arXiv subjects

Jekan Thangavelautham

Publications and source records attributed to Jekan Thangavelautham.

At least 37 records · Page 2Linked to original sources

arXiv2019

Attitude Control of an Inflatable Sailplane for Mars Exploration

Exploration of Mars has been made possible using a series of landers, rovers and orbiters. The HiRise camera on the Mars Reconnaissance Orbiter (MRO) has captured high-resolution images covering large tracts of the surface. However, orbital images lack the depth and rich detail obtained from in-situ exploration. Rovers such as Mars Science Laboratory and upcoming Mars 2020 carry state-of-the-art science laboratories to perform in-situ exploration and analysis. However, they can only cover a small area of Mars through the course of their mission. A critical capability gap exists in our ability to image, provide services and explore large tracts of the surface of Mars required for enabling a future human mission. A promising solution is to develop a reconnaissance sailplane that travels tens to hundreds of kilometers per sol. The aircraft would be equipped with imagers that provide that in-situ depth of field, with coverage comparable to orbital assets such as MRO. A major challenge is that the Martian carbon dioxide atmosphere is thin, with a pres-sure of 1% of Earth at sea level. To compensate, the aircraft needs to fly at high-velocities and have sufficiently large wing area to generate the required lift. Inflatable wings are an excellent choice as they have the lowest mass and can be used to change shape (morph) depending on aerodynamic or con-trol requirements. In this paper, we present our design of an inflatable sail-plane capable of deploying from a 12U CubeSat platform. A pneumatic de-ployment mechanism ensures highly compact stowage volumes and minimizes complexity.

astro-ph.IM↗

arXiv2019

Propelling Interplanetary Spacecraft Utilizing Water-Steam

Water has been identified as a critical resource both to sustain human-life but also for use in propulsion, attitude-control, power, thermal and radiation pro-tection systems. Water may be obtained off-world through In-Situ Resource Utilization (ISRU) in the course of human or robotic space exploration that replace materials that would otherwise be shipped from Earth. Water has been highlighted by many in the space community as a credible solution for affordable/sustainable exploration. Water can be extracted from the Moon, C-class Near Earth Objects (NEOs), surface of Mars and Martian Moons Pho-bos and Deimos and from the surface of icy, rugged terrains of Ocean Worlds. However, use of water for propulsion faces some important techno-logical barriers. A technique to use water as a propellant is to electrolyze it into hydrogen and oxygen that is then pulse-detonated. High-efficiency elec-trolysis requires use of platinum-catalyst based fuel cells. Even trace ele-ments of sulfur and carbon monoxide found on planetary bodies can poison these cells making them unusable. In this work, we develop steam-based propulsion that avoids the technological barriers of electrolyzing impure water as propellant. Using a solar concentrator, heat is used to extract the water which is then condensed as a liquid and stored. Steam is then formed using the solar thermal reflectors to concentrate the light into a nanoparticle-water mix. This solar thermal heating (STH) process converts 80 to 99% of the in-coming light into heat.

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arXiv2019

An Autonomous Passive Navigation Method for Nanosatellite Exploration of the Asteroid Belt

There are more than 750,000 asteroids identified in the main belt. These asteroids are diverse in composition and size. Some of these asteroids can be traced back to the early solar system and can provide insight into the origins of the so-lar system, origins of Earth and origins of life. Apart from being important tar-gets for science exploration, asteroids are strategically placed due to their low-gravity well, making it low-cost to transport material onto and way from them. They hold valuable resources such as water, carbon, metals including iron, nickel and platinum to name a few. These resources maybe used in refueling depots for interplanetary spacecraft and construction material for future space colonies, communication relays and space telescopes. The costs of getting to the main asteroid belt, combined with large numbers of objects to be explored encourage the application of small spacecraft swarms. The size and capability of the result-ing nano-spacecraft can make detection from Earth difficult. This paper dis-cusses a method by which a spacecraft can establish ephemeris autonomously using line of sight measurements to nearby asteroids with Extended Kalman Filtering techniques, without knowing accurate ephemeris of either the asteroids or the spacecraft initially. A description of the filter implementation is followed by examples of resultant performance.

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arXiv2019

Motion Planning on an Asteroid Surface with Irregular Gravity Fields

There are thousands of asteroids in near-Earth space and millions in the Main Belt. They are diverse in physical properties and composition and are time capsules of the early solar system. This makes them strategic locations for planetary science, resource mining, planetary defense/security and as inter-planetary depots and communication relays. However, asteroids are a chal-lenging target for surface exploration due it its low but highly nonlinear gravity field. In such conditions, mobility through ballistic hopping possess multiple advantages over conventional mobility solutions and as such hop-ping robots have emerged as a promising platform for future exploration of asteroids and comets. They can traverse large distances over rough terrain with the expenditure of minimum energy. In this paper we present ballistic hopping dynamics and its motion planning on an asteroid surface with highly nonlinear gravity fields. We do it by solving Lambert's orbital boundary val-ue problem in irregular gravity fields by a shooting method to find the initial velocity required to intercept a target. We then present methods to localize the hopping robot using pose estimation by successive scan matching with a 3D laser scanner. Using the above results, we provide methods for motion planning on the asteroid surface over long distances. The robot will require to perform multiple hops to reach a desired goal from its initial position while avoiding obstacles. The study is then be extended to find optimal tra-jectories to reach a desired goal by visiting multiple waypoints.

cs.RO↗

arXiv2019

Guidance, Navigation and Control of Asteroid Mobile Imager and Geologic Observer (AMIGO)

The science and origins of asteroids is deemed high priority in the Planetary Science Decadal Survey. Major scientific goals for the study of planetesimals are to decipher geological processes in SSSBs not determinable from investigation via in-situ experimentation, and to understand how planetesimals contribute to the formation of planets. Ground based observations are not sufficient to examine SSSBs, as they are only able to measure what is on the surface of the body; however, in-situ analysis allows for further, close up investigation as to the surface characteristics and the inner composure of the body. To this end, the Asteroid Mobile Imager and Geologic Observer (AMIGO) an autonomous semi-inflatable robot will operate in a swarm to efficiently characterize the surface of an asteroid. The stowed package is 10x10x10 cm (equivalent to a 1U CubeSat) that deploys an inflatable sphere of ~1m in diameter. Three mobility modes are identified and designed: ballistic hopping, rotation during hops, and up-righting maneuvers. Ballistic hops provide the AMIGO robot the ability to explore a larger portion of the asteroid's surface to sample a larger area than a stationary lander. Rotation during the hop entails attitude control of the robot, utilizing propulsion and reaction wheel actuation. In the event of the robot tipping or not landing up-right, a combination of thrusters and reaction wheels will correct the robot's attitude. The AMIGO propulsion system utilizes sublimate-based micro-electromechanical systems (MEMS) technology as a means of lightweight, low-thrust ballistic hopping and coarse attitude control. Each deployed AMIGO will hop across the surface of the asteroid multiple times.

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arXiv2019

Spacecraft Swarm Attitude Control for Small Body Surface Observation

Understanding the physics of small bodies such as asteroids, comets, and planetary moons will help us understand the formation of the solar system, and also provide us with resources for a future space economy. Due to these reasons, missions to small bodies are actively being pursued. However, the surfaces of small bodies contain unpredictable and interesting features such as craters, dust, and granular matter, which need to be observed carefully before a lander mission is even considered. This presents the need for a surveillance spacecraft to observe the surface of small bodies where these features exist. While traditionally, the small body exploration has been performed by a large monolithic spacecraft, a group of small, low-cost spacecraft can enhance the observational value of the mission. Such a spacecraft swarm has the advantage of providing longer observation time and is also tolerant to single point failures. In order to optimize a space-craft swarm mission design, we proposed the Integrated Design Engineering & Automation of Swarms (IDEAS) software which will serve as an end-to-end tool for theoretical swarm mission design. The current work will focus on developing the Automated Swarm Designer module of the IDEAS software by extending its capabilities for exploring surface features on small bodies while focusing on the attitude behaviors of the spacecraft in the swarm. We begin by classifying space-craft swarms into 5 classes based on the level of coordination. In the current work, we design Class 2 swarms, whose spacecraft operate in a decentralized fashion but coordinate for communication. We demonstrate the Class 2 swarm in 2 different configurations, based on the roles of the participating spacecraft.

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arXiv2019

Laser Communication and Coordination Control of Spacecraft Swarms

Swarms of small spacecraft offer whole new capabilities in Earth observation, global positioning and communications compared to a large monolithic spacecraft. These small spacecrafts can provide bigger apertures that increase gain in communication antennas, increase area coverage or effective resolution of distributed cameras and enable persistent observation of ground or space targets. However, there remain important challenges in operating large number of spacecrafts at once. Current methods would require a large number of ground operators monitor and actively control these spacecrafts which poses challenges in terms of coordination and control which prevents the technology from scaled up in cost-effective manner. Technologies are required to enable one ground operator to manage tens if not hundreds of spacecrafts. We propose to utilize laser beams directed from the ground or from a command and control spacecraft to organize and manage a large swarm. Each satellite in the swarm will have a customized "smart skin" con-taining solar panels, power and control circuitry and an embedded secondary propulsion unit. A secondary propulsion unit may include electrospray pro-pulsion, solar radiation pressure-based system, photonic laser thrusters and Lorentz force thrusters. Solar panels typically occupy the largest surface area on an earth orbiting satellite. A laser beam from another spacecraft or from the ground would interact with solar panels of the spacecraft swarm. The laser beam would be used to select a 'leader' amongst a group of spacecrafts, set parameters for formation-flight, including separation distance, local if-then rules and coordinated changes in attitude and position.

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arXiv2019

Advanced Inflatable De-Orbit Solutions for Derelict Satellites and Orbital Debris

The exponential rise in small-satellites and CubeSats in Low Earth Orbit (LEO) poses important challenges for future space traffic management. At altitudes of 600 km and lower, aerodynamic drag accelerates de-orbiting of satellites. However, placement of satellites at higher altitudes required for constellations pose important challenges. The satellites will require on-board propulsion to lower their orbits to 600 km and let aerodynamic drag take-over. In this work we analyze solutions for de-orbiting satellites at altitudes of up to 3000 km. We consider a modular robotic de-orbit device that has stowed volume of a regular CubeSat. The de-orbit device would be externally directed towards a dead satellite or placed on one by an external satellite servicing system. Our solutions are intended to be simple, high-reliability devices that operate in a passive manner, requiring no active electronics or utilize external beamed power in the form of radio frequency, microwave or laser to operate. Utilizing this approach, it is possible for an external, even ground based system to direct the de-orbit of a spacecraft. The role of an external system to direct the de-orbit is important to avoid accidental collisions. Some form of propulsion is needed to lower the orbit of the dead satellite or orbital debris. We considered green (non-toxic) propulsion methods including solar radiation pressure, solar-thermal propulsion using water steam, solar-electrolysis propulsion using water and use of electrodynamic tethers. Based on this trade-study we identify multiple solutions that can be used to de-orbit a spacecraft or orbital debris.

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arXiv2019

Attitude Control of Spacecraft Swarms for Visual Mapping of Planetary Bodies

Planetary bodies such as asteroids, comets, and planetary moons are high-value science targets as they hold important information about the formation and evolution of our solar system. However, due to their low-gravity, variable sizes and shapes, dedicated orbiting spacecraft missions around these target bodies is difficult. Therefore, many planetary bodies are observed during flyby encounters, and consequently, the mapping coverage of the target body is limited. In this work, we propose the use of a spacecraft swarm to provide complete surface maps of a planetary body during a close encounter flyby. With the advancement of low-cost spacecraft technology, such a swarm can be realized by using multiple miniature spacecraft. The design of a swarm mission is a complex multi-disciplinary problem. To get started, we propose the Integrated Design Engineering & Automation of Swarms (IDEAS) software. In this work, we will introduce the development of the Automated Swarm Designer module of the software and apply it to total surface mapping of asteroid 433 Eros through flybys.

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arXiv2018

A Milli-Newton Propulsion System for the Asteroid Mobile Imager and Geologic Observer (AMIGO)

Exploration of small bodies, namely comets and asteroids remain a challenging endeavor due to their low gravity. The risk is so high that missions such as Hayabusa II and OSIRIS-REx will be performing touch and go missions to obtain samples. The next logical step is to perform longer-term mobility on the surface of these asteroid. This can be accomplished by sending small landers of a 1 kg or less with miniature propulsion systems that can just offset the force of asteroid gravity. Such a propulsion system would ideally be used to hop on the surface of the asteroid. Hopping has been found to be most efficient form of mobility on low-gravity. Use of wheels for rolling presents substantial challenges as the wheel can't gain traction to roll. The Asteroid Mobile Imager and Geologic Observer (AMIGO) utilizes 1 kg landers that are stowed in a 1U CubeSat configuration and deployed, releasing an inflatable that is 1 m in diameter. The inflatable is attached to the top of the 1U lander, enabling high speed communications and a means of easily tracking lander from an overhead mothership. Milligravity propulsion is required for the AMIGO landers to perform ballistic hops on the asteroid surface. The propulsion system is used to navigate the lander across the surface of the asteroid under the extremely low gravity while taking care to not exceed escape velocity.Although the concept for AMIGO missions is to use multiple landers, the more surface area evaluated by each lander the better. Without a propulsion system, each AMIGO will have a limited range of observable area. The propulsion system also serves as a rough attitude control system (ACS), as it enables pointing and regulation over where the lander is positioned via an array of MEMS thrusters.

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arXiv2018

An On-Orbit CubeSat Centrifuge for Asteroid Science and Exploration

There are thousands of asteroids in near-Earth space and millions expected in the Main Belt. They are diverse in their physical properties and compositions. They are also time capsules of the early Solar System making them valuable for planetary science, and are strategic for resource mining, planetary defense/security and as interplanetary depots. But we lack direct knowledge of the geophysical behavior of an asteroid surface under milligravity conditions, and therefore landing on an asteroid and manipulating its surface material remains a daunting challenge. Towards this goal we are putting forth plans for a 12U CubeSat that will be in Low Earth Orbit and that will operate as a spinning centrifuge on-orbit. In this paper, we will present an overview of the systems engineering and instrumentation design on the spacecraft. Parts of this 12U CubeSat will contain a laboratory that will recreate asteroid surface conditions by containing crushed meteorite. The laboratory will spin at 1 to 2 RPM during the primary mission to simulate surface conditions of asteroids 2 km and smaller, followed by an extended mission where the spacecraft will spin at even higher RPM. The result is a bed of realistic regolith, the environment that landers and diggers and maybe astronauts will interact with. The CubeSat is configured with cameras, lasers, actuators and small mechanical instruments to both observe and manipulate the regolith at low simulated gravity conditions. A series of experiments will measure the general behavior, internal friction, adhesion, dilatancy, coefficients of restitution and other parameters that can feed into asteroid surface dynamics simulations. Effective gravity can be varied, and external mechanical forces can be applied.

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arXiv2018

Modular Inflatable Composites for Space Telescopes

There is an every-growing need to construct large space telescopes and structures for observation of exo-planets, main-belt asteroids and NEOs. Space observation capabilities can significant enhanced by large-aperture structures. Structures extending to several meters in size could potentially revolutionize observation enabling technologies. These include star-shades for imaging distant objects such as exo-planets and high-resolution large aperture telescopes. In addition to size, such structures require controllable precision surfaces and high packing efficiencies. A promising approach to achieving high compaction for large surface areas is by incorporating compliant materials or gossamers. Gossamer structures on their own do not meet stiffness requirements for controlled deployment. Supporting stiffening mechanisms are required to fully realize their structural potential. The accuracy of the 'active' surface constructed out of a gossamer additionally also depends on the load bearing structure that supports it. This paper investigates structural assemblies constructed from modular inflatable membranes stiffened pneumatically using inflation gas. These units assembled into composites can yield desirable characteristics. We present the design of large assemblies of these modular elements.

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arXiv2018

Coordination and Control of Multiple Climbing Robots in Transport of Heavy Loads through Extreme Terrain

The discovery of ice deposits in the permanently shadowed craters of the lunar North and South Pole Moon presents an important opportunity for In-Situ Resource Utilization. These ice deposits maybe the source for sustaining a lunar base or for enabling an interplanetary refueling station. These ice deposits also preserve a unique record of the geology and environment of their hosts, both in terms of impact history and the supply of volatile compounds, and so are of immense scientific interest. To date, these ice deposits have been studied indirectly and by remote active radar, but they need to be analyzed in-situ by robotic systems that can study the depths of the deposits, their purity and composition. However, these shadowed craters never see sunlight and are one of the coldest places in the solar system. NASA JPL proposed use of solar reflectors mounted on crater rims to project sunlight into the crater depths for use by ground robots. The solar reflectors would heat the crater base and vehicles positioned at the base sufficiently to survive the cold-temperatures. Our approach analyzes part of the logistics of the approach, with teams of robots climbing up and down to the crater to access the ice deposits. The mission will require robots to climb down extreme environments and carry large structures, including instruments and communication devices.

cs.RO↗

arXiv2018

De-orbiting Small Satellites Using Inflatables

Small-satellites and CubeSats offer a low-cost pathway to access Low Earth Orbit at altitudes of 450 km and lower thanks to miniaturization and advancement in reliability of commercial electronics. However, at these low altitudes, atmospheric drag has a critical effect on the satellite resulting in natural deorbits within months. As these small systems further increase in reliability and radiation tolerance they will be able readily access higher orbits at altitudes of 700 km and higher, where atmospheric drag has little to no effect. This requires alternative technologies to either de-orbit these small spacecrafts at the end of life or move them to a safe parking orbit. Use of propulsion and de-orbit mechanisms have been proposed, however they require active control systems to be trigged. Other typical de-orbit mechanism relies on complex mechanisms with many moving parts. In this work, we analyze the feasibility of using inflatable de-orbit devices that are triggered passively when a spacecraft is tumbling. Inflatables have already been proposed as hypersonic deccelerators that would carry large payload to the Martian surface. However, these systems are quite complex and need to withstand high-forces, temperature and enable survival of a critical payload. Furthermore, inflatables have been proposed as communication antennas and as structures using a class of sublimates that turn into gas under the vacuum of space. These inflatables system are relatively simple and does not require a specialized inflation system.

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arXiv2018

Satellite Capture and Servicing Using Networks of Tethered Robots Supported by Ground Surveillance

There is ever growing demand for satellite constellations that perform global positioning, remote sensing, earth-imaging and relay communication. In these highly prized orbits, there are many obsolete and abandoned satellites and components strewn posing ever-growing logistical challenges. This increased demand for satellite constellations pose challenges for space traffic management, where there is growing need to identify the risks probabilities and if possible mitigate them. These abandoned satellites and space debris maybe economically valuable orbital real-estate and resources that can be reused, repaired or upgraded for future use. On-orbit capture and servicing of a satellite requires satellite rendezvous, docking and repair, removal and replacement of components. Launching a big spacecraft that perform satellites servicing is one credible approach for servicing and maintaining next-generation constellations. By accessing abandoned satellites and space debris, there is an inherent heightened risk of damage to a servicing spacecraft. Under these scenarios, sending multiple, small-robots with each robot specialized in a specific task is a credible alternative, as the system is simple and cost-effective and where loss of one or more of robot does not end the mission. Eliminating the need for a large spacecraft or positioning the large spacecraft at safe distance to provide position, navigation and tracking support simplifies the system and enable the approach to be extensible with the latest ground-based sensing technology. In this work, we analyze the feasibility of sending multiple, decentralized robots that can work cooperatively to perform capture of the target satellite as first steps to on-orbit satellite servicing.

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arXiv2018

On-Orbit Smart Camera System to Observe Illuminated and Unilluminated Space Objects

The wide availability of Commercial Off-The-Shelf (COTS) electronics that can withstand Low Earth Orbit conditions has opened avenue for wide deployment of CubeSats and small-satellites. CubeSats thanks to their low developmental and launch costs offer new opportunities for rapidly demonstrating on-orbit surveillance capabilities. In our earlier work, we proposed development of SWIMSat (Space based Wide-angle Imaging of Meteors) a 3U CubeSat demonstrator that is designed to observe illuminated objects entering the Earth's atmosphere. The spacecraft would operate autonomously using a smart camera with vision algorithms to detect, track and report of objects. Several CubeSats can track an object in a coordinated fashion to pinpoint an object's trajectory. An extension of this smart camera capability is to track unilluminated objects utilizing capabilities we have been developing to track and navigate to Near Earth Objects (NEOs). This extension enables detecting and tracking objects that can't readily be detected by humans. The system maintains a dense star map of the night sky and performs round the clock observations. Standard optical flow algorithms are used to obtain trajectories of all moving objects in the camera field of view. Through a process of elimination, certain stars maybe occluded by a transiting unilluminated object which is then used to first detect and obtain a trajectory of the object. Using multiple cameras observing the event from different points of view, it may be possible then to triangulate the position of the object in space and obtain its orbital trajectory. In this work, the performance of our space object detection algorithm coupled with a spacecraft guidance, navigation, and control system is demonstrated.

cs.CV↗

arXiv2018

Planning and Navigation of Climbing Robots in Low-Gravity Environments

Advances in planetary robotics have led to wheeled robots that have beamed back invaluable science data from the surface of the Moon and Mars. However, these large wheeled robots are unable to access rugged environments such as cliffs, canyons and crater walls that contain exposed rock-faces and are geological time-capsules into the early Moon and Mars. We have proposed the SphereX robot with a mass of 3 kg, 30 cm diameter that can hop, roll and fly short distances. A single robot may slip and fall, however, a multirobot system can work cooperatively by being interlinked using spring-tethers and work much like a team of mountaineers to systematically climb a slope. We consider a team of four or more robots that are interlinked with tethers in an 'x' configuration. Each robot secures itself to a slope using spiny gripping actuators, and one by one each robot moves upwards by crawling, rolling or hopping up the slope. In this paper, we present a human devised autonomous climbing algorithm and evaluate it using a high-fidelity dynamics simulator. The climbing surfaces contain impassable obstacles and some loosely held rocks that can dislodge. Under these conditions, the robots need to autonomously map, plan and navigate up or down these steep environments. Autonomous mapping and navigation capability is evaluated using simulated lasers, vision sensors. The human devised planning algorithm uses a new algorithm called bounded-leg A*. Our early simulation results show much promise in these techniques and our future plans include demonstration on real robots in a controlled laboratory environment and outdoors in the canyons of Arizona.

cs.RO↗

arXiv2018

Path Planning and Navigation Inside Off-World Lava Tubes and Caves

Detailed surface images of the Moon and Mars reveal hundreds of cave-like openings. These cave-like openings are theorized to be remnants of lava-tubes and their interior maybe in pristine conditions. These locations may have well preserved geological records of the Moon and Mars, including evidence of past water flow and habitability. Exploration of these caves using wheeled rovers remains a daunting challenge. These caves are likely to have entrances with caved-in ceilings much like the lava-tubes of Arizona and New Mexico. Thus, the entrances are nearly impossible to traverse even for experienced human hikers. Our approach is to utilize the SphereX robot, a 3 kg, 30 cm diameter robot with computer hardware and sensors of a smartphone attached to rocket thrusters. Each SphereX robot can hop, roll or fly short distances in low gravity, airless or low-pressure environments. Several SphereX robots maybe deployed to minimize single-point failure and exploit cooperative behaviors to traverse the cave. There are some important challenges for navigation and path planning in these cave environments. Localization systems such as GPS are not available nor are they easy to install due to the signal blockage from the rocks. These caves are too dark and too large for conventional sensor such as cameras and miniature laser sensors to perform detailed mapping and navigation. In this paper, we identify new techniques to map these caves by performing localized, cooperative mapping and navigation.

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