<p>Current small satellite propellant tank design is driven by three factors: volume op-timization, manufacturing capability, and propellant management. Conformal propellanttanks offer solutions to the design challenges of optimizing satellite volume and manufac-turing costs. Conformal propellant tank designs that meet these challenges have unknowneffects on propellant management. Compounding this uncertainty is the industry shift to-wards new green propellants with large contact angles. Improper propellant managementcan deliver gas to a thruster or leave propellant trapped away from the tank outlet whiledraining. Both scenarios reduce the lifespan of satellites.</p> <p>Stamping is one manufacturing process that can produce tanks that optimize volumeand are relatively easy to manufacture. The effects of the stamping process on tank shapeand propellant management is evaluated through testing four different tank geometries. Thestamping process sometimes leaves behind a seam where two sides of a tank are joinedtogether. A total of six tank and vane combinations are tested. One set of traditional tanksserve as a control. Three tanks tested share vane geometry and have different interiors toevaluate the effects of the stamping process on propellant management. The first tank hasa smooth interior, the second has a seam at the joints and the third tank has a seam andridges for increased stiffness. The last two tanks have an interior in the shape of an arc andhave different vanes. The experiment is flown on the ZeroG airplane to test the tank andvane designs in a weightless environment.</p> <p>The experiment consists of a payload rack, eleven experimental pods and one powerdistribution pod. Each experimental pod is designed to be modular and independent fromall other experimental pods. Each experimental pod hosts a camera, electrical box, secondcontainment and fluid system with four tanks.</p> <p>The results of this study show no discernible difference could be observed between tankswith or without a seam from the stamping process. When ridges are added to a tank thatare parallel to the contact line, liquid may not wick into the ridge if it is dry. If the ridgeis wet the liquid spreads out on the surface of the tank further. The differences betweenpropellant positioning for zero and nonzero contact angle fluids are discussed</p> <p><br></p>

<p dir="ltr"> As part of humanity's constant effort to explore and expand, the race to establish a cislunar economy is afoot. The Cryobubbles experiment seeks to advance the state of the art in long-term cryogenic propellant management, a field that is an integral part of exploring the next great frontier. The Cryobubbles experiment was created to understand an unexpected bubble formation phenomenon during a tank-pressure control strategy test of NASA's Zero Boil-off Tank (ZBOT) on the International Space Station. A few hypotheses about the causes of bubble formation were developed, and thanks to a NASA flight opportunities grant, the Cryobubbles experiment was designed and manufactured with a \$95,000 budget to test these hypotheses on a parabolic flight.</p><p dir="ltr"> This master's thesis explains the importance of understanding the causes of bubble formation and the thermodynamic operating point chosen to replicate ZBOT conditions. The operation of the experiment and the design of technologies developed to make these operations work are also discussed. Some notable technologies include an insulation sizing algorithm created to maintain the experiment operating point, cryogenically rated viewports that allow for high-quality video recording of the experiment, and copper coils sized to allow for the safe use of noncryogenic equipment in a cryogenic test setup. All of these designs were constrained by a budget, a fast-approaching flight test deadline, and safety considerations.</p><p dir="ltr"> At the time of this writing, the experiment has been fully designed, manufactured, and assembled. The next step is to conduct testing.</p>

<p>As the small satellite market has grown from a niche of the space economy to a full commercial force,  microthrusters remain an area of significant growth in the space industry as new technologies mature. The \textit{Film-Evaporation Microelectricalmechanical Tunable Array} (FEMTA) is one such device. FEMTA is \textit{microelectricalmechanical system} (MEMS) device that harnesses the microcapillary action of water and vacuum boiling to generate thrust. The water propellant is not chemically altered at all by the process; it is simply evaporated. This technology has been tested in relevant laboratory environments, and a suborbital flight opportunity in 2023 as a payload on a Blue Origin New Shepard rocket  will grant FEMTA a demonstration in a space environment. The flight will provide 150 seconds of weightlessness at the zenith of the suborbital flight path before the booster returns to land. During weightlessness, the experiment will be exposed to the ambient environment allowing for a full capability test of the thruster. The experiment is meant to demonstrate the propellant management system for FEMTA in 0G and measure the thrust produced by a FEMTA thruster.</p> <p><br></p> <p>The propellant management system portion of the experiment consists of an oversized version of the subsystem intended for use in the thruster. The propellant management system uses a hydrofluoroether to inflate a diaphragm to ensure constant wetting of the propellant tank exit and nozzle inlet. The experiment will take tank pressure data and flow sensor data to understand the system's behavior. The system is duplicated for redundancy and to double the possible data. This system requires further testing before being prepared for launch, vibrational testing, thermal testing, and vacuum testing. </p> <p><br></p> <p>The 0G thrust experiment and plume analysis portion of the experiment consists of numerical modeling and a novel thrust measurement approach. \textit{Direct Simulation Monte Carlo} (DSMC) is being applied to understand the pressure, density, and temperature distributions of the plume of water vapor produced by the FEMTA thruster. The FEMTA nozzle environment is challenging to simulate with computational fluid dynamics  or DSMC due to chaotic transient effects and because both the continuum and molecular regimes must be considered. The current analysis consisted of a two-dimensional model and investigated the effect of meniscus location and contact angle on thrust generated.</p> <p><br></p> <p>It is not possible to use traditional thrust measurement devices (sensitive torsional thrust stands or microsensors intended for use on small satellites) for microthrusters on a rocket booster. Two  novel approaches for performing thrust measurement in the range of 100 microNewtons have been investigated. The first approach ionizes the FEMTA thruster plume and analyzes the plasma by optical emission spectroscopy. The theory states that the relative intensity of a given wavelength observed correlates to the density of the species in the plasma. The density of water would be directly correlated to the thrust generated by FEMTA during the experiment, as more water is evaporated as thrust is increased. This method is no longer being considered for the suborbital experiment but did yield promising results. </p> <p><br></p> <p>The second approach employs a d'Arsonval meter, a photo-interrupt, and an Arduino controller. The d'Arsonval meter consists of a stationary permanent magnet with a moving coil and a pointer. Increasing the voltage in the coil causes a torque on the system due to the magnetic field induced by the permanent magnet. This torque causes a deflection of the pointer that is proportional to the voltage applied. The flag of the sensor will be placed in the path of the gas jet from the thruster. The force caused by the jet pressure will move the flag. An Arduino controller will vary the voltage to hold the flag in place. As the mass flow rate increases, the reaction force required to hold the flag in place will increase. This sensor can be calibrated using an analog cold gas system that passes various gases (air nitrogen, argon, etc.) through an orifice nozzle at mass flow rates that are set by a mass flow rate controller. DSMC analysis has been performed to understand the flow field and flow properties and how they directly relate to the force experienced by the flag sensor. </p> <p>An undergraduate course has supported parts of the work described in this dissertation. This course has applied the Vertically Integrated Projects approach to project-based learning. This method and its results were analyzed and lessons learned as well as a blueprint for future application of this method to other small satellite projects are discussed.</p>

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