RU2517004C2 - Cyclotron plasma engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to space engineering, particularly, to electric jet engines and is designed to control space craft of low thrust (up to 5 N). Cyclotron plasma engine comprises plasma accelerator housing, solenoids (inductors) and electric circuit with compensating cathodes. Note here that self-contained ion source, electron and ion flow splitter. Asynchronous cyclotron makes said plasma accelerator. Cyclotron is divided into dees by two coaxial pairs of parallel grids with clearances. Said dees make homogeneous, identical and invariable electric fields of opposite-direction of electric-field vectors. Cyclotron comprises the ferromagnetic adapters with inductors in quantity complying with the number of plasma accelerator outlet channel thrust development directions. Outlet straight gas dielectric channels of this engine communicate with said main adapters via pass electric valves. Said channels are communicated via ferromagnetic adapters wit inductors.

EFFECT: higher specific burn, decreased weight and overall dimensions, lower power consumption.

3 cl, 2 dwg

Description

The invention relates to space technology, to the class of electric propulsion engines (ERE) (plasma accelerators) and is intended to control the movement of spacecraft (SC) small (up to 5N) thrust.

There are many schemes of electric propulsion devices. All of these circuit diagrams are known in the art. The most promising when operating electric propulsion in space conditions can be considered an engine (it is fair to assume that storage and supply of neutral gas are not included in the concept of “engine”), having a plasma accelerator (PU) with an external magnetic field or, in other words, PU with the so-called closed drift, which is taken as a prototype. The prototype contains: a through anode for supplying low-temperature plasma - a working fluid (RT); a cylindrical and annular in cross-section (add, - coaxial) accelerator channel (CC) - dielectric chamber; electromagnets surrounding all the outer walls of the criminal code, creating a radial magnetic field inside the channel; an electric circuit creating a longitudinal electric field between the anode and the output cathode, as well as creating electron emission from the cathode-compensator. Electrons of a moderately ionized plasma of the RT, falling into a radial magnetic field, drift in spirals with a small step of turns. When they collide with them, neutral gas molecules ionize and, accelerating in an electric field, fly out of the CC. The energy accumulated by ions in the PU is close to the potential difference between the anode and cathode. Electrons due to collisions with ions, atoms, the wall of the CC and under the influence of oscillations arrive at the anode and are mixed with the ion flow through the cathode-compensator through the electric circuit at the outlet of the CC [1] {Plasma accelerators, ed. L. A. Artsimovich [et al.], M., 1973}.

It is possible to create a plasma when there is an “ignition” electrode-cathode between the anode and cathode. The arising discharge in the anode-ignition electrode circuit initiates the main current in the anode-cathode circuit. The heated RT entering through the anode is ionized by electrons moving towards it. Ions are accelerated in a longitudinal electric field created in the UK.

The prototype, in principle, gives good results and has acceptable weight and size characteristics, however, the limitation on power consumption on board the spacecraft limits its use. In fact, the energy of such accelerators ranges from 100 eV to 10,000 eV, which requires the application of a potential difference from 100V to 10,000V, and as a result, the velocity of the outflow of ions from the UK will be about (10 ¹ -10 ² ) km / s. The situation cannot be corrected by increasing the length of the criminal code - this would require correspondingly greater voltage in the criminal code. All currently available PUs have one or another type of straightforward CC.

The task is to create an electric propulsion engine, in its potential significantly exceeding all known engines of this class used in space flight practice, i.e. the objective is to increase the specific impulse of thrust while maintaining and possibly reducing the weight and size characteristics of the propulsion systems on the spacecraft at a relatively low power consumption. The goal is achieved by the fact that the plasma engine containing the casing of the control unit, inductors (solenoids), an electric circuit with compensating cathodes, introduced an autonomous source of low-temperature plasma (RT ionizer), a separator of electron and ion flows and a plasma accelerator, which is an asynchronous cyclotron divided along the dounts by two coaxial pairs of parallel grids with gaps that create uniform, equal and constant accelerating electric fields of mutually opposite directions vector of tension, having, according to the number of main thrust directions, output gas channels — ferromagnet adapters, which are cores that correct the direction of movement of electromagnet ions, bent at a given angle, and the adapters are connected to through-flow electrovalves and through them, to create a verified direction of the thrust axis — output direct sections of the gas dielectric channels of the engine, between which the same ferromagnet adapters with inductors are installed.

The technical result is achieved due to the fact that acceleration of heavy gas ions, for example xenon, is possible, unlike all the known technical solutions of electric propulsion, along quasi-cyclic helices provided in a certain way assembled by a cyclotron, inside which not only units, but ion masses are accelerated, with the device being obviously comparatively compact , while the specific impulse (the rate of plasma outflow from the engine) in its class of small thrust space engines increases by 1-2 orders of magnitude without affecting the mass characteristics of the engine body. The specific impulse of thrust is the most important characteristic of the engine.

The analysis of the prior art by the applicant has established that there are no analogues that are characterized by sets of features identical to all the features of the claimed cyclotron plasma engine (CPD), therefore, the claimed invention meets the condition of “novelty”. The search results for known technical solutions in this and related fields of technology (astronautics, plasma technology), in order to identify features that match the distinctive features of the prototype of the claimed invention, showed that they do not follow explicitly from the prior art. None of the distinguishing features of this invention: neither a plasma source autonomous from the accelerator, nor a cyclotron in general, nor an asynchronous cyclotron operating on direct electric current, in particular, nor correcting electromagnets “pulling” to given thrust vectors, were previously used for the manufacture of electric propulsion, and therefore all the distinguishing features meet the condition of "inventive step".

The invention is illustrated in figure 1, which shows the electrokinematic diagram of the CPU, top view, and figure 2, which shows the PU, side view.

The following notation is introduced:

1 - ionizer of the working fluid - gas;

2 - separator flows of charged particles;

3 - channel for supplying RT ions to the accelerator;

4 - jet;

5 - a pair of check solenoid valves;

6 - accelerator body (cyclotron);

7 - the main ferromagnet adapter with an inductor;

8 - ferromagnet adapter with an inductor;

9 - output gas dielectric channels of the engine;

10 - cathode-compensator;

11 - accelerating nets of duants;

12 - solenoids in the outer core-ferromagnet PU - cyclotron;

13 - external core-ferromagnet;

14 - outlet PU - cyclotron;

In - magnetic induction.

The cyclotron has a working volume (V _c ) not exceeding 0.02 m ³ (radius 0.25 m, height ~ 10 cm), the larger side of the rectangular cross section of the outlet 14 (Fig. 2) in the inner wall of the cyclotron corresponds to the height of its working cylinder. The volume is quite sufficient for the operating mode of the cyclotron, its value, in principle, is not critical, the height is not critical, and the height is only the radius for given values of magnetic induction and the final speed of ions. The height of the working cylinder corresponds to the diameter of the outlet of the main adapters 7. To create a uniform (in the sense of straight lines of force) magnetic field inside the working cylinder, the cyclotron body 6 is surrounded by solenoids 12, the length of which is several times longer than the height of the working cylinder, and the cyclotron working cylinder is located in the middle part groups of solenoids.

Adapters 7.8 - ferroalloy tubes, which are the cores of electromagnets (solenoids).

The number of main adapters 7 (adapters that are part of the accelerator body) and pairs of through-through electrovalves 5 should correspond to the number of directions for creating traction; the number of pipes 9 of the exhaust gas channels of the engine and adapters 8 is determined by the possibility of installing the end of the gas channel of the engine so that the output axis of the channel coincides with the desired direction of thrust, and the thrust vector passes through the center of mass of the spacecraft. The outer radius of the pipes must correspond to the inner (r _transition ) radii of the adapters. Solenoids with ferromagnet adapters built into them are needed to correct the path of ionized particles.

The angles of deviation of the path of the flow of charged particles from the directions of the lines of force of the magnetic field in the adapters and from the longitudinal axes in the sections of the gas channels of the engine (see "Justification ...") do not affect the nature of the translational motion of the particles - this is almost regular inevitable contact of particles on the periphery of the wall flow gas channel. The number of particles per cubic meter, with a normal consumption of RT - xenon currently on domestic spacecraft 6 · 10 ^-6 kg / s (which this invention is not going to exceed), is 6 · 10 ^-6 · Δt _slave / (V _C · 131 · 1.7 · 10 ^-27 ) = 1.3 · 10 ¹⁷ , where Δt _slave = 10 ^-4 s is the time the CPU goes to operating mode (see paragraph 3 "Justification ...") is a high vacuum (10 ¹⁹ -10 ¹³ ) - nothing terrible can happen in him.

The installation of the CPD on the spacecraft, due to the peculiarities of the spacecraft design solution, will require constant adjustment of the number of straight sections of the gas channels of the engine and adapters.

Justification of the proposed solution

We take as a basis:

- load current I = 5 A;

- voltage on tires U = 300 V / 27 V;

- the radius of the working cylinder of the cyclotron R = 0.25 m;

- the length of the solenoid for the working cylinder L = 0.5 m;

- the initial speed of Xe ν = 0 m / s;

- the final speed of Xe ν is _finite = 150.000 m / s (10 × 15 km / s);

- ion charge q = 1.6 · 10 ^-19 C;

- the mass of the ion m = 131 · 1.7 · 10 ^-27 kg;

- Acceleration of ions occurs in an alternating electric field - as a starting option.

1. Inside the working space of the cyclotron is located, as a capacitor, device 11 (two pairs of parallel grids connected to a direct current source) for an accelerating electric field with a potential difference of 300 V. The work performed with the Xe ion in the gap between the plates of the capacitor is

$$A=U\cdot q=\frac{m}{2}({\nu }_2^2-{\nu }_{\mathrm{one}}^2).\text{(one)}$$

To determine the increment of speed per half-turn, we take: the initial speed at the entrance to the accelerating gap ν ₁ = 0; the final velocity at the exit from the gap ν ₂ = Δν, then

, $$\Delta \nu =\sqrt{\frac{2U\cdot q}{m}}=\sqrt{\frac{600\cdot \mathrm{1,6}\cdot {10}^{-19}}{131\cdot 1.7\cdot {10}^{-27}}}=20762\text{m / s}$$

,

where U = E · d;

E, d - respectively, the electric field strength and the distance between the mesh plates of the duants,

and for a full revolution (two gaps) - 29362 m / s.

It follows from (1) that over time, the electric field no longer has the same effect on the increment of the particle’s velocity, as in the beginning, the increment of the current radius of curvature of the particle’s motion in the magnetic field of the cyclotron tends to zero over an infinitely long interval of operation of the cyclotron. However, for a voltage of 300 V when the cyclotron enters the operating mode, a speed increment of 2800 m / s is achieved per revolution, which ensures the achievement of the task. You can do with a standby voltage of 27V. The current radius r, according to the condition of synchronism [2] {Reference on Yavorsky Physics} (p. 446) r / ν = const, based on the final values, is 1,667 · 10 ^-6 · ν (m), the revolution period is 1.05 · 10 ^-5 c. According to the period, the AC frequency is ~ 100 kHz.

In general, RT ions (xenon) do not have to “twist” the circles a lot: for U, equal to 300 V, the number of circles is 26-27.

2. The magnetic field causes the Lorentz force, and the ion moves in a circle from gap to gap without acceleration. At each point of motion, the osculating circle has a radius, respectively

$$r=\frac{m}{|\; |\; |q|\; |\; |}\cdot \frac{\nu }{B},\text{(B-magnetic field induction)}\text{. (2)}$$

, (T - квазипостоянный период)r ~ ν, $$r/\nu =T/2\pi =\frac{m}{q\cdot B}=const$$

, (T - quasi-constant period)

We substitute the output characteristics of the cyclotron in (2):

$$B=\frac{131\cdot 1.7\cdot {10}^{-27}\cdot \mathrm{1,5}\cdot {10}^5}{\mathrm{1,6}\cdot {10}^{-19}\cdot 0.25}=0.835Tl.$$

Therefore, ν is _finite = 150 km / s - and 0.25 m of radius

The acceleration process is automated, does not go beyond the dimensions of the device and guarantees a given final speed ν of _finite .

The magnetic field strength N in accelerators cannot exceed (1.2-1.6) · 10 ⁶ A / m, [2] (p. 447), in our case we get 0.67 · 10 ⁶ A / m.

The specified magnetic field inside the solenoid in a vacuum is created [2] (p. 434)

$$N=\frac{B\cdot L}{I\cdot {\mu }_0}=\frac{(0.835/K)\cdot 0.5}{5\cdot \mathrm{four}\pi \cdot {10}^{-7}}\approx 94000\text{turns}\text{, (3)}$$

, в случае соленоида (К - коэффициент ослабления в центральной части соленоида);Where $$K=\frac{L}{\sqrt{\mathrm{four}{R}^2+L^2}}$$

, in the case of a solenoid (K is the attenuation coefficient in the central part of the solenoid);

µ ₀ - magnetic constant, V · s / A · m.

It's a lot. True, the coefficient K from the center to the edges of the working cylinder PU varies from 0.7 to 1, but this problem does not solve. The cross-sectional diameter of the wire is 0.005 mm. The voltage at the ends of the solenoid, with a total length of copper wire l ~ 1.5 · 10 ⁵ m (active resistance ρ · l / S = 135 Ohm, ρ≈0.0178 μOhm · m - resistivity; S = 2 · 10 ^-5 mm ² - cross-sectional area), is 675 V. A current of 5 A cannot stand such a wire. It is necessary that the cross-section diameter at a current of 5 A be 0.5 mm, not less. We do so. With the radius of the circumference of the working part of the cyclotron 0.25 m and the circumference of 1.57 m, we place around this working part a group (n) of 100 solenoids with a length of 0.5 m. The number of turns of a cross section of a diameter of 0.5 mm in each solenoid is 1000. Inside such a large group of solenoids (at I = 5A, K = 0.7), a magnetic field is formed with induction, according to (3), 0.0088 T. The resistance of a copper wire with a cross-sectional diameter of 0.5 mm is ρ · l / S (l = 49.32 m is the total length of the wire of a single solenoid, m; S = 0.196 mm ² is the cross-sectional area), which means 4.5 Ohms. The voltage (U) on each of the solenoids will be ~ 22 V, when connected in series, we assume a total voltage at the ends of the group of solenoids of 300 V. Then the total number of solenoids (n ₁ ) will require ~ 13-14. Since a magnetic field induction of 0.835 T is required, it is ~ 100 times large, and also because you always need to look for economical solutions, all n ₁ solenoids 12, geometrically coinciding with the solenoids of the “n” group, are placed inside the core-ferromagnets, conditionally representing, in the number of directions for creating traction, equal parts cut along a cylindrical pipe of length L, the inner radius of which is the inner radius R of the cyclotron. Conditionally - because in fact there is one core-ferromagnet 13 (Fig. 2), inside which there are groups of solenoids separated by equal intervals inside the PU - cyclotron, characterized by a small side of a rectangular cross section of the outlet in the working cylinder of the PU 6 or - holes 14 of the main adapters 7. The core has the required magnetic field gain (k) (in our case, k = 0.835 / 0.0088≈100). The distance between the centers of the inductors is about 11.5 cm. As is known, the intrinsic magnetic field of a ferromagnet can be hundreds of times higher than the external magnetic field. In a specific calculation of the electrical circuit of the inductor can have more than one row of turns.

Increase the radius of the wire section to 1 mm. Then: S = 3.14 mm ² ; N = 2 × 500 (two rows of turns); N / L - the same, 2000; l = 49.32 m; wire resistance is 4 times less, 1,120 m; U = 5.6 V; n ₁ = 54; the distance between the centers of the inductors is ~ 2.9 cm. With an outer radius of the coils of 1 cm, the minimum distance between them is 9 mm. This option should be considered close to optimum.

The total volume of the wire on the inductance coils according to the last variant of the cross section does not exceed 8.4 dm ³ , which corresponds to a cube with a side of 20.3 cm.

3. The time (Δt _slave ) of the exit to the regime (the time of “scrolling" of the RT) is about 10 ^-4 s.

4. Everything written above speaks about the qualitative characteristics of the process. In practice, in view of the fact that organizing the introduction of the minimum ion dose to the accelerator for the cyclotron to work in its strict sense will be problematic, and this will lead to extremely low engine thrust, it is necessary to arrange such a feed rate of the RT that after a while it is the time to reach the operating mode ( time of preparation of the engine), the stationary process of the movement of ions throughout the entire volume of the cyclotron ensued, and the cyclotron would operate in a continuous mode. The engine preparation time will be commensurate with the time given in paragraph 3. The space charge (the interaction of electric fields) is the cause of gas pressure. Substances (charged particles) carry out physical interaction exclusively through electrostatic fields.

The resulting plasma pressure increases the efficiency of the cyclotron. It is known that plasma has elastic properties. An increase in the space charge ensures that the plasma in the cyclotron behaves like a liquid in a turbine with two blades tightly fitted to the walls - it rotates throughout the volume with the current angular velocity. It is the electrostatic expansion that pushes the RT ions into the output channel-adapter chosen for the operation of the CPD and increases their final speed (gained due to the cyclotron). This approach will be called the tornado principle.

5. The internal working surfaces of the cyclotron and the gas outlet channels of the CPD to minimize RT turbulence and wall heating are made mirror-like.

6. The main thing. An alternating current generator is excluded from the CPD. We apply regular direct current from the spacecraft power system. Replacing one accelerating gap and an alternating electric field with two equivalent gaps and constant electric fields is absolutely equivalent. The condition of synchronism is associated with the period of oscillation of an alternating electric field. There is no alternating electric field - there is no conceptual synchronism. And therefore, we can talk about the asynchronous nature of the cyclotron, bearing in mind that particles are always accelerated on time. Any given voltage can be applied to the nets of 11 dunts - after all, we are only talking about the time to reach the final speed. The exhaust valves of the gas channel selected for operation remain open for the entire duration of the engine operation.

The electric field vectors of the pairs of grids 11 (in slotted diagonal gaps) are mutually opposite.

So, the novelty and inventive step are both in relation to the device of the plasma engine as a whole, and in the use of direct current, the rejection of the principle of synchronization and the use of the principle of "tornado" in the acceleration unit of the engine.

7. Regarding the use of RT ions, ferromagnets 7, 8 with motion coils correcting the motion of RT, with inductors.

If a charged particle moves in the magnetic field of the adapter (the magnitude of the magnetic induction along the magnetic field is constant, despite the curved profile of the adapter, is constant) so that its velocity vector is angle α with the direction of magnetic induction B, then the path of the particle is a helix with a radius

$$r=\frac{m}{|\; |\; |q|\; |\; |}\cdot \frac{\nu }{B}\cdot \sin \alpha ,\text{(four)}$$

and screw pitch

$$h=\frac{2\pi }{B}\frac{m\cdot \nu }{|\; |\; |q|\; |\; |}\cdot \cos \alpha .\text{(5)}$$

The larger the specified value of B, the smaller r and α, and the particle follows the lines of force of the magnetic field. The main thing is that the condition r <r is _transient. . We have r _transition. = 0.05 m. For probable radii of curvature of the bend of the adapter, we have α <10 °. Then from (4) it follows B = 0.72 T, from (5) it follows that heavy ions, not only with respect to the angle Of, but also with respect to the pitch of the helical path, practically follow the magnetic field lines, since h = 1 , 8 m with an adapter length of 15 cm. With such an adapter length A = 0.6 (magnetic field inhomogeneity is desirable: the closer to the adapter walls, the greater the magnetic induction) the final deviation of particles from the directions of the magnetic field lines inside the adapter at a speed of 1 , 5 · 10 ⁵ m will not exceed 2.6 cm. If the adapters are effective With active ferromagnet cores of electromagnets, it is always possible (item 2) to calculate the output parameters of an inductance coil - a solenoid, this is a problem to be solved for each specific bend angle of the adapter.

8. The ratio of the length of the solenoids creating a magnetic field in the working cylinder of the cyclotron and the core of the ferromagnet external to them to the height of the working cylinder (C) should be about 5: 1. This ratio ensures the straightness of the lines of force inside the working cylinder of the PU - cyclotron, which is important for the stationary process of particle acceleration. When the magnetic field lines are bent, the plasma undergoes delamination, and the planes of the layers through which the elementary magnetic fluxes pass intersect. This leads to a decrease in the efficiency of PU. An increase in C does not significantly affect the quality of particle acceleration, but it leads to an increase in the mass and overall dimensions of the product.

Claims (3)

1. A cyclotron plasma engine comprising a plasma accelerator body, solenoids (inductors), an electric circuit with compensating cathodes, characterized in that there are: an autonomous ion source; separator of flows of electrons and ions; a plasma accelerator, which is an asynchronous cyclotron, divided along the dounts by two coaxial pairs of parallel grids with gaps that create uniform, equal and constant accelerating electric fields of mutually opposite directions of tension vectors, which, in terms of the number of main directions for creating thrust, the output channels of the plasma accelerator are the main ferromagnet adapters with inductors; output direct gas dielectric channels of the engine, connected to the main adapters through passage electrovalves, and between themselves - ferromagnet adapters with inductors. 2. The cyclotron plasma engine according to claim 1, characterized in that the solenoids (electromagnetic coils) are serially connected and entirely placed inside the ferromagnet, which is a common core external to them, and with respect to the plasma accelerator, a cylindrical tube, the inner radius of which is the internal radius of the working wall of the plasma accelerator, in which, according to the number of main directions for creating thrust, there are rectangular cutouts - the outlet openings of the plasma accelerator. 3. The cyclotron plasma engine according to claim 2, characterized in that the ratio of the length of the solenoids and the outer core of the ferromagnet to the height of the working cylinder of the plasma accelerator is 5: 1.

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