Description:PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
Embodiments of the present disclosure generally relate to micro-propulsion systems, and more particularly relate to a capillary-fed evaporative micro-thruster apparatus and method for generating thrust in a satellite. The capillary-fed evaporative micro-thruster apparatus and method may include the vaporization of liquid propellant and controlled generation of thrust for satellite maneuvering and attitude regulation.
BACKGROUND
Generally, the ongoing developments in the space sector, directed towards reducing the cost of launching and deploying satellites, have encouraged the adoption of compact small satellites, including standardized CubeSat platforms, for scientific, commercial, and research applications. However, the deployment of compact small satellites encounters micro-propulsion related challenges due to restrictive size, mass, and available power. In contemporary, compact small satellites mission profiles, involving precise attitude control, orbit transfer, and station-keeping maneuvers, demand on-board micro-propulsion systems delivering finely metered low-magnitude thrust within the micronewton to millinewton range. Concurrently, strict volume, mass, and power constraints imposed by compact satellite platforms require micro-propulsion architectures maintaining reliable and sustained mission performance.
Additionally, the various micro-propulsion technologies have been investigated to satisfy the thrust and control requirements of compact small satellite missions. The technologies include field-emission electric micro-propulsion systems (FEEP), miniaturized colloid devices (electrospray) thrusters, pulsed-plasma, and resistojet thrusters, together with miniaturized forms of cold-gas, chemical, and hall effect thrusters. However, many conventional micro-propulsion arrangements occupy a significant portion of the already limited spacecraft volume or require complex electrical drive circuitry, specialized propellant handling assemblies, or intricate thermal management architectures. Hence, within the range of micro-propulsion technologies, micro-resistojet systems, and in particular Vaporizing Liquid Microthrusters (VLMs), gain recognition for utilizing low-pressure liquid propellants stored in lightweight tanks, reducing overall propellant storage mass and associated structural reinforcement requirements otherwise necessary for high-pressure containment.
However, the existing VLM implementations have been demonstrated across different fabrication platforms. One approach uses silicon-based micro-electro-mechanical structures to examine packaging influence on heating and vapor generation. Another approach incorporates microfabricated channels formed through wet chemical etching of silicon to vaporize preheated liquid propellants. Additional developments adopt ceramic-based substrates including Low Temperature Co-Fired Ceramic (LTCC) and High Temperature Co-Fired Ceramic (HTCC), offering reduced thermal conductivity and simplified fabrication processes compared to silicon. Further known implementations include Film-Evaporated MEMS Tunable Array (FEMTA) arrangements to generate vapor at a controlled meniscus near the nozzle exit, and the VLM arrangements incorporating integrated microsensors with localized heating elements for regulating vapor-liquid distribution and temperature.
Consequently, the VLM based micro-propulsion systems continue to exhibit thrust instability and operational reliability challenges. Therefore, the vaporization within micro-scale channels induces two-phase boiling dynamics leading to fluctuating vapor generation and inconsistent thrust. Hence, the systems operating with water or similar liquid propellants is more susceptible to passive propellant leakage and unintended liquid expulsion under low-pressure conditions encountered in space. Additionally, ice formation at or near the nozzle exit in low-vacuum environments restricts flow and degrades micro-propulsion performance. Attempts to counteract instability through additional sensing elements or localized heaters result in increased structural complexity, fabrication difficulty, and power consumption. Accordingly, existing VLM based micro-propulsion systems remain limited in effectively controlling vaporization stability and propellant handling, reducing suitability for compact satellite missions with severe resource constraints.
However, despite ongoing advancements, conventional VLM based micro-propulsion systems continue to exhibit limitations in thrust stability and operational reliability. In particular, micro-flow boiling instabilities within microchannels of the heating chamber frequently result in fluctuating vapor-generation rates and inconsistent thrust output. Conventional configurations also experience passive propellant leakage, unintended expulsion of liquid water under low-pressure conditions, and ice accumulation at the nozzle exit in low-vacuum environments, each issue contributing to degraded micro-propulsion performance. Additionally, the conventional VLM based micro-propulsion configurations provide functional thrust generation and in consequence, the persistent boiling-driven vaporization instability and propellant handling limitations constrain suitability for compact satellite missions operating under strict mass and power constraints.
Consequently, there is a need in the art for a capillary-fed evaporative micro-thruster apparatus and method for generating thrust in a satellite, to address at least the aforementioned issues in the prior arts.
SUMMARY
This summary is provided to introduce a selection of concepts, in a simple manner, which is further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the subject matter nor to determine the scope of the disclosure.
An aspect of the present disclosure provides a capillary-fed evaporative micro-thruster apparatus for generating thrust in a satellite. The capillary-fed evaporative micro-thruster apparatus includes a propellent reservoir, an evaporation chamber, a capillary wick structure, a heating element and a nozzle with a shutter disposed at an opening of the nozzle. The propellent reservoir may store a liquid propellant. The evaporation chamber may be in fluid communication with the propellant reservoir. The capillary wick structure connects the propellant reservoir to the evaporation chamber. Further, the liquid propellant may be passively transported from the propellant reservoir to the evaporation chamber via a capillary action. Furthermore, the evaporation chamber and the propellant reservoir may be individually sealed components coupled through the capillary wick to form a continuous liquid transport path. The heating element may be thermally coupled to at least one portion of the capillary wick structure within the evaporation chamber. Further, the heating element, locally heat the liquid propellant delivered by the capillary wick structure. Furthermore, the heating element induces evaporation of the liquid propellant at a wick surface of the capillary wick structure within the evaporation chamber. The nozzle positioned at the one end of the evaporation chamber, with a shutter disposed at an opening of the nozzle, discharge the vapor to generated thrust.
Another aspect of the present disclosure includes a method for generating thrust in a satellite using a capillary-fed evaporative micro-thruster apparatus. The method includes, storing, by a capillary-fed evaporative micro-thruster apparatus, a liquid propellant in a propellant reservoir. Further, the method includes, transferring passively, by the capillary-fed evaporative micro-thruster apparatus, the liquid propellant to an evaporation chamber from propellant reservoir via a capillary wick structure by passive capillary action. Furthermore, the method includes, applying, by the capillary-fed evaporative micro-thruster apparatus, localized heat to the capillary wick structure within the evaporation chamber to evaporate the transferred liquid propellant and generate vapor. Subsequently, the method includes, expelling, by the capillary-fed evaporative micro-thruster apparatus, the generated vapor through a nozzle, with a shutter disposed at an opening of the nozzle, to generate thrust.
To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identify the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
FIG. 1 illustrates an exemplary block diagram representation of a capillary-fed evaporative micro-thruster apparatus and method for generating thrust in a satellite, in accordance with some embodiments of the present disclosure;
FIG. 2 illustrates an exemplary cross-sectional view of a capillary-fed evaporative micro-thruster apparatus and method for generating thrust in a satellite such as those shown in FIG. 1, in accordance with some embodiments of the present disclosure;
FIG. 3 illustrates an exemplary schematic diagram of the experimental setup of a capillary-fed evaporative micro-thruster apparatus and method for generating thrust in a satellite, in accordance with some embodiments of the present disclosure;
FIG. 4 illustrates an exemplary pictorial representation depicting the experimental setup of the various operational configurations of the evaporation chamber, in accordance with some embodiments of the present disclosure;
FIG. 5 illustrates a graphical representation of the capillary wicking behaviour and the corresponding reservoir pressure response during the controlled pressure feeding process, in accordance with some embodiments of the present disclosure;
FIG. 6 illustrates a graphical representation of the temporal variation of pressure and temperature during the controlled pressure feeding process and corresponding choked mass flow rate, in accordance with some embodiments of the present disclosure;
FIG. 7 illustrates a graphical representation of the temporal variation of pressure and temperature, in different components of the device and vacuum chamber and the mass flow rate and power, during the controlled pressure feeding process, in accordance with some embodiments of the present disclosure, in accordance with some embodiments of present disclosure;
FIG. 8 illustrates a graphical representation of the variations in mass flow rate, thrust, and specific impulse from the device, along with a comparative bar chart against existing micro-propulsion technologies, in accordance with some embodiments of present disclosure; and
FIG. 9 illustrates an exemplary flowchart of a method for generating thrust in a satellite, in accordance with some embodiments of present disclosure.
Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure. It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
In the present document, the word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or implementation of the present subject matter described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.
The terms “comprises”, “comprising”, “includes”, “including” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, device or method that includes a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or method.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the invention. In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
In the present disclosure, terms such as “upper”, “lower”, “left”, “right”, “front”, “rear”, “vertical”, “horizontal”, “side”, “bottom”, and the like, may refer to an orientation or a positional relationship based on that shown in the drawings, and are merely relational terms, which are used for convenience in describing structural relationships of various components or elements of the present invention, and do not denote any one of the components or elements of the present disclosure, and are not to be construed as limiting the present invention.
In the present disclosure, terms such as “fixedly attached”, “movably coupled”, “connected”, “coupled”, and the like are to be construed broadly and refer to either a fixed connection, or a movable, or an integral or removable connection; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the terms in the present disclosure can be determined according to circumstances by a person skilled in the relevant art or the art and is not to be construed as limiting the present disclosure.
Embodiments of the present disclosure provides a capillary-fed evaporative micro-thruster apparatus for generating thrust in a satellite. The capillary-fed evaporative micro-thruster apparatus includes a propellant reservoir, an evaporation chamber, a capillary wick structure, a heating element, and a nozzle with a shutter disposed at an opening of the nozzle. The propellant reservoir may be configured to store a liquid propellant. The evaporation chamber may be in fluid communication with the propellant reservoir. The capillary wick structure may be positioned to establish a continuous liquid transport path between the propellant reservoir and the evaporation chamber, enabling passive transfer of the propellant via capillary action, without requiring active pumping components. Further, the propellant reservoir and the evaporation chamber may be individually sealed components mechanically and fluidically coupled through the capillary wick structure. The heating element may be thermally coupled to a portion of the capillary wick structure located within the evaporation chamber. The heating element may be configured to locally supply heat to the liquid propellant delivered through the capillary wick structure, thereby facilitating evaporation of the liquid propellant at the wick surface. The nozzle may be positioned at one end of the evaporation chamber, with a shutter disposed at an opening of the nozzle and may be configured to discharge the generated vapor to produce thrust.
Furthermore, the method for generating thrust in a satellite using a capillary-fed evaporative micro-thruster apparatus includes storing a liquid propellant in a propellant reservoir. The method further includes passively transporting the liquid propellant from the propellant reservoir to an evaporation chamber through a capillary wick structure by capillary action. The method additionally includes applying localized heat to the portion of the capillary wick structure disposed within the evaporation chamber to evaporate the transported liquid propellant and generate vapor. The method then includes expelling the generated vapor through a nozzle, with a shutter disposed at an opening of the nozzle, to produce thrust.
Referring now to the drawings, and more particularly to FIGs. 1 through FIG. 9 where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments, and these embodiments are described in the context of the following exemplary system and/or method.
FIG. 1 illustrates an exemplary block diagram representation of a capillary-fed evaporative micro-thruster apparatus 100 and method for generating thrust in a satellite, in accordance with some embodiments of the present disclosure. In an embodiment, the capillary-fed evaporative micro-thruster 100 may include a propellant reservoir 102 (interchangeably referred to as reservoir 102), a capillary wick structure 104, an evaporation chamber 106, a heating element 108 ((interchangeably referred to as heater 108), a nozzle 110, and a shutter 112 disposed at an opening of the nozzle 110.
In an embodiment, the propellant reservoir 102 may be configured to store a liquid propellant. Further, the liquid propellant may include liquids such as, but not limited to, deionized water, ethanol, a dielectric working fluid, a methanol, a fluorinated fluid, and/or combinations thereof, as well as other similar liquid propellants. Further, the propellant reservoir 102 may be configured to maintain a reservoir pressure during transportation of the liquid propellant, corresponding to a saturation pressure of the liquid propellant at a feeding temperature.
In an embodiment, the evaporation chamber 106 may be configured to fluidly connected to the propellant reservoir 102 via the capillary wick structure 104. Further, the evaporation chamber 106 may function as a dedicated zone for liquid-to-vapour conversion. Further, the evaporation chamber 106 may incorporate the shutter disposed at an opening of the nozzle 110 for enabling controlled expansion of the generated vapour. Further, the evaporation chamber 106 may be configured to configured to maintain a steady-state pressure during operation, independent of external vacuum chamber pressure variations, for suppressing ice formation at the wick surface under low-vacuum conditions, and to obtain choked flow through the nozzle 110 which may include a shutter 112 disposed at an opening of the nozzle 110.
Further, the propellant reservoir 102 and the evaporation chamber 106 may be fabricated from materials such as, but not limited to, acrylic, glass, silicon, metallic, polymeric, and/or ceramic materials joined by adhesive sealing and/or micro-bonding techniques. Further, the material acrylic may be preferred due to the characteristics such as transparency, enabling visual accessibility during experimental testing. Further, for materials such as acrylic, adhesive sealing may be used, as acrylic supports the method. For other materials, appropriate sealing techniques may be adopted, for example, fusion welding for metallic components and/or suitable bonding processes for ceramic-based designs.
In an embodiment, the capillary wick structure 104 may be connected to the propellant reservoir 102 to the evaporation chamber 106. Further, the capillary wick structure 104 may be axially inserted through a central aperture of an intermediate plate connecting the propellant reservoir 102 and the evaporation chamber 106.
Further, the capillary wick structure 104 may include, but not limited to a porous hydrophilic material having a predefined capillary retention limit to retain the liquid propellant against a pressure differential under low-vacuum conditions. Further, the porous hydrophilic material may include materials such as but not limited to, cellulose paper, sintered metal, porous ceramic, fibrous, composite fiber, micro-machined body with interconnected pores of sub millimeter dimension.
Further, the capillary wick structure 104 may passively transport the liquid propellant from the propellant reservoir 102 to the evaporation chamber 106 via a capillary action. Further, the propellant reservoir 102 and the evaporation chamber 106 may be individually sealed components coupled through the capillary wick structure 104 to form a continuous liquid transport path. Further, the capillary wick structure 104 may be hydrophilic and possess sufficient capillary (retention) pressure to hold the liquid propellant against vacuum.
In an embodiment, the heating element 108 may be thermally coupled to at least one portion of the capillary wick structure 104 within the evaporation chamber 106. Further, the heating element 108 may include a thin polyimide film incorporating a flexible resistive heater circumferentially wound around a predefined section of the capillary wick structure disposed within the evaporation chamber 106. Further, the thin polyimide film may include resistive material such as, but not limited to, titanium, nickel-chromium, constantan, micro-fabricated heaters, and the like. Further, the heating element 108 may be configured to locally heat the liquid propellant delivered by the capillary wick structure 104. Further, the heating element 108 may induce evaporation of the liquid propellant at a wick surface of the capillary wick structure 104 within the evaporation chamber 106. Further, the capillary wick structure 104 may be thermally insulated from the propellant reservoir 102 region to limit heat transfer to stored propellant.
In an embodiment, the shutter 112 disposed at an opening of the nozzle 110, may be positioned at the one end of the evaporation chamber 106, configured to discharge the vapor to generated thrust. Further, the shutter 112 disposed at an opening of the nozzle 110, may be configured to discharge the vapor as a choked flow state to generate a stable thrust output independent of external vacuum pressure variations.
Those skilled in the art will recognize that, for simplicity and clarity, the full structure and operation of all data processing systems suitable for use with the present disclosure are not being depicted or described herein. Instead, only so much of the capillary-fed evaporative micro-thruster 100 as is unique to the present disclosure or necessary for an understanding of the present disclosure is depicted and described. The remainder of the construction and operation of the capillary-fed evaporative micro-thruster 100 may conform to any of the various current implementations and practices that were known in the art.
FIG. 2 illustrates an exemplary cross-sectional view 200 of a capillary-fed evaporative micro-thruster 100 apparatus and method for generating thrust in a satellite such as those shown in FIG. 1, in accordance with some embodiments of the present disclosure. Further, the cross-sectional view 200 of a capillary-fed evaporative micro-thruster 100 may include a base plate 202, the reservoir 102, an intermediate plate 204, a wick temperature (Tw) 206, the heater 108, an evaporating length of wick 208, an evaporation chamber 106, a nozzle plate 210, a nozzle 110, a shutter 112, an evaporation chamber temperature (TEC) 212, an evaporation chamber pressure (PEC) 214, a DC power supply 216, a reservoir temperature (TR) 218, a water feedline 220 (interchangeably referred to as vacuum pump).
In an embodiment, the capillary-fed evaporative micro-thruster 100 may include the base plate 202 enclosing a bottom portion of the reservoir 102 and the intermediate plate 204 enclosing a top portion of the reservoir 102. Further, the evaporation chamber 106 may be disposed on the intermediate plate 204, with the nozzle plate 210 enclosing an upper portion of the evaporation chamber 106.
Further, the base plate 202 positioned at the bottom may serve as the foundation of the capillary-fed evaporative micro-thruster 100. Further, the base plate 202 may include a planar base surface having a circular and/or spherical profile, configured to support the reservoir 102 and establish a sealed mounting arrangement. Further, the reservoir 102 may be mounted directly on top of the base plate 202 for storing the working fluid such as the DI Water (Deionized Water). Further, the intermediate plate 204 may be positioned on top of the reservoir 102.
Further, the intermediate plate 204 may include a central hole having a diameter of 9.9 ± 0.1 mm, configured to accommodate the capillary wick structure 104. Further, the intermediate plate 204 may have a thickness of 6 mm and may be coupled to the reservoir 102 for structural stability and sealing.
Further, the capillary wick structure 104 may include a paper-based material with an outer diameter of 10 mm and a length of 100 mm, the capillary wick structure 104 may be inserted through the central hole of the intermediate plate 204 to draw liquid from the reservoir 102 into the evaporation chamber 106 via capillary action.
Further, a flexible polyimide film-insulated heater 108, such as Omega KHLVA-203 having dimensions of 20 mm width and 35 mm length, may be wrapped around the capillary wick structure 104 to induce localized heating. Further, only the cylindrical surface of the capillary wick structure 104 located above the heater 108, corresponding to an evaporating length of wick 208 of approximately 27 mm, may remain exposed for evaporation, while the remaining portion may be insulated.
Further, the reservoir 102 and the evaporation chamber 106 may include cylindrical shape with inner diameter of 30mm and outer diameter of 38mm and a length of 80mm. Further, the evaporation chamber 106 may be mounted above the intermediate plate 204 to surround the exposed capillary wick structure 104 and heater 108. Further, a nozzle plate 210 may be arranged on top of the evaporation chamber 106, the nozzle plate 210 including a central orifice of 0.6 mm diameter forming a nozzle 110 with a shutter disposed at an opening of the nozzle 110, configured to permit vapor to escape and generate thrust. Further, all the components of the reservoir 102 and the evaporation chamber 106 may be bonded using materials such as, but not limited to, 3M Scotch-Weld Epoxy DP100 to ensure vacuum sealing. Further, the capillary-fed evaporative micro-thruster 100 may include temperature sensors configured to measure the wick temperature (TW) 206, the evaporation chamber temperature (TEC) 212, and the reservoir temperature (TR) 218, and a pressure sensor configured to monitor an evaporation chamber pressure (PEC) 214.
Further, feedthroughs may be provided to allow electrical connections for the sensors and the heater 108 while maintaining vacuum integrity. Further, the reservoir 102 may include a fluid inlet and/or outlet configured for DI Water (Deionized Water) and/or connection to a vacuum pump 220. Further, the heater 108 may be powered via a DC power supply 216. Further, in operation, the Deionized Water (DI Water) from the reservoir 102 may be wicked through the capillary wick structure 104 into the evaporation chamber 106, locally evaporated by the heater 108. Further, the resulting vapor may be expelled through the shutter 112 disposed at an opening of the nozzle 110 to produce thrust, with temperature and pressure sensors enabling operational monitoring. Further, capillary-fed evaporative micro-thruster 100 may be fabricated using materials such as, but not limited to, acrylic to enable visualization of liquid wicking through the capillary wick structure and the corresponding depletion of liquid inside the reservoir, which supports monitoring of the evaporation rate and vapor flow.
FIG. 3 illustrates an exemplary schematic diagram of the experimental setup 300 of a capillary-fed evaporative micro-thruster 100 apparatus and method for generating thrust in a satellite, in accordance with some embodiments of the present disclosure. In an embodiment, the schematic diagram of the experimental setup 300 may include a vacuum chamber 302, a vacuum pump 220, a fluid reservoir 316, a solenoid switch 318, a pressure controller 320, a plurality of valves including, a valve (V1) 310, a valve (V2) 312, a valve (V3) 314, a pressure sensor 322, a thermocouple feedthrough 328, an electric feedthrough 330, a camera 326, a computer 334, a DAQ 332, a temperature sensor 324 and a DC power supply 216.
In an embodiment, the vacuum chamber 302 may include a device 304 with the evaporation chamber 106, the reservoir 102, a vacuum chamber feedthrough 306, and a water level measuring scale 308 and plurality of thermocouples such as the evaporation chamber temperature (TEC) 212, wick temperature (TW) 206 and reservoir temperature (TR) 218.
In an embodiment, the vacuum chamber 302 may include a cuboidal chamber constructed using acrylic material with a wall thickness of 25 mm and an internal volume of approximately 30 cm³, configured to include transparent walls for visual monitoring of liquid level variations and capillary-fed evaporation behaviour occurring inside the vacuum chamber 302.
Further, the vacuum pump 220 may include a double-stage rotary vacuum pump 220 such as, but not limited to, for example, Indvac-IVP-250 (250 LPM), coupled to the vacuum chamber 302 for evacuating the chamber. Further, the pressure within the vacuum chamber 302 may be maintained at approximately 50 ± 10 Pa (Pascals) using a solenoid switch 318 actuated by the pressure controller 320 including a vacuum pressure transducer. Further, the pressure controller 320 may include, such as, but not limited to, for example, Thyracont VD6S2230. Further, the response time of the pressure controller 320 may be 200ms. Further, the vacuum pressure transducer may include, such as, but not limited to, for example, Thyracont VSP63MA4. Further, the vacuum pressure transducer may include a response time of 50ms and an accuracy of an accuracy of ten percent of full scale over a measurement range of 20 to 0.002 mbar (millibar). Further, the vacuum chamber 302 may include the thermocouple feedthrough 328, the electric feedthrough 330, and plurality of valves including the valve (V1) 310, the valve (V2) 312, and the valve (V3) 314 configured for water feeding and vacuum pump 220 connections. Further, the vacuum pressure transducer and thermocouple TVC may be used to monitor the pressure and temperature within the vacuum chamber 302.
Further the temperature of the reservoir 102 may be measured by the reservoir temperature (TR) 218 and the pressure and the temperature inside the evaporation chamber 102 of the device 304 may be measured by the pressure sensor 322 and the thermocouple TEC, respectively. Further, the data acquisition system, DAQ 332 may include, for example, a Keysight DAQ970A, configured to record the temperature and pressure measurements at a sampling rate of 1 Hz. Further, the collected data may be transferred to the computer 334 for display, processing, storage, and analysis.
Further, the heating element 108 may be powered using the DC power supply 216, such as, for example, but not limited to, a GW Instek, GPP-4323, configured to deliver voltage and current with measurement accuracy of approximately ±(0.03% + 10 mV) and ±(0.03% + 10 mA), respectively, for controlled heating of the capillary wick structure 104 to induce evaporation.
Further, the depletion of liquid inside the reservoir 102 during operation may be visually monitored through the transparent acrylic structure of the vacuum chamber 302 using the camera 326, such as, but not limited to, a DSLR (Digital Single-Lens Reflex) camera (Nikon D850) operating at approximately 60 fps and spatial resolution of approximately 40 μm/pixel, enabling quantitative evaluation of evaporation rate and vapor-generation behaviour.
FIG. 4 illustrates an exemplary pictorial representation depicting the experimental setup 400 of the various operational configurations of the evaporation chamber, in accordance with some embodiments of the present disclosure. In an embodiment, the pictorial representation depicting the experimental setup 400 of the various operational configurations of the evaporation chamber. Further, various configurations may include three parts of the experimental setup 400 such as, without evaporation chamber 402, without controlled pressure feeding 404 and with controlled pressure feeding 406.
Further, the experimental setup 400 without evaporation chamber 402 may include part (a-c) depicting the ice formation without the evaporation chamber 106. Further, the experimental setup 400 without controlled pressure feeding 404 may include part (d-f) depicting the prevention of ice formation using the evaporation chamber 106. Further, the experimental setup 400 with controlled pressure feeding 406 may include part (g-i), depicting the ejection of liquid from the surface of the capillary wick structure 104, using the evaporation chamber 106.
Further, the part (a-c) of the FIG. 4 illustrates a sequence of time-resolved images depicting the sudden formation of ice on the surface of the capillary wick structure 104 due to the absence of the evaporation chamber 106. Further, in the arrangement, the capillary wick structure 104 remains directly exposed to a low-pressure environment inside the vacuum chamber 302. Further, upon feeding the water into the propellant reservoir 102 under low vacuum condition, for example, approximately 100 Pa inside wick structure the vacuum chamber 302, and the water rises through the capillary wick structure 104 via capillary action and reaches the surface of the capillary wick structure 104. Further, under low-pressure conditions, rapid evaporation may occur at the surface of the capillary wick structure 104, leading to pronounced evaporative cooling and the immediate formation of ice.
Further, the part (d-f) of FIG. 4 illustrates a sequence of time-resolved images depicting the effect of the evaporation chamber 106 enclosing the capillary wick structure 104. Further, the evaporation chamber 106 forms a confined region around the capillary wick structure 104, and vapor generated at the surface of the capillary wick structure 104, escapes solely through the shutter 112 disposed at an opening of the choked nozzle 110. Further, due to the restricted vapor release path, the pressure within the evaporation chamber 106 attains a comparatively higher steady-state level, for example, approximately 1110 Pa (Pascals) under a no-power condition. Further, under elevated chamber pressure conditions, evaporative effect becomes too weak to support frost development, which results for the surface of the capillary wick structure 104 to stay free of ice. Further, the supplied liquid rising to the surface of the capillary wick structure 104 may not fully convert to vapor, and the leftover liquid may gather throughout the evaporation chamber 106 and form visible liquid collect around the area of the capillary wick structure 104.
Further, similar to ice formation, water ejection from the surface of the capillary wick structure 104 and subsequent accumulation across the evaporation chamber 106 represents another undesirable effect observed under low vacuum pressure. Further, a capillary wick structure 104 may include reduced pore scale to retain water at the surface and limits outward movement. Further, the shutter 112 disposed at an opening of the nozzle 110 outlet, has a scale below a critical value near one micro-meter to prevent water escape. Further, smaller pore scale strengthens capillary retention force under low vacuum pressure, lowering the likelihood of water ejection. Further, control of pore scale at the level enables fabrication on solid-state substrates using established micro–nano patterning techniques. Further, for a paper-based capillary wick structure 104, achieving the required pore scale may include a challenge. Further, to counter water ejection under low vacuum pressure, a regulated pressure feed methodology ensures control over liquid movement.
Further, the part (g–i) of FIG. 4 illustrates a sequence of time-resolved images depicting the effect of applying a controlled pressure feeding approach to address water accumulation around the capillary wick structure 104. Further, through regulation of the pressure differential between the propellant reservoir 102 and the evaporation chamber 106, the rate of water transport into the capillary wick structure 104 remains balanced relative to the rate of vapor release. Further, the controlled pressure feeding approach suppresses water ejection and pooling near the capillary wick structure 104 and promotes stable evaporation from the exposed surface of the capillary wick structure 104. Further, under the regulated pressure condition, the surface of the capillary wick structure 104 remains free of ice formation and excess water accumulation.
FIG. 5 illustrates a graphical representation of the capillary wicking height 502 behaviour and the corresponding reservoir pressure 504 response during the controlled pressure feeding process 500, in accordance with some embodiments of the present disclosure. Further, the graphical representation of the wicking height 502 behaviour may include part (a) and corresponding reservoir pressure 504 may include part (b). Further, the part (a) of the FIG. 5 may include the variation of capillary rise height of the liquid within the capillary wick structure 104 over time during the controlled pressure feeding process. Further, the controlled pressure feeding method ensures the pressure difference across the capillary wick structure 104, denoted (〖∆P〗_CW ), remains below the capillary retention limit 〖(∆P〗_ret) during the feeding process 〖∆P〗_ret>〖∆P〗_CW. Further, the pressure difference across the capillary wick structure 104 may be expressed as 〖∆P〗_CW=P_R-P_EC, where P_R represents pressure at the propellant reservoir 102 and P_EC represents pressure at the evaporation chamber 106. Further, the capillary retention limit of the capillary wick structure 104 may be determined through capillary rate-of-rise tests, tracking spontaneous rise of liquid due to capillary forces upon contact with the capillary wick structure 104. Further, the capillary retention limit may be calculated using Washburn equation, expressed as 〖∆P〗_ret=h(με/K dh/dt+ρg), where μ represents the dynamic viscosity of the liquid, ε and K represents the porosity and permeability of the capillary wick structure 104, h represents height of the liquid column, ρ represents density of the liquid, g represents the gravitational acceleration, and dh/dt represents velocity of the meniscus. Further, the rise velocity dh/dt may be obtained from the curve of capillary rise height versus time, shown as an inset of part (a) of the FIG. 5. The capillary retention limit may characterize based on capillary rise behaviour of a wick structure, as illustrated by representative height-versus-time data of part (a) of FIG. 5. Further, such characterization may be performed using an analytical and/or empirical relation consistent with capillary flow principles, including Washburn-type behaviour, to relate capillary driving forces with viscous and gravitational effects.
Further, the capillary retention limit may be derived from fitting parameters and/or characteristic ratios obtained from such relations, without limitation to a specific computational tool and/or numerical method. Further, the resulting capillary retention limit may be dependent on the properties of the wick used, including material composition, porosity, permeability, pore geometry, and surface characteristics, and therefore may vary across different wick configurations. Further, the wick structures configured to provide relatively high capillary retention limits support enhanced fluid retention, stability, and transport performance of capillary-driven systems. Further, the inset of part (a) of FIG. 5 may represent a representative flow regime where capillary, viscous, and gravitational forces collectively govern fluid motion, enabling estimation of capillary performance characteristics associated with the evaluated wick structure. Further, the values obtained through such analysis provide illustrative or comparative reference supporting evaluation of capillary performance associated with selected wick configurations.
Further, the part (b) of the FIG. 5 may include the vacuum chamber 302 and evaporation chamber 106 reaching approximately 4000 Pa, followed by water supplied to the reservoir by opening the valve (V3) 314. Further, the opening of the valve (V3) 314, the pressure of the propellant reservoir 102 rises almost instantaneously to the saturation pressure of water corresponding to the feeding temperature (approximately 4010 Pa at 29 °C). Further, the verification occurred through a separate water-feeding experiment with pressure and temperature measurements of the propellant reservoir 102. Further, after feeding the desired quantity of water to the propellant reservoir 102, the valve (V3) 314 may be closed.
FIG. 6 illustrates a graphical representation of the temporal variation of pressure and temperature during the controlled pressure feeding process and corresponding choked mass flow rate 600, in accordance with some embodiments of the present disclosure. Further the FIG. 6 may include part (a) depicting the Pressure-time graph 602 and part (b) depicting the Temperature-time 604. Further, the part (a) depicting the Pressure-time graph 602 of the FIG. 6 may include the measured pressure values of the evaporation chamber 106 and the vacuum chamber 302. Further, the water imbibed through the capillary wick structure 104 may evaporate and the generated vapor flows out through the shutter 112 disposed at an opening of the choked nozzle 110. Further, the presence of the evaporation chamber 106 around the capillary wick structure 104 may expose the capillary wick structure 104 to a relatively high pressure compared to configurations without the evaporation chamber 106, preventing ice formation at the surface of the capillary wick structure 104. Further, following the completion of the feeding process, the vacuum chamber 302 pressure may decrease to approximately 50 Pa, while the evaporation chamber 106 pressure may sustain at a higher steady-state value of approximately 1110 Pa, owing to continuous evaporation from the surface of the capillary wick structure 104 and choked flow through the nozzle 110 via the shutter 112 disposed at an opening of the nozzle 110.
Further, the part (b) depicting the Temperature-time 604 of the FIG. 6 may include the temperature of the evaporation chamber 106, the vacuum chamber 302, the propellant reservoir 102 and the surface of the capillary wick structure 104 during and after the controlled pressure feeding process. Further, the decrease of the wick temperature (Tw) 206 at steady state of 10.5 ± 0.6 °C may indicate evaporative cooling. Further, the evaporation chamber temperature (TEC) 212 and reservoir temperature (TR) 218 may reach a steady-state values of 24.3 ± 0.6 °C and 23.8 ± 0.6 °C, respectively. Further, the choked state of the nozzle 110 may be verified by varying the vacuum chamber 302 pressure from 50 Pa to 500 Pa and returning to 50 Pa, while monitoring the evaporation chamber pressure (PEC) 214 and temperatures such as evaporation chamber temperature (TEC) 212, reservoir temperature (TR) 218, and wick temperature (Tw) 206. Further, the during the steady state conditions, the evaporation chamber pressure (PEC) 214 and temperatures such as evaporation chamber temperature (TEC) 212, reservoir temperature (TR) 218, and wick temperature (Tw) 206, may remain unchanged despite variations of external vacuum chamber pressure, confirming, the device 304 operates under choked flow. Further, the verification under no power input may be performed by measuring the mass flow from the device 304 at vacuum chamber 302 pressures of 50 Pa and 500 Pa. Further, the mass flow may remain approximately 0.2 mg per second over two hours, confirming choked flow through shutter 112 disposed at an opening of the nozzle 110. Further, the controlled pressure feeding method may be applied for all subsequent characterization experiments, and devices used for characterization with evaporation chamber 106 and propellant reservoir 102 with an inner diameter of 30 mm, outer diameter of 38 mm, and length of 80 mm, with a nozzle 110 diameter of 0.6 mm.
FIG. 7 illustrates a graphical representation of the temporal variation of pressure and temperature, in different components of the device and vacuum chamber and the mass flow rate and power, during the controlled pressure feeding process 700, in accordance with some embodiments of the present disclosure, in accordance with some embodiments of present disclosure. Further, the graphical representation of the temporal variation may include part (a) depicting a Pressure – Time graph 702, part (b) depicting a Temperature – Time graph 704 and part (c) depicting a Mass flow rate – Power graph 706.
Further, the part (a) depicting a Pressure – Time graph 702 of the FIG. 7 may include the measured pressure values of the vacuum chamber 302 and the evaporation chamber 106 during the controlled pressure feeding process. The vacuum chamber pressure maintains approximately 50 ± 10 Pa, while the evaporation chamber pressure (PEC) 214, attains a steady-state value of 1110 ± 80 Pa under no power input. As the power input to the device increases, evaporation from the surface of the capillary wick structure 104 rises, resulting in higher steady-state pressure in the evaporation chamber 106, increasing from 1110 ± 80 Pa to 3160 ± 80 Pa as power input increases from 0 W to 3 W.
Further, part (b) depicting a Temperature – Time graph 704, of FIG. 7 may include the temperature variation of the vacuum chamber 302, the evaporation chamber 106, the propellant reservoir 102, and the surface of the capillary wick structure 104 during the controlled pressure feeding process. Further, under no power input, the wick temperature (Tw) 206 drops to 10.5 ± 0.6 °C due to evaporative cooling, while the evaporation chamber temperature (TEC) 212 and reservoir temperature (TR) 218 may reach 24.3 ± 0.6 °C and 23.8 ± 0.6 °C, respectively, which may be lower than the vacuum chamber temperature of 28 ± 0.6 °C. Thus, the evaporation chamber pressure (PEC) 214 increases from, for example, 1110 ± 80 Pa to 3160 ± 80 Pa, and evaporation chamber temperature (TEC) 212 rises from 24.3 ± 0.6 °C to 29.9 ± 0.6 °C when the power input to the device 304 increases from 0 W to 3 W. Further, as the power input increases, the evaporation chamber temperature (TEC) 212 and wick temperature (Tw) 206, reaches higher steady-state values, reflecting enhanced evaporation and elevated steady-state conditions.
Further, part (c) depicting a Mass flow rate – Power graph 706 of FIG. 7 include the steady-state pressure and temperature values established within the evaporation chamber 106, defining the altered inlet (stagnation) conditions of the nozzle 110. Under the altered conditions, the nozzle 110 with a shutter 112 disposed at an opening of the nozzle 110, attains a choked state, causing an increase of the choked mass flow rate with a corresponding increase of power input as depicted in the part (c).
FIG. 8 illustrates a graphical representation of the variations in mass flow rate, thrust, and specific impulse from the device 800, along with a comparative bar chart against existing micro-propulsion technologies, in accordance with an embodiment of the present disclosure. Further, the graphical representation of the variations in mass flow rate, thrust, and specific impulse from the device 800 may include part (a), part (b), and part (c). Further, the part (a) depicts the graph of the mass flow rate 802, the part (b) depicts the graph of the thrust 804, and the part (c) depicts the graph of the specific impulse 806.
Further, the variation of the choked mass flow rate, thrust, and specific impulse of the device 304 at different power inputs. Further, the choked mass flow rate increases with increasing power input, as measured from the device 304, while thrust and specific impulse may be determined using the relationships F=m ̇_device V_e+(P_e-P_VC ) A_e and I_SP=F/(m ̇_device g), respectively. Further, the results show about the higher power input leading to increased evaporation, higher pressure, and temperature inside the evaporation chamber 106, and correspondingly higher thrust and specific impulse performance of the device 304.
Further, the part (a) of the FIG. 8 may include the measured choked mass flow rate from the device 304 at different power inputs. Further, as power input increases, evaporation from the surface of the capillary wick structure 104 rises, leading to higher pressure and temperature inside the evaporation chamber 106.
Further, the part (b) of FIG. 8 may include the measured thrust output from the device 304 corresponding to different power inputs. Further, the increased evaporation and higher steady-state pressure and temperature inside the evaporation chamber 106 may result as higher thrust output from the device 304.
Further, the part (c) of FIG. 8 may include a comparative analysis of the thrust-to-power ratio (TPR) and specific impulse-to-power ratio (SIPR) of the device 800 against existing micro-propulsion technologies. Further, the TPR achieved by the device 304, approximately 233 µN/W, may be comparable to several existing propulsion techniques and exceed the TPR of certain other systems. Further, the specific impulse-to-power ratio of the device, approximately 33.3 s/W, may be lower than some electric propulsion systems which may require significantly higher operating power, typically greater than 15 W. Further, the thrust-to-power ratio (TPR) and specific impulse-to-power ratio (SIPR) serve as critical performance metrics for micro-propulsion systems, considering the size and power limitations of small satellites.
FIG. 9 illustrates an exemplary flowchart of a method 900 for generating thrust in a satellite, in accordance with some embodiments of present disclosure.
At step 902, the method 900 includes, storing, by the capillary-fed evaporative micro-thruster 100, a liquid propellant within a propellant reservoir 102 and establishing a capillary connection between the propellant reservoir 102 and the evaporation chamber 106 through a capillary wick structure 104.
At step 904, the method 900 includes, transferring passively, by the capillary-fed evaporative micro-thruster 100, the liquid propellant from the propellant reservoir 102 to the evaporation chamber 106 via the capillary wick structure 104, by passive capillary action and maintaining a pressure difference across the capillary wick structure 104, within a predefined capillary retention limit to retain the liquid propellant, against pressure variations under low-vacuum conditions.
At step 906, the method 900 includes, applying localized heat, by the capillary-fed evaporative micro-thruster 100, to the capillary wick structure 104 of the evaporation chamber 106, to evaporate the transferred liquid propellant and generate vapor, and the localized heat may be supplied as a power input to generate a thrust output.
At step 908, the method 900 includes, expelling, by the capillary-fed evaporative micro-thruster 100, the generated vapor through the shutter 112 disposed at an opening of the nozzle 110, under a choked flow state to generate a stable thrust output independent of external vacuum pressure variations. Further, vacuum chamber 302 pressure is regulated and a solenoid valve operated based on such regulation to control the pressure difference between propellant reservoir 102 and evaporation chamber 106 below a predefined capillary retention limit during propellant feeding.
The written description describes the subject matter herein to enable any person skilled in the art to make and use the embodiments. The scope of the subject matter embodiments is defined by the claims and may include other modifications that occur to those skilled in the art. Such other modifications are intended to be within the scope of the claims if they have similar elements that do not differ from the literal language of the claims or if they include equivalent elements with insubstantial differences from the literal language of the claims.
A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the invention. When a single device or article is described herein, it will be apparent that more than one device/article (whether they cooperate) may be used in place of a single device/article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be apparent that a single device/article may be used in place of the more than one device or article or a different number of devices/articles may be used instead of the shown number of devices or programs. The functionality and/or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality/features. Thus, other embodiments of the invention need not include the device itself.
The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments. Also, the words “comprising”, “having”, “containing”, and “including”, and other similar forms are intended to be equivalent in meaning and be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based here on. Accordingly, the embodiments of the present invention are intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.
 
, Claims:CLAIMS:
We claim:
1. A capillary-fed evaporative micro-thruster (100) apparatus for generating thrust in a satellite, comprising:
a propellant reservoir (102) configured to store a liquid propellant;
an evaporation chamber (106) in fluid communication with the propellant reservoir (102);
a capillary wick structure (104) connecting the propellant reservoir (102) to the evaporation chamber (106), configured to passively transport the liquid propellant from the propellant reservoir (102) to the evaporation chamber (106) via a capillary action, wherein the evaporation chamber (106) and the propellant reservoir (102) are individually sealed components coupled through the capillary wick to form a continuous liquid transport path;
a heating element (108) thermally coupled to at least one portion of the capillary wick structure (104) within the evaporation chamber (106), configured to:
locally heat the liquid propellant delivered by the capillary wick structure (104); and
induce evaporation of the liquid propellant at a wick surface of the capillary wick structure (104) within the evaporation chamber (106);
and a nozzle (110) comprising a shutter (112) disposed at an opening of the nozzle (110), positioned at the one end of the evaporation chamber (106), configured to discharge the vapor to generated thrust.
2. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, wherein the evaporation chamber (106) is configured to maintain a steady-state pressure during operation, independent of external vacuum chamber (302) pressure variations, for suppressing ice formation at the wick surface under low-vacuum conditions, and to obtain choked flow through the nozzle (110) with the shutter 112 disposed at an opening of the nozzle (110).
3. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, wherein the propellant reservoir (102) is configured to maintain a reservoir pressure during transportation of the liquid propellant, corresponding to a saturation pressure of the liquid propellant at a feeding temperature.
4. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, wherein the nozzle (110) comprising the shutter 112 disposed at an opening of the nozzle (110) is configured to discharge the vapor in a choked flow state to generate a stable thrust output independent of external vacuum pressure variations.
5. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, wherein the capillary wick structure (104) comprises a porous hydrophilic material with a pre-defined capillary retention limit to retain the liquid propellant against a pressure difference in low-vacuum conditions.
6. The capillary-fed evaporative micro-thruster (100) as claimed in claim 5, wherein the pressure difference is controlled between the propellant reservoir (102) and the evaporation chamber (106) within a pre-defined capillary retention limit of the capillary wick structure (104), by regulating pressure in a vacuum chamber (302) and operating a solenoid valve during the feeding of the liquid propellant, and wherein, after feeding is completed, the pressure inside the evaporation chamber (106) self-adjusts in response to the applied heating power so as to provide the required evaporation mass flow rate.
7. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, wherein the capillary wick is axially inserted through a central aperture of an intermediate plate connecting the propellant reservoir (102) and the evaporation chamber (106).

8. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, wherein the heating element (108) is a thin polyimide film and comprising a flexible resistive heater circumferentially wound around a predefined section of the capillary wick structure (104) located within the evaporation chamber (106) and the capillary wick structure (104) is thermally insulated from a region of propellant reservoir (102).
9. The capillary-fed evaporative micro-thruster (100) as claimed in claim 1, further comprises one or more sensors configured to measure in-situ measurements corresponding to at least one of a temperature, a pressure and a liquid propellant level within the evaporation chamber (106) and the propellant reservoir (102), for monitoring heat and mass transfer during operation.
10. A method (900) for generating thrust in a satellite using a capillary-fed evaporative micro-thruster (100) apparatus, comprising:
storing, by a capillary-fed evaporative micro-thruster (100) apparatus, a liquid propellant in a propellant reservoir (102);
transferring passively, by the capillary-fed evaporative micro-thruster (100) apparatus, the liquid propellant to an evaporation chamber (106) from propellant reservoir (102) via a capillary wick structure (104) by passive capillary action;
applying, by the capillary-fed evaporative micro-thruster (100) apparatus, localized heat to the capillary wick structure (104) within the evaporation chamber (106) to evaporate the transferred liquid propellant and generate vapor; and
expelling, by the capillary-fed evaporative micro-thruster (100) apparatus, the generated vapor through a nozzle (110) to generate thrust, wherein the nozzle (110) comprises a shutter 112 disposed at an opening of the nozzle (110).
11. The method (900) as claimed in claim 10, further comprises:
establishing, by the capillary-fed evaporative micro-thruster (100) apparatus, a capillary connection between the propellant reservoir (102) and the evaporation chamber (106) through the capillary wick structure (104); and
maintaining, by the capillary-fed evaporative micro-thruster (100) apparatus, a pressure difference across the capillary wick structure (104) within a pre-defined capillary retention limit to retain the liquid propellant against a pressure difference in low-vacuum conditions.
12. The method (900) as claimed in claim 10, further comprises:
regulating, by the capillary-fed evaporative micro-thruster (100) apparatus, pressure in a vacuum chamber (302);
operating, by the capillary-fed evaporative micro-thruster (100) apparatus, a solenoid valve based on the regulation; and
controlling, by the capillary-fed evaporative micro-thruster (100) apparatus, the pressure difference between the propellant reservoir (102) and the evaporation chamber (106) below a pre-defined capillary retention limit of the capillary wick structure (104) during the propellant feeding to the propellant reservoir (102), based on the regulation and the operation.
13. The method (900) as claimed in claim 10, wherein the generated vapor is expelled in a choked flow state to generate a stable thrust output independent of external vacuum pressure variations.

14. The method (900) as claimed in claim 10, wherein applying localized heat comprises supplying a power input for generating a thrust output.