Álvaro Romero-Calvo

Georgia Institute of Technology | GT · School of Aerospace Engineering

Water electrolysis is a key technology for oxygen and hydrogen production in space, finding application in environmental control and life support systems, propulsion technologies, and high-density energy storage devices. However, the management of multiphase flows in microgravity is complicated due to the absence of buoyancy. Diamagnetic buoyancy c...

Low gravity fluid management is key to a variety of spaceflight applications from life support systems aboard the international space station to propellant management in satellite tanks. Various methodologies have been developed to drive fluids to their desired positions in a microgravity environment, but these traditional strategies are not partic...

Novel active sensing technologies have been recently proposed to touchlessly measure the electrostatic potential of non-cooperative objects in Geosynchronous Equatorial Orbit and cislunar space. This technology involves a servicing spacecraft that makes us of an electron beam or UV laser to excite secondary electron and photoelectron emissions. The...

A method has been proposed to estimate the electric potential of co-orbiting spacecraft remotely using x-rays that are excited by an electron beam. Prior work focused on the theoretical foundation and experimental validation of this approach using flat target plates. Although useful for concept validation, flat plates do not adequately represent th...

A coupled ferrohydrodynamic interface-tracking model is introduced for the analysis of the equilibrium, linear stability, and modal response of magnetic liquid interfaces in surface tension-dominated axisymmetric multiphase flows. The incompressible viscous mass and momentum balances are solved together with the steady-state Maxwell equations by fo...

The active deorbiting and passivation of launch vehicles has become key for the implementation of modern space debris mitigation guidelines. Appropriate engine restart conditions must be provided as part of this process. Ullage motors have been traditionally employed to induce active settling and ensure a gas-free propellant supply to the engines....

The absence of strong buoyancy forces severely complicates the management of multiphase flows in microgravity. Different types of space systems, ranging from in-space propulsion to life support, are negatively impacted by this effect. Multiple approaches have been developed to achieve phase separation in microgravity, whereas they usually lack the...

The commercialization of the sub-orbital environment, the ambition to make humans a multi-planetary species, and the urgent need for sustainable space operations are driving the development of a new generation of space systems. The use of electromagnetic forces (and electromagnetism, in general) is proposed in this dissertation to enable mid-distan...

The secondary electron method has been recently proposed to touchlessly sense the electrostatic potential of non-cooperative objects in geosynchronous equatorial orbits and deep space. This process relies on the detection of secondaries generated at the target surface, that is actively irradiated by an electron beam. Although the concept has alread...

Ultraviolet lasers are proposed as a replacement for low-energy electron beams to induce the emission of secondary electrons in touchless spacecraft potential sensing technologies. Theoretical considerations show that the measurement process becomes significantly less sensitive to the electrostatic environment and leads to more robust, controllable...

A method has been proposed to estimate the electric potential of co-orbiting spacecraft remotely using x-rays that are excited by an electron beam. Recent work experimentally investigated the remote electric potential estimation of objects with complex shapes and differentially-charged components, and a new analysis method was proposed that enables...

Electrostatic perturbations can have significant effects during terminal proximity operations in high earth orbits, with torque levels exceeding 5 mN-m during severe charging events. These torques can impart 1°/s rotational rates to uncontrolled bodies, such as debris or servicing clients, during rendezvous and proximity operations. A sub optimal,...

The active deorbiting and passivation of launch vehicles has become key for the implementation of modern space debris mitigation guidelines. Appropriate engine restart conditions must be provided as part of this process. Ullage motors have been traditionally employed to induce active settling and ensure a gas-free propellant supply to the engines....

The management of fluids in space is complicated by the absence of relevant buoyancy forces. This raises significant technical issues for two-phase flow applications. Different approaches have been proposed and tested to induce phase separation in low-gravity; however, further efforts are still required to develop efficient, reliable, and safe devi...

The Electrostatic Charging Laboratory for Interactions between Plasma and Spacecraft (ECLIPS) research vacuum chamber has recently been developed as part of the Autonomous Vehicle Systems Laboratory at the University of Colorado Boulder. The experimental spacecraft charging research facility allows conducting experiments relevant to charged astrody...

A method has been recently proposed to estimate the electric potential of co-orbiting spacecraft remotely using x-rays that are excited by an electron beam. Prior work focused on the theoretical foundation and experimental validation of this method using flat target plates. Although useful for the validation of this concept, flat plates do not adeq...

Novel active sensing methods have been recently proposed to measure the electrostatic potential of non-cooperative objects in geosynchronous equatorial orbit and deep space. Such approaches make use of electron beams to excite the emission of secondary electrons and X-Rays and infer properties of the emitting surface. However, the detectability of...

[The final version of this work can be found at http://doi.org/10.2514/1.A35355] The secondary electron method has been recently proposed to touchlessly sense the electrostatic potential of non-cooperative objects in geosynchronous equatorial orbits and deep space. This process relies on the detection of secondaries generated at the target surface,...

This paper describes an inexpensive, non-invasive, and highly adaptable surface reconstruction device for opaque liquids. The instrument was developed to study the lateral sloshing of ferrofluids in microgravity as part of the UNOOSA DropTES 2019 StELIUM project. Its design is driven by the geometrical and mechanical constraints imposed by ZARM’s d...

The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers due to its effects on the dynamics and operation of space vehicles. Magnetic settling forces may be employed to position a susceptible liquid and address these issues. Although proposed in the early 1960s, this approach remains largely unexplored. I...

The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers and operators. Those include the generation of significant attitude disturbances, the uncontrolled displacement of the center of mass of the vehicle or the production of gas bubbles, among others. Magnetic fields can be used to induce the reorientat...

This paper addresses the operation in microgravity of the surface reconstruction device whose design is detailed in the first part of the manuscript. The system, employed during the drop tower campaign of the UNOOSA DropTES 2019 StELIUM experiment, studies the axisymmetric and lateral oscillations of a ferrofluid solution in microgravity. The free...

[The final version of this work can be found at http://doi.org/10.2514/1.A35190] Novel active sensing technologies have been recently proposed to measure the electrostatic potential and characterize non-cooperative objects in Geosynchronous Equatorial Orbit (GEO) and deep space. Such technologies make use of electron beams to excite the emission of...

[The final version of this work can be found at https://doi.org/10.1016/j.actaastro.2021.12.037] The Electrostatic Charging Laboratory for Interactions between Plasma and Spacecraft (ECLIPS) research vacuum chamber facility has recently been developed as part of the Autonomous Vehicle Systems Laboratory at the University of Colorado Boulder. This e...

[The final version of this paper can be found in http://arc.aiaa.org/doi/abs/10.2514/1.A35021] The management of fluids in space is complicated by the absence of strong buoyancy forces. This raises significant technical issues for two-phase flows applications, such as water electrolysis or boiling. Different approaches have been proposed and test...

The term sloshing refers to the movement of liquids in partially filled containers. Low-gravity sloshing plays an important role in the configuration of space vehicles, as it affects their dynamics and complicates the propellant management system design. Magnetic forces can be used to position a susceptible fluid, tune its natural frequencies, and...

Liquid sloshing represents a major challenge for the design and operation of space vehicles. In low-gravity environments, a highly non-linear movement can be produced due to the lack of stabilizing forces. This gives rise to significant disturbances that impact on the propulsion and attitude control systems of the spacecraft. The employment of magn...

The formulation of the total force exerted by magnetic fields on ferrofluids has historically been a subject of intense debate and controversy. Although the theoretical foundations of this problem can now be considered to be well established, significant confusion still remains regarding the implementation of the associated expressions. However, th...

[The final version of this paper can be found in https://doi.org/10.1016/j.actaastro.2021.06.045] The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers and operators. Those include the generation of significant attitude disturbances, the uncontrolled displacement of the center of mass of the vehicle o...

The sloshing of liquids in microgravity is a relevant problem of applied mechanics with important implications for spacecraft design. A magnetic settling force may be used to avoid the highly non-linear dynamics that characterize these systems. However, this approach is still largely unexplored. This paper presents a quasi-analytical low-gravity sl...

[The final version of this work can be found at https://doi.org/10.1016/j.actaastro.2021.08.029 and https://doi.org/10.1016/j.actaastro.2021.07.020] Liquid level measurement devices are required in experimental sloshing research. Several techniques with different capabilities and degrees of complexity have been historically proposed to cover this n...

The Lunar Meteoroid Impact Observer (LUMIO) is a 12U CubeSat designed to observe, quantify, and characterize the impact of meteoroids on the lunar surface. The combination of a highly demanding Concept of Operations (ConOps) and the characteristics of the deep-space environment determine the configuration of the spacecraft. This paper presents the...

Liquid sloshing represents a major challenge for spacecraft design and operation. In low-gravity environments, a highly non-linear movement is produced due to the lack of stabilizing forces. This gives rise to significant disturbances that impact on the attitude control system of the vehicle. The employment of magnetically susceptible fluids may op...

The increasing density of space debris in the Low Earth Orbit and the need to face long-term manned missions have raised the interest on vehicle health monitoring systems. Active monitoring techniques involving a network of sensors may assist in the impact detection and evaluation process, reducing the cost and risk of such activities. However, any...

Abstract presented to the 26th European Low Gravity Research Association Biennial Symposium and General Assembly.

The sloshing of magnetic liquids has distinctive characteristics that may become useful for the control of propellants in space. Magnetic fields can be used to shift the natural frequencies and damping ratios of an oscillating fluid. In the framework of the UNOOSA DropTES Programme, StELIUM (Sloshing of magnetic LIqUids in Microgravity) will study...

The term sloshing refers to the forced movement of liquids in partially filled containers. In a low-gravity environment, the liquid mixes with pressurizing gas bubbles and adopts a random position inside the tank, resulting in unwanted perturbations and a complicated design. Liquid sloshing has consequently been a major concern for space engineers...

The term sloshing refers to the forced movement of liquids in partially filled containers. In a low-gravity environment, the liquid mixes with pressurizing gas bubbles and adopts a random position inside the tank, resulting in unwanted perturbations and a complicated design. Liquid sloshing has consequently been a major concern for space engineers...

Technical Experiment Report of the European Space Agency Drop Your Thesis! 2017 team "The Ferros". Site: http://eea.spaceflight.esa.int/portal/exp/?id=9692

The effective discrimination between patients at risk of Arrhythmic Mortality (AM) and Non-Arrhythmic Mortality (NAM) constitutes one of the important unmet clinical needs. Successful risk assessment based on Electrocardiography (ECG) records is greatly improved by the combination of different indices reflecting not only the pathological substrate...

Ferrofluids are colloidal suspensions of magnetic nanoparticles in a carrier liquid. It is beneficial, for both fundamental research and future applications of ferrofluids in space, to obtain reliable measurements of the dynamics of ferrofluids in microgravity. This field remains unexplored since experiments in microgravity are expensive and the ac...

Ferrofluids are colloidal suspensions of magnetic nanoparticles in a carrier liquid. It is beneficial, for both fundamental research and future applications of ferrofluids in space, to obtain reliable measurements of the dynamics of ferrofluids in microgravity. This field remains unexplored since experiments in microgravity are expensive and the ac...

The purpose of this project is the development and testing of a new geographical surface heat exchange measurement technique. The proposed approach is based on the indirect evaluation of advective moist air heat fluxes and employs the most simple instrumentation available at the moment, consisting on a network of automatic meteorological stations....