a solution-finding and decision-making tool to support the stabilising performed by means of magnetic fields, for improving the reliability of the process in progress, multi-scale optimisation and fidelity management.
The magnets and the parts of the expansion turbine must be cooled. The magnets are located in two positions: those of the starter - generator and those where the plasma is formed. The problem of cooling is resolved by drawing off compressed air from the first rotors which make up the compressor, before the air becomes too hot. The drawing of compressed air is preferably carried out where there is the second rotor of the compressor and on the inner part where there are the rotors with the smallest internal diameter. This air will flow to cool the magnetic rotor of the starter - generator. It will escape from the blades of the turbine where the discharge pressure of the cooling air is slightly higher than the residual expansion pressure. It may also be discharged entering in the blades of the largest rotor - the last of the discharge - of the expansion turbine. These blades have a greater thickness and holes which discharge in the direction of the line of flow of the turbine.
Another route for cooling the entire turbine -propulsion system body is by using compressed air which at the mouth of the compressor is channelled and thrust into the gap between the outer cylindrical duct 101, which is fixed, and the other inner duct 102 which rotates at 30,000 rpm. This circular crown gap is crossed by this flow of air which arrives at the plasma outer zone where it can enter until wrapping around the magnets and then discharge to the outside. In addition to the cooling and magnetic confining it is also possible to create a double chamber - in the plasma duct - where fresh air flows which passes through in the direction of the outlet holes moving away from the plasma surfaces as occurs in the combustion chambers of gas turbines.
All the particular features of the invention have been described with reference to the accompanying drawings; the description and these drawings obviously illustrate an example of the inventive techniques described.
The present invention is defined by the appended claims.

The components shown in the drawings are listed below with the respective identification numbers.

1. AIR INLET A

2. LASER

3. PRECOMRESSION OF AIR

4. COOLANT AIR CIRCULATION

5. COUNTER-ROTATING AXIAL COMPRESSOR

6. FIXED SHAFT

7. HALBACH ARRAY MAGNETIC OUTER ROTOR

8. ELECTRIC GENERATOR STATOR

9. FIRST HEATING MEANS

10. COUNTER-ROTATING TURBINE

11. CATHODES

12. ANODES

13. INCLINED MAGNETIC RING

14. MAGNETS

15. ANTENNA (FIGURE 6)

16. SOLENOIDS (FIGURE 5)

17. SUPERSONIC BELL-SHAPED NOZZLE

Ai IONISED AIR

Ar RESIDUAL EXPANDED AIR

E ELECTRICITY

3a ROTOR

3b STATOR

PI COUNTER-ROTATING BLADES

P2 COUNTER-ROTATING BLADES

PL PLASMA

PW THRUST POWER

100 TURBINE BODY

101 EXTERNAL CYLINDRICAL DUCT

102 COUNTER-ROTATING CYLINDRICAL DUCT WITH BLADES

103 COUNTER-ROTATING CYLINDRICAL DUCT WITH BLADES, INSIDE DUCT 102

104 CIRCULAR GAP BETWEEN 102 AND 103

200 PLASMA PROPULSION SYSTEM WITH THERMAL ARC X IN ZONE 202 AND PLASMA DUCT 201

201 PLASMA DUCT

202 DUCT WITH THERMAL ARC X PROVIDED WITH CATHODES 11 AND ANODES 12.

Claims

A plasma propulsion system comprising:
a plant (100) with an air turbine (A) designed to receive a supply of air from an outside environment, and a plasma propulsion unit (200) designed to increase a speed of the air after a corresponding ionisation and passage of the air into plasma phase,

wherein the plant (100) for the air turbine comprises:
• first compressing means (3) designed for a first compression of the air;

• second compressing means (5) designed for a second compression of the air pre-compressed by the first compressing means (3);

• first heating means (9) designed to heat the air previously compressed by the first (3) and second (5) compressing means;

• a starter electricity generator designed to produce electricity;

• a counter-rotating power turbine (10) which can be operated by the air heated for producing expanded air, wherein the turbine is designed to:

• perform compression using the first compressing means (3) and the second compressing means (5);

• produce electricity (E);

• discharge residual expanded air (Ar) as a function of the air compressed and heated with part of the electricity produced;

wherein the plasma propulsion unit (200), associated with the air turbine plant (100), comprises:
• a duct (201) for plasma flow designed to receive the residual expanded air (Ar) discharged by the power turbine (10);

• a connecting portion (202) located between the power turbine and the duct (201) for plasma flow wherein the connecting portion has a decreasingcross-section to speed-up the air (Ar) in the direction of the duct (201) for plasma flow and comprises an anode (12) and a cathode (11) configured to generate a thermal arc (X) by means of an RF oscillator, so that the residual air passing through the connecting portion (202) subjected to the thermal arc (X) becomes an ionised and heated air (Ai);

• magnetic means (13,14,16) fixed in such a way as to surround the duct for plasma flow in a ring and designed to generate a corresponding magnetic field, wherein said anode, said cathode and said thermal arc are located in said magnetic field, wherein said magnetic means are configured to generate a plasma from said heated and ionised air;

• a source of radio frequency or microwaves applied with helical antennas adjacent to and encircling the duct (201) for plasma flow in the magnetic field (B) generated by the magnetic means (13, 14, 16);
• a laser source configured to emit a laser wave which passes linearly along the centre of the duct (201) for plasma flow, so as to accelerate said plasma just generated in the magnetic field (b) generated by the magnetic means (13:14; 16);

• discharging means (17) for discharging the plasma (PL) generated in the duct (201) for plasma flow and comprising a divergent supersonic nozzle (17) with an antenna (15) and shaped in the form of a bell where the discharging means (17) in the outlet of the plasma (PL) create a thrust power (PW) produced by the propulsion system.
The plasma propulsion system according to claim 1 wherein the first compressing means (3) comprise a stator (3b) and a rotor (3a) associated with a fixed shaft (6) of the turbine plant (100).
The plasma propulsion system according to any one of the preceding claims, wherein the second compressing means (5) comprise a counter-rotating axial compressor comprising a first plurality of blades (pi) which rotate inversely relative to a second plurality of blades (p2).
The plasma propulsion system according to any one of the preceding claims, wherein the electricity generator is designed to produce a three-phase alternating current and is characterised by stator fixed to the axis and an outer magnetic rotor of the Halbach array type fixed to an inner counter-rotating duct (103).
The plasma propulsion system according to any one of the preceding claims, wherein the first heating means (9) comprise several series of micro blades counter-rotating relative to each other made of metal alloys which are hard and resistant to heat situated in a circular gap 104 defined by two cylindrical ducts (102) and (103) designed to rotate in a counter-rotation fashion relative to each other with respect to a fixed shaft (6) thus forming, with continuous rotations, a plurality of mini thermal arcs designed to immediately raise the temperature of the compressed air in transit.
The plasma propulsion system according to any one of the preceding claims, wherein the annular magnetic means (13, 14, 16) comprise one or more between:
magnetic and electromagnetic rings;

two solenoids with central choking of the axial flow of the plasma controlled by a magnetic ring with ortho-radial flow;

Accelerator with multi-phase solenoid (16) equipped with further circular magnetic rings of the Halbach array type inside.
A plasma propulsion method comprising the steps of:
• preparing an air turbine plant (100) designed to receive a supply of air from an outside environment and a plasma propulsion unit (200) equipped with a duct (201) for the plasma flow, associated with the air turbine plant (100) and designed to increase a speed of the air after a corresponding ionisation and passage of the air into plasma phase;

• in the air turbine plant (100), performing a first compression of the air and a second compression of the air previously compressed;

• heating by thermal arc (X) the air previously compressed by means of the first and second compression;

• expanding the heated air in a power turbine (10) for:
∘ performing compression using the first compressing means (3) and the second compressing means (5);

∘ producing electricity (E);

∘ discharging residual expanded air (Ar) as a function of the air compressed and already heated with part of the electricity (E) produced;

• simultaneously carrying out the steps of:
a) Increasing the speed of the residual air (Ar) in such a way as to reduce the pressure by reducing the transit cross section (202) of the residual air (Ar) at the outlet from the power turbine (10);

b) Applying to the residual air (Ar) the thermal arc (X) by generating a pulsed radio frequency in a magnetic field (B) wherein the magnetic field (B) is generated by annular magnetic means (13) or multiphase solenoids (16) fixed in such a way as to surround in a ring the duct (201) for plasma flow;
where the two simultaneous steps a) and b) determine, starting from the residual air (Ar) that dropped in temperature at the end of the previous passage in the power turbine (10), a ionised and heated air (Ai) suitable for a passage to the plasma state;

• receiving the ionised and heated air (Ai) in the duct (201) of the plasma propulsion unit (200);

• determining a passage to the plasma state and subsequent step of energising and accelerating the plasma, using energising means comprising:
a hybrid radio frequency or microwave with one or more helical antennas encircling the duct (201);

a laser source which emits a laser wave which passes linearly along the centre of the duct (201) for plasma flow,

• discharging the plasma (PL) generated in the duct 201, comprising a divergent supersonic nozzle (17) with radio frequency antenna (15), resulting in an outflow of the plasma (PL) from the propulsion unit (200) representing a thrust power (PW) produced by the propulsion method.
A plasma propulsion method according to claim 7 wherein the magnetic means (14, 16) comprise an accelerator with multiphase solenoid equipped inside with further circular magnetic rings of the Halbach array type wherein the direction of the magnetic field generated by the multiphase solenoid in position parallel to the axis of the propulsion duct substantially determines the longitudinal thrust direction of the plasma (PL) with a helical movement towards the discharge nozzle (17).
The plasma propulsion method according to claim 7 or 8 and any one of the preceding claims, comprising the step of energising and accelerating the plasma (PL) using the excitation means comprising one or more quadruple helical antennas (15) with rectangular cross section using a lower hybrid wave designed to energise and accelerate the plasma (PL) wherein the radio frequency applied is 2.45 GHz.
The plasma propulsion method according to any one of claims 7 to 9, wherein the laser source emits a first pulse and a second pulse, wherein the first pulse has an energy equal to 10% of the energy available to the laser, and the second pulse starts from a distance of a period from the first pulse and has an energy of 90% of the energy available to the laser, wherein said second pulse has twice the frequency of the first pulse.
The plasma propulsion method according to any one of claims 7 to 10, comprising a step carried out using a computer configured for synchronising or correlating the cyclotronic frequencies of resonance and of repetition in the process for generating plasma with magnetic density produced by the solenoid and to facilitate a process of ionisation and acceleration of the plasma at the same radio frequency.