Patent GB-949240-A (GB)
Title: Reaction propulsion means
IPC: B64G1/40
Filed: 1961-10-03
Abstract: 949,240. Jet propulsion plant. AEROJET-GENERAL CORPORATION. Oct. 3, 1961 [Nov. 23, 1960], No. 35646/61. Heading F1J. A jet propulsion system for producing thrust in a substantial vacuum comprises a body of liquid having a vapour pressure not greater than 10<SP>-5</SP> mm of mercury at about 20‹C, the liquid being contained in a chamber having minute openings through which the liquid can pass, liquid dispersion means being disposed adjacent the openings. Means are provided for subjecting the contained liquid to a relatively high electric potential, and further means are provided for creating and maintaining a gradient electrostatic field in spaced relation to the liquid dispersion means whereby charged droplets of the liquid are ejected from the dispersion means as the result of the high potential and are focused and accelerated in any desired direction, there also being means for injecting negative particles into the droplets after they have been focused and accelerated. In Fig. 1 liquid 34 is contained in a chamber 32 which is provided with openings 28 in one wall thereof, the liquid being subjected to a high positive voltage by means of a circular electrode 36 which is connected to the positive terminal of the electrostatic generator 10 through line 20. The generator may be a Van de Graaff type generator driven by a turbine 14, the working fluid of which is heated in a nuclear reactor 12. The liquid passes through the openings 28 under the influence of a force such as applied pressure or capillary attraction. A drift tube assembly 38 is arranged adjacent the openings 28 and comprises drift tubes or accelerating rings surrounding the stream of the charged colloidal droplets 40. The drift tube 30 nearest the discharge openings 28 is connected to the positive line 20 of the generator 10 through a portion 44 of the voltage divider 46, the remaining drift tubes being connected to further tappings along the divider, so that the voltage gradient varies from positive adjacent the openings 28 to neutral at the first drift tube 30 and to a high negative valve at the furthest drift tube 42. A shield member enclosing an electron or negative ion emitter 48 is disposed adjacent the drift tube 42, the emitter being powered by a separate voltage source, not shown and the shield being connected to the same high negative potential as the ring 42. The function of the emitter 48 is to overcome the space charge repulsion phenomena. The spray bank assembly is shown in greater detail in Fig. 2, the assembly comprising a plurality of steel pins 52 which project through the openings 28<SP>1</SP>. The alternative spray bank assembly shown in Fig. 4 comprises a plurality of capillary tubes 58 through which the liquid 34<SP>11</SP> passes, the liquid being atomised from the pointed outer ends thereof. The potential at the spray bank electrode 36 may be +100 kilovolts and that at the furthest drift tube 42-1,000 kilovolts. In Fig. 6 the spray bank is a combination of the needle and capillary tube arrangements shown in Fig. 2 and 4. The means for neutralizing the space charge in this embodiment comprises passing the colloid beam through a rarefied neutral gas stream 60 in such a manner that corona discharge induced by voltage gradients on the charged colloidal particles occurs in the gas 60, the electric charge on the rapidly moving colloidal droplets being transferred to the slower moving gas. The gas 60 is formed by heating liquid contained in a tank 62, the vapour being supplied to the nozzle 66 by a pump 64, the gas being subsequently passed to a condenser 70. Further spray bank assemblies utilizing sharp knife edges instead of points are described. Suitable liquids for use as propellants are dioctylphthalate, polypropylene glycol and glycerine. Desirable properties of the liquid are given. The liquid may alternatively be subjected to a high negative voltage, the resulting charged particles being passed through a gradient electrostatic field which becomes more positive in potential. The point of emission of the atomised droplets may alternatively be maintained at earth potential, the accelerating rings or drift tubes being maintained at high negative or positive voltage. The term colloid is used in the Specification to mean a substance in a state of fine division, the particles thereof varying in diameter from about 0À2 to about 0À005 micron.