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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Lunar Rover Optimization Platform for Wheel Traction Studies

Robotic mobility systems expand the reach of future scientific and exploration missions to celestial bodies. Understanding the traction performance of these systems is necessary knowledge that informs mission-level requirements, such as power budgets and navigation envelopes. This paper covers the design, development, and verification of the four wheeled Lunar Rover Optimization Platform (LROP). This mass optimized platform is targeted to emulate future medium class rovers weighing up to 90 kg. The LROP has the ability to conduct various wheel design experiments such as obstacle traversal, slope ascent, and drawbar pull over a wheel loading range of 4.5 to 22.7 kg. The platform also has the ability to shift its center of gravity (CG) laterally and longitudinally to explore the CG shift effects on mobility performance. This knowledge is valuable for future rover designers exploring different payload packaging solutions. In this paper results from obstacle traversal test with varying angle of attack (AOA) and longitudinal CG position are reported along with results from slope ascent testing which proved-out the LROPs capabilities.

Stephen Gerdts↗
NASA NTRS1980

Optimal platform skewing for Space Shuttle inertial measurement unit redundancy management

Constraints are applied to a general quaternion which describes the skewing between platforms of the Space Shuttle IMU. Once a skewing is derived, the use of the failure magnitude to threshold ratio makes possible predictions of the identification sensitivities for various failure modes. This in turn simplifies analyses and identifies portions of the flight envelope where second failure coverage is lacking. The square root of 6 and square root of 2 skewings have been baselined for use during nominal entry; the realignment software will be used on orbit to reskew the IMUs to the optimal configuration.

Rasmussen, M. C.↗
NASA NTRS2013

Engineering of Data Acquiring Mobile Software and Sustainable End-User Applications

The criteria for which data acquiring software and its supporting infrastructure should be designed should take the following two points into account: the reusability and organization of stored online and remote data and content, and an assessment on whether abandoning a platform optimized design in favor for a multi-platform solution significantly reduces the performance of an end-user application. Furthermore, in-house applications that control or process instrument acquired data for end-users should be designed with a communication and control interface such that the application's modules can be reused as plug-in modular components in greater software systems. The application of the above mentioned is applied using two loosely related projects: a mobile application, and a website containing live and simulated data. For the intelligent devices mobile application AIDM, the end-user interface have a platform and data type optimized design, while the database and back-end applications store this information in an organized manner and manage access to that data to only to authorized user end application(s). Finally, the content for the website was derived from a database such that the content can be included and uniform to all applications accessing the content. With these projects being ongoing, I have concluded from my research that the applicable methods presented are feasible for both projects, and that a multi-platform design for the mobile application only marginally drop the performance of the mobile application.

Smith, Benton T.↗
NASA NTRS1994

Natural frequency of uniform and optimized tetrahedral truss platforms

Qualitative and quantitative estimates for the fundamental frequency of uniform and optimized tetrahedral truss platforms are determined. A semiempirical equation is developed for the frequency of free-free uniform trusses as a function of member material properties, truss dimensions, and parasitic (nonstructural) mass fraction Mp/Mt. Optimized trusses with frequencies approximately two times those of uniform trusses are determined by varying the cross-sectional areas of member groups. Trusses with 3 to 8 rings, no parasitic mass, and member areas up to 25 times the minimum area are optimized. Frequencies computed for ranges of both Mp/Mt and the ratio of maximum area to minimum area are normalized to the frequency of a uniform truss with no parasitic mass. The normalized frequency increases with the number of rings, and both frequency and the ratio of maximum area to minimum area decrease with increasing Mp/Mt. Frequency improvements that are achievable with a limited number of member areas are estimated for a 3-ring truss by using Taguchi methods. Joint stiffness knockdown effects are also considered. Comparison of optimized and baseline uniform truss frequencies indicates that tailoring can significantly increase structural frequency; maximum gains occur for trusses with low values of Mp/Mt. This study examines frequency trends for ranges of structural parameters and may be used as a preliminary design guide.

Wu, K. Chauncey↗
NASA NTRS2003

The promise of macromolecular crystallization in microfluidic chips

Microfluidics, or lab-on-a-chip technology, is proving to be a powerful, rapid, and efficient approach to a wide variety of bioanalytical and microscale biopreparative needs. The low materials consumption, combined with the potential for packing a large number of experiments in a few cubic centimeters, makes it an attractive technique for both initial screening and subsequent optimization of macromolecular crystallization conditions. Screening operations, which require a macromolecule solution with a standard set of premixed solutions, are relatively straightforward and have been successfully demonstrated in a microfluidics platform. Optimization methods, in which crystallization solutions are independently formulated from a range of stock solutions, are considerably more complex and have yet to be demonstrated. To be competitive with either approach, a microfluidics system must offer ease of operation, be able to maintain a sealed environment over several weeks to months, and give ready access for the observation and harvesting of crystals as they are grown.

Review↗
NASA NTRS1984

Exploration of the Solar System by Airborne Astronomy

The contributions of airborne astronomy to the knowledge of our solar system are reviewed, beginning in 1967 when planetary observations became a vigorous part of NASA's airborne astronomy initiatives using aircraft outfitted with 30 cm diameter telescopes for infrared observations at altitudes between 12 and 15 km. These early facilities and their successor, the Kuiper airborne observatory (KAO), profoundly influenced many areas of planetary science by providing optimized platforms for the conduct of certain types of remote sensing experiments that were incompatible with both ground-based and spacecraft environments. Specific topics reviewed include energy balance in the outer planets, the composition and structure of planetary atmospheres, and planetary ring systems.

Larson, H. P.↗
NASA NTRS2001

Sampling of Trace Atmospheric Constituents Above the Surface of Mars from a Montgolfiere Balloon

We suggest that use of an aerially deployed, solar-heated balloon, or Montgolfiere, during a Martian polar summer could provide an optimal platform for atmospheric measurements near the surface. Solar Montgolfieres are empty balloons with a hole in the bottom that fill with ambient atmosphere while failing and are rapidly heated in by the sun, thus providing buoyancy. Such a balloon would be driven by the Martian winds in the constant sunlight of a high latitude entry and could provide a traverse of thousands of kilometers. It would encircle the Martian north polar region over a period,likely lasting over one earth month, and its altitude could be controlled as low as 100 meters to as high as 4000 meters above the surface. The significant payload of tens of kilograms allowed by this technology could readily accommodate the mass of instrumentation and the power source needed for a sensitive search for disequilibrium species that might provide the atmospheric signature of localized subsurface biological or geological activity. A mass spectrometer used in combination with gas enrichment techniques can provide sensitivities to sub parts per billion for several species of interest. Additional highly specific and sensitive detectors can search for other species or measurements of their mixing ratio variation along the path of the balloon. It would be useful to combine these atmospheric measurements with electromagnetic sounding to search for variations in subsurface conductivity that might indicate the presence of subsurface water. After a month of operation, the balloon could also soft land the DBMS to provide additional data on soil samples from a 1-2 meter subsurface drill. In order to float a 30-kg payload at altitudes between 100 m and 4000 m above the Martian north polar surface, an aluminized polyethylene Montgolfiere would be approximately 29 meters in diameter and have a mass of 27 kg. Altitude variations could be accomplished by means of an upper vent to release hot gas, as has been tested at JPL, or be means of a simple, internal winch mechanism to decrease the volume of the balloon. JPL has successfully deployed three polyethylene Montgolfieres at 4-6 mbar pressure in the Earth's stratosphere and will be deploying a 20-m diameter polyethylene Montgolfiere later in 2001.

Jones, Jack A.↗
NASA NTRS2008

Deformation, Ecosystem Structure, and Dynamics of Ice (DESDynI)

The National Research Council Earth Science Decadal Survey, Earth Science Applications from Space, recommends that DESDynI (Deformation, Ecosystem Structure, and Dynamics of Ice), an integrated L-band InSAR and multibeam Lidar mission, launch in the 2010- 2013 timeframe. The mission will measure surface deformation for solid Earth and cryosphere objectives and vegetation structure for understanding the carbon cycle. InSAR has been used to study surface deformation of the solid Earth and cryosphere and more recently vegetation structure for estimates of biomass and ecosystem function. Lidar directly measures topography and vegetation structure and is used to estimate biomass and detect changes in surface elevation. The goal of DESDynI is to take advantage of the spatial continuity of InSAR and the precision and directness of Lidar. There are several issues related to the design of the DESDynI mission, including combining the two instruments into a single platform, optimizing the coverage and orbit for the two techniques, and carrying out the science modeling to define and maximize the scientific output of the mission.

Donnellan, Andrea↗
NASA NTRS2017

BioWires: Conductive DNA Nanowires in a Computationally-Optimized, Synthetic Biological Platform for Nanoelectronic Fabrication

DNA is an ideal template for a biological nanowire-it has a linear structure several atoms thick; it possesses addressable nucleobase geometry that can be precisely defined; and it is massively scalable into branched networks. Until now, the drawback of DNA as a conducting nanowire been, simply put, its low conductance. To address this deficiency, we extensively characterize a chemical variant of canonical DNA that exploits the affinity of natural cytosine bases for silver ions. We successfully construct chains of single silver ions inside double-stranded DNA, confirm the basic dC-Ag+-dC bond geometry and kinetics, and show length-tunability dependent on mismatch distribution, ion availability and enzyme activity. An analysis of the absorbance spectra of natural DNA and silver-binding, poly-cytosine DNA demonstrates the heightened thermostability of the ion chain and its resistance to aqueous stresses such as precipitation, dialysis and forced reduction. These chemically critical traits lend themselves to an increase in electrical conductivity of over an order of magnitude for 11-base silver-paired duplexes over natural strands when assayed by STM break junction. We further construct and implement a genetic pathway in the E. coli bacterium for the biosynthesis of highly ionizable DNA sequences. Toward future circuits, we construct a model of transcription network architectures to determine the most efficient and robust connectivity for cell-based fabrication, and we perform sequence optimization with a genetic algorithm to identify oligonucleotides robust to changes in the base-pairing energy landscape. We propose that this system will serve as a synthetic biological fabrication platform for more complex DNA nanotechnology and nanoelectronics with applications to deep space and low resource environments.

DNA↗
NASA NTRS2012

Parametric Deformation of Discrete Geometry for Aerodynamic Shape Design

We present a versatile discrete geometry manipulation platform for aerospace vehicle shape optimization. The platform is based on the geometry kernel of an open-source modeling tool called Blender and offers access to four parametric deformation techniques: lattice, cage-based, skeletal, and direct manipulation. Custom deformation methods are implemented as plugins, and the kernel is controlled through a scripting interface. Surface sensitivities are provided to support gradient-based optimization. The platform architecture allows the use of geometry pipelines, where multiple modelers are used in sequence, enabling manipulation difficult or impossible to achieve with a constructive modeler or deformer alone. We implement an intuitive custom deformation method in which a set of surface points serve as the design variables and user-specified constraints are intrinsically satisfied. We test our geometry platform on several design examples using an aerodynamic design framework based on Cartesian grids. We examine inverse airfoil design and shape matching and perform lift-constrained drag minimization on an airfoil with thickness constraints. A transport wing-fuselage integration problem demonstrates the approach in 3D. In a final example, our platform is pipelined with a constructive modeler to parabolically sweep a wingtip while applying a 1-G loading deformation across the wingspan. This work is an important first step towards the larger goal of leveraging the investment of the graphics industry to improve the state-of-the-art in aerospace geometry tools.

Anderson, George R.↗
NASA NTRS1980

Structural sizing considerations for large space platforms

Structural optimization studies are made using mathematical programming techniques to examine minimum mass structural proportions of deployable and erectable tetrahedral truss platforms subject to the integrated effects of practical design requirements. Considerations integrated into the optimization process are: 1) lowest natural frequencies of the platform and individual platform components (struts); 2) packaging constraints imposed by the Shuttle cargo bay capacity; 3) initial curvature of the struts; 4) column buckling of the struts due to gravity gradient, orbital transfer, strut length tolerance, or design loads; and 5) practical lower limits for strut diameter and wall thickness. Ultra-low mass designs are shown to be possible with strut proportions much more slender than those conventionally used for earthbound application.

Heard, W. L., Jr.↗
NASA NTRS1991

Experimental verification of Space Platform battery discharger design optimization

The detailed design of two candidate topologies for the Space Platform battery discharger, a four module boost converter (FMBC) and a voltage-fed push-pull autotransformer (VFPPAT), is presented. Each has unique problems. The FMBC requires careful design and analysis in order to obtain good dynamic performance. This is due to the presence of a right-half-plane (RHP) zero in the control-to-output transfer function. The VFPPAT presents a challenging power stage design in order to yield high efficiency and light component weight. The authors describe the design of each of these converters and compare their efficiency, weight, and dynamic characteristics.

Sable, Dan M.↗
NASA NTRS1992

Optimal microgravity vibration isolation - An algebraic introduction

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platforms. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward (preview) gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega) (exp 4). Low frequency accelerations (less than 50 Hz) are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics quaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Hampton, R. D.↗
NASA NTRS1991

Microgravity vibration isolation: An optimal control law for the one-dimensional case

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platform. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega) exp 4. Low frequency accelerations are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics guaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Hampton, Richard D.↗