US3350884A - Propellent supply to electro-thermic ejectors - Google Patents

Description

SEARCH ROD! Nov. 7, 196 D. P. L. J. COLOMBANI ETAL 3,350,884 PROPEL LENT SUPPLY TO ELECTRO-THERMIC EJECTORS I Filed Aug. 5, 1964 4 Sheets-Sheet 1 s A w n E b I m 84 I T a 7 44, a M A L .U E p m m L 8 C W\ M #W /M "'ZW/IYIIIII/IIIIIIIIIII 0 meg, cam

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United States Patent 3,350,884 PRGTELLENT SUPPLY T0 ELECTRO-THERMEQ EJECTORS Don Pierre Louis Jean Colomhani, Versailles, and Franck Guillaume Michel Ferric, Cachan, France, assignors to Societe Nationale dEtude et de (Construction de Moteurs dAviation, Paris, France, a company of France Filed Aug. 5, 1%4, Ser. No. 387,782 Claims priority, application France, Aug. 19, 1963,

11 Claims. lot. 60-2493) The present invention relates to the field of space and in particular to the use of electro-thermic ejectors for the propulsion of space devices. It has more particularly for its object the supply of propellent to these ejectors together with means especially permitting the preparation of the propellents.

In space propulsion, propellents with low molecular weights are the most advantageous by reason of the high speeds of ejection required. In this latter category, those which are also gaseous provide the lightest ejection fluids, but have the disadvantage of necessitating tanks of large capacity because of their low specific mass, even if they are employed in the liquid state. For example, the specific mass of liquid hydrogen is of the order of 0.07 kg./cu. drn. and in consequence it requires tanks of large size which must furthermore be cryogenic and therefore heavy and complicated.

The invention overcomes these drawbacks by permitting the storage in non-cryogenic tanks of propellents of low molecular weight, in the form of solid or liquid substances having a relatively high specific mass.

In accordance with the present invention, a solid or liquid substance of relatively high specific mass is decomposed into at least one constituent in the liquid state and one constituent in the gaseous state, having a low molecular weight, and these constituents are introduced separately as propellents into the electro-thermic ejector.

This substance may be for example, lithium hydride obtained in the solid state (powder or granules). Its relatively high specific mass (0.8 kg./cu. dm.) makes it possible, for an equal ejectable mass, to adopt tanks which are much smaller and much lighter than if liquid hydrogen were employed and also avoids the complication of cryogenic tanks.

In addition, ionized hydrogen has the disadvantage that it is very difiicult to return to the state of equilibrium in the discharge nozzles of the ejectors utilized for spatial propulsion. The congealing of the gas is thus a considerable cause of loss of energy. On the other hand, the simultaneous use as a propellent of hydrogen and lithium, derived from the decomposition of HLi has the advantage of facilitating the return to equilibrium, which permits an increase in the efiiciency of the device.

The invention also comprises means for decomposing a solid or liquid substance, and for separating the constituents in the gaseous phase and in the liquid phase, in the weightless state.

The process of decomposition of a solid or liquid substance into at least one liquid constituent and at least one gaseous constituent within the field of gravity is known per se, and depends on the substance chosen. With certain substances, it is only necessary to apply heat. This is the case, for example, in the decomposition of lithium hydride in powder or in finely-divided form, into hydrogen and liquid lithium. The separation of the hydrogen and the lithium is easy on the earth where the benefit of the elfect of gravity is obtained. This en- 3,35%,884 Patented Nov. 7, 1967 ables the liquid lithium, which is much heavier, to occupy the bottom of the heated receptacle, from which it is extracted by a conduit system. As regards the hydrogen, which is lighter, this can be evacuated through an orifice pierced in the upper portion of the receptacle. The circulation of the fluids is then eilected by the pressure resulting from the increase in temperature, or by appropriate pumps. In the case of lithium, for example, a magnetic pump will preferably be employed.

On the other hand, in the utilization in space, the lack of gravity complicates the problem presented by the separation of the liquid and gaseous constituents.

In particular, in the case of lithium hydride, the contact between the solid HLi and the hot wall of the receptacle in which the heating is carried out is much more dficult to effect since the particles of HLi move about in the whole of the free space of this receptacle. It is therefore necessary to take physical action in order to apply these particles against the walls.

In addition, the lithium particles, although heavier, have no reason to become separated from the hydrogen molecules and they continue to move about together if there is not applied a physical factor capable of grouping together the lithium on one side and the hydrogen on the other.

According to the invention, the absence of gravity is overcome by compressing the solid or liquid substance during the process of decomposition and. the liquid constituents are separated from the gaseous constituents, either by creating a gravity held, for example by centrifuging, or by filtering the gaseous constituents, for example through a porous wall.

The description which follows below with reference to the accompanying drawings (which are given by way of example only and not in any limitative sense) will make it quite clear how the invention can be carried into effect, the particular features which are brought out either in the text or in the drawings being understood to form part of the said invention.

FIG. 1 shows in vertical section a device Which can be used to effect the decomposition and the separation of the constituents in the field of gravity.

FIG. 2 shows an axial section of a device which enables this decomposition and separation to be efiected in the absence of gravity.

FIG. 3 represents a view in longitudinal section of another device which operates in the absence of gravity.

FIG. 4 shows a detail of an alternative form of the devices of FIGS. 2 and 3, seen in partial longitudinal section.

FIG. 5 is a plan view showing diagrammatically how the device of FIG. 4 can be operated.

FIGS. 6 and 7 show diagrammatically two forms of construction of an electro-thermic ejector supplied separately with liquid propellent and gaseous propellent, seen in longitudinal section.

The device shown in FIG. 1 is intended for the decomposition of lithium hydride into hydrogen and lithium, and for the separation of these constituents. It is utilizable on the ground, and more generally in a place where a field of gravity exists.

The device comprises essentially a fluid-tight chamber, preferably cylindrical, constituted by a tank 1 and its cover 2.

The tank 1 is formed by a partition with a triple wall la, 1b, 1c. The space 3 between the inner wall 10 and the central wall lb contains a heating resistance 4 which can be supplied from the terminals 5 and 6 of a source of electric current. The space 7 between the central casing 112 and the outer casing in is filled with a heatinsulating material.

The tank 1 comprises an evacuation conduit 3 at its lower portion.

The cover 2 with a double wall 2a, 2b, also contains an insulating material. It is also provided with an evacuation conduit 9. This cover is fixed on the receptacle by appropriate means (not shown). Air-tightness is ensured by a copper joint 1%. The rise in temperature can be supervised by a pyrometer probe 11. The HLi in powder form is introduced into the tank 1, the latter is then closed and the electric current is applied to the resistance 4. As a result of the temperature rise which results from the passage of the current, the HLi first melts and then decomposes before vaporization. By levigation, the two products of the decomposition become separated: the gaseous hydrogen escapes from the upper portion through the pipe 9 formed in the cover 2, while the liquid lithium collects in the lower part of the tank and is evacuated through the pipe 8.

The device shown in FIG. 2 is utilizable in a space apparatus, in a weightless condition, gravity being created by a field of centrifugal forces due to the rotation of the apparatus in which the decomposition and the separation of the hydrogen and the lithium take place.

With this device, a receptacle 1d provided with a flexible bottom 12 is in communication at its other extremity with a conduit 24. Along the course of this conduit there are successively seen:

A sleeve 18 surrounding the pipe 24 and containing an electric resistance 4 connected to the terminals 5 and 6, and a source of electric current or any other heating device;

A gear pump 25 of known type, utilizable for liquid metals;

A single or double helicoid 24a, surrounded by a heating sleeve 27, similar to the sleeve 18, and containing an electric resistance 28 or any other heating means. A pipe 8a intended for the outlet of the lithium separated by the helicoid, starts from the periphery of the latter, in the vicinity of its extremity. A pipe 9a, intended for evacuating the hydrogen, starts from the extremity of e the helicoid, in the extension of its axis.

The flexible bottom 12 may be for example a diaphragm of natural or synthetic rubber, for example of synthetic rubber manufactured from butadiene and which is sold under the name of Buna. It is fixed on the tank 1d by means of a removable ring 13 held in place by an edge 14 of this tank. A gas under pressure is applied against the upper face of the flexible bottom 12 through a conduit 14a removably fixed at 1412 on the upper extremity of the tank 1d.

The solid HLi (in powder or granular form) is introduced into the tank It! after having removed the flexible bottom 12 and the conduit 14a, which are then replaced in position. The solid HLi contained in the tank 1d is pushed by the gas under pressure acting on the diaphragm 12 and is evacuated through the conduit 24. This latter is heated by the electric resistance 4. It may also be heated by other means, for example in the case of propulsion of a satellite, by means of hot gases extracted from other apparatus of this satellite and passing through an appropriate heat exchanger.

The HLi, thus brought up to a temperature intermediate between its melting temperature and its temperature of decomposition, passes in the liquid state into the pump 25 which sends it under pressure into the helicoid 26, in which it is heated by the electric resistance 28 of the sleeve 27 to a temperature of about 1,000 C., at which it decomposes into gaseous hydrogen and liquid lithium.

The mixture of liquid lithium hydride, gaseous hydrogen and liquid lithium, pushed by the delivery pressure of the pump 25, begins a movement of rotation induced by the reaction forces of the surface of the helicoid or helicoids. After decomposition, the centrifugal force separates the lithium from the hydrogen approximately following the surface 29. The liquid lithium which is more dense, is projected to the periphery from which it is evacuated through a conduit 8a, while the less dense gaseous hydrogen remains in the centre from which it can be extracted through the pipe 9a.

The separated hydrogen and lithium are thus made available for supplying an electro-thcrrnic ejector.

The device shown in FIG. 3 also operates under conditions of absence of gravity. It comprises a tank 16, the filling extremity of which is arranged like that of the tank of FIG. 2, and similarly comprises a flexible bottom 12 fixed by a keeper-ring 13 and being subjected on its upper face to the pressure brought in through the conduit 14a. At the opposite end, this tank 1e terminates in a convergent neck 15 with a filter 16 at its inlet and a neck 17 at its outlet. A sleeve 18a surrounds the neck 15 and encloses an electric resistance 4 which can be supplied from the terminals 5 and 6 of a source of electric current. The sleeve may also be heated by other means, such as hot fluids. The neck 15 opens into a receptacle 19 of large diameter, provided with a cover 20 which closes it hermetically by means of a joint 1011. This receptacle is divided into two chambers 20 and 21 separated by a partition formed by two portions 22 and 23, the central portion 22 being porous.

The cover 2c and the partition 22 are passed through by the sleeve 18a containing the electric resistance 4, so that the outlet opening 17 of the neck 15 of the tank 12 opens into the second chamber 21.. Pipes 8b and 9b provide outlet openings on the chambers 21 and 20 respectively.

After removing the flexible bottom 12, as in the case of FIG. 2, the HLi is introduced in granular or powder form into the tank 16. The flexible bottom is replaced hermetically, the conduits 8b and 9b are closed and the resistance 4 is put under tension.

The pressure of a gas brought in through the conduit 14a is then applied on the flexible diaphragm. The portion of the HLi powder in the vicinity of the filter 16 melts at about 700 C. As soon as the fluidity is sufiicient, the substance under pressure passes through the filter 16. The temperature rises very rapidly since the heat is applied over a smaller and smaller section of the neck 15 so that the HLi is decomposed at the outlet 17 of the neck 15. The temperature should however remain sutficiently low so as not: to cause vaporization of the lithium. The conduits 8b and 9b are then opened. The mixture of liquid lithium and gaseous hydrogen thus passes, under the action of the pressure, into the chamber 21 and moves from the center towards the periphery. The porous wall 22 permits the hydrogen to pass only into the chamber 20, from which it is evacuated through the pipe 9b, when so required under partial vacuum, if the pressure on the flexible bottom 12 is not sufiicient.

The thickness of the layer of mixture is small and the portion of the mixture in contact with the wall 22 constantly changes due to its forward movements. The diam eter of the receptacle 19 is calculated so that only the liquid lithium reaches the periphery, from which it is evacuated by the pipes 8b. The time of contact of the substances with the porous wall can obviously be increased by giving them a longer travel, by sub-dividing the chamber 21 with partitions of suitable shape, of spiral shape for example, or by increasing the contact surface by non-planar faces.

Under the action of the pressure applied to the bottom 12, the lithium and hydrogen, thus separated, can be introduced into a thermo-electric ejector.

In order to apply the pressure on the lithium hydride in powder or granular form, any device equivalent to the diaphragm 12 of FIGS. 2 and 3 can be employed, for example the arrangement shown in FIGS. 3 and 5. In these figures, a piston is mounted inside the tank 1d. A joint 31 provides a fluid-tight seal. Three toothed wheels 32 fixed on the piston and arranged at along its periphery engage with three toothed racks 33 mounted along the generator lines of the cylinder which forms the wall of the tank. The three toothed wheels can be actuated separately or may be operated by a single shaft 34, arranged in the center (FIG. 5), and coupled mechanically to the toothed wheels, for example by bevel pinions 35, 36, 37 and 38, the first being keyed on the shaft 34, the following two on the intermediate shafts 39 and the last on the axis of the toothed wheels 32.

FIGS. 6 and 7 show diagrammatically two methods of supplying an electro-thermic ejector with a liquid propellent and a gaseous propellent, for example with lithium and hydrogen separated by the means above described.

The ejector is essentially constituted by a cathode 40 and an anode 41, between Which is struck an arc or a spark. When the apparatus is supplied with direct or alternating current from a source 42, an arc is obtained, whereas when the source 42 is made-up of condensers which discharge into the ejector, the operation is carried out discontinuously by sparks at a certain recurrent frequency. The propellent, which is introduced in a manner which will be described below, arrives in turbulence around the cathode and is then ionized by the passage of the current. These ionized gases then pass out at high speed through the discharge nozzle 43. An insulating sleeve 44 is interposed between the electrodes 40 and 41.

In FIG. 6, the anode 41 is of refractory metal which is a relatively poor conductor, such as stainless steel, and is enclosed in a casing 45 which forms around it a space 46 adapted to receive liquid lithium under pressure through an orifice 47. The anode 41 is pierced slightly downstream of the extremity of the cathode 40 with an orifice 48 for the introduction of the lithium, and this orifice may be constituted by a circular slot or by holes arranged in a ring.

The liquid lithium coming in under pressure to the annular cavity 46 passes through the orifice or orifices 48 and forms at the outlet into the ionization chamber 49 a surface having the form of a convex meniscus 48a which, by reason of the excellent conductivity of liquid lithium, serves as an anode proper and receives the impact of the are or the sparks which are formed between this surface and the cathode 40. The injection pressure of the liquid lithium is higher than that existing in the chamber 49. It is regulated in such manner that the whole of the lithium which flows out is vaporized by the jet at high temperature, taking account of the dimensions of the orifices 48. The separating surface 48a thus remains stationary, the flow-rate of the supply being equal to that of the consumption. The ionization of the lithium after its vaporization causes it to assist the production of the jet with the hydrogen. Although liquid lithium is much more conductive than the wall 41, the position of the orifices 48 is chosen in such manner that the liquid meniscuses 48a forming the wall of the anode are closer to the cathode than any other part of the discharge nozzle 43, so that the electrically-charged particles can effectively impinge against them.

The cathode 40 is fixed to a cathode carrier 50 which is separated from the anode by the insulator 44 and comprises an axial conduit 51 which opens into the ionization chamber 49 through the orifices 52, the hydrogen under pressure comes in through the conduit 51, passes out through the orifices 52 round the cathode and proceeds towards the point of the said cathode.

The form of construction of FIG. 7 only differs from that of FIG. 6 in that the cathode 4i] is pierced with a conduit 53 which is extended into the cathode carrier by a pipe 54, around which the conduit 51 forms an annular passage 51a communicating with the orifices 52. In this form of embodiment, the liquid lithium is sent simultaneously into the cavity 46 of the anode and into the conduit 54 communicating with the conduit 53 of the cathode, while the hydrogen is sent into the annular passage 51a and passes into the chamber 49 through the orifices 52, as in the arrangement shown in FIG. 6.

With this arrangement, the cathode 40 is also made of a metal which is relatively a poor conductor. The liquid lithium coming in through the conduit 53 forms at the outlet 53a of this conduit into the ionization chamber a meniscus which serves as the cathode proper, receiving the impact of the are or the sparks and vaporizing the lithium by a process similar to that which has been described with reference to the anode.

It will of course be evident that the orifices 48 and 52 (FIG. 6) or the orifices 48, 53a and 52 must be arranged and dimensioned so that the lithium and hydrogen produced by the decomposition of the lithium hydride are consumed as propellents in the electro-thermic ejector in suitably determined proportions.

What we claim is:

1. A method of supplying propellent to an electrothermic ejector, said method comprising the steps of: storing a nongaseous fluid substance of relatively high specific mass and capable of decomposing into at least one constituent of low molecular weight in the liquid state and one constituent of low molecular weight in the gaseous state; effecting the decomposition of said substance into said constituents; separating the constituent in the liquid state from the constituent in the gaseous state; and introducing separately as propellent into said electro-thermic ejector, the constituent in the liquid state on the one hand and the constituent in the gaseous state on the other.

2. A method as claimed in claim 1, in which said substance is lithium hydride.

3. A device for supplying propellent to an electrothermic ejector located in a field of gravity, said device comprising a heat-insulated tank adapted to receive lithium hydride in a finely-divided state, means for heating said tank to the temperature of decomposition of said lithium hydride so as to decompose said hydride to liquid lithium and gaseous hydrogen, means for collecting said liquid lithium at the lower portion of said tank and for conveying it under pressure into said electrothermic ejector, and means for collecting the gaseous hydrogen at the upper part of said tank and conveying it into said ejector.

4. A device as claimed in claim 3, in which said electrothermie ejector comprises an anode device, a cathode device, electrical energizing means for producing sparks across the gap between the anode device and the cathode device, and orifices for the introduction of the lithium arranged so as to receive the impact of said sparks, said means for sending the lithium under pressure into the ejector being disposed in such manner that the lithium forms at the outlet of said orifices a free surface which is renewed as and when the lithium is consumed in said ejector.

5. A device for supplying propellent to an electrothermic ejector in the absence of gravity, said device comprising a tank adapted to receive a non-gaseous fluid substance capable of being decomposed into at least one constituent in the liquid state and one constituent in the gaseous state, means in said tank for decomposing said substance into said constituents, means for applying pressure on said substance during the process of decomposition, means for separating the liquid constituent from the gaseous constituent, means for collecting said liquid constituent and for conveying it under pressure into said ejector, and means for collecting said gaseous constituent and for conveying it into said ejector.

6. A device as claimed in claim 5, in which said tank comprises an elastic diaphragm dividing the tank into a first chamber adapted to receive the non-gaseous fluid substance and a second chamber, and means for feeding a fluid under pressure into said second chamber to pressurize the same.

7. A device as claimed in claim 5, in which said tank is cylindrical and comprises a piston slidably mounted in said cylindrical tank and defining in said tank a chamber adapted to receive said non-gaseous fluid substance, and mechanical means for displacing said piston so as to compress said substance.

8. A device as claimed in claim 5, further comprising a separating device provided with helicoidal walls, means for sending said liquid and gaseous constituents mixed together and under pressure into said separating device, means for collecting the liquid constituent at the periphery of said separating device, and means for collecting the gaseous constituent in the axis of said separator device.

9. A device as claimed in claim 5, further comprising a separator device provided with a filtering wall dividing said separator into a first chamber and a second chamber, means for conveying the solid and liquid constituents mixed and under pressure into said first chamber in such manner that they flow along said filtering wall, means for collecting the liquid constituent in said first chamber and means for collecting said gaseous constituent in said second chamber.

10. A device as claimed in claim 9, and further comprising means for evacuating said second chamber.

11. A device as claimed in claim 5, in which said electro-therrnic ejector comprises an anode device, a cathode device, electrical energizing means for producing sparks across the gap between the anode device and the cathode device, and orifices for the introduction of said lithium arranged so as to receive the impact of the sparks, said means for sending the lithium under pressure into said ejector being arranged in such manner that the lithium forms at the outlet of said orifices a free surface which is renewed as and when said lithium is consumed in said ejector.

References Cited UNITED STATES PATENTS 3,082,314 3/1963 Arata et al. 219--75 3,149,459 9/1964 Ulam 60-35.5 3,159,967 12/1964 Webb 60-355 3,233,404 2/1965 Huber ct al. 60-35.5

CARLTON R. CROYLE, Primary Examiner.

MARK NEWMAN, Examiner.

Claims (1)

1. A METHOD OF SUPPLYING PROPELLENT TO AN ELECTROTHERMIC EJECTOR, SAID METHOD COMPRISING THE STEPS OF: STORING A NONGASEOUS FLUID SUBSTANCE OF RELATIVELY HIGH SPECIFIC MASS AND CAPABLE OF DECOMPOSING INTO AT LEAST ONE CONSTITUENT OF LOW MOLECULAR WEIGHT IN THE LIQUID STATE AND ONE CONSTITUENT OF LOW MOLECULAR WEIGHT IN THE GASEOUS STATE; EFFECTING THE DECOMPOSITION OF SAID SUBSTANCE INTO SAID CONSTITUENTS; SEPARATING THE CONSTITUENT IN THE LIQUID STATE FROM THE CONSTITUENT IN THE GASEOUS STATE; AND INTRODUCING SEPARATELY AS PROPELLENT INTO SAID ELECTRO-THERMIC EJECTOR, THE CONSTITUENT IN THE LIQUID STATE ON THE ONE HAND AND THE CONSTITUENT IN THE GASEOUS STATE ON THE OTHER.

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