SEARCH · Engineering Papers
Results for “space structures”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
An evaluation of structural analysis methodologies for space deployable structures
UNKNOWN
Building large structures in space
The building of large structures in space would be required for the establishment of a variety of systems needed for different forms of space utilization. The problems involved in the building of such structures in space and the approaches which can be used to solve these problems are illustrated with the aid of an example involving a concept for packaging, transporting, and assembling two representative large space structures. The structure of a radio-astronomy telescope 200 m in diam was felt to be representative of the many medium-size structures of the Shuttle era. A typical very large structure is represented by the supporting structure for the transmission system of a 5000-Mw space solar power station.
Space shuttle structural fatigue considerations
Space shuttle structural fatigue analysis
The challenges of manufacturing graphite-epoxy structural columns for space platforms
A description is given of the manufacturing processes developed for large-quantity production of space structure graphite/epoxy composite tubes. The tubes are to be delivered to orbit by the Space Shuttle and assembled by astronaut-assisted assembly machines. The tooling and manufacturing system uses a novel method of dry fiber placement which carefully controls fiber position and orientation and a non-autoclave cure for the epoxy resin. The means of dimensional tolerance control over differential thermal expansion between metal tooling and graphite tubes, resin shrinkage during cure, hot pressurized resins in close tolerance tooling, and tool wear, are examined in detail. A successful pilot production program is also reported.
On the stability and structure of shock waves in interplanetary space
Structure of interplanetary shock waves formed by interaction of geomagnetic field and solar wind - earth bow shock
A methodology for choosing candidate materials for the fabrication of planetary space suit structures
A study of space suit structures and materials is under way at NASA Ames Research Center, Moffett Field, CA. The study was initiated by the need for a generation of lightweight space suits to be used in future planetary Exploration Missions. This paper provides a brief description of the Lunar and Mars environments and reviews what has been done in the past in the design and development of fabric, metal, and composite suit components in order to establish criteria for comparison of promising candidate materials and space suit structures. Environmental factors and mission scenarios will present challenging material and structural requirements; thus, a program is planned to outline the methodology used to identify materials and processes for producing candidate space suit structures which meet those requirements.
Designing structures for large space systems
A questionnaire was compiled to identify technology deficiencies and point to research and development activities required in support of the large space structures program. Problem areas identified in setting criteria for such structures include improved flightworthiness, satisfying cost constraints, assessing new loads and environments, improved mission performance and life, and preservation of the ecology.
Interparticle spacing and structural ordering in superlattice PbS nanocrystal solids undergoing ligand exchange
Controlling the interparticle spacing in quantum dot (QD) thin films is the most readily accessible way to control transport rates between neighboring QDs and a critical component of device optimization. Here, we use X-ray scattering measurements to accurately measure the interparticle spacing in films of highly monodisperse lead sulfide (PbS) QDs that have undergone a variety of device-relevant ligand exchanges. We tabulate these values for use in simulations and data analysis. We find that monothiol and dithiol ligand species typically result in interparticle spacing values that are equal to the length of a single monothiol or dithiol ligand. Additionally, we find that spin-coating a thick film of QDs followed by a long-duration ligand exchange results in a more complete ligand exchange than spin-coating many thin layers with short-duration ligand exchanges in between. The former method also preserves a remarkable degree of the long-range ordering that was present in the film prior to ligand exchange. These results shed light on ways to produce highly-ordered QD solids with compact and functional ligands, which could lead to enhanced interdot coupling and transport phenomena.
Lagrangian space consistency relation for large scale structure
Consistency relations, which relate the squeezed limit of an (N+1)-point correlation function to an N-point function, are non-perturbative symmetry statements that hold even if the associated high momentum modes are deep in the nonlinear regime and astrophysically complex. Recently, Kehagias & Riotto and Peloso & Pietroni discovered a consistency relation applicable to large scale structure. We show that this can be recast into a simple physical statement in Lagrangian space: that the squeezed correlation function (suitably normalized) vanishes. This holds regardless of whether the correlation observables are at the same time or not, and regardless of whether multiple-streaming is present. Furthermore, the simplicity of this statement suggests that an analytic understanding of large scale structure in the nonlinear regime may be particularly promising in Lagrangian space.
Future directions in materials and structures for space applications
A comprehensive evaluation is made of materials and structural technology requirements for future space transportation systems, large spacecraft, and space structures. Exceptional promise is noted in carbon-carbon composites for large area thermal protection systems. High temperature test facilities, techniques, and instrumentation systems have unfortunately been neglected, and a materials systems data base suitable for high confidence design of long life space structures has yet to be compiled with a view to material environments in low earth and geosynchronous orbits. A coordinated analysis, ground test, and in-orbit experimentation program for candidate structure designs is called for.
Understanding Space Shuttle Structural Dynamics
The Space Shuttle consists of a orbiter, external tank, solid rocket boosters, payload, main engines, mobile launch platform and launch pad (Ground Ops). Structural Dynamics - All structures will vibrate at certain frequencies. The dynamics of the Space Shuttle must be understood in order to make sure it can survive, to control it, to make sure that it can perform its mission, and to keep it from aging prematurely. We understand the structural dynamics of the Space Shuttle by modelling, testing and flying it.
Autonomous Assembly of Modular Structures in Space and on Extraterrestrial Locations
The fulfillment of the new US. National Vision for Space Exploration requires many new enabling technologies to accomplish the goal of utilizing space for commercial activities and for returning humans to the moon and extraterrestrial environments. Traditionally, flight structures are manufactured as complete systems and require humans to complete the integration and assembly in orbit. These structures are bulky and require the use of heavy launch vehicles to send the units to the desired location, e.g. International Space Station (ISS). This method requires a high degree of safety, numerous space walks and significant cost for the humans to perform the assembly in orbit. For example, for assembly and maintenance of the ISS, 52 Extravehicular Activities (EVA's) have been performed so far with a total EVA time of approximately 322 hours. Sixteen (16) shuttle flights haw been to the ISS to perform these activities with an approximate cost of $450M per mission. For future space missions, costs have to be reduced to reasonably achieve the exploration goals. One concept that has been proposed is the autonomous assembly of space structures. This concept is an affordable, reliable solution to in-space and extraterrestrial assembly operations. Assembly is autonomously performed when two components containing onboard electronics join after recognizing that the joint is appropriate and in the precise position and orientation required for assembly. The mechanism only activates when the specifications are correct and m a nominal range. After assembly, local sensors and electronics monitor the integrity of the joint for feedback to a master controller. To achieve this concept will require a shift in the methods for designing space structures. In addition, innovative techniques will be required to perform the assembly autonomously. Monitoring of the assembled joint will be necessary for safety and structural integrity. If a very large structure is to be assembled in orbit, then the number of integrity sensors will be significant. Thus simple, low cost sensors are integral to the success of this concept. This paper will address these issues and will propose a novel concept for assembling space structures autonomously. The paper will present Several autonomous assembly methods. Core technologies required to achieve in space assembly will be discussed and novel techniques for communicating, sensing, docking and assembly will be detailed. These core technologies are critical to the goal of utilizing space in a cost efficient and safe manner. Finally, these technologies can also be applied to other systems both on earth and extraterrestrial environments.
Dynamic modeling and adaptive control for space stations
Of all large space structural systems, space stations present a unique challenge and requirement to advanced control technology. Their operations require control system stability over an extremely broad range of parameter changes and high level of disturbances. During shuttle docking the system mass may suddenly increase by more than 100% and during station assembly the mass may vary even more drastically. These coupled with the inherent dynamic model uncertainties associated with large space structural systems require highly sophisticated control systems that can grow as the stations evolve and cope with the uncertainties and time-varying elements to maintain the stability and pointing of the space stations. The aspects of space station operational properties are first examined, including configurations, dynamic models, shuttle docking contact dynamics, solar panel interaction, and load reduction to yield a set of system models and conditions. A model reference adaptive control algorithm along with the inner-loop plant augmentation design for controlling the space stations under severe operational conditions of shuttle docking, excessive model parameter errors, and model truncation are then investigated. The instability problem caused by the zero-frequency rigid body modes and a proposed solution using plant augmentation are addressed. Two sets of sufficient conditions which guarantee the globablly asymptotic stability for the space station systems are obtained.
Inflatable structures in space
Material composition, weight, size, and unfolding factors entering into design of inflatable space station structures
Large space system control technology model order reduction study
The mission control requirements for large space structures are presented as well as some of the problems associated with the active control of large structures in space. A generic model is introduced that contains most of the desired features in the modeling and control problem for large space structures.
Integration Assessment of Visiting Vehicle Induced Electrical Charging of the International Space Station Structure
The International Space Station (ISS) undergoes electrical charging in low Earth orbit (LEO) due to positively biased, exposed conductors on solar arrays that collect electrical charges from the space plasma. Exposed solar array conductors predominately collect negatively charged electrons and thus drive the metal ISS structure electrical ground to a negative floating potential (FP) relative to plasma. This FP is variable in location and time as a result of local ionospheric conditions. ISS motion through Earth s magnetic field creates an addition inductive voltage up to 20 positive and negative volts across ISS structure depending on its attitude and location in orbit. ISS Visiting Vehicles (VVs), such as the planned Orion crew exploration vehicle, contribute to the ISS plasma charging processes. Upon physical contact with ISS, the current collection properties of VVs combine with ISS. This is an ISS integration concern as FP must be controlled to minimize arcing of ISS surfaces and ensure proper management of extra vehicular activity crewman shock hazards. This report is an assessment of ISS induced charging from docked Orion vehicles employing negatively grounded, 130 volt class, UltraFlex (ATK Space Systems) solar arrays. To assess plasma electron current collection characteristics, Orion solar cell test coupons were constructed and subjected to plasma chamber current collection measurements. During these tests, coupon solar cells were biased between 0 and 120 V while immersed in a simulated LEO plasma. Tests were performed using several different simulated LEO plasma densities and temperatures. These data and associated theoretical scaling of plasma properties, were combined in a numerical model which was integrated into the Boeing Plasma Interaction Model. It was found that the solar array design for Orion will not affect the ISS FP by more than about 2 V during worst case charging conditions. This assessment also motivated a trade study to determine acceptable plasma electron current levels that can be collected by a single or combined fleet of ISS-docked VVs.
Baseline tests of an autonomous telerobotic system for assembly of space truss structures
Several proposed space missions include precision reflectors that are larger in diameter than any current or proposed launch vehicle. Most of these reflectors will require a truss structure to accurately position the reflector panels and these reflectors will likely require assembly in orbit. A research program has been conducted at the NASA Langley Research Center to develop the technology required for the robotic assembly of truss structures. The focus of this research has been on hardware concepts, computer software control systems, and operator interfaces necessary to perform supervised autonomous assembly. A special facility was developed and four assembly and disassembly tests of a 102-strut tetrahedral truss have been conducted. The test procedures were developed around traditional 'pick-and-place' robotic techniques that rely on positioning repeatability for successful operation. The data from two of the four tests were evaluated and are presented in this report. All operations in the tests were controlled by predefined sequences stored in a command file, and the operator intervened only when the system paused because of the failure of an actuator command. The tests were successful in identifying potential pitfalls in a telerobotic system, many of which would not have been readily anticipated or incurred through simulation studies. Addressing the total integrated task, instead of bench testing the component parts, forced all aspects of the task to be evaluated. Although the test results indicate that additional developments should be pursued, no problems were encountered that would preclude automated assembly in space as a viable construction method.