Showing papers presented at "IEEE Aerospace Conference in 2014"

Unmanned Aircraft Systems (UAS) research and future analysis

Abstract: The primary objective of this report is to develop relationships between market forecasted use of unmanned aircraft and economic incentives. This paper summarizes a technical report produced by the Volpe National Transportation Systems Center (Volpe Center) entitled “Unmanned Aircraft Systems (UAS) Service Demand 2015–2035: Literature Review and Projections of Future Usage” [1]. The report included analysis of the UAS technical areas, including command, control, and communications (C3) subsystems. The C3 area includes classic aviation components of Communication, Navigation, and Surveillance (CNS). The analysis includes survey and data collection of mission types and aircraft parameters to be used to develop technology forecasts for technical/product areas of unmanned systems and their use in the National Airspace System (NAS). The study addresses constraints pertaining to technology diffusion and regulatory changes needed to show where incentives can accelerate UAS integration into the NAS. Specific focus for this paper is the use of incentives in CNS.

Integrated model-based systems engineering (MBSE) applied to the Simulation of a CubeSat mission

Abstract: Small satellite missions are becoming increasingly complex as scientists and engineers propose to utilize them to accomplish more ambitious science and technology goals. Small satellites such as CubeSats are challenging to design because they have limited resources, coupled subsystems, and must operate in dynamic environments.

Design and development of a free-floating hexrotor UAV for 6-DOF maneuvers

Abstract: This paper presents design and development of an experimental testbed for nonlinear geometric controls of a rigid body. We develop a fully actuated hexrotor UAV that uses six variable pitch propellers to control six degrees of freedom maneuvers, namely three position and three attitude variables, independently. In contrast to the popular quadrotor UAVs that can hover at a single attitude, the hexrotor presented in this paper is capable of hovering at any attitude provided that thrust is sufficiently large. A geometric controller is also developed on the special Euclidean group to track given desired position and attitude trajectories under the effects of unknown disturbances. These are particularly useful for ground tests for large angle rotational dynamics of spacecraft that are combined with arbitrary translational motions. A numerical example that involves a nontrivial maneuver and preliminary experimental tests are also presented.

ADAPT demonstrations of onboard large-divert Guidance with a VTVL rocket

Abstract: The Autonomous Ascent and Descent Powered-Flight Testbed (ADAPT) is a closed-loop, free-flying testbed for demonstrating descent and landing technologies of next-generation planetary landers. The free-flying vehicle is the Masten Space Systems Xombie vertical-takeoff, vertical-landing suborbital rocket. A specific technology ADAPT is demonstrating in the near-term is Guidance for Fuel-Optimal Large Diverts (G-FOLD), a fuel-optimal trajectory planner for diverts during powered descent, which is the final kilometers of descent to landing on rocket engines. Previously, ADAPT used Xombie to fly optimal large-divert trajectories, extending Xombie's divert range to 750 m. However, these trajectories were planned off-line with G-FOLD. This paper reports the successful Xombie flight demonstrations of large diverts using G-FOLD on board to calculate divert trajectories in real time while descending. The culminant test flight of the last year was an 800 m divert that was initiated at an altitude of 290 m while moving away from and crosswise to the landing pad. Hence, G-FOLD had to calculate a constrained divert trajectory that reversed direction, was fully three-dimensional, with horizontal motion nearly three times the initial altitude, and it did so in ∼100 ms on board Xombie as it was descending. Xombie then flew the divert trajectory with meter-level precision, demonstrating that G-FOLD had planned a trajectory respecting all the constraints of the rocket-powered vehicle. The steps to reach this flight demonstration of on-board generation of optimal divert trajectories and the system engineering for future ADAPT payloads are also presented.

Next generation rope-like robot for in-space inspection

Abstract: Design of continuum robots, i.e. robots with continuous backbones, has been an active area of research in robotics for minimally invasive surgery, search and rescue, object manipulation, etc. Along the same lines, NASA developed “Tendril”, the first long and thin continuum robot of its kind, intended for in-space inspection applications. In this paper, we describe and discuss the key disadvantages of state of the art mechanical design producing undesirable effects during operation. We then provide the specifics of a new, next generation, thin rope-like robot with a modified mechanical design for better performance having key features like controllable bending along its entire length, local compression and potentially smaller actuation package.

Inflatable antenna for cubesat: fabrication, deployment and results of experimental tests

Abstract: CubeSats and small satellites have potential to provide means to explore space and to perform science in a more affordable way. As the goals for these spacecraft become more ambitious in space exploration, moving from Low Earth Orbit (LEO) to Geostationary Earth Orbit (GEO) or further, the communication systems currently implemented will not be able to support those missions. One of the bottlenecks is the antennas’ size, due to the close relation between antenna gain and dimensions. Current antennas for CubeSats are mostly dipole or patch antennas with limited gain. Deployable (not inflatable) antennas for CubeSats are currently being investigated, but these solutions are affected by the challenge of packaging the whole deployable structure in a small spacecraft. The work that we propose represents the first attempt to develop an inflatable antenna for CubeSats. Inflatable structures and antennas can be packaged efficiently, occupying a small amount of space, and they can provide, once deployed, large dish dimension and correspondent gain. Inflatable antennas have been previously tested in space (Inflatable Antenna Experiment, STS-77). However they have never been developed for small spacecraft such as CubeSats, where the packaging efficiency, the deployment, and the inflation represent a challenge. Previous works developed by the authors described trade-off analysis, preliminary design and radiation model for the antenna. The research presented in this paper is focused specifically on implementation and testing. Details of the antenna’s fabrication and related issues are illustrated as well as the mechanism to fold and deploy the antenna in space. Finally, results of the experimental tests (vacuum chamber and anechoic chamber) are described. Future work in the development of the antenna will include the improvement of the fabrication process and the design of a 3U CubeSat mission to be proposed as a technical demonstration.

Cost and risk analysis of small satellite constellations for earth observation

Abstract: Distributed Space Missions (DSMs) are gaining momentum in their application to Earth science missions owing to their ability to increase observation sampling in spatial, spectral, temporal and angular dimensions. Past literature from academia and industry have proposed and evaluated many cost models for spacecraft as well as methods for quantifying risk. However, there have been few comprehensive studies quantifying the cost for multiple spacecraft, for small satellites and the cost risk for the operations phase of the project which needs to be budgeted for when designing and building efficient architectures. This paper identifies the three critical problems with the applicability of current cost and risk models to distributed small satellite missions and uses data-based modeling to suggest changes that can be made in some of them to improve applicability. Learning curve parameters to make multiple copies of the same unit, technological complexity based costing and COTS enabled small satellite costing have been studied and insights provided.

OBC-NG: Towards a reconfigurable on-board computing architecture for spacecraft

Abstract: The computational demands on spacecraft are rapidly increasing. Current on-board computing components and architectures cannot keep up with the growing requirements. Only a small selection of space-qualified processors and FPGAs are available and current architectures stick with the inflexible cold-redundant structure. The objective of the ongoing project OBC-NG (On-board Computer - Next Generation) is to find new concepts for on-board-computer to fulfill future requirements. The concept presented in this paper is based on a distributed reconfigurable system, consisting of different nodes for processing, management and interface operations. OBC-NG will exploit the high performance of commercial off-the-shelf (COTS) hardware parts. To compensate the shortcomings of COTS parts the OBC-NG redundancy approach differs from the classic way and error mitigation techniques will work mainly on software level. This paper discusses the hardware and software architecture of the system as well as the redundancy and reconfiguration concept. Our ideas will be proven in an OBC-NG prototype, planned for the next year.

Geiger-mode APD single-photon cameras for 3D laser radar imaging

Abstract: We describe the design and performance of short-wave infrared 3D imaging cameras with focal plane arrays (FPAs) based on Geiger-mode avalanche photodiodes (GmAPDs) with single photon sensitivity for laser radar imaging applications. The FPA pixels incorporate InP/InGaAs(P) GmAPDs for the detection of single photons with high efficiency and low dark count rates. Based on the design of the GmAPD detectors, FPAs have been optimized for source wavelengths near either 1.0 µm or 1.5 µm. We present results and attributes of fully integrated camera sub-systems with 32 × 32 and 128 × 32 formats, which have 100 µm pitch and 50 µm pitch, respectively. We also address the sensitivity of the fundamental GmAPD detectors to radiation exposure, including recent results that correlate detector active region volume to sustainable radiation tolerance levels. For GmAPD detector designs that are compatible with our existing FPA platform, these discrete device results indicate that sensors with our current level of performance can be designed to tolerate radiation exposure of at least 8 krad with acceptable levels of dark count rate elevation.

A critical analysis of additive manufacturing technologies for aerospace applications

Abstract: In the restricted budget environments of recent years, the aerospace and defense sectors are primarily driven by cost, in addition to level of system performance and development schedule. Some of the current techniques listed for additive manufacturing are still very relevant in current industry and technologies are being developed to further improve effectiveness. Specialized products often require development of new processes and facilities which are very capital intensive. Laser based additive manufacturing has shown the potential to reduce the development costs and eliminated the complexity factor. As a result, it becomes possible to manufacture structures of complex shapes and sizes. Efforts are still ongoing for developing a cost effective solution to additive manufacturing of non-metals and metals. There are several parameters which are used to judge the additive technology such as surface finish, tensile strength of the product manufactured, intricacy of design, variety of materials with which the technology can work etc. Some of the newer technologies such as laser consolidation have the potential to not only develop near net shape parts but also repair broken metal components but also repair broken metal components by printing the damaged areas over the existing metal bodies. Abilities like this will not only enable the aerospace sector to reduce their time to development but also reuse some of the critical and non-critical components in the space missions at very low costs. This paper looks at the different additive manufacturing technologies which can be used for the manufacturing of aerospace components from a number of different parameters, their advantages and disadvantages and tries to assess their feasibility for production of components for practical applications. Apart from this, the paper shall also cover the latest developments in this field and try to assess what will be their implications on the management of critical components for use in the aerospace sector.

Fault-Tolerant Distributed approach to satellite On-Board Computer design

Abstract: In this paper, a novel design of a satellite Fault-Tolerant Distributed On-Board Computer (FTD-OBC) is proposed. The FTD-OBC fault-tolerance and task migration functions rely on a distributed coordination method, which is supported by an Adaptive Middleware for Fault-Tolerance (AMFT) block. The proposed distributed computer is adaptive and reconfigures itself in case of a failure seamlessly by migrating the tasks of a faulty node to other nodes. The FTD-OBC design is assessed against the popular centralized and Triple Modular redundant OBCs. The analysis demonstrates that the distributed OBC design achieves much higher reliability along with the inherent advantage of a higher computing performance. Experimental results are reported, which show that the proposed FTD-OBC is able to quickly migrate computing tasks when a fault occurs within a node, enabling seamless continuous operation.

A novel pump design for an efficient and compact Electro-Hydraulic Actuator IEEE aerospace conference

Abstract: This paper presents an innovative design solution for a compact Electro-Hydraulic Actuator (EHA). Although the current trend in many mobile applications is towards Electro Mechanical Solutions (EMAS) instead of Hydraulic Actuation systems (HAS), the use of HEAs could represent the best technological compromise. In fact, EHA can combine the power to weight ratio advantage of hydraulic technology with the versatility and ease of control of electric technology. Compared to EMAS, which are often equipped with low efficiency load holding mechanisms, EHAs can also offer superior energy efficiency.

Initial results for air-ground channel measurements & modeling for unmanned aircraft systems: Over-sea

Abstract: As is widely known, unmanned aircraft systems (UAS) are expected to greatly expand in use within the national airspace system over the coming decades. With UAS civil spectral allocations planned for two bands—L-band (960–977 MHz) and C-band (5030–5091 MHz)—work is already being conducted on air interfaces and network design for control and non-payload communications (CNPC). Since most prior work studied the narrowband air-ground (AG) channel with very tall ground-site towers in open, clear areas, key wideband channel characteristics for UAS have not been thoroughly addressed. In this paper we provide some of our initial results on measurements and modeling of the AG channel, for a project sponsored by NASA Glenn Research Center. The measurements on which we report were conducted with a ground site in a coastal setting, with flights over the Pacific Ocean. These measurements were of the simultaneous channel impulse responses in both bands, and employed two receivers for each band to assess antenna diversity as well as differences across the bands. After a brief discussion of project goals, test equipment, and the measurement campaign, we provide analysis of power delay profiles and path loss, for several flight paths that cover moderate and low-elevation-angle conditions. We report on delay dispersion statistics, and channel parameter correlations across frequency and antennas for the over-sea setting. We also briefly discuss how our measured profiles will be used to develop statistical models for the AG channel. These models will be of use for communication system engineers conducting analysis, simulations, and design of future UAS CNPC systems.

System analysis of smart gateways techniques applied to Q/V-band high throughput satellites

Abstract: The future generation of High Throughput Satellite (HTS) for broadband distributed user access is strictly connected to the use of Ka-band and beyond frequencies. This is related to the requirement of reaching the so-called “terabit connectivity” to support the increasing bit rate requirements.

SOS for SoS: A new paradigm for system of systems modeling

Abstract: Systems of Systems (SoS) modeling is becoming increasingly important in both civilian and military systems. The Department of Defense (DoD) Defense Acquisition Guidebook, [1] defines a SoS as a “set or arrangement of systems that results when independent and useful systems are integrated into a larger system that delivers unique capabilities.” Organizations are changing their emphasis from “We need a new system” to “We need to achieve a specific outcome.” As these outcomes become more complex and the associated systems more complex, the management, modeling and simulation of these SoS becomes equally challenging. Often, the SoS is modeled in all its complexity, often at a single level of abstraction or level of detail. Instead of a “megamodel” approach, a standards-based “model of models” approach is what is necessary. This approach will use the Object Management Group (OMG) Unified Profile for DoDAF and MODAF (UPDM) for modeling enterprise architectures from capabilities to detailed components, and the Reusable Asset Specification (RAS) for defining reusable assets. Combining UPDM and RAS provides a Model of Models approach with the main model specifying assets in various levels of details. The models specified by these assets can be referenced when detailed analysis is required, or hidden when a SoS viewpoint is required, allowing the analyst to see the forest through the trees. The paper will also include an assessment of the applicability and effectiveness of this approach. The International Conference on Systems Engineering (INCOSE) System of Systems Working Group (SoSWG) has collected a set of “Pain Points on SoS” from a variety of international sources. This paper will review these pain points and discuss how the application of a Model of Model approach, combined with standards-based modeling tools and a reusable assets approach can help to alleviate some of the pain currently being felt by SoS architects and managers. Hopefully, this response to their SOS will deliver some much-needed assistance.

Simulation of spacecraft damage tolerance and adaptive controls

Abstract: The nature of adaptive controls, or controls for unpredictable systems, lends itself naturally to the concept of damage tolerant controls in high performing systems, such as aircraft and spacecraft. Recent technical demonstrations of damage tolerant aircraft prove the concept of adaptive controls in an operational environment. Research covered by this paper expands on the topic by discussing the application of adaptive controls to spacecraft and theory behind simulating damage tolerant control implementation. Simulation is then used to demonstrate the stability of adaptive controls when experiencing sudden mass loss and rapid changes in inertia.

SpaceCube v2.0 space flight hybrid reconfigurable data processing system

Abstract: This paper details the design architecture, design methodology, and the advantages of the SpaceCube v2.0 high performance data processing system for space applications. The purpose in building the SpaceCube v2.0 system is to create a superior high performance, reconfigurable, hybrid data processing system that can be used in a multitude of applications including those that require a radiation hardened and reliable solution. The SpaceCube v2.0 system leverages seven years of board design, avionics systems design, and space flight application experiences. This paper shows how SpaceCube v2.0 solves the increasing computing demands of space data processing applications that cannot be attained with a standalone processor approach.

A conformal conical phased array antenna for modern radars

Abstract: In this paper a new conformal array antenna of conical structure has been proposed. A conical phased array antenna can steer the radar beam electronically in both azimuth and elevation to cover a hemi-sphere mesh surrounding the radar antenna. Beam steering can be accomplished either continuously or discretely at definite directions. The proposed technique not only overcomes the limitations of mechanical steering systems and surveillance radar dead cone but also improves the radar tracking capability. Moreover, it is suitable to be used in MIMO radars and enemy deception systems. Element weights of the conical phased array antenna are optimized using a genetic algorithm (G.A). The optimization process improves the beam pattern peak side lobe level (PSLL) while maintaining a narrow beam width. A high resolution phase shifter and adaptive attenuator have been used for each element to acquire both the desired phase and optimum weight for conical array beam pattern. Beam pattern is simulated and tested using a Matlab Program. Improvement achieved in both antenna gain and PSLL are 18.8 and 8 dB respectively. There is a 6° tilting angle and 24° half power beam width.

Satellite-to-satellite coverage optimization approach for opportunistic inter-satellite links

Abstract: This paper presents an approach to optimize orbit geometries under satellite to satellite coverage criteria. The method described herewith is applicable to any space system concept featuring inter-satellite-links, including system concepts introducing links of opportunity between heterogeneous spacecraft at different orbits not designed a priori as a constellation. The latter is the case of federated satellite systems, that have recently been proposed as open satellite constellation concepts for opportunistic sharing of data relay and on board storage services. Federated satellite systems make use of unused telecommunications capacity available in participating spacecraft at any given time. This paper describes the satellite to satellite coverage optimization problem, a proposed optimization approach, and its analytical validation. The convergence of results is shown in terms of spatial discretization, temporal discretization and simulation period. The approach is demonstrated in a LEO to LEO network scenario, where orbital parameters of a single spacecraft are optimized to supply the maximum coverage to an example set of 6 LEO spacecraft, at different inter-satellite-link slant ranges. It is shown that increasing the inter-satellite-link maximum range above 6,000 km does not lead to further coverage benefits at LEO altitude. Orbit optimization for LEO coverage is also performed on a set of three spacecraft. In both cases, the optimum solutions feature polar inclination orbits, suggesting that said orbits may be advantageous for LEO satellite-to-satellite applications. This paper ends with conclusions outlining the future work on the satellite to satellite coverage optimization.

Results of the MIT Space Communication and Navigation architecture study

Abstract: NASA is currently conducting an architecture study for the next-generation Space Communication and Navigation system. This is an extremely complex problem with a variety of options in terms of band selection (RF, from S-band to Ka-band and beyond, or optical), network type (bent-pipe, circuit-switched, or packet-switched), fractionation strategies (monolithic, mother-daughters, homogeneous fractionation), orbit and constellation design (GEO/MEO/LEO, number of planes, number of satellites per plane), and so forth. When all the combinations are considered, the size of the tradespace grows to several millions of architectures. The ability of these architectures to meet the requirements from different user communities and other stakeholders (e.g., regulators, international partners) needs to be assessed. In this context, a computational tool was developed to enable the exploration of such large space of architectures in terms of both performance and cost. A preliminary version of this tool was presented in a paper last year. This paper describes an updated version of the tool featuring a higher-fidelity, rule-based scheduling algorithm, as well as several modifications in the architecture enumeration and cost models. It also discusses the validation results for the tool using real TDRSS data, as well as the results and sensitivity analyses for several forward-looking scenarios. Particular emphasis is put on families of architectures that are of interest to NASA, namely TDRSS-like architectures, architectures based on hosted payloads, and highly distributed architectures.

Three-dimensional path planning for unmanned aerial vehicles based on fluid flow

Abstract: Using the principles of fluid mechanics for flow around objects, a three dimensional (3D) path planning method for unmanned aerial vehicles (UAVs) in complex environments is studied. As a potential field method, it theoretically guarantees to avoid local minima with smooth paths and the modeling of environment is simple. First, an analytical solution is derived to determine the steady 3D fluid flow acting on a single spherical obstacle. Subsequently, an interpolation function is introduced to multiple obstacles avoidance. Finally, the maneuverability constraints of the UAV are imposed and flight paths are obtained. Added the effect of human factors, a Generalized Fuzzy Competitive Neural Network (G-FCNN) is proposed to evaluate the flight paths. In simulation, the path is smoother and more reasonable. In terms of evaluation, G-FCNN could considerate multiple factors and the result is satisfied.

Cooperative space object tracking via multiple space-based visible sensors with communication loss

Abstract: Accurate and timely space object tracking is important for space surveillance missions Among various sensors such as ground-based radars, a space-based visible (SBV) sensor has been considered as an important sensing technology to achieve the stringent goals of space surveillance due to its high-accuracy angle measurements, faster observation rates, and large sensing coverage To achieve certain tracking accuracy requirements, multiple sensors and cooperative tracking algorithms are often used However, communication loss is often ignored although it commonly exists in communications of different sensor applications In this paper, a space object tracking separated extended information filter (SEIF) algorithm uses multiple space-based visible (SBV) sensors to track targets The algorithm is evaluated through implementation in a space object tracking scenario supported by the NASA General Mission Analysis Tool (GMAT) The root mean square error is used to compare the performance of the proposed algorithm and classical algorithms, such as the EIF The simulation results indicate that the performance of the SEIF is better than that of the EIF when there is a communications loss between different sensors

Performance characterization of Phase Gradient Autofocus for inverse synthetic aperture LADAR

Abstract: Phase Gradient Autofocus (PGA) is an effective algorithm for estimating and removing piston-phase errors from spotlight-mode synthetic aperture radar (SAR) data. For target scenes dominated by a point source, the algorithm has been shown to be optimal in the sense that it approaches the Cramer-Rao bound for carrier-to-noise ratios (CNRs) as low as −5 dB. In this paper, we explore PGA's effectiveness against ground-based inverse synthetic aperture LADAR (ISAL) observations of spacecraft, where the target characteristics and phase errors are quite different than in the SAR case. At optical wavelengths, the power spectrum of the piston-phase errors will be dominated less by platform motion and more by atmospheric variations. In addition, space objects will have fewer range-resolution cells across them than would a typical extended SAR scene. This research characterizes the performance limitations of PGA for an ISAL system as a function of CNR and the number of range-resolution cells across the scene. A high-fidelity wave-optics simulation is used to generate representative test data for input to the PGA algorithm. Emphasis is placed on finding the lower limits of performance for which image reconstruction is possible.

Crew size impact on the design, risks and cost of a human mission to mars

Abstract: Numerous scenarios have been proposed for a human mission to Mars. The crew size is typically between three and six astronauts. According to experts in human factors, a crew of three is possible but a crew of six is more appropriate. However, it is shown in this paper that the impact of the number of astronauts on the design, the risks, and the cost of the first mission might be much more important than expected. Different domains are considered: There is a direct impact on the consumables and astronauts' affairs. Reducing the size of the crew from six to three astronauts allows an IMLEO (Initial Mass in Low Earth Orbit) reduction on the order of 34%. There is an important impact on the choice of EDL (Entry, Descent and Landing) systems. According to our calculations, reducing the size of the crew from six to three astronauts allows sufficient mass savings and volume reduction for the choice of large capsules with a 70° sphere cone heat shield. If it is confirmed, this choice enables important mass savings for EDL systems, on the order of 26% for the landing vehicles. Aerocapture would also be enabled for the interplanetary manned vehicle, allowing complementary mass savings. Finally, considering the total reduction of the payload that has to be sent to Mars, it might be possible to avoid the LEO (Low Earth Orbit) assembly and to send the interplanetary vehicles directly to Mars. All in all, reducing the size of the crew from six to three astronauts is probably a game-changing option. In addition, if six astronauts were the preferred crew size on the surface of Mars, the best option according to the IMLEO criterion would be, without question, a duplication of the scenario with three astronauts.

Asteroid Redirect Robotic Mission feasibility study

Abstract: The Asteroid Redirect Robotic Mission (ARRM) concept seeks to rendezvous with, capture, and redirect to translunar space an entire small near-Earth asteroid with a mass of up to approximately 1000 metric tonnes. It would focus the capabilities of the science, technology, and the human exploration communities on a grand challenge creating a new synergy between robotic and human missions to advance human space exploration beyond low Earth orbit for the first time in 50 years. This paper addresses the key aspects of the ARRM concept and the options studied to assess its technical feasibility. Included are evaluations of the expected number of potential targets, their expected discovery rate, the necessity to adequately characterize candidate mission targets, the process to capture a non-cooperative asteroid in deep space, and the power and propulsion technologies required for transportation back to the Earth-Moon system. A class of distant retrograde lunar orbits that are stable for more than 250 years are identified as potential locations for storing the redirected asteroid. These orbits are reachable by the Asteroid Retrieval Vehicle transporting a 1000-t asteroid and are also reachable by crewed missions using the Space Launch System and Orion. The study concludes that the key aspects of finding, capturing and redirecting an entire small, near-Earth asteroid to the Earth-Moon system by the first half of the next decade are technically feasible. The study was conducted from January 2013 through July 2013 by the Jet Propulsion Laboratory (JPL) in collaboration with Glenn Research Center (GRC), Johnson Space Center (JSC), Langley Research Center (LaRC), and Marshall Space Flight Center (MSFC).

A framework to analyze processor architectures for next-generation on-board space computing

Abstract: Due to harsh and inaccessible operating environments, space computing presents many unique challenges with respect to stringent power, reliability, and programmability constraints that limit on-board processing performance and mission capabilities. However, the increasing need for real-time sensor and autonomous processing, coupled with limited communication bandwidth with ground stations, are increasing the demand for high-performance, on-board computing for next-generation space missions. Since currently available radiation-hardened space processors cannot satisfy this growing demand, research into various processor architectures is required to ensure that potential new space processors are based on architectures that will best meet the computing needs of space missions. To enable this research, we present a novel framework to analyze potential processor architectures for space computing. By using this framework to analyze a wide range of existing radiation-hardened and emerging commercial processors, tradeoffs between potential space computing architectures can be determined and considered when designing new space processors or when selecting commercial architectures for radiation hardening and use in space missions. We demonstrate the ability of the framework to generate data for various architectures in terms of performance and power, and analyze this data for initial insights into the effects of processor architectures on space mission capabilities. The framework provides a foundation for the analysis of a broad and diverse set of processor architectures for potential use in next-generation, on-board space computing.

Testing of safety-critical systems: An aerospace launch application

Abstract: This paper proposes an approach for testing of safety critical systems. It is based on a behavioral and a fault model. The two models are analyzed for compatibility and necessary changes are identified to make them compatible. Then transformation rules are used to transform the fault model into the same model type as the behavioral model. Integration rules define how to combine them. This approach results in an integrated model which then can be used to generate tests using a variety of testing criteria. The paper illustrates this general framework using a CEFSM for the behavioral model and a Fault Tree for the fault model. We apply the approach to an Aerospace launch application.

PlanetVac: Pneumatic regolith sampling system

Abstract: This paper describes a PlanetVac mission concept utilizing a pneumatic system for sample acquisition and delivery, and the design and testing of a prototype system. The lander uses sampling tubes embedded within each lander foot pad. Each tube can deliver in excess of 20 grams of regolith and small rocks directly into science instruments or a sample return spacecraft for earth return. To demonstrate this mission approach, a small lander with four legs and two sampling tubes has been designed, built, and tested. Testing has been performed in vacuum chamber and with two planetary simulants: Mars Mojave Simulant (MMS) and lunar regolith simulant JSC-1A. One sampling system was connected to an earth return rocket while the second sampling system was connected to a deck mounted instrument inlet port. Demonstrations included a drop from a height of ∼50 cm onto the bed of regolith, deployment of sampling tubes, acquisition of regolith into an instrument (sample container) and the rocket, and the launch of the rocket. In all tests, approximately 20 grams of sample has been delivered to the regolith box and approximately 5 grams of regolith has been delivered into a rocket. The gas efficiency was calculated to be approximately 1000∶1; that is 1 gram of gas lofted 1000 grams of regolith.

Formation establishment and reconfiguration using differential elements in J2-perturbed orbits

Abstract: A practical algorithm is developed for on-board planning of n-impulse fuel-optimal maneuvers for establishment and reconfiguration of spacecraft formations. The method is valid in circular and elliptic orbits and includes first-order secular J 2 effects. The dynamics are expressed in terms of differential mean orbital elements, and relations are provided to allow the formation designer to transform these into intuitive geometric quantities for visualization and analysis. The maneuver targeting problem is formulated as an optimal control problem in both continuous and discrete time. The continuous-time formulation cannot be solved directly in an efficientmanner, and the discrete-time formulation, which has an analytical solution, does not directly yield the optimal thrust times. Therefore, a practical algorithm is designed by iteratively solving the discrete-time formulation while using the continuous-time necessary conditions to refine the thrust times until they converge to the optimal values. Simulation results are shown for a variety of reconfiguration maneuvers and reference orbits, including simulations with and without navigation errors for the NASA CubeSat Proximity Operations Demonstration mission.

Experimental results of a controllable electrostatic/gecko-like adhesive on space materials

Abstract: Many space applications, such as docking, satellite capture, or robotic inspection, could benefit from the use of a controllable (i.e. on-off) adhesive capable of functioning on a wide range of surfaces. This paper focuses on the experimental results of such an adhesive, which combines the benefits of both electrostatic and directional dry adhesives (i.e. gecko-like adhesives). The electrostatic element consists of a conductive electrode pattern embedded inside a soft silicone polymer dielectric. Between the electrodes and the substrate lies a dry adhesive element comprised of directional fibrillar structures. The combination of these two technologies creates a positive feedback cycle in which, depending on surface roughness and material, adhesive levels can be greater than the sum of the two individual technologies. The electrostatic adhesive serves to initially engage the micro-wedges with the surface substrate. As they engage, the micro-wedges bring the electrostatic element closer to the surface, which further increases its adhesion. This consequently allows more of the dry adhesive micro-wedges to engage, particularly on rough surfaces. This paper presents the results of experimental testing of these adhesives over a range of different space-grade materials. These include different paints, composites, and blankets. Results show that the hybrid adhesive performs up to 7.1× greater than electrostatic adhesives alone.